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The
Model 65 Bass Manager is designed to enhance the monitoring of
multi-channel audio sources during the recording, mixing, mastering, and
distribution process. The Model 65 is applicable for any multi-channel
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 channels are
full bandwidth, and use the industry-standard designation of left,
center, right, left surround, and right surround. The ".1"
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 low-frequency energy from the five main channels can be
separated and then routed to one or more subwoofer loudspeakers. The
Model 65 includes filters to accomplish this, providing a smooth and
sonically pleasing crossover of 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
multi-channel formats restrict the frequency response of the LFE
channel. To emulate this process, a low-pass filter can be inserted into
the LFE signal chain. 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. This
allows 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 crossover
frequency of 80 Hz. 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 6 dB when assigned to both subwoofer outputs.
LFE
Input
The
Model 65 contains an input channel that is specifically intended for
connection to an LFE source. To simulate some multi-channel 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 low-pass sections, provides a 48 dB-per-octave slope with
the –6 dB point at 120 Hz. To allow accurate monitoring of some formats, a
front-panel switch allows 10 dB 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 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 +4 dBu, maintaining a unity gain input-to-output
relationship. The two subwoofer outputs are handled somewhat differently,
having nominal output levels of –6 dBu. This reduced operating level
allows sufficient audio headroom when phase coherent signals from the main
inputs are routed, by way of the low-pass filters, to the subwoofer
outputs.
Support
for Two Subwoofers
As
previously discussed, the outputs of the high-pass filters associated with
the five main inputs are routed to the five main outputs. 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 1 handle only LFE information, while
subwoofer 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 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 flow to one or both of the subwoofer outputs.
Remote
Control
Three
remote control functions are available: remote LFE low-pass filter,
remote LFE mute, and remote subwoofer output 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
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 activated.
When
remote LFE mute is active, 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
remote subwoofer output 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
6 dB, and fed to both subwoofers.
Expansion
Capability
Provision
has been made to allow multiple Model 65 units to be easily
interconnected. 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
multi-channel 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. The high- and low-pass filter frequencies
associated with the main inputs can be individually adjusted. This
allows the crossover frequencies to be configured on a
channel-by-channel basis. While the factory default crossover frequency
is set for nominally 80 Hz, selecting an alternate crossover frequency,
symmetrical or asymmetrical, is simple. To adjust any of these filters
requires only changing resistors. Sockets are present in the Model 65's
circuit board, eliminating the need to solder.
The
high- and low-pass filters associated with the main inputs are
implemented by cascading 2nd order Sallen-Key filter circuits. Jumpers
on the Model 65's circuit board allow individual selection of
12 dB/octave or 24 dB/octave response. The factory-default configuration
for the high-pass filters is 12 dB/octave, complementing the internal
filters contained in many amplified loudspeaker systems. Other speaker
systems may benefit from the use of the 24 dB/octave setting. In
addition, a third jumper position allows the input signal to be directly
routed to the output. This "flat" selection supports
loudspeaker systems that already contain filters to provide the desired
high-pass response. As for the low-pass filters, the factory
configuration is 24 dB/octave, supporting the needs of many subwoofer
loudspeakers. Alternately, the 12 dB/octave settings can be used to match
the Model 65 with other monitor systems.
Installation
The
Model 65 mounts in one space of a standard 19-inch rack. Mains input
voltage is factory selected for 100, 120, or 220/240 V, 50/60 Hz, operation.
The Model 65's input connector is directly compatible with Studio
Technologies’ StudioComm for Surround Model 68A Central Controller. The
channel layout arrangements of the two systems are identical, making
interconnection simple. Other input sources are easily interfaced using
wiring compatible with the industry-standard 25-pin connection scheme. The
seven out-puts connect to the monitor amplifiers, or amplified
loudspeakers, using standard 3-pin XLR-type cables. Each Model 65 also
contains a 9-pin D-subminiature connector. Pins on this "D-sub"
are used to provide access to the remote control functions as well as link
multiple Model 65s.
Model
65 Specifications
Audio
Inputs: 6
Type: electronically balanced, compatible with balanced or unbalanced
signals
Impedance: 24 k ohms
Nominal Level: +4 dBu
Main
Input Channel High-Pass Filters: 5
Type:two cascaded 2nd order Sallen-Key; factory configured for
12 dB/octave; field configurable for flat, 12, or 24 dB/octave response
Response: –3 dB @ 80 Hz, nominal, 12 dB/octave; –6 dB @ 80 Hz, nominal,
24 dB/octave; field configurable
Main
Input Channel Low-Pass Filters: 5
Type: two cascaded 2nd order Sallen-Key; factory configured for
24 dB/octave; field configurable for 12 or 24 dB/octave response
Response: –3 dB @ 80 Hz, nominal, 12 dB/octave; –6 dB @ 80 Hz, nominal,
24 dB/octave; field configurable
Main
Input Channels to Subwoofer Outputs:
Overall Gain: –10 dB, nominal
Routing: subwoofer output 1, 2, or both; assigning to subwoofer outputs 1
and 2 implements 6 dB additional attenuation; factory default routing to
subwoofer output 1
LFE
Input Channel to Subwoofer Outputs:
Overall Gain: –10 or 0 dB, nominal, switch or remote control selectable
Routing: subwoofer output 1, 2, or both; assigning to subwoofer outputs 1
and 2 implements 6 dB additional attenuation; factory default routing to
subwoofer output 1
LFE
Input Channel Low-Pass Filter:
Type: four cascaded 2nd order Sallen-Key sections; 48 dB/octave (8th order)
Response: –6 dB @ 120 Hz, nominal, field configurable
Operation: switch or remote control selectable, on/off
Audio
Outputs: 7
Type: electronically balanced, direct coupled, intended to drive balanced
or unbalanced loads of 600 ohms or greater
Output Impedance: 50 ohms, nominal
Nominal Level, Main Channels: +4 dBu
Nominal Level, Subwoofer Channels: –6 dBu
Maximum Output Level: +27 dBu into 10 k ohms, +26 dBu into 600 ohms
Frequency Response: 20 Hz-20 kHz ±0.1 dB, measured with bass management
bypassed
Distortion (THD+N): 0.005%, measured at 1kHz, +4 dBu
S/N Ratio: 85 dB, ref +4 dBu out
Crosstalk: 78 dB, ref +4 dBu in
Remote
Control Inputs: 3
Functions: remote LFE low-pass filter, remote LFE mute, remote subwoofer
output mono
Type: +5 V logic, activates on closure to system common
Expansion
Capability: allows multiple Model 65s to be directly
interconnected; user-created interface cable required
Connectors:
Audio Inputs: 1, 25-pin D-subminiature female
Audio Outputs: 7, 3-pin XLR-type male
Aux (Remote Control/Expansion): 1, 9-pin D-subminiature female
AC Mains: 1, 3-blade IEC-type
AC
Mains Requirement: 100, 120, or 220/240 V, ±10%, factory
configured, 50/60 Hz, 12 W
Dimensions
(Overall):
19.00 inches wide (48.3 cm)
1.72 inches high (4.4 cm)
6.65 inches deep (16.9 cm)
Mounting:
one standard space in a 19-inch rack
Weight:
7.0 pounds (3.2 kg)
Specifications
subject to change without notice.
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