Krell Industries Stereo System MASTER REFERENCE SUBWOOFER User Manual

M A S T E R R E F E R E N C E S U B W O O F E R  
O W N E R ’ S R E F E R E N C E  
 
Overview  
This owner’s reference is written to assist you with the seamless integration of the  
Master Reference Subwoofer into your audio/video system. Due to the size and  
weight of the subwoofer, there are special placement and installation issues that  
require your attention. In addition, to use the programmable electronic crossover,  
you need to set system configurations before you play music. Please read and  
follow this guide carefully to ensure safe installation, set-up, and operation of the  
Master Reference Subwoofer in your listening environment.  
This owner’s reference is divided into seven sections:  
SECTION ONE: About Krell, pages 2-13  
This section describes the Krell Legacy, Krell’s revolutionary CAST technology, and  
defines key terms used in this reference.  
Krell Legacy. Krell’s ongoing pursuit of high-end audio excellence.  
Revolutionary Krell CAST Technology. Krell’s revolutionary method of connecting  
analog audio components for unparalleled sonic performance.  
Ensuring Maximum Performance. A description of Krell’s innovative technologies  
and design for the Master Reference Subwoofer as well as the core technologies  
developed for all Krell components.  
Definition of Terms. Key terms used throughout the Master Reference Subwoofer  
owner’s reference.  
SECTION TWO: Unpacking and Placement, pages 14-17  
This section describes the procedures for unpacking and placement of the Master  
Reference Subwoofer in the listening room.  
Unpacking. Removing the subwoofer from its shipping crate and safely moving the  
subwoofer into the listening room.  
Placement. Options for placing the subwoofer in the listening room; and the AC  
Power Guidelines.  
SECTION THREE: Features, pages 18-29  
This section provides illustrations of the Master Reference Subwoofer front panel,  
back panel, and remote control, and descriptions of front panel, back panel, and  
remote control features.  
continued  
iii  
1
 
(Overview continued)  
SECTION FOUR: Connections and Configurations, pages 30-41  
This section provides information on connecting and configuring the Master  
Reference Subwoofer before playing music.  
Connections. Integrating the Master Reference Subwoofer with other components  
in your system using CAST, balanced, or single-ended connections, as well as  
connecting the Master Reference Subwoofer (for stereo and low frequency effect  
operation).  
Configurations. Instructions for setting configurations before you play music and  
how to save your settings to presets.  
SECTION FIVE: Operation, pages 42-43  
This section provides instructions for how to power on and power off manually.  
SECTION SIX: Optional Connections, pages 44-46  
This section describes the remote connection options that enable you to power on  
and control the Master Reference Subwoofer automatically.  
Krell Link Connections and Operation. Describing how Krell Link works.  
Connecting and operating components connected through Krell Link.  
RS-232 Connection. Describing an additional remote connection for receiving  
commands from a computer-based control system.  
12 VDC (12 V Trigger) Connections. Describing an additional remote control option for  
the Master Reference Subwoofer and other components that contain a 12 V trigger.  
SECTION SEVEN: Optional Configurations, pages 47-49  
This section provides instructions for setting optional configurations, including  
turning LEDs on and off and selecting AC Mains operation.  
WARRANTY, pages 50-51  
RETURN AUTHORIZATION PROCEDURE, page 52  
iv  
 
List of Illustrations  
Figure 1, page 16  
Master Reference Subwoofer Placement Options  
Figure 2, page 18  
Master Reference Subwoofer Front Panel  
Figure 3, page 20  
Master Reference Subwoofer Back Panel (Power)  
Figure 4, page 21  
Master Reference Subwoofer Back Panel (Inputs and Outputs)  
Figure 5, page 25  
Master Reference Subwoofer Remote Control  
v
 
 
A Letter from Dan D’Agostino  
Dear Audio Enthusiast,  
Thank you for your purchase of the Master Reference Subwoofer.  
The Master Reference Subwoofer is the result of my ongoing quest for designing  
reference caliber audio components.  
I have been designing audio amplifiers for high performance audio systems for more  
than thirty years. The Master Reference Subwoofer represents the culmination of  
many years of engineering research and discerning listening. All of my insights and  
discoveries about the synergy between high performance amplifiers and low frequency  
music reproduction have come together in the design of this component.  
I developed this subwoofer to be compatible not only with Krell’s proprietary CAST  
components but also with the wide range of loudspeakers that are preferred by  
music enthusiasts. Krell’s one-of-a-kind programmable electronic crossover makes  
this possible. The crossover includes three filters—Bessel, Butterworth, and Linkwitz-  
Riley—that adjust and match the subwoofer to any system and loudspeaker con-  
figuration. No other subwoofer offers this level of refinement. The Master Reference  
Subwoofer eliminates the loss of sound quality and power that occurs as music  
moves between the high and low frequency ranges. This Krell subwoofer produces  
low frequency sound the way it was meant to be heard—resonant, precise, and  
utterly reliable—without compromising the fidelity of the performance.  
To me, the Master Reference Subwoofer is the logical next step in my personal  
passion for designing and developing high performance audio equipment. Innovative  
software controls and proprietary circuitry in a custom-machined chassis add  
dimension to your stereo and home theater systems, placing their low-end capability  
at the very vanguard of technology.  
Thank you again for your decision to purchase the Master Reference Subwoofer.  
Designing and building the finest audio components continues to be my life’s work. I  
am pleased to share my most recent triumph in audio engineering and design with you.  
Sincerely,  
Daniel D’Agostino  
Chief Executive Officer  
1
 
SECTION  
ONE  
About Krell  
This section describes the Krell Legacy, Krell’s revolutionary CAST technology, and  
defines key terms used in this reference.  
The Krell Legacy  
“I design every Krell component to set the standard  
for workmanship, style, and performance.”  
Dan D’Agostino  
High-end audio is a demanding pursuit—an ongoing quest for excellence in  
music reproduction that drives equipment manufacturers to strive for the absolute  
in design and performance. With a keen understanding of this passionate drive,  
Krell Industries, Inc. was founded in 1980.  
Over the past two decades, Krell has earned a distinguished reputation for engineering  
innovation and product excellence. The company’s history is replete with product  
introductions that have deeply impacted the high-end audio industry. The most  
discriminating audiophiles and product reviewers have consistently recognized Krell  
components for standard-setting performance.  
The Master Reference Subwoofer represents the next era at Krell Industries, Inc.—  
the era of loudspeaker design and manufacture—which will join the ongoing legacy  
of Krell amplifiers. For three decades, Krell C.E.O. Dan D’Agostino has built amplifiers  
legendary for their ability to deliver optimum performance from any loudspeaker.  
This experience has yielded invaluable insights about the nature of loudspeaker  
design, which Krell has characteristically incorporated into its first subwoofer.  
The Master Reference Subwoofer is a full-fledged, reference caliber subwoofer  
that features a programmable crossover and proprietary circuit technology not  
found in any other subwoofer. The result is a subwoofer that raises your music  
and home theater systems to new levels of tonal quality, precision, and accuracy.  
2
 
From the first Krell product — the KSA-100 — to the present, Dan D’Agostino has  
continually “pushed the envelope” of performance in his search for greater amplifier  
power and now, subwoofer power. His exploration of technologies, driven by his  
never-ending quest to elevate the standard of excellence, has resulted in break-  
through audio designs. Over the years, the Krell line of power amplifiers, including  
benchmark products such as the KRS-100, KRS-200, and the Audio Standard  
models, has established a legacy of unparalleled sonic performance. The Master  
Reference Subwoofer brings that level of performance to the low frequency range.  
Dan D’Agostino remains committed to the development of new designs and tech-  
nologies. And the Krell legacy will continue to evolve with products that deliver  
innovative engineering, perfection in build quality, and outstanding audio performance.  
continued  
3
 
(SECTION ONE: About Krell continued)  
Revolutionary Krell CAST Technology  
The Master Reference Subwoofer is designed with Current Audio Signal Transmission  
circuit technology, termed CAST. This circuitry is a revolutionary method of connect-  
ing analog audio components for unparalleled sonic performance. The innovative  
use of the new Krell CAST in combination with existing Krell Current Mode technology  
enables you to create entire CAST systems that reproduce music with incredible  
range, tonality, and precision.  
The Traditional Audio System and Voltage Signal Transmission  
Signal is transmitted in the voltage domain between two components in a traditional  
audio system. Each component is a discrete entity displaying unique characteristics  
that affect the musical signal independently. Each component is unaware of the other  
components in the system. The cables that connect the components also have  
their own electrical characteristics that affect the sonic presentation of the audio  
system.  
A New Approach: Current Audio Signal Transmission  
CAST circuitry recognizes signal transmitted between each component in the cur-  
rent domain instead of the voltage domain. CAST transmission unifies individual  
components and their interconnects into an electrically linked whole. The sonic  
presentation of the entire system remains intact.  
The Basics of CAST  
Here’s how a CAST audio system works with the Master Reference Subwoofer.  
Each CAST source amplifies current internally, using Krell Current Mode circuitry.  
CAST circuitry then outputs this current signal. When the signal is received by a  
CAST input on a Master Reference Subwoofer, Krell Current Mode circuitry again  
manages the signal until the signal reaches the loudspeaker. An entire CAST system  
behaves as if it is one component because it maintains the musical signal in the  
current domain from beginning to end. Anomalies of signal transmission between  
components are eliminated. Cable impedances and their effects on the transmitted  
signal are non-existent.  
4
 
