Wilson Audio WATCH Dog Subwoofer Series-2 - Manual (Page 52)

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3. If you have either a spectrum analyzer or a sound pressure level (SPL) meter,
you should measure and document the in-room response of your L & R
loudspeakers, running full-range, without subwoofer contribution. This will
give you a baseline measurement. While you can measure each channel
individually, it is more expedient to measure both simultaneously using the
(Mono) test signals. Measurement locations for the microphone should
include one at ear height at the main listening location. Additional locations
could include two meters, both left and right, of the primary listening posi-
tion, as well as halfway between the primary position and the back wall.
These readings must be averaged together. Expect measurements taken
close to walls to show substantially more LF energy than those taken near
the center of the room. Use the dB-C weighting, or better yet, if available,
the “Flat”/ non-weighted scale of your instrument. See Figure 8 which com-
pares dB-A & dB-C weighting. The more commonly used dB-A scale, on the
other hand, is intended to correspond to the ear’s “frequency response” at
low SPL and should never be used to calibrate low frequency levels. Please
note that, even at 50 Hz, the dB-C scale is still down approximately 2 dB
relative to 800 Hz. Don’t be disappointed, therefore, if your dB-C scale
measurements show a gradual roll off in the bass. If your measurements do
follow the profiled roll off, it indicates a very linear speaker/room response.
Use track 2, (pink noise), for spectrum analysis measurements. For meas-
urements using a SPL meter, use tracks 6 through 16, (1/3 octave BLN
beginning at 200 Hz and going down to 20 Hz). Document your measured
results.
Warning: Tracks 17 through 27 are sine wave tones at the 1/3-octave cen-
ter frequencies. These should not be used to perform in-room frequency
response estimates due to gross inaccuracies which will be created by standing
waves. Pure tones are included to scan for mechanical resonances and other
distortions.