Setup guide

Dirac Theater Setup Guide Version 1.01
Document # 9301H40300V1.01
11
5. Check the Multiple speaker checkbox for any channel that services more than one loudspeaker.
The Multiple speakers checkbox must be checked for loudspeakers that are horizontal arrays, such
as the surround channels in many cinemas. Checking this box will skip the impulse response
correction on those channels, and instead only apply magnitude response correction. Impulse
response correction for a channel is meaningless when a single channel services more than one
loudspeaker. See Figure 9.
Figure 9. Soundcard Setup Screen
6. Check USB Preamp gain levels.
a. Place the microphone in a central listening position, approximately equal distance to all
loudspeakers.
b. Before playing the test signal turn down the front panel fader. You can use a VNC client to
attach remotely to the AP20. (Doing so allows you to change the AP20 fader setting without
having to climb the stairs to the projection booth.)
Set the overall noise level in the room to 85 dBC using test noise controlled from the Proxy
application, and using the AP20 set to its lowest output level.
Start with a low playback level on the amplifier to avoid speaker damage. Ideally the actual
room level of the test noise should be about 85 dBC when measured with a standard sound
level meter. Start with the fader set at 5.0 and work your way to 85 dBC. The input level
shown next to the play button should be -15dB +/-2dB. If the sound level is too loud or too
quiet simply change the preamp gain for that input on the USB Preamp. As you move
between channels the displayed gain will change slightly. This is normal.
Once set and you begin collecting samples, do not change the microphone preamp gain.
Doing so invalidates the samples that you took previous to the adjustment.
If an output channel is connected to more
than one loudspeaker, check “Multiple
speakers” for that channel.