CAST and Krell Current Mode Combined  
CAST technology combined with Krell Current Mode circuitry take signal transmission  
to the next evolutionary level. Krell Current Mode is the technology developed to  
transfer the musical signal within a component, used in Krell components since  
1995. Krell has now added CAST technology, a new method of transferring the  
musical signal between components. In essence, Krell Current Mode maintains  
the integrity of the signal within the Master Reference Subwoofer and CAST pre-  
serves the transmitted signal between source components and the Master Reference  
Subwoofer. Together, CAST and Krell Current Mode technologies unify separate Krell  
components into a single global circuit.  
CAST Cables  
CAST systems use cables manufactured by Krell and made by other manufactur-  
ers specially licensed by Krell. Thin, flexible CAST cables are constructed with the  
same build quality as Krell components and are aesthetically matched to the Krell  
product line. An all-metal body and locking connectors with gold contacts are part  
of the no-compromise specification developed as a standard for every CAST  
cable made.  
The Best Musical Performance  
A CAST system brings you significant improvements in every performance area:  
speed, precision, dynamic range, depth and width of the sound stage, transient  
impact, tonal balance, harmonic distortion, and more. The goal behind designing  
CAST into the Master Reference Subwoofer reflects the company goal for every  
Krell product. Krell strives for the delivery of the best performance of a musical event  
for you, using the full expression of technology to date.  
Thank you for your appreciation of our research and development effort.  
continued  
5
 
(SECTION ONE: About Krell continued)  
Ensuring Maximum Performance  
The function of the Master Reference Subwoofer is to  
reproduce, with unprecedented authority and fidelity, the  
lowest reaches of the audio spectrum, thereby extending  
the low frequency capabilities of even the finest music  
and home theater systems.  
The Krell Master Reference Subwoofer sets a new standard in powered subwoofer  
design. At the heart of the Master Reference Subwoofer is its proprietary interface.  
This programmable electronic crossover provides unparalleled matching for subwoofer  
and system components and allows seamless integration with any loudspeaker  
configuration. Additional innovative technologies such as Active Motion Control are  
specifically designed to unleash the full power of the built-in Krell amplifier while  
assuring that the special characteristics of low frequency sound are meticulously  
reproduced. Innovative technology teamed with Krell’s outstanding core technology  
ensure maximum power, precision, and performance in the low frequency range.  
Innovative Subwoofer Technology and Design  
Programmable Electronic Crossover  
The programmable electronic crossover is a design tour de force. It seamlessly  
matches the Master Reference Subwoofer to the characteristics of your system.  
You can select and adjust high-pass and low-pass filter profiles and parameters.  
Three filter profiles with unique response characteristics integrate the Master  
Reference Subwoofer with any loudspeaker and listening setup. Each filter profile  
includes parameters for frequency, slope, and level, allowing you to further fine-tune  
the subwoofer to your system. These adjustments are easy to select using the  
Master Reference Subwoofer’s step-by-step menu and remote control.  
Krell Active Motion Control  
The traditional approach to subwoofer design is to incorporate a standard servo  
circuit that uses feedback to control the drivers at higher output levels. Doing so  
effectively controls the drivers, but it can also dampen the musical dynamics, losing  
the visceral impact of the low frequency range.  
6
 
Active Motion Control is a unique circuit topology developed by Krell specifically  
for the Master Reference Subwoofer. An instrument grade accelerator, mounted to  
one of the drivers, relays information about the driver’s position to the Active Motion  
Control circuit, where it is compared to the musical waveform at the amplifier input  
stage. Amplifier parameters are then adjusted to ensure that driver motion is faithful  
to the input signal, and feedback is precisely applied to preserve sonic impact. Krell  
Active Motion Control allows the Master Reference Subwoofer to achieve complete  
driver control and deliver true-to-life low frequency sound at the same time.  
Enclosure  
The enclosure is an essential part of any loudspeaker and is particularly significant  
in subwoofer design. Low frequency energy causes some of the most stable materials  
to resonate. Enclosure resonance degrades performance and destroys linearity. Krell  
engineering has attacked these design challenges with a vigorous application of  
technology, know-how, and innovative build materials.  
The enclosure for the Master Reference Subwoofer is made of 1 in. thick, aircraft-  
aluminum billet. Each of the two driver baffles is a substantive 21/4 in. thick. The  
subwoofer assembly is held together by 68 machine screws, size 1/4 20 x 1 in. The  
precision machine finish is black anodized to a pearl-like luster. Fully assembled, the  
Master Reference Subwoofer weighs 396 pounds. This subwoofer does not resonate.  
Drivers  
The high performance demands of the Master Reference Subwoofer require drivers  
of exceptional capability. Krell has researched every aspect of driver design and  
construction to produce remarkable transducers. The Master Reference Subwoofer  
contains two 15 in. drivers, which have been custom crafted to Krell’s own rigorous  
specifications. The drivers are mounted at opposite ends of the case, firing outward,  
away from one another. They are wired in phase: One driver’s motion has the effect  
of canceling the motion of the other, rendering the enclosure free of operationally  
induced vibrations.  
continued  
7
 
(SECTION ONE: About Krell continued)  
(Drivers continued)  
Two 80 oz. strontium ferrite magnets are affixed to the custom-made, cast  
magnesium speaker frame. The magnet assembly has been contoured to produce  
a powerful, focused, magnetic field. A robust, doped (reinforced) paper cone,  
chosen for its high strength and low weight, is affixed at one end to the speaker  
frame via a special rubber surround. This surround has a unique geometry that  
resists cavitating (turning inside out) under high pressures. At the other end of  
the cone, Krell utilizes a dual-spider arrangement in order to maintain the superi-  
or alignment of the concentric mechanical assembly under all performance con-  
ditions. An extra-long voice coil controls the drivers even at maximum excursion.  
Krell Core Technologies  
Krell CAST and Krell Current Mode  
These circuit topologies combine to transmit audio waveforms between compo-  
nents in the current rather than the voltage domain. Krell components using Krell  
Current Mode circuitry and CAST technology perform as if they are part of a single  
circuit. The resulting speed and bandwidth produce outstanding accuracy and  
realism in music reproduction.  
Krell Proprietary Output Devices  
Loudspeaker control is paramount in any audio system. Control is even more critical  
in subwoofers, in which the audio band is limited to the extreme low frequencies.  
Krell amplifiers are known for the control they exert on even the most complex  
loudspeaker loads. Part of this capacity is a result of the proprietary output devices  
used in all Krell amplifiers. These devices, manufactured for Krell by Motorola,  
allow for high gain and low output impedance. These circuits enable the amplifier  
to deliver enormous amounts of current with relative ease and with less distortion.  
8
 
Totally Balanced Operation  
Balanced circuits ensure optimum signal to noise ratios, signal preservation, and  
accuracy of delivery under every condition; however, the primary benefit of balanced  
circuitry is loudspeaker control. The Master Reference Subwoofer finesses the low  
frequency range with totally balanced operation from input to output, employing  
CAST or XLR inputs. In the output stage of each Master Reference Subwoofer,  
independent circuit paths amplify the positive and negative output signals to exercise  
absolute control over loudspeaker systems and force the loudspeakers to generate  
music and low frequency effects that are precisely representative of the original  
signal.  
The Input Stage. The input stage of each subwoofer accepts signals in two ways:  
The CAST input accepts signals in the current domain, or the XLR input accepts  
signals in the voltage domain.  
We recommend using CAST inputs, for the best subwoofer  
performance. When the CAST connection is used, the signal  
received by each amplifier remains in the current domain and  
is transmitted unchanged through the Krell Current Mode  
input and output stages, with absolutely no degradation.  
Krell CAST and Krell Current Mode are more fully explained  
on pages 4-5.  
When the XLR connection is used, a signal in the voltage domain is delivered to  
the input stage. Each amplifier converts this signal to the current domain. The  
signal in the current domain is then sent through the output stage of the subwoofer  
without alteration.  
continued  
9
 
(SECTION ONE: About Krell continued)  
(Totally Balanced Operation continued)  
The Output Stage. In the output stage of a conventional amplifier, loudspeaker  
control is accomplished by driving the positive speaker terminal only. Each Master  
Reference Subwoofer uses two Krell Current Mode circuit paths, one to drive the  
positive and one to drive the negative terminals of the loudspeakers. These signals  
work together to drive the loudspeakers in a precise “push-pull” dialogue that  
preserves all the characteristics of the recording.  
The Master Reference Subwoofer sets a new standard for ultimate subwoofer  
power and performance. Its ability to reproduce the impact and tonal quality of  
low frequency sound is unparalleled, as is the ease with which it can match any  
system or speaker configuration. The Master Reference Subwoofer represents the  
culmination of the latest research and development from Krell Industries, Inc.  
and represents the next exciting innovation in the long line of exceptional audio  
components from The Leader in Audio Engineering—Krell.  
10  
 
