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VSeries_Sub_Manual
5/12/04
6:12 PM
that it produces the smoothest frequency response at the listening position. In addi-
tion, since the subwoofer's output will interact with the other monitor speakers in the
room, it is important to consider the subwoofer and near-field speakers as a total
system. If you have access to a Real Time Analyzer and a calibration microphone,
then setting up the room can be fairly painless. However, it can also be done with a
generic SPL meter, or even your own ears, once you know what to listen for.
At this stage, you have only the subwoofer operating. Once you find its optimum
position and settings, then it will be time to turn on the complete monitoring system
to see that all components interact properly. What you are attempting to do is find a
place in the room where the subwoofer interacts smoothly with the acoustics to even
out the bass response at the listening position. One novel way to do this is to
reverse the normal position of the subwoofer and listening spot by temporarily mov-
ing the subwoofer to your seat position in front of the console. Then play back pink
noise in the 30 to 80 Hz range or music with robust bass information. Now by mov-
ing the SPL meter (or your ears) around the various potential speaker positions in
the room, you can listen for where the bass sounds the loudest. That is where the
speaker loading would potentially be at its greatest.
Once you find the optimal spot, place the subwoofer at that position and listen to it
from the console position. Even without an SPL meter you can then use stepped
band-pass, pink noise and sine-wave sweeps to evaluate how even the bass
response is. Move the subwoofer around a foot at a time until the bass response is
as even as possible at the listening position. Remember that you do not want any
single frequency to be exaggerated during monitoring, as that will result in the final
music mix having too little bass. One caveat: if your subwoofer's optimum position is
under your console, make sure to protect it from your (and your client's) feet. You do
not want to repeatedly kick holes in the sub....
Finally, go to the next section on setting the level and determining the proper posi-
tion of the phase switch on the subwoofer.
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Setting Subwoofer Levels
Once the subwoofer is in position, its level needs to be matched with the near-field
speakers. For stereo systems, the process is straightforward. Obtain an SPL (Sound
Pressure Level) meter. Set the low-pass filter on the KRK subwoofer back plate to
80 Hz (12 o'clock position) — if you will be using the internal high-pass filtered out-
puts from the subwoofer to the near-field speakers.
Now, route 1-octave wide, band-pass pink noise to the monitor system, which will be
sent to the main speakers through the subwoofer or bass-management filters. A
good choice is 500 to 1,000 Hz band-passed pink noise, which is within the funda-
mental frequency range of many vocalists, and minimizes high-frequency problems
but doesn't excite the subwoofer. Set this to a comfortable monitoring level.
(Typically 85 decibels SPL using the C response curve on the SPL meter)
Next, route 1-octave, band-passed, bass pink noise to the subwoofer via the same
filter path. A good noise choice is 35 to 70 Hz, which is below the 80-Hz frequency
of the subwoofer high-pass filter, but sufficiently high enough that most subwoofers
will have adequate response in that band. Set the gain of the subwoofer level control
until it matches the same 85-decibel SPL level.
Then, turn up the low-pass filter control on the subwoofer to 130 Hz. This allows the
bass energy between the near-field speakers and subwoofer to overlap. While listen-
ing to it from the console mixing position, route pink noise with a band-pass of 80 Hz
to 130 Hz to the speaker system. Have someone flip the phase switch between 0
and 180 degrees, and then back, and note which position sounds loudest. The loud-
est position is correct and in phase. Now return the low-pass filter to the 80-Hz posi-
tion (or another frequency if you are using external high-pass filters for the near-field
speakers). Your subwoofer should now be properly aligned for phase, level and
spectral response.
Beyond Stereo to 5.1
Surround
When using a subwoofer for the
LFE channel in a 5.1 surround
monitoring system, note that the
LFE channel is set with an addi-
tional 10 dB of monitoring gain.
To set this level, we recommend
using 2-octave-wide, band-
passed, pink noise from 20 to
80 Hz for the LFE channel and
500 Hz to 2,000 Hz for the
near-field speakers. After
adjusting each near-field speak-
er one at a time to 85 dB SPL,
adjust the LFE channel 10-dB
louder or 95 dB SPL. Use the
LFE level trim for this adjust-
ment rather than the subwoofer
gain control, which would cor-
rupt the subwoofer bass management levels set in the previous section.
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