Krell MRS Owners manual

MRS

MASTER REFERENCE SUBWOOFER

OWNER’S REFERENCE

Master Reference Subwoofer Owner’s Reference, v00.1

Krell Industries, Inc.
45 Connair Road
Orange, CT 06477-3650 USA

TEL [phone]
FAX [phone]
E-MAIL [e-mail]
WEBSITE http://www.krellonline.com

This product complies with the EMC directive (89/336/EEC) and the low-voltage directive
(73/23/EEC).

WARNINGS

Do not place flammable material above or beneath the subwoofer.

Before making connections to the subwoofer, ensure that the back panel power switch is in the
down position. Make sure all cable terminations are of the highest quality, free from frayed ends,
short circuits, or cold solder joints.

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.

THERE ARE NO USER SERVICEABLE PARTS INSIDE THE MASTER REFERENCE SUBWOOFER.

Please contact Krell if you have any questions not addressed in this manual.

This product is manufactured in the United States of America. Krell®is a registered trademark of Krell Industries, Inc., and is restricted for use by
Krell Industries, Inc., its subsidiaries, and authorized agents. Krell CAST
Krell Current Mode

Logic," and the double-D symbol are trademarks of Dolby Laboratories. Confidential Unpublished Works. Copyright 1992–1997 Dolby Laboratories,
Inc. All rights reserved. All other trademarks and tradenames are registered to their respective companies.

© 2000 by Krell Industries, Inc. All rights reserved P/N 304372

™

, and Krell Link™are trademarks of Krell Industries, Inc. Manufactured under license from Dolby Laboratories. "Dolby," "Pro

™

is a patent pending of Krell Industries, Inc. Krell Active Motion Control™,

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.

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(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

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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

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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 Linkwitz­Riley—that adjust and match the subwoofer to any system and loudspeaker con­figuration. 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

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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.”

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.

Dan D’Agostino

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.

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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 break­through 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 tech­nologies. And the Krell legacy will continue to evolve with products that deliver
innovative engineering, perfection in build quality, and outstanding audio performance.

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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 connect­ing 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 cur­rent 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.

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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 pre­serves 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 manufactur­ers 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.

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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.

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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, aircraft­aluminum billet. Each of the two driver baffles is a substantive 2
subwoofer assembly is held together by 68 machine screws, size
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.

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/4 in. thick. The

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/4 20 x 1 in. The

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.

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(Drivers continued)

Tw o 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 superi­or alignment of the concentric mechanical assembly under all performance con­ditions. 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 compo­nents 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.

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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.

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(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.

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Definition of Terms

Following are the definitions of key terms used in your owner’s reference manual.

Configurations

Krell Link

Balanced

By-pass Output

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

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 intercon­nect cables.

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.

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(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 band­width 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

Single-ended

Off

Operational Mode

Stand-by Mode

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.

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

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.

When the power button on the front panel is pressed and the
blue power LED illuminates, the component is in the opera­tional mode and ready to play music.

A low power consumption status that keeps the audio and reg­ulator circuits at idle. Krell recommends leaving the component
in the stand-by mode when it is not playing music.

Krell Active Motion

Control

Technology

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.

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