(SECTION ONE: About Krell continued)  
Definition of Terms  
Following are the definitions of key terms used in your owner’s reference manual.  
Configurations  
Krell Link  
A method of configuring multiple Krell preamplifiers, amplifiers,  
and associated components and synchronizing their stand-by/  
operational modes. Using Krell Link in/out connections and  
MIDI cables, the remote capabilities of the linked components  
are controlled by one component, called the control component.  
The linked components respond to stand-by and operational  
mode commands from the control component.  
Inputs and Outputs  
Balanced  
A symmetrical input or output circuit that has equal impedance  
from both input terminals to a common ground reference point.  
The industry standard for professional and sound recording  
installations, balanced connections have 6 dB more gain than  
single-ended connections and allow the use of long intercon-  
nect cables.  
By-pass Output  
An output that allows you to integrate additional Master Reference  
Subwoofers into your system. The input signal of a component  
connected to the by-pass output passes directly through the  
subwoofer with no modification.  
High-pass Output  
An output that transmits the signal from the high-pass filter of  
the programmable electronic crossover to the amplifiers driving  
the main left and right loudspeakers.  
Note  
There is no low-pass (subwoofer) connector on the Master Reference  
Subwoofer. The low-pass output is connected directly to the internal  
amplifier.  
continued  
11  
 
(SECTION ONE: About Krell continued)  
(Definition of Terms continued)  
Krell CAST  
Current Audio Signal Transmission (CAST) is a proprietary Krell  
circuit technology for connecting analog components, in which  
the audio waveform is transmitted between components in the  
current rather than the voltage domain. The speed and band-  
width that CAST provides yield astounding levels of accuracy  
and realism. Krell components connected via CAST perform as  
if they are all part of a single circuit.  
Low Frequency Effect  
(LFE) Input  
LFE enriches the low end of a musical score and enhances  
nearly subsonic content, such as explosions or other special  
effects. It is part of the Dolby 5.1 specification, with a bandwidth  
of 5 to 120 Hz.  
Single-ended  
A two-wire input or output circuit in which the ground connection  
is made last and broken first. Use care when using single-ended  
connections. Turn the system off prior to making or breaking  
single-ended connections. Single-ended connections are not  
recommended for configurations requiring long cable runs.  
Operation  
Off  
When the power switch on the rear panel is placed in the down  
position and the red stand-by LED turns off, the component is off.  
Operational Mode  
When the power button on the front panel is pressed and the  
blue power LED illuminates, the component is in the opera-  
tional mode and ready to play music.  
Stand-by Mode  
A low power consumption status that keeps the audio and reg-  
ulator circuits at idle. Krell recommends leaving the component  
in the stand-by mode when it is not playing music.  
Technology  
Krell Active Motion  
Control  
A proprietary Krell circuit designed to continuously compare the  
position of a loudspeaker to the analog waveform at the amplifier  
input. Active Motion Control provides an extra measure of  
loudspeaker control without the transient distortion associated  
with simple servo designs.  
12  
 
Krell Current Mode A proprietary Krell circuit topology in which the audio gain stages  
operate in the current domain. Krell Current Mode provides  
speed and bandwidth performance that is not possible with  
less sophisticated voltage designs.  
Programmable A proprietary full-function crossover designed for the Master  
Electronic Crossover Reference Subwoofer. The crossover is comprised of two  
sections: the high-pass filter and the low-pass, or sub, filter.  
The user fine-tunes each section by selecting the filter type  
(profile), and adjusting the profile’s parameters including slope,  
frequency, and level, to enhance low frequency reproduction.  
13  
 
SECTION  
TWO  
Unpacking and Placement  
This section describes the procedures for safely unpacking and placing the Master  
Reference Subwoofer.  
Unpacking  
Each Master Reference Subwoofer shipping crate measures 26 in. (66 cm) wide  
x 32 in. (81.3 cm) high x 35 in. (88.9 cm) deep and contains one Master Reference  
Subwoofer. The combined weight of the crate and subwoofer is 494 lb. (224.5 kg).  
Each Master Reference Subwoofer is 18.8 in. (47.8 cm) wide x 20.1 in. (51.1 cm) high  
x 28.5 in. (72.4 cm) deep, and weighs 396 lb. (180 kg). Krell recommends that you  
have four people to safely lift the subwoofer to its place in the listening area. Two  
people are needed to remove the shipping crate top from the base.  
The shipping crate is specially constructed to open safely and easily. Inside, the  
subwoofer rests on the reinforced base of the crate. The crate top is fastened to  
the base with Phillips head screws. The only tools you need to remove the sub-  
woofer from the crate are a Phillips head screwdriver and a flat blade screwdriver.  
The steps below provide procedures for unpacking the Master Reference  
Subwoofer.  
To Unpack the Master Reference Subwoofer:  
1. Locate the gold screws at the bottom of the shipping crate.  
2. Completely remove all screws.  
3. Insert the head of a flat blade screwdriver between the crate top and base,  
just enough to loosen the top.  
1 person needed  
4. With one person grasping each end of the shipping crate, pull steadily straight  
up. The crate top will slowly slide up and off. Set aside.  
2 people needed  
Do not remove the plastic wrapping from the unit at this time.  
14  
 
In the packing crate you will find:  
1 Master Reference Subwoofer  
In the space underneath the subwoofer, you will find:  
1 power cord  
1 remote control  
2 AAA-size 1.5 volt batteries for the remote control  
1 T-10 Torx wrench for the remote control  
To Remove the Subwoofer from the Packing Crate:  
1. Remove all accessories from the packing crate.  
1 person needed  
2. Lift the subwoofer off the crate base and gently place it on the floor. Set the  
crate base aside.  
4 people needed  
3. Move the subwoofer to the desired location.  
4 people needed  
IMPORTANT  
Do not attempt to lift the subwoofer by the grill on the side of the unit.  
continued  
15  
 
(SECTION TWO: Unpacking and Placement continued)  
Figure 1 Master Reference Subwoofer Placement Options  
Scenario 1: Stereo  
3
1
2
1 Left Loudspeaker  
2 Right Loudspeaker  
3 Master Reference  
4
Subwoofer  
4 Optimum Listening  
Position  
Scenario 2: Home Theater, Rear Projection  
1 Left Front  
Loudspeaker  
2 Center Speaker  
3 Master Reference  
Subwoofer  
3
2
5
1
4
4 Right Front  
Loudspeaker  
5 Rear Projection TV  
6 Left Rear  
Loudspeaker  
7 Right Rear  
Loudspeaker  
8
6
7
8 Optimum Listening  
Position  
Scenario 3: Home Theater, Front Projection  
1 Left Front  
Loudspeaker  
4
2 Center Speaker  
3
3 Master  
Reference  
Subwoofer  
2
1
5
4 Screen  
5 Right Front  
Loudspeaker  
6 Left Rear  
Loudspeaker  
7 Right Rear  
Loudspeaker  
8
6
7
8 Optimum  
Listening Position  
16  
 
Placement  
Before you install the Master Reference Subwoofer, review the following guidelines to  
choose the location for the subwoofer. This facilitates a clean, trouble-free installation.  
Make sure the Master Reference Subwoofer, in addition to other items (amplifiers,  
other system components, furniture) in the listening room, does not exceed the  
listening room’s maximum floor load.  
Each Master Reference Subwoofer requires at least two inches (5 cm) of clearance  
on each side and in front, and at least two inches (5 cm) of clearance above and  
to the rear of the subwoofer for adequate ventilation.  
IMPORTANT  
For optimum sound quality, place your subwoofer at least one foot away from any wall.  
Your Master Reference Subwoofer can operate from a number of positions in  
your listening room. The range of control provided by the programmable electronic  
crossover, plus the subwoofer size and construction, help ensure excellent perfor-  
mance from nearly any location. Figure 1, on page 16, illustrates three possible  
placement options, which are described below.  
Option 1: Stereo. Place the Master Reference Subwoofer midway between the left  
and right loudspeakers.  
Option 2: Home Theater, Rear Projection. Place the Master Reference Subwoofer  
between the center and left front or between the center and right front loudspeakers,  
preferably one foot from any wall.  
Option 3: Home Theater, Front Projection. Place the Master Reference Subwoofer  
midway between the left and right front loudspeakers and between the center speaker  
and the screen.  
If you employ Krell CAST technology, you can use CAST interconnect cables of any  
length. Try to keep cable length to a minimum if you select single-ended operation.  
AC Power Guidelines  
The Master Reference Subwoofer should be operated from a dedicated AC power  
line rated at a minimum of 20 amps.  
Please contact your authorized Krell dealer, distributor, or Krell before using any  
devices to alter or stabilize the AC power for the Master Reference Subwoofer.  
17  
1
 
SECTION  
THREE  
Features  
This section provides illustrations of the Master Reference Subwoofer front panel,  
back panel, and remote control, and descriptions of front panel, back panel, and  
remote control features.  
Front Panel Description  
See Figure 2.  
The Master Reference Subwoofer front panel provides power on and subwoofer  
status displays. Front panel features and their descriptions follow.  
Figure 2 Master Reference Subwoofer Front Panel  
2
3
5
4
STAND-BY  
POWER  
1 Power Button  
2 Power LED  
3 Stand-by LED  
4 Front Panel Display  
5 Infrared Sensor  
Master Reference Subwoofer  
1
18  
 
