JBL rmc User Manual
The Room Mode Correction™ System
What Is RMC?
Developed by JBL Professional, RMC™ is a system designed to calibrate and correct low
frequency (LF) response in typical listening rooms and production facilities. The LSR6328P
full range monitor and LSR6312SP Subwoofer contain a single section parametric equaliz-
er that can be adjusted to compensate for the major low frequency response peak caused
by standing waves in a particular listening space. The LSR6332, LSR25P and other sys-
tems can experience the benefits of RMC when an LSR6312SP is used in the system.
frequency (LF) response in typical listening rooms and production facilities. The LSR6328P
full range monitor and LSR6312SP Subwoofer contain a single section parametric equaliz-
er that can be adjusted to compensate for the major low frequency response peak caused
by standing waves in a particular listening space. The LSR6332, LSR25P and other sys-
tems can experience the benefits of RMC when an LSR6312SP is used in the system.
The RMC process allows you to optimize the low frequency response of your system in
your work environment. Using the tools provided in the RMC Kit, simply follow the instruc-
tions step-by-step and allow approximately 30 minutes to perform the adjustment process
for a stereo system. You will experience a noticeable improvement in the sound quality of
your system.
your work environment. Using the tools provided in the RMC Kit, simply follow the instruc-
tions step-by-step and allow approximately 30 minutes to perform the adjustment process
for a stereo system. You will experience a noticeable improvement in the sound quality of
your system.
What are Room Modes? Room modes are low frequency resonances caused by standing
waves involving the geometry of the room and its boundary surfaces. The most prominent
modes are the ones that occur between opposite surfaces. If response peaks due to these
modes are not corrected, your mixes may be bass-shy, because you will tend to overcom-
pensate for what may sound like too much bass in the program. Response peaks due to
room modes can be accurately removed by introducing a carefully-tailored inverse
response, which RMC provides. You may also encounter response dips, which are due to
local reflections and interferences between the loudspeaker and listening position. The
most common reflections are from the floor. You should be aware that no system of equal-
ization can correct for a response dip. Dips can only be compensated for by repositioning
loudspeakers and/or listeners in the playback environment. Figure 1 illustrates the typical
situation as it exists in most production rooms. The measured response at the listener is
shown in the right portion of the figure. In most rooms, the response rise due to the domi-
nant mode will usually be in the range from about 40 Hz to 60 Hz, and the response dips
due to floor reflections will be seen in the range from 50 Hz to about 90 Hz.
waves involving the geometry of the room and its boundary surfaces. The most prominent
modes are the ones that occur between opposite surfaces. If response peaks due to these
modes are not corrected, your mixes may be bass-shy, because you will tend to overcom-
pensate for what may sound like too much bass in the program. Response peaks due to
room modes can be accurately removed by introducing a carefully-tailored inverse
response, which RMC provides. You may also encounter response dips, which are due to
local reflections and interferences between the loudspeaker and listening position. The
most common reflections are from the floor. You should be aware that no system of equal-
ization can correct for a response dip. Dips can only be compensated for by repositioning
loudspeakers and/or listeners in the playback environment. Figure 1 illustrates the typical
situation as it exists in most production rooms. The measured response at the listener is
shown in the right portion of the figure. In most rooms, the response rise due to the domi-
nant mode will usually be in the range from about 40 Hz to 60 Hz, and the response dips
due to floor reflections will be seen in the range from 50 Hz to about 90 Hz.
RMC provides a method for equalizing the peak shown in Figure 1, but the dip, if it is
severe, must be corrected through rearrangement of loudspeaker and listening positions.
In most cases however, "floor bounces" are not problematic.
severe, must be corrected through rearrangement of loudspeaker and listening positions.
In most cases however, "floor bounces" are not problematic.
Listening Position
Peak
Null
Peak
Mode Structure
dB
Speaker Position
Most Modes: Most Floor Dips
25 - 60 Hz
65 - 90 Hz
Peak Due to Axial Mode
Dip Due to Floor Reflection
Frequency (Hz)
dB
3
Figure 1