Performing a Frequency Sweep
Though there are a number of ways to perform an accu-
rate frequency sweep, we’ve detailed the steps involved
in the most basic method below.
a. Sit in your favorite seat and hold your Radio
Shack SPL meter at a 45-degree angle half way
between horizontal and vertical.
b. The meter should be placed at ear level when
seated in the primary listening position, and is
best if supported by a stationary object such as
an end table or tripod.
c. Set the control on the meter to ‘C-weighting’
and ‘slow’.
d. Assuming you have already calibrated all chan-
nels to reference level (see the owner’s manual
for your main speakers or receiver/processor for
how to do this), the RS1000 should be calibrated
to 75dB (or 85dB if your receiver/processor uses
that standard).
e. Play a 31.5Hz track from the R-DES installer/test
tone CD, and record BOTH the frequency, which
corresponds to the track on the test disc, and
the sound pressure level (volume) as shown on
the meter.
f. Next, play the tracks from 31.5 to 120Hz and
record the sound pressure level for each fre-
quency played.
Important Note: The Radio Shack sound meter uses C-
weighting which compensates for the lower sensitivity
of the human ear at low frequencies. We want to meas-
ure the actual SPL. If you use a test disc that does not
automatically compensate for this (such as the R-DES
disc), a correction key is needed to ensure proper re-
sponse before your final measurements are plotted. We
suggest gathering your data using the readings on the
meter and
then
correcting your results with the com-
pensation coefficients shown at the end of this manual.
If you are utilizing the Onix Graph Paper program in-
cluded with R-DES, it has an option to compensate for
C-weighting.
Phase Adjustment
The phase dial controls the relative phase of the woofer
to best reinforce the rest of the speaker. Adjustments
to this control will change the woofer’s interaction with
the rest of your speaker system, providing the least can-
cellation, and thus the best response in any room. With
SPL meter in hand (or, better yet, on a tripod), at the
listening position, play an 80Hz tone (for this exercise
the receiver or pre-pro’s crossover point must be set to
80Hz). Be sure not to play your system too loud. Start
with the phase control in the "0" position. Record the
reading on your SPL meter. Repeat with the dial in the
9 o’clock position (45 degrees), 12 o’clock (90 degrees),
3 o’clock (135 degrees) and 180 degrees. Select 0, 45,
90, 135 or 180 based on which position results in the
biggest peaks in sound pressure levels (i.e. reads highest
on the meter). This setting indicates the least amount
of bass wave cancellation, and should be held constant
until the subwoofer or other speakers in your room are
moved, or placement is altered in any way. You may
very well find the "90" setting to be optimum. If you
want to tweak the system for best performance, instead
of only recording the readings at 80Hz, you should play
test tones from 31.5Hz through 120Hz with the phase set
to 0, 45, 90, 135 and 180. The best setting is the one
that results in the biggest peaks in sound pressure levels
(i.e. reads highest on the meter) as well as the flattest
response across the range of frequencies.