1 Power Button  
Use this button to switch the Master Reference Subwoofer from the stand-by to  
the operational mode.  
2 Power LED  
The blue power LED illuminates when the Master Reference Subwoofer is in the  
operational mode and flashes when any remote control key is pressed.  
3 Stand-by LED  
The red stand-by LED illuminates when the back panel power switch is in the up  
position and the Master Reference Subwoofer is in the stand-by mode.  
4 Front Panel Display  
The front panel display provides operating status messages, including power,  
crossover filter selection and status, phase, and menu options and settings.  
5 Infared Sensor  
The infrared sensor, located inside the front panel display, receives commands  
from the Master Reference Subwoofer remote control. For proper remote control  
operation, make sure the infrared sensor is not covered or obstructed.  
continued  
19  
 
(SECTION THREE: Features continued)  
Figure 3 Master Reference Subwoofer Back Panel (Power)  
7 6  
Figure 3  
Power  
6 Power Switch  
7 AC Input Specification  
8 IEC Power Connector  
Figure 4  
Back Panel Remote Connections  
9 Krell Link In and Out  
10 12 VDC In and Out  
11 12 VDC LFE In  
50/60 Hz  
12 RC-5 In  
13 RS-232  
Inputs  
KRELL INDUSTRIES, INC.  
45 CONNAIR ROAD  
ORANGE, CT 06477-3650  
USA  
14 Left and Right CAST Inputs  
15 Left and Right Balanced Inputs  
16 Left and Right Single-ended  
Inputs  
MADE IN USA  
17 LFE CAST Input  
8
18 LFE Balanced Input  
19 LFE Single-ended Input  
Outputs  
20 Left and Right CAST High-pass  
Outputs  
21 Left and Right Balanced  
High-pass Outputs  
22 Left and Right Single-ended  
High-pass Outputs  
23 Left and Right CAST By-pass  
Outputs  
24 Left and Right Balanced By-pass  
Outputs  
25 Left and Right Single-ended  
By-pass Outputs  
20  
 
Figure 4 Master Reference Subwoofer Back Panel (Inputs and Outputs)  
9
10  
11  
12 13  
IN KRELL OUT  
LINK  
12VDC  
OUT  
RC-5  
IN  
IN  
LFE  
IN  
RS-232  
14  
16  
17  
19  
18  
INPUT  
LEFT  
INPUT  
RIGHT  
INPUT  
LFE  
15  
20  
22  
HIGH-PASS  
OUTPUT  
LEFT  
HIGH-PASS  
OUTPUT  
RIGHT  
21  
23  
25  
BY-PASS  
OUTPUT  
LEFT  
BY-PASS  
OUTPUT  
RIGHT  
Master Reference Subwoofer  
24  
NO USER SERVICEABLE PARTS INSIDE  
CAST PAT. PENDING  
continued  
21  
 
(SECTION THREE: Features continued)  
Back Panel Description  
See Figures 3 and 4.  
The Master Reference Subwoofer back panel provides input and output connections,  
remote connections, and power. Back panel features and their descriptions follow.  
Power  
6 Power Switch  
Use this switch to power the Master Reference Subwoofer from off to the stand-by  
mode.  
7 AC Input Specification  
The Master Reference Subwoofer is designed to be used with 50/60 Hz power lines  
only.  
8 IEC Power Connector  
The Master Reference Subwoofer is equipped with a standard female IEC power  
connector, for use with the provided AC power cord.  
Back Panel Remote Connections  
9 Krell Link In and Out  
The Master Reference Subwoofer is equipped with a Krell Link communications  
input and output data port. Krell Link allows synchronized remote power on and  
off of other components with Krell Link, such as Master Reference Amplifiers or  
Full Power Balanced Stereo or Monaural Amplifiers. See Krell Link, on page 44,  
for more information.  
10 12 VDC In and Out  
The Master Reference Subwoofer is equipped with an input that receives and an  
output that sends 12 VDC power on/off (12 V trigger) signals from and to other Krell  
components and other devices that incorporate a 12 V trigger. See 12 VDC (12 V  
Trigger), on page 46, for more information. Also consult the owner’s reference manual  
of each component used in a custom installation to take full advantage of the remote  
capabilities of the Master Reference Subwoofer.  
11 12 VDC LFE In  
The Master Reference Subwoofer is equipped with a 12 VDC (12 V trigger) LFE input.  
This input allows you to activate low frequency effect using the 12 V trigger setup of  
another preamplifier or preamp/processor. Both the Krell Home Theater Standard  
Surround preamp/processor and the Krell Current Tunnel CAST preamplifier have  
12 V trigger setups.  
22  
 
12 RC-5 In  
The Master Reference Subwoofer is equipped with an RC-5 input that makes  
custom installation easy and secure by accepting baseband RC-5 input commands  
from hardwired remote controllers. The RC-5 input can be used, for example, when  
the subwoofer’s IR sensor (5) is obscured from direct view.  
13 RS-232  
The Master Reference Subwoofer is equipped with an RS-232 port, which receives  
messages from a computer-based control system, providing integrated control of  
all subwoofer functions. See RS-232, on page 46, and the RS-232 Port: Sending  
Commands and Interpreting Data developer’s reference for more information.  
Notes  
The 12 VDC output current is limited to 30 ma.  
If the subwoofer is powered on via the 12 V trigger and the signal is active, the front panel  
power button (1) or RS-232 cannot power it off. You must use the 12 V trigger.  
Inputs  
14 Left and Right CAST Inputs  
The Master Reference Subwoofer is equipped with one pair of left and right CAST  
inputs via 4-pin bayonet connectors for use with Krell CAST-equipped preamplifiers  
or surround preamp/processors.  
15 Left and Right Balanced Inputs  
The Master Reference Subwoofer is equipped with one pair of left and right balanced  
inputs via XLR connectors.  
16 Left and Right Single-ended Inputs  
The Master Reference Subwoofer is equipped with one pair of left and right single-  
ended inputs via RCA connectors.  
17 LFE CAST Input  
The Master Reference Subwoofer is equipped with a low frequency effect (LFE) CAST  
input. This input is connected to a CAST-equipped surround preamp/processor,  
for use with Dolby 5.1 and DTS encoded software.  
18 LFE Balanced Input  
The Master Reference Subwoofer is equipped with a low frequency effect (LFE)  
balanced input. This input is connected to a preamp/processor, for use with Dolby  
5.1 and DTS encoded software.  
continued  
23  
 
(SECTION THREE: Features continued)  
(Inputs continued)  
19 LFE Single-ended Input  
The Master Reference Subwoofer is equipped with a low frequency effect (LFE)  
single-ended input. This input is connected to a surround preamp/processor, for  
use with Dolby 5.1 and DTS encoded software.  
Outputs  
20 Left and Right CAST High-pass Outputs  
The Master Reference Subwoofer is equipped with left and right CAST high-pass  
outputs, for connection to the CAST inputs of a Full Power Balanced Amplifier  
or Master Reference Amplifier.  
21 Left and Right Balanced High-pass Outputs  
The Master Reference Subwoofer is equipped with left and right balanced high-pass  
outputs, for connection to the balanced inputs of an amplifier.  
22 Left and Right Single-ended High-pass Outputs  
The Master Reference Subwoofer is equipped with left and right single-ended  
high-pass outputs, for connection to the single-ended inputs of an amplifier.  
23 Left and Right CAST By-pass Outputs  
The Master Reference Subwoofer is equipped with left and right CAST by-pass  
outputs, for connection to the CAST inputs of another Master Reference Subwoofer.  
24 Left and Right Balanced By-pass Outputs  
The Master Reference Subwoofer is equipped with left and right balanced  
by-pass outputs, for connection to the balanced inputs of another Master Reference  
Subwoofer.  
25 Left and Right Single-ended By-pass Outputs  
The Master Reference Subwoofer is equipped with left and right single-ended  
by-pass outputs, for connection to the single-ended inputs of another Master  
Reference Subwoofer.  
Note  
You can connect to any input (CAST, balanced, or single-ended) and output at any high-pass  
output. All high-pass outputs are active at once. For example, a signal from a source con-  
nected to the Master Reference Subwoofer through a CAST input can be output as CAST,  
balanced, and single-ended.  
While you can connect at any input, you can output only at one by-pass output. By-pass  
outputs are active only one-at-a-time. For example, the CAST input is available only at the  
CAST by-pass output. The balanced input is available only at the balanced by-pass output.  
The single-ended input is available only at the single-ended by-pass output.  
24  
 
Figure 5 Master Reference Subwoofer Remote Control  
POWER  
CAST PHASE  
28  
27  
26  
29  
PRESET  
1
2
3
4
THTR  
SAVE  
31  
30  
Power  
UNIT  
1
2
3
4
26 Power Key  
32  
33  
Operation Keys  
27 CAST Key  
28 Phase Key  
29 Preset Key  
30 Thtr (Theater) Key  
31 Save Key  
ALL  
MUTE  
34  
SECTION  
SUB  
HIGH MENU ENTER  
38  
37  
35  
36  
PARAMETER  
32 Unit Key  
TYPE SLOPE FREQ LEVEL  
ADJUST  
33 All Key  
42  
41  
39  
40  
34 Mute Key  
Filter Selection Keys  
35 Section Sub Key  
36 Section High Key  
43  
Menu Keys  
37 Menu Key  
38 Enter Key  
Filter Parameter Keys  
39 Type Key  
40 Slope Key  
MRS  
41 Freq(uency) Key  
42 Level Key  
Level Adjust Keys  
43 Adjust Up and Down Keys  
continued  
25  
 
