Studio Technologies 65 User Manual

for Surround

Model 65 Bass Manager

User Guide

Issue 4, January 2004

This User Guide is applicable for serial numbers:

M65-00151 and later

Copyright © 2004 by Studio Technologies, Inc., all rights reserved

5520 West Touhy Avenue

Skokie, Illinois 60077 U.S.A.

Telephone [phone]

Fax [phone]

www.studio-tech.com

[e-mail]

50087-0104, Issue 4

for Surround

Table of Contents

Foreword ..................................................................... 5

Introduction................................................................... 7

Installation .................................................................... 10

Configuration ............................................................... 15

Operat i o n..................................................................... 23

Specifications .............................................................. 25

Block Diagram

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Foreword

I am pleased to present the Model 65 Bass Manager. As President of Studio Technologies,
I take a very personal approach when designing products. Growing older has increased
my appreciation of the more subtle things in life—be they a part of nature or the nuances
contained in a well-designed piece of electronic equipment. Do the technical and operational
aspects of a product work together to “feel” right? A Studio Technologies’ design is ready to
go only when I am completely satisfied.

Many fine people worked toward making the Model 65 “happen.” Mitch Budniak (ace con­sulting engineer) designed many of the circuits. Jim Cunningham contributed to the analog
design. Carrie Loving provided engineering support. Al Lux designed the printed circuit
board. Fred Roeck performed the mechanical design. Joe Urbanczyk coordinated the
product testing procedures.

Please contact me with your questions, comments, and suggestions. I can be
reached by voice at [phone], fax at [phone], or via e-mail by way
of [e-mail].

Sincerely,
Gordon K. Kapes

President

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Introduction

What This User Guide Covers

This User Guide is designed to assist you
when installing, configuring, and using the
Model 65 Bass Manager.

System Overview

Model 65 Bass Manager

The Model 65 Bass Manager is designed
to enhance the monitoring of multichannel
audio sources during the recording, mixing,
mastering, and distribution process. The
Model 65 is applicable for any multichannel
monitoring environment where some or
all channels are not supported with loud­speakers having extended low-frequency
response. Resources are included in the
Model 65 to make it appropriate for cinema,
music, and broadcast applications. The
Model 65’s design is oriented toward di­rectly supporting 5.1-type applications. The
five main input channels are full bandwidth,
and use the industry-standard designation
of left, center, right, left surround, and right
surround. The “.1” input channel is desig­nated as LFE, which is also referred to
as low-frequency effects, “boom,” or sub­woofer. The LFE term originated in cinema
formats but is now part of music and broad­cast formats as well.

The overall goal of the Model 65 is very
simple: Ensure that the entire audio band­width of all channels can be accurately
monitored. Many loudspeaker systems have
inherent low-frequency limitations, prevent­ing a true picture of the source material from
being presented. To overcome this, the low­frequency energy from the five main chan­nels can be separated and routed to one or

two subwoofer loudspeakers. The Model 65
includes filters to accomplish this, providing
a smooth and sonically pleasing crossover
of the signals being routed to the main and
subwoofer loudspeakers.

The Model 65 also supports several
format-specific parameters required for
accurate LFE channel monitoring. To mini­mize digital bandwidth, some multichannel
formats restrict the frequency response of
the LFE channel. To emulate this process, a
low-pass filter can be inserted into the LFE
signal path. For compatibility with some
cinema formats, gain can also be added to
the LFE signal.

While the Model 65 is intended primarily for
use in 5.1 applications, additional special­ized features and capabilities are also
included. These allow the unit to be config­ured to meet the needs of a broad range of
monitoring applications.

Main Inputs

The Model 65 contains five full-bandwidth
input channels, which are intended for
connection to left, center, right, left surround,
and right surround sources. The electroni­cally balanced inputs are compatible with
balanced or unbalanced sources. Associ­ated with each of the five main inputs is a
crossover circuit, created by means of
separate high- and low-pass filters. The
filters are factory-configured to provide a
nominal crossover frequency of 80Hz. The
output of each high-pass filter is routed to
the output circuit of its corresponding chan­nel. The output of each low-pass filter can
be individually assigned to subwoofer output
1, subwoofer output 2, or subwoofer outputs
1 and 2. To prevent level build up, the signal
is attenuated 6dB when assigned to both
subwoofer outputs.

