Studiophile BX10s Subwoofer • User Guide
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Studiophile BX10s Subwoofer
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Introduction
Thank you for choosing the Studiophile Series BX10s active subwoofer. M-Audio
is well known for direct-field studio loudspeaker monitors, and now after
extensive research and development, we are proud to present the Studiophile
BX10s subwoofer.
Our designers created the BX10s from the ground up; then we employed some
of Los Angeles’ top mix engineers to help us test and refine the design—ensuring
that it meets the most demanding needs for professional and project studio
monitoring environments. The goal was to develop a subwoofer that integrates
seamlessly with the M-Audio BX5a and BX8a active studio monitors, extending
the low-frequency response of the total monitoring system down to 20Hz.
Moreover, the BX10s is versatile enough to work well with any combination
of active studio monitors in a 2-channel stereo or multichannel surround
environment.
For professional engineers at commercial studios and home studio owners alike,
the BX10s helps set a new standard in studio monitoring.
What’s in the Box?
Your Studiophile BX10s box contains:
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One BX10s active powered subwoofer with removable driver
protection grill
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One detachable AC power cord
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One non-latching footswitch for subwoofer bypass function
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Four removable cone-shaped feet
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This manual
Studiophile BX10s Features
Subwoofer Driver
The drive unit contains a 10-inch composite diaphragm, high-temperature
voice coil, and damped rubber surround. It is designed to deliver a tight and
punchy low-frequency response (in contrast to the “boomy” or hyped response
characteristic of underdamped subwoofers). The driver’s high Bl factor
(electromagnet force factor) creates a powerful motor that allows the cone to
follow the input signal very accurately, resulting in a low-frequency extension par
excellence. Furthermore, the driver’s large magnetic structures are shielded to
ensure the subwoofer unit won’t wreak havoc with nearby devices that may be
susceptible to magnetic-field interference.
Power Amplifier
In order to generate a powerful, tight bass response, the BX10s uses a 240-
watt amp, featuring a custom discrete transistor architecture. The amplifier has
a carefully designed damping factor which, in conjunction with the mechanical
and electromechanical systems built into the driver, helps eliminate the natural
tendency of the driver to “ring” after input stimuli have ceased. This is chiefly
responsible for the BX10s’ extremely accurate and controlled bass response. You
will notice that kick drums and staccato bass notes reproduced by the BX10s are
tight and solid, as though coming from a large acoustic suspension system.
Bass Reflex Port
The BX10s has a vented enclosure—containing a custom bass-reflex port tube
with a circular cross section on the rear of the cabinet. The port provides a
means for the rear output of the driver to contribute to the total output of the
system—but only over a very narrow range of frequencies centered around a
“Helmholtz resonance” (determined by the compliance and mass of the air in the
port tube). The port effectively gives the subwoofer a smooth response down to
20Hz, and since its low-frequency contribution complements that of the front-
firing woofer driver, the woofer stays linear and distortion-free throughout the
passband (because its movement stays within its maximum excursion limits).
Enclosure
Like the other components, the BX10s’ enclosure has an important role in
shaping the overall sonic response. In order to provide more stable performance,
the BX10s employs a special high acoustic efficiency medium density fiberboard
(MDF) and unique interior reinforcement designed to absorb vibration and
impact generated as the subwoofer reproduces high SPL signals and transients.
Additionally, the cabinet uses carefully placed acoustic foam to absorb internal
reflections and dampen standing waves; the acoustic foam also converts the
air system inside the cabinet from an adiabatic process into an isothermal one,
making the enclosure behave as though it were larger—resulting in a system
more capable of reproducing very low frequency signals naturally and evenly.
Versatile Crossover
You can use the BX10s in a variety of monitoring contexts, from 2-channel to
multichannel (e.g., 5.1) systems, and as an accompaniment to practically any direct-
field monitors. To this end, we’ve provided a versatile yet efficient way to tailor
the response of the subwoofer to work well in any typical monitoring system.
For use in a 2-channel system, there is a linked high-pass/low-pass filter control
that allows you to adjust the crossover frequency. You can set it anywhere from
50Hz to 200Hz. It splits the signal by routing everything below that frequency
to the subwoofer and everything above it to your main monitors. And by using a
4th-order Linkwitz-Riley topology, the circuit enables you to achieve the flattest
net response through the crossover point. For multichannel systems, the BX10s
can reproduce just the output of the LFE (low-frequency effects) channel, or it
can reproduce the bass from some or all of the main channels using conventional
multichannel bass management schemes. In this multichannel context, you can
simply “open up” the BX10s fully by setting it to 200Hz (for use with external
bass managers), or you can set it to 120Hz (to comply with the Dolby Digital
standard for the LFE band limit). Further, there’s a 10dB boost switch that allows
you to migrate easily between your calibrated 2-channel and 5.1-channel Dolby
Digital levels.
Subwoofer Bypass/Defeat
If you connect the enclosed footswitch to the Subwoofer Bypass jack on the
back of the BX10s, you can use it selectively to bypass the BX10s (including
the amp, driver, and crossover), and send the full-bandwidth program directly
to your main monitors. This way you can audition mixes with and without the
low-frequency extension the BX10s provides—all from the convenience of your
mix position. As a visual indicator, the blue power LED on the front baffle of the
subwoofer flashes red when it’s in bypass mode. (Note: you can use any binary
footswitch—such as an electronic keyboard sustain pedal—but we’ve provided
one for your convenience.)
Phase Select
Because low-frequency signals have long wavelengths compared to the dimensions
of most rooms, subwoofers often tend to cause room modes and cancellations
that can be quite dramatic. For this reason, we’ve included a phase inversion
switch, which—as the name suggests—causes a π (or 180°) phase shift in the
subwoofer’s output. This can allow you more degrees of freedom in choosing
where to locate the BX10s (and consequently, the crossover frequency phase
alignment) in your monitoring environment.
“Sleep” Mode
By enabling this mode, the subwoofer will fall into standby in the absence of an
input signal, using less power and muting the output; the presence of an input
signal can then “wake up” the subwoofer and it will revert to normal operation.
When the BX10s is “asleep” the LED on its front face turns a solid red.
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