(SECTION THREE: Features continued)  
Remote Control Description  
Battery Installation and Removal  
The Master Reference Subwoofer control uses two AAA-size 1.5 Volt batteries.  
Batteries are included with the shipment. To install the batteries:  
1. Remove the backplate, using the supplied T-10 Torx wrench.  
2. Install the batteries, following the battery position diagram on the plastic  
battery receptacle.  
3. Replace and secure the backplate.  
The remote control is ready for operation.  
Replace the batteries when the remote control functions intermittently. Remove the  
batteries if the remote control is not used for a long period of time. Battery leakage  
can damage the remote control.  
26  
 
Remote Control Functions  
See Figure 5.  
The Master Reference Subwoofer remote control provides power, subwoofer  
functions, and menu and programming options, as well as stand-by and operational  
mode commands for components connected through Krell Link. Remote control  
features and their descriptions follow.  
Power  
26 Power Key  
Use this key to switch the Master Reference Subwoofer from the stand-by to the  
operational mode.  
Operation Keys  
27 CAST Key  
Use this key to select CAST operation for an available input. The front panel  
display (4) will indicate when CAST is selected. See Step II. Connecting the  
Master Reference Subwoofer to Your System, on page 32, for information on  
CAST input options.  
Note  
The Master Reference Subwoofer will not switch to CAST unless a CAST input is connected.  
28 Phase Key  
Use this key to invert the phase of the low-pass filter output.  
29 Preset Keys  
Use these keys to store and select customized menu settings. See Step VI. Saving  
Your Settings to Presets, on page 40, for more information.  
30 Thtr (Theater) Key  
Use this key to store and select customized menu settings. Krell recommends  
reserving this preset for the stereo/LFE combination or LFE only connection options.  
See Step VI. Saving Your Settings to Presets, on page 40, for more information.  
31 Save Key  
Use this key to save menu settings. The front panel display (4) shows SAVE and  
the selected preset number when this feature is activated.  
continued  
27  
 
(SECTION THREE: Features continued)  
(Operation Keys continued)  
32 Unit Keys  
Use these keys to assign an ID to each component when multiple subwoofers  
are installed in a configuration. For instructions on assigning an ID, see Optional  
Configurations, on page 48, for more information.  
33 All Key  
Use this key to control all subwoofers at once, for example, to mute, power on, or  
set preset configurations for all subwoofers in a configuration.  
34 Mute Key  
Use this key to mute the low-pass (sub) and the high-pass filter output. To unmute,  
press the mute key again. To customize the mute key operation, see Optional  
Configurations, on page 48.  
Filter Selection Keys  
35 Section Sub Key  
Use this key to access the low-pass (sub) filter parameters for your system. The  
filter’s type, frequency, slope, and level can be adjusted. See Steps III and IV, on  
pages 36-40, for more information.  
36 Section High Key  
Use this key to access the high-pass filter parameters for your system. The filter’s  
type, frequency, slope, and level can be adjusted. See Steps III and IV, on pages  
36-40, for more information.  
Menu Keys  
37 Menu Key  
Use this key to activate the menu system, to customize subwoofer settings. The  
front panel display (4) shows MENU when the menu key is pressed. Use the adjust  
up and down keys (43) to scroll through menu selections.  
38 Enter Key  
Use this key to set a menu selection or to access a submenu selection.  
28  
 
Filter Parameter Keys  
39 Type Key  
Use this key to select the filter profile desired. The front panel display (4) shows  
the current selection. See Step III. Configure the Programmable Electronic  
Crossover, on page 36, for filter options and instructions.  
40 Slope Key  
Use this key to adjust the slope of the high-pass or low-pass filter. The front panel  
display (4) shows the selected setting. See Step III. Configure the Programmable  
Electronic Crossover, on page 36, for slope adjustment instructions.  
41 Freq(uency) Key  
Use this key to select the cutoff frequency for the high-pass or low-pass filter. The  
front panel display (4) shows the selected setting. See Step III. Configure the  
Programmable Electronic Crossover, on page 36, to select the desired fre-  
quency setting.  
42 Level Key  
Use this key to adjust the level of the high-pass or low-pass filter. The front panel  
display (4) shows the selected setting. See Step IV. Match the High-pass and  
Low-pass Filter Levels, on page 38, for more information.  
Level Adjust Keys  
43 Adjust Up and Down Keys  
Use these keys to adjust volume levels and to scroll through filter and menu selec-  
tions.  
29  
 
SECTION  
FOUR  
Connections and Configurations  
See Figures 3 and 4.  
Overview  
This page outlines the connections (Steps I and II) and configurations (Steps III  
through VI ) for the Master Reference Subwoofer. These instructions let you set up your  
subwoofer for optimum performance. Detailed instructions begin on page 31.  
Krell recommends that you configure your Master Reference Subwoofer in the  
following order.  
Step I. Choose the Connections  
This step discusses the CAST, balanced, and single-ended connections  
that are available on the Master Reference Subwoofer, explains switching  
between CAST and balanced inputs, and lists factory defaults.  
Step II. Connecting the Master Reference Subwoofer to Your System  
This step explains how to connect CAST, balanced, and single-ended inputs  
and outputs, to integrate the subwoofer into your system. It also explains the  
three connection options available: stereo, LFE, and stereo/LFE.  
Step III. Configure the Programmable Electronic Crossover  
This step explains how to configure the subwoofer’s low-pass and high-pass  
filters, by selecting the appropriate filter profile (Butterworth, Bessel, or  
Linkwitz-Riley), and adjusting the slope, frequency, and level parameters for  
each filter profile.  
Step IV. Match the High-pass and Low-pass Filter Levels  
This step explains how to match the high-pass and low-pass filter levels using  
the Master Reference Subwoofer’s built-in noise generator.  
Step V. Select the Phase  
This step explains how to select normal or inverted phase, to complete the  
configuration and ensure optimum music quality.  
Step VI. Saving Your Settings to Presets  
This step explains how to save configuration settings to presets and how to  
recall presets.  
30  
 
Connections and Configurations  
The remote control is the main input device for the Master Reference Subwoofer.  
All initial setup and subsequent system configuration adjustments must be made  
through the remote control or via the RS-232 port.  
For maximum performance, the Master Reference Subwoofer must be connected  
to other components in the system via the appropriate CAST, balanced, or single-  
ended inputs and outputs; connected for stereo and low frequency effect; and the  
low-pass and high-pass filters configured to fit your system.  
Step I. Choose the Connections  
This section discusses the CAST, balanced, and single-ended connections that are  
available on the Master Reference Subwoofer, explains switching between CAST  
and balanced inputs, and lists factory defaults.  
CAST and Balanced Connections  
Krell recommends using its proprietary Krell CAST system for unparalleled sonic  
performance for connections between the Master Reference Subwoofer and other  
CAST-equipped components. The Master Reference Subwoofer also offers balanced  
and single-ended operation.  
IMPORTANT  
Connecting non-CAST components to CAST inputs or outputs can damage your  
equipment and void your warranty.  
Do not attempt to change CAST cable terminations or CAST inputs or outputs to  
RCA or XLR connectors. It is electrically impossible to convert CAST input or  
output connections for balanced or single-ended voltage operation.  
Please read the Warranty, on pages 50-51, to understand the warranty limitations of  
the Master Reference Subwoofer.  
continued  
31  
 
(SECTION FOUR: Connections and Configurations continued)  
Switching Between CAST and Balanced Inputs  
The Master Reference Subwoofer offers a number of user-controlled options for  
choosing inputs and for switching from one input to another, using the remote  
control in conjunction with the menu option. See B. To Activate CAST Inputs,  
on page 34 for more information.  
If you activate CAST or VOLTAGE in the menu, and have only one CAST or balanced  
source connected, the subwoofer automatically chooses the selected source and  
indicates the selection as either CAST or VOLTAGE in the front panel display (4).  
If you activate CAST or VOLTAGE in the menu, and have a source connected to a CAST  
input (14) as well as a source connected to a balanced input (15), the subwoofer  
defaults to the CAST input.  
Factory Defaults  
The Master Reference Subwoofer is shipped with the following default settings.  
Low- and High-pass Filters  
Filter  
Frequency  
Slope  
BUTTERWORTH  
100 HZ  
6 DB/OCT.  
0
Level  
Default Menu Functions  
Mute  
LFE  
ALL  
OFF  
Unit ID  
CAST  
LED  
UNIT 0  
CAST NONE  
LED ON  
AC OFF  
AC Mains  
Step II. Connecting the Master Reference Subwoofer to Your System  
This section explains how to connect CAST, balanced, and single-ended inputs  
and outputs to integrate the subwoofer into your system. It also explains the three  
connection options available: stereo, LFE, and stereo/LFE.  
A. To Connect the Subwoofer  
1. Make sure that all power sources and components are off before connecting  
inputs and outputs.  
2. Neatly organize wiring between the Master Reference Subwoofer and all system  
components. Separate AC wires from audio cables to prevent hum or other  
unwanted noise from being introduced into the system.  
32  
 
