Originally Posted by CherylJosie
Then I immediately noticed that the center speaker is 3dB louder in the subwoofer output and speaker levels than the all surround channels including synthesized high/wide.
The front l/r are 3dB higher in the subwoofer output and speaker level than the center but that makes sense because there are two channels running simultaneously as opposed to one when I do the cal. The center should be 3dB lower than the rest of the system, not 3dB higher than the surrounds. This makes no sense from a calibration standpoint to put 6dB of attenuation into the surrounds.
Anyone run into this before?
This morning I think I figured out the issue.
For convenience I have been calibrating channels/room in pairs of channels since the EQ and crossovers function in pairs for the most part. The only way to energize some of the channels/speakers connected to my TX-NR929 without adding synthesized information to the mix is to use the Full Mono or All Channel Stereo setting, set non-tested speakers to full range or none (depending on interactions between crossover settings in the receiver) to eliminate bass managed crossovers from the subwoofer that are not being investigated, and disconnect all speakers that are not being measured at the time.
For convenience I have also been using the Stereo and Mono settings to calibrate the front LCR and subwoofer without having to unplug so many wires, as well as the Direct setting for REW calibration.
Examples: I used Mono with center disconnected and crossover at 150Hz to calibrate the subwoofer for its maximum expected frequency of operation. Then I reconnected the center to set its crossover and EQ. Then I used Stereo to set the front crossover and EQ, noting that as expected all the levels were up 3dB from Mono. Then when I switched to Full Mono to cal the rest of the channels (including the High and Wide that have no distinct stream content of their own in any case), I noticed the level mismatch.
I suppose the issue is that with Full Mono setting, the receiver is acoustically summing all channels with the exact same signal and that could result in significantly elevated SPL in that mode. Presumably Onkyo added 6dB of attenuation to that sound mode to avoid large jump in SPL.
My guess is that the degree of attenuation may also depend on how many of the 11 possible channels have been configured, but I have not tested that speculation.
This attenuation is not the sort of thing a novice would necessarily expect. I have worked as an engineer for decades and it caught me off guard simply because there is no detailed documentation on the actual function of each sound mode and I never gave such considerations any thought until now, being a relative novice at home theater calibration.
Does AVS Forum