6
TECHNICIAN’S ADJUSTMENT SECTION (A Video of this setup process is linked on our website and
on our YouTube channel. It is the same process as the Model Seven setup shown. Setup worksheets
are also available on the website)
Only a qualified technician or owner with an Analog Radio Shack S.P.L. Meter and matching test disc should
adjust the room compensation controls. This procedure can take several hours. PLEASE NOTE: If you are
calibrating a single SUB THREE you will only employ tracks 1-11 with the Preamp set to Mono. If you don’t
have a mono setting you will need a low-cost “Y” adaptor to drive both left and right channels simultaneously,
main speaker included.
The steady state test signal can cause the SUB THREE amplifier to run warm. This disk is calibrated to the
Radio Shack analog S.P.L. Meter. Owners take your time, it’s possible.
TECHNICIAN’S GUIDE TO ADJUSTING THE ROOM COMPENSATION AND LOW-FREQUENCY LEVEL
CONTROLS.
1. Set the S.P.L Meter at the listening position at ear height. Turn on the S.P.L. Meter to the 70dB scale, “C”
weighting, “Fast” response.
2. Insert test disc into a CD Player, set the volume on the preamp to a low level. CD automatically does left
first.
3. On the SUB THREE Amplifier set the low frequency contour control to minimum (#1) and verify that all
eleven room compensation band are set straight up (slot vertical). Set low frequency level to 0dB.
4. Play tracks nine through eleven and note on paper the meter readings for all three tracks. Adjust the
preamp volume up or down until these tracks average 70dB. Example: track nine 69dB, track ten 72dB and
track eleven 68dB. This is your reference volume do not adjust until this entire calibration is complete for both
speakers.
5.Play track one through eleven and adjust each band to 25 to 33% of the meter reading noted in step # 4.
Play tracks:
Meter Reading: Noted Step # 4:
Adjust Bands to approximately 33% target
Track#
1
2 3
4
5
6
7
8
9
10 11
SPL Reading +4 +6 –3 +8
+10 –6 +3 –3 +2 +1 +3
Target
+1 +2 –1 +2.5 +3
–2 +1 -1 +.5 0
+1
Note: Do not try to adjust every peak or dip all the way to 0 dB. Our studies have shown that adjusting all the
peak and dips to 0dB can cause a non-musical sound with audible equalization effects. Your Sub is now
properly compensated for the room.
6. To set Stereo SUBs play tracks twenty four through twenty six and note on paper the meter readings for
these tracks. Adjust the right SUB THREE Low Frequency Level Control up or down until these three tracks
average 70dB like the left channel. Save this last set of reading for use in step# 7.
7. Play tracks sixteen through twenty six and adjust the right speaker bands as in step# 5. Note: Occasionally
full adjustment of one or more of the bands will not adjust to the target value for the right or left SUBs, get it as
close as possible. If one or more of the bands turned maximum up or down makes little or no difference on
the meter, leave it adjusted straight up (slot vertical). Your speakers are now calibrated to the room.
Note: The eleven bands correspond to the frequencies below:
Track Number 1
2
3
4
5
6
7
8
9
10
11
Frequency
20 24 30 36 42 50 60 72 84 100 120