3. Connect the cables from the left and right Krell CAST 4-pin inputs (14) on the  
back panel to the left and right main preamplifier or processor outputs. For bal-  
anced or single-ended operation, connect the interconnect cables from either the  
left and right balanced (15) or the single-ended inputs (16) on the Master Reference  
Subwoofer back panel to your left and right preamplifier or processor outputs.  
4. Connect the cable from the Krell CAST 4-pin LFE input (17) on the back panel  
to the sub(woofer) output of your processor. For balanced or single-ended  
operation, connect the interconnect cables from either the balanced LFE input  
(18) or the single-ended LFE input (19) on the subwoofer back panel to the  
sub(woofer) output of your processor.  
5. Connect the cables from the left and right Krell CAST 4-pin high-pass outputs  
(20) on the back panel to the left and right CAST-equipped inputs of your power  
amplifier. For balanced or single-ended operation, connect the interconnect  
cables from either the left and right balanced high-pass outputs (21) or the left  
and right single-ended high-pass outputs (22) on the back panel to the left  
and right balanced or single-ended inputs of your power amplifier.  
Notes  
The Master Reference Subwoofer allows the connection of two independent preamplifier/source  
components to the CAST and either the balanced or the single-ended inputs. For example, you  
may want to connect two discrete front-end systems: Use the CAST input as the connection  
to a dedicated two-channel system in which the KPS 25sc Krell Playback System is the CAST  
source. Use the balanced input as the connection to a home theater system.  
You cannot connect the balanced input and the single-ended input at the same time.  
6. If you have more than one subwoofer, connect the cables from the left and  
right Krell CAST 4-pin by-pass outputs (23) on the back panel to the left and  
right CAST-equipped inputs on another subwoofer. For balanced or single-  
ended operation, connect the interconnect cables from either the left and  
right balanced by-pass outputs (24) or the left and right single-ended by-pass  
outputs (25) on the back panel to the left and right balanced or single-ended  
inputs of another subwoofer.  
See Unit ID Menu, on page 48, for information on assigning ID numbers for  
controlling multiple subwoofers in a system.  
continued  
33  
 
(SECTION FOUR: Connections and Configurations continued)  
(Step II. Connecting the Master Reference Subwoofer to Your System continued)  
7. Plug the AC power cord into the IEC connector on the subwoofer back panel.  
Plug the other end into the AC outlet.  
IMPORTANT  
The CAST and LFE inputs must be enabled through the menu to be operational. To  
activate the low frequency effect (LFE), see Choosing Stereo, LFE, or Stereo/LFE,  
below.  
B. To Activate CAST Inputs  
Use the menu to select which CAST inputs to enable.  
1. Press the menu key (37).  
2. Use the adjust keys (43) to select the CAST menu. The front panel display (4)  
shows CAST.  
3. Press the enter key (38). The front panel display shows CAST MAIN.  
4. Use the adjust keys to select the preferred setting. Options are:  
CAST MAIN  
CAST LFE  
CASTNONE  
CASTALL  
Enables CAST for the main input.  
Enables CAST for the LFE input.  
No CAST inputs are enabled.  
Enables all CAST inputs.  
5. Press the enter key to set the selection and return to the main menu.  
6. Press the menu key to exit the menu mode.  
Note  
All CAST inputs specified in the selected menu must be present before the Master Reference  
Subwoofer will switch to CAST. For example, if the system is set for CASTALL but there are  
no connections to the LFE input, no CAST switching will occur.  
34  
 
C. Choosing Stereo, LFE, or Stereo/LFE  
Your Master Reference Subwoofer can operate in stereo mode, low frequency effect  
(LFE) mode, or stereo/LFE mode. For optimum subwoofer performance, Krell  
recommends using the stereo/LFE combination.  
The connections and configurations described above in Connecting the Master  
Reference Subwoofer to Your System and Configuring the Programmable  
Electronic Crossover connect and configure your subwoofer to operate in stereo  
mode. To add the LFE enhancement, follow these steps:  
1. Make sure the cable from the sub output on your processor is connected to the  
LFE input (17, 18, or 19) on the Master Reference Subwoofer.  
2. Activate the LFE input, using the menu function.  
3. Press the menu key (37).  
4. Use the adjust keys (43) to select the LFE menu. The front panel display (4)  
shows LFE ON.  
5. Use the adjust keys to select the preferred LFE setting. Options are:  
LFE ON  
The LFE input is enabled. If you choose this setting, Krell  
recommends saving it using the Theater preset (30).  
The LFE input is disabled.  
LFE OFF  
LFE AUTO The LFE input is controlled by the LFE 12 VDC (12 V trigger)  
input. If you choose this option, Krell recommends saving it  
as part of the listening room setup on your surround processor.  
You must connect a 12 V trigger cable.  
6. Press the enter key to set the selection and return to the main menu.  
7. Press the menu key to exit the menu mode.  
Notes  
To confirm that the Master Reference Subwoofer output is operational, activate the noise  
generator for the sub output of your surround sound preamplifier/processor.  
Krell recommends configuring one of the triggers on the Home Theater Standard to turn off the  
LFE when the surround processor is in stereo mode, to avoid generating unwanted noise.  
D. When to Use LFE Only Option  
Use the LFE only option, without stereo, if you wish to bypass the programmable  
electronic crossover.  
continued  
35  
 
(SECTION FOUR: Connections and Configurations continued)  
Step III. Configure the Programmable Electronic Crossover  
This section explains how to configure the subwoofer’s two sections, the low-pass (sub)  
and high-pass filters, by selecting the appropriate filter profile (Butterworth, Bessel,  
or Linkwitz-Riley), and adjusting the slope, frequency, and level parameters for each  
filter profile.  
Configuring the programmable electronic crossover is required for stereo and  
stereo/LFE operation. Krell recommends performing the configuration in the order  
indicated below.  
A. Select the Low-pass Filter  
Press the section sub key (35) on the remote control to access the low-pass filter  
parameters. The front panel display (4) shows SUB ADJ.  
B. Select the Low-pass Filter Profile  
Press the type key (39) to access the filter profile. Press the adjust keys (43) to  
select the profile you want. The Master Reference Subwoofer has three low-pass  
filter profiles available: Bessel, Butterworth and Linkwitz-Riley.  
C. Adjust the Low-pass Filter Parameters  
IMPORTANT  
Adjust the parameters in this order: slope, frequency, and level.  
1. Low-pass Filter Slope  
a. Press the slope key (40).  
b. Use the adjust keys (43) to adjust the slope (in 6 dB increments). The  
low-pass filter has a range from 6 dB to 48 dB.  
2. Low-pass Filter Frequency  
a. Press the frequency key (41).  
b. Use the adjust keys (43) to select the desired frequency setting (in 10 Hz  
increments). The frequency selectable ranges from 30 to 100 Hz.  
36  
 
3. Low-pass Filter Level  
a. Press the level key (42).  
b. Use the adjust keys (43) to select the desired level setting (in 1 dB incre-  
ments). Level range is 6 dB.  
Note  
See Step IV. Match the High-pass and Low-pass Filter Levels, on page 38, for more  
information on level matching.  
D. Select the High-pass Filter  
Press the section high key (36) on the remote control to select the high-pass  
filter. The front panel display (4) shows HIGH ADJ.  
E. Select the High-pass Filter Profile  
Press the type key (39) to access the filter profile. Press the adjust keys (43) to  
select the profile you want. The Master Reference Subwoofer has three filters  
profiles available: Bessel, Butterworth and Linkwitz-Riley.  
F. Adjust the High-pass Filter Parameters  
IMPORTANT  
Adjust the parameters in this order: slope, frequency, and level.  
1. High-pass Filter Slope  
a. Press the slope key (40).  
b. Use the adjust keys (43) to adjust the slope (in 6 dB increments). The  
high-pass filter has a range from 6 dB to 24 dB.  
2. High-pass Filter Frequency  
a. Press the frequency key (41).  
b. Use the adjust keys (43) to select the desired frequency setting (in 10 Hz  
increments). The frequency selectable ranges from 30 Hz to 100 Hz.  
3. High-pass Filter Level  
a. Press the level key (42).  
b. Use the adjust keys (43) to select the desired level setting (in 1 dB  
increments).  
continued  
37  
 
(SECTION FOUR: Connections and Configurations continued)  
Step IV. Match the High-pass and Low-pass Filter Levels  
This section explains how, once the programmable electronic crossover has been  
configured, to match the high-pass and low-pass filter levels using the Master  
Reference Subwoofer’s built-in noise generator.  
Step A describes muting the low-pass filter while adjusting the high-pass flter level.  
Step B describes muting the high-pass filter while adjusting the low-pass filter level.  
You can choose to match the high-pass to the low-pass or vice versa. Either is  
correct. Make sure that the amplifier connected to the high-pass outputs is on and  
in the operational mode.  
A. Adjust the High-pass Filter  
1. Press the menu key (37). The front panel display (4) shows MENU.  
2. Use the up adjust key (43) to select NOISEGEN.  
3. Press the enter key (38). The display shows NOISEOFF.  
4. Press the up adjust key to select NOISE ON.  
5. Press the enter key. After a two second delay, you will hear noise generator  
output through both the Master Reference Subwoofer and your front speakers.  
6. Use the up adjust key to select MUTE. The front panel display shows MUTE.  
7. Press the enter key. The front panel display shows the current setting for mute.  
8. Press the up adjust key to select LPF ONLY.  
9. Press the enter key.  
10. Press the menu key to exit the menu mode.  
11. Press the mute key (34) on the remote control to mute the low-pass filter. You  
hear noise only from the high-pass filter.  
12. Press the section high key (36).  
13. Press the level key (42).  
14. Use the adjust keys to raise or lower the high-pass filter level so that it matches  
that of the low-pass filter (sub).  
15. Make sure you unmute the low-pass filter, after you have adjusted the  
high-pass filter.  
38  
 