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LFE Input

The Model 65 contains an input channel that
is specifically intended for connection to an
LFE source. To simulate some multichannel
formats, a low-pass filter can be inserted,
using a front-panel switch or remote control
signal, into the LFE signal path. The filter,
created by cascading four 2nd-order Sallen­Key low-pass sections, provides a 48dB­per-octave slope with the –6dB point at
120Hz.

To allow accurate monitoring of some
cinema formats, a front-panel switch allows
10dB of gain to be added to the LFE signal.
This ensures that the proper relative level is
maintained between the LFE signal and the
low-frequency energy derived from the five
main inputs. As with the main inputs, the
LFE signal can be assigned to subwoofer
output 1, subwoofer output 2, or subwoofer
outputs 1 and 2.

Outputs

The Model 65 provides five main and two
subwoofer outputs. Each of the outputs is
electronically balanced and can be con­nected to balanced or unbalanced loads. To
minimize the chance of loudspeaker dam­age, power up/power down mute relays are
associated with each output. The nominal
level of the five main outputs is +4dBu,
maintaining a unity gain input-to-output
relationship. The two subwoofer outputs are
handled somewhat differently, having a
nominal output level of –6dBu. This reduced
operating level allows sufficient audio head­room when phase coherent signals from the
main inputs are routed, by way of the low­pass filters, to the subwoofer outputs.

Model 65 Front Panel

Bass management

bypass function

Model 65 Back Panel

AC mains

connection

LFE +10dB

gain

LFE low-

pass filter

Main and subwoofer

output connections

Remote control

and expansion

connections

±17V LED

Main and LFE

audio input

connections

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Support for Two Subwoofers

As previously discussed, the outputs of
the low-pass filters associated with the
five main inputs, along with the LFE signal,
can be assigned to either or both of the
subwoofer outputs. The two subwoofer
outputs allow flexibility when designing a
loudspeaker system. A system could be
configured to support subwoofers that are
position-oriented, such as “sub left front”
and “sub right front.” Or, the subwoofers
could be configured according to program
content, such has having subwoofer output 1
handle only LFE information, while sub­woofer output 2 handles the low-passed
signals from the main inputs.

Bass Management Bypass

A Model 65 feature allows the bass
management function to be disabled by
means of a front-panel switch. This function
can be useful, especially during the monitor
system installation and room-tuning pro­cess. When the bypass function is enabled,
the five main input signals route directly to
the main outputs. In addition, the outputs of
the low-pass filters associated with the main
inputs no longer route to either of the sub­woofer outputs. However, when the bass
management bypass function is active the
LFE signal continues its normal routing,
flowing to either or both of the subwoofer
outputs.

Remote Control

Three remote control functions are avail­able: LFE low-pass filter enable, LFE mute,
and subwoofer mono. The remote control
functions are specifically provided for use
during the recording or mixing process. An
effective installation could utilize foot
switches or console-mounted buttons to
allow easy operator access to the remote
control functions.

Remote control of the LFE low-pass filter
allows real-time confirmation of LFE con­tent. Some release formats require that LFE
program content be band restricted. Under
this condition, a valid audio mix would have
no change in its sonic character when the
LFE low-pass filter is enabled.

When LFE mute is enabled, normal bass
management operation continues, but the
LFE signal is not routed to either of the
subwoofer outputs. This function allows
a direct check of the impact an LFE signal
is having on an overall mix.

The subwoofer mono function is provided to
allow confirmation of the phase-coherency
of the two subwoofer outputs. When the
function is enabled, the subwoofer signals
are combined (summed), attenuated by
6dB, and fed to both subwoofers.

Expansion Capability

Provision has been made to allow multiple
Model 65 units to be easily interconnected.
For example, by using two units, ten main
and two LFE inputs are supported, as well
as providing ten main and two subwoofer
output channels. For other special applica­tions a virtually unlimited number of units can
be interconnected.

Flexibility

The Model 65 is designed to be used
directly “out of the box,” providing effective
bass management for most 5.1 applica­tions. However, installation-specific require­ments, along with the evolving world of
multichannel audio, make flexibility impera­tive. With the Model 65 you can use it “our
way,” or easily perform a minor or major
reconfiguration. A competent technician can
field-adjust a number of key bass manage­ment parameters.

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