page 19
powered subwoofers
notes
rev 17.0898
only THX components have these filters), they should be turned on or set to THX (if you
have a choice, use the frequency closest to 80 Hz. The
surround channels in a Pro-Logic
only system do not have switchable filters.
B.
Set the center channel to Normal, unless you have a THX controller. With a THX
controller, set the center channel to the THX setting.
C.
Turn off all limiters and compressors, auto azimuth controls, auto balance controls, etc.
D.
If the processor/receiver/receiver has an input level control, calibrate it per the
manufacturer’s instructions.
E.
If the component has a digital input, and you are using a source component with a digital
output, always use the digital input, not the analog input.
8.
Set levels for each channel. You can take a measurement at the listening position to establish
the reference level, but it is usually more accurate to take levels at about one meter from each speaker.
Set all channels to exactly the same level.
Use a Sound Level Meter. Point it directly at the speaker being measured. Set all channels to
the same level, using the processor/receiver/receiver’s internal test signal. Set the meter to “C”
weighting and “Slow” response. Set the levels to 75 dB if you have a THX processor/receiver/receiver
or are using the Video Essentials disc as a source for setting levels.
NOTE: If you using identical speakers anywhere in your system (e.g., S-150THX speakers for the
left, center, and right channels), all of those channels should be set to the same level. If your meter
measures a different level, it is probably a limitation of this type of meter measurement method and
not an actual audible level difference. Set the channels using identical speakers to the same level,
unless you actually hear a difference later when you are doing listening to verify the system setup.
9.
Check phase. Make sure that all five main channel speakers are wired in phase. The Video
Essentials disc has tests for main speaker phase.
10. Make sure that the subwoofer and main speakers are in phase at the 80 Hz crossover point.
Listen to something with a consistent bass line around 80 Hz while a partner switches the “Phase”
control on the subwoofer from “+” to “-”. The switch position that results in the greatest bass at the
listening position is the correct setting.
11. Play something that is familiar to you through the system to verify the system’s overall
performance. If something does no sound right, recheck your connections and settings. Re-measure,
re-check, re-align.
12. Switch the processor/receiver to each input that you will use. Check your settings for each
input and each mode. Some processor/receivers require that you enter settings separately for each
mode and/or input.
13. Before playing the system, check levels and speaker alignment one last time. Make sure that
you write down all processor settings for future reference.