Notes  
You can switch the low-pass filter on and off using the mute key, to help compare the filter  
levels. Every time you adjust the level, the front panel display shows the numeric value of the  
level. After three seconds of inactivity, the screen becomes blank. You have adjusted the  
high-pass filter.  
You can also use a sound pressure level meter for this process; however, it is not required.  
B. Adjust the Low-pass Filter  
1. Press the menu key (37).  
2. Press the up adjust key (43) to select MUTE.  
3. Press the enter key (38). The front panel display (4) shows the current settings  
for mute.  
4. Press the up adjust key to select HPF ONLY.  
5. Press the enter key.  
6. Press the menu key to exit the menu mode.  
7. Press the mute key (34) to mute the high-pass filter. You hear noise only from  
the Master Reference Subwoofer.  
8. Press the section sub key (35).  
9. Press the parameter level key (42).  
10. Use the adjust keys to raise or lower the low-pass filter level so that it matches  
that of the high-pass filter.  
11. Make sure you unmute the high-pass filter, after you have adjusted the  
low-pass filter.  
Notes  
You can switch the high-pass filter on and off using the mute key, to help compare the filter  
levels. Every time you adjust the level, the front panel display shows the numeric value of  
the level. After three seconds of inactivity, the screen becomes blank. You have adjusted  
the low-pass filter.  
You can use this process to adjust your system level for individual CDs or DVDs.  
When the noise generator is on, all other inputs are turned off and the by-pass output is  
muted to keep loud noise from going to the next device.  
continued  
39  
 
(SECTION FOUR: Connections and Configurations continued)  
C. To End Noise Generation  
1. Press the menu key (37) to select the main menu.  
2. Press the up adjust key (43) to select NOISEGEN.  
3. Press the enter key (38), then press the up adjust key to select NOISE OFF.  
4. Press the enter key to end noise generation and return to the main menu.  
5. Press the menu key to exit the menu mode.  
Step V. Select the Phase  
This section explains how to select normal or inverted phase, to complete the  
configuration and ensure optimum music quality.  
1. With the subwoofer in the stand-by mode, press the power button (1) or power  
key (26).  
2. Begin playing a music or video selection.  
3. Press the phase key (28) to switch between normal and inverted phases.  
4. Listen for when the sound is clearer. You do not have to press the enter key to  
set the phase.  
Your subwoofer is ready to play music.  
Step VI. Saving Your Settings to Presets  
You can save the settings selected in Steps I – V in the subwoofer memory, using  
one of the five presets (29, 30) on the Master Reference Subwoofer Remote Control.  
Notes  
Krell recommends using preset Thtr (30), the theater key, to save your stereo/LFE configuration  
settings. Use presets 1 through 4 to save other desired settings.  
Settings stored in preset 1 become the default when the subwoofer is turned off and  
returned to the operational mode.  
40  
 
To save a setting configuration to a preset:  
1. Press the save key (31).  
2. Press the preset number to which the settings will be assigned. The front panel  
display (4) shows SAVING then SAVED.  
Note  
If you press save then decide you do not wish to save, press the save key again before  
pressing the preset key.  
Recalling Presets  
1. Press the preset key (29, 30).  
2. The preset number appears in the front panel display (4).  
41  
 
SECTION  
FIVE  
Operation  
This section explains how to manually power on your system and subwoofer for  
operation and explains the importance of powering on in the appropriate order.  
After the subwoofer is connected with your system, you can power on the subwoofer  
for operation. The order in which you power on your system is critical. To avoid the  
possibility of system-damaging transients, always turn on sources first, followed by  
preamplifiers/processors, the amplifiers, and finally the Master Reference Subwoofer.  
The Steps for Subwoofer Operation follow:  
1. Power on your source components (for example, CD, DVD).  
2. Power on the preamplifier and surround processor.  
3. Power on your amplifiers.  
4. Move the power switch (6) on the back panel of the Master Reference Subwoofer  
to the up position. You will hear a series of clicks. The red stand-by LED (3) on  
the front panel illuminates.  
5. Press the power button (1) on the front panel or the power key (26) on the  
remote control to switch between the stand-by and the operational mode.  
The blue power LED (2) illuminates. The subwoofer is now ready to play music.  
6. To return to the stand-by mode, press the power button again. The red stand-by  
LED illuminates.  
Krell recommends leaving the Master Reference Subwoofers in the stand-by  
mode between listening sessions.  
Note  
See Krell Link, on pages 44-45, for information on operating the Master Reference  
Subwoofer using Krell Link.  
42  
 
If You Wish to Turn Your System Off:  
Turn your system off if it will not be used for a long period of time. It is critical that  
you turn off your system in the following order.  
1. Press the power button (1) to return the Master Reference Subwoofer to the  
stand-by mode. The red stand-by LED illuminates (2).  
2. Move the power switch (6) on the back panel to the down (off) position.  
3. Turn off the amplifiers.  
4. Turn off the preamplifier(s) and surround processor.  
5. Turn off the source components.  
System Protection  
The Master Reference Subwoofer incorporates a complement of sophisticated  
protection circuits to safeguard your system. This circuitry constantly evaluates  
the operation of the Master Reference Subwoofer and provides protection  
against potentially damaging DC input or output. Regulator operation is also  
continuously monitored to ensure constant voltage to the output stage. These  
protective systems are designed to prevent damage to the Master Reference  
Subwoofer or loudspeakers caused by other defective components, faulty  
wiring, system mishandling, or subwoofer failure.  
Subwoofer Care  
Because the Master Reference Subwoofer is capable of enormous power output,  
it important to exercise care during system operation.  
Avoid any action that can generate large transient signals. Always mute the  
preamplifier output before switching between active sources or cueing a source  
component.  
Do not change inputs to the subwoofer while the subwoofer is on.  
Use care when listening at high volume levels. Always lower the volume level at  
the first sound of loudspeaker distress.  
43  
 
SECTION  
SIX  
Optional Connections  
This section describes three optional connections for the Master Reference Subwoofer.  
Krell Link connections (9) allow you to synchronize subwoofer operation with other  
Krell components that have Krell Link in and out connectors. The RS-232 port (13)  
allows you to connect the subwoofer to a computer-based control system. The 12  
VDC (12 V trigger) input and output (10) allow you to integrate the subwoofer into  
a system with other components that use a 12 Volt trigger.  
Krell Link  
Krell Link in/out connectors on the back panel allow you to integrate the Master  
Reference Subwoofer into systems that include multiple preamplifiers, amplifiers  
and associated components, to synchronize their operation with a remote control.  
When the Krell Link in/out connectors are used, the remote capabilities of linked  
components are controlled from one component, called the control component.  
The linked components respond to stand-by and operational commands from the  
control component via MIDI cables.  
Notes  
The Master Reference Subwoofer cannot be used as the control component.  
The Master Reference Subwoofer remote control takes priority over Krell Link commands.  
The CAST features of the Master Reference Subwoofer cannot be switched via Krell Link.  
Krell Link uses standard five-pin MIDI communication cables, sometimes called MIDI Plus  
cables. These MIDI cables can be purchased from your authorized distributor or dealer, or  
from an audio supply store.  
Connecting Components Through Krell Link  
Use one or more five-pin MIDI cables (sometimes called MIDI Plus cables) to create  
an active Krell Link with Master Reference Subwoofers.  
1. Turn all components off. This ensures components are synchronized when the  
MIDI cables are connected.  
2. Select the control component. It must be in plain view for proper remote control  
operation.  
44  
 
3. Connect one end of a MIDI cable to the Krell Link out connector, on the control  
component back panel.  
4. Connect the other end of a MIDI cable to the Krell Link in connector, on the back  
panel of the next component.  
5. To link another component, connect another MIDI cable to the Krell Link out  
connector on the back panel of the second component. Connect the remaining  
end of the MIDI cable to the Krell Link in connector, on the back panel of a  
third component.  
6. Link additional components, if desired.  
The components are now ready for operation with Krell Link.  
Krell Link Operation  
1. When all components are linked, as described above, place each component  
in the stand-by mode. This ensures all components are synchronized when  
signals from the control component are sent to linked components.  
2. Switch the control component to the operational mode using the component’s  
power key on the remote control. The linked components simultaneously  
switch to the operational mode.  
An individual linked component can be manually switched between the stand-by  
and the operational modes from its front panel. Switching a linked component  
temporarily breaks the chain of linked components. To re-establish linked operation,  
return all components to the stand-by mode.  
Note  
Other Krell components can be configured to allow you to disconnect or reconnect the  
Krell Link feature without physically disconnecting or reconnecting the components and  
MIDI cables. See the owner’s reference for your Krell component.  
continued  
45  
 
(SECTION SIX: Optional Connections continued)  
RS-232  
The RS-232 port (13) allows you to send operational instructions directly into the  
Master Reference Subwoofer from a computer-based control system, providing  
integrated control of all subwoofer functions. This feature also allows the Master  
Reference Subwoofer to report operational status, through the RS-232 status feed-  
back system.  
For information on how to send RS-232 commands to operate the Master Reference  
Subwoofer, see the RS-232 Port: Sending Commands and Interpreting Data  
developer’s reference.  
12 VDC (12 V Trigger)  
The 12 VDC (12 V trigger) output (10) on the Master Reference Subwoofer allows  
you to turn other components on or off, or to and from stand-by automatically,  
through the remote control. The 12 V trigger input (10) allows you to turn the sub-  
woofer on using the remote control of another component with a 12 V trigger. This  
feature allows whole systems or parts of systems to be easily coordinated.  
The 12 VDC LFE input (11) for the Master Reference Subwoofer can be used to  
turn the LFE inputs (17, 18, 19) on or off. See C. Choosing Stereo, LFE, or  
Stereo/LFE, on page 35, for more information.  
46  
 
SECTION  
SEVEN  
Optional Configurations  
Five optional configurations are available on the Master Reference Subwoofer, to  
further customize subwoofer operation. Instructions for optional configurations follow.  
AC Mains Menu  
This option allows the Master Reference Subwoofer to be powered on from an AC  
wall receptacle with a dedicated switch, rather than from the back panel switch or  
other remote option.  
1. Press the menu key (37).  
2. Use the adjust keys (43) to select the AC Mains menu. The front panel display (4)  
shows AC MAINS.  
3. Press the enter key (38). The front panel display shows AC OFF.  
4. Use the adjust keys to select AC ON or AC OFF.  
5. Press the enter key to set the selection and return to the main menu.  
6. Press the menu key to exit the menu mode and return to normal operation.  
LED Menu  
This option allows you to turn front panel LEDs (2,3) on and off.  
1. Press the menu key (37).  
2. Use the adjust keys (43) to select the LED menu. The front panel display (4)  
shows LED.  
3. Press the enter key (38). The front panel display shows LED ON.  
4. Use the adjust keys to select ON or OFF.  
5. Press the enter key to set the selection and return to the main menu.  
6. Press the menu key to exit the menu mode and return to normal operation.  
continued  
47  
 
(SECTION SEVEN: Optional Configurations continued)  
Mute Menu  
This option allows you to customize the mute key to mute all subwoofer outputs or  
only selected outputs. Also see Step IV. Match the High-pass and Low-pass  
Filter Levels, on page 38, for more information on mute key configuration.  
1. Press the menu key (37).  
2. Use the adjust keys (43) to select the mute menu. The front panel display (4)  
shows MUTE.  
3. Press the enter key (38). The front panel display shows LPF ONLY.  
4. Use the adjust keys to select the preferred muting configuration for high-pass  
filter (hpf), low-pass filter (lpf), or by-pass filter (byp). Muting options are: LPF ONLY,  
HPF ONLY, BYP ONLY, LPF + HPF, LPF + BYP, HPF + BYP, and ALL.  
5. Press the enter key to set the selection and return to the main menu.  
6. Press the menu key to exit the menu mode and return to normal operation.  
Unit ID Menu  
The Unit ID menu allows you to set a unit ID for each subwoofer, when you use  
multiple subwoofers in your system. Different unit IDs let you control each subwoofer  
separately by pressing one of the unit keys (32) (1, 2, 3, 4) on the remote control.  
You can also control all subwoofers at once by pressing the all key (33) on the  
remote control.  
Note  
Once you assign an ID to a subwoofer, you must use one of the unit keys on the remote  
control to control the subwoofer.  
1. Press the menu key (37).  
2. Use the adjust keys (43) to select the Unit ID menu. The front panel display (4)  
shows UNIT ID.  
3. Press the enter key (38). The front panel display shows UNIT 0.  
4. Use the adjust keys to scroll through available options (UNIT 0 through UNIT 4).  
5. Press the enter key to set the preferred selection and return to the main menu.  
6. Press the menu key to exit the menu mode and return to normal operation.  
48  
 
Exit Menu  
This option allows you to exit the menu mode.  
1. Press the menu key (37) or use the adjust keys (43) to select the exit menu.  
The front panel display (4) shows EXIT.  
2. Press the enter key (38). You exit the menu mode.  
49  
 
Warranty  
Each Krell Master Reference Subwoofer has a limited warranty of five years for parts  
and labor on circuitry, for all sections except the loudspeaker driver assemblies. The  
loudspeaker driver assemblies have a warranty of one year, for defects due to man-  
ufacture only. Should this product fail to perform at any time during the warranty,  
Krell will repair it at no cost to the owner, except as set forth in this warranty.  
This warranty does not apply to damage caused by acts of God or nature.  
The warranty described on this page shall be in lieu of any other warranty, expressed  
or implied, including, but not limited to, any implied warranty of merchantability or  
fitness for a particular purpose. There are no warranties which exceed beyond  
those described in this document. If this product does not perform as warranted  
herein, the owner’s sole remedy shall be repair. In no event will Krell be liable for  
incidental or consequential damages arising from purchase, use, or inability to use  
this product, even if Krell has been advised of the possibility of such damages.  
Proof of purchase in the form of a bill of sale or receipted invoice substantiating that  
the unit is within the warranty period must be presented to obtain warranty service.  
The warranty begins on the date of the original retail purchase, as noted on the bill  
of sale or receipted invoice from an authorized Krell dealer or distributor. Previously  
owned equipment, when re-purchased from an authorized Krell dealer or distributor,  
has the balance of the original warranty, based on the original date of manufacture.  
The warranty for Krell products is valid only in the country to which they were  
originally shipped, through the authorized Krell distributor for that country, and at  
the factory. There may be restrictions on or changes to Krell’s warranty because  
of regulations within a specific country. Please check with your distributor for a  
complete understanding of the warranty in your country.  
If a unit is serviced by a distributor who did not import the unit, there may be a  
charge for service, even if the product is within the warranty period.  
Freight to the factory is your responsibility. Return freight within the United States  
(U.S.A.) is included in the warranty. If you have purchased your Krell product outside  
the U.S.A. and wish to have it serviced at the factory, all freight and associated  
charges to the factory are your responsibility.  
Krell will pay return freight to the U.S.A.-based freight forwarder of your choice.  
Freight and other charges to ship the unit from the freight forwarder to you are also  
your responsibility.  
50  
 
Krell is not responsible for any damage incurred in transit. Krell will file claims  
for damages as necessary for units damaged in transit to the factory. You are  
responsible for filing claims for shipping damages during the return shipment.  
Krell does not supply replacement parts and/or products to the owner of the unit.  
Replacement parts and/or products will be furnished only to the distributor perform-  
ing service on this unit on an exchange basis only; any parts and/or products  
returned to Krell for exchange become the property of Krell.  
No expressed or implied warranty is made for any Krell product damaged by  
accident, abuse, misuse, natural or personal disaster, or unauthorized modification.  
Any unauthorized voltage conversion, disassembly, component replacement,  
perforation of chassis, updates, or modifications performed to the unit will  
void the warranty.  
IMPORTANT  
Connecting non-CAST components to CAST inputs or outputs can damage your  
equipment and void your warranty. Do not attempt to change CAST cable ter-  
minations or CAST inputs or outputs to RCA or XLR connectors. It is electrically  
impossible to convert CAST input or output connections for balanced or single-  
ended voltage operation.  
The operating voltage of this unit is determined by the factory and can only be  
changed by an authorized Krell distributor or at the factory. The voltage for this  
product in the U.S.A. cannot be changed until six months from the original  
purchase date.  
In the event that Krell receives a product for warranty service that has been modified  
in any way without Krell authorization, all warranties on that product will be void.  
The product will be returned to original factory layout specifications at the owner’s  
expense before it is repaired. All repairs required after the product has been returned  
to original factory specifications will be charged to the customer, at current parts  
and labor rates.  
All operational features, functions, and specifications and policies are subject to  
change without notification.  
To register your product for warranty benefits, please complete and return  
the Warranty Registration Card enclosed in the shipping box within 15 days  
of purchase. Thank you.  
51  
 
Return Authorization Procedure  
If you believe there is a problem with your component, please contact your dealer,  
distributor, or the Krell factory to discuss the problem before you return the component  
for repair. To expedite service, you may wish to complete and e-mail the Service  
Request Form in the Service Section of our website at:  
To contact the Krell Service Department  
TEL  
203-799-9954, Monday-Friday  
9:00 am to 5:00 PM EST  
203-799-9796  
FAX  
E-MAIL  
Krell Master Reference Subwoofer  
PRODUCT  
SERIAL NUMBER  
To return a product to Krell, please follow this procedure so that we may  
serve you better.  
1. Obtain a Return Authorization Number (R/A number) and shipping address from  
the Krell Service Department.  
2. Insure and accept all liability for loss or damage to the product during shipment  
to the Krell factory and ensure all freight (shipping) charges are prepaid.  
The product may also be hand delivered if arrangements with the Service Department  
have been made in advance. Proof of purchase will be required for warranty validation  
at the time of hand delivery.  
IMPORTANT  
Use the original packaging to ensure the safe transit of the product to the factory,  
dealer, or distributor. Krell may, at its discretion, return a product in new packaging  
and bill the owner for such packaging if the product received by Krell was boxed in  
nonstandard packaging or if the original packaging was so damaged that it was  
unusable. If Krell determines that new packaging is required, the owner will be  
notified before the product is returned.  
To purchase additional packaging, please contact your authorized Krell dealer,  
distributor, or the Krell Service Department for assistance.  
52  
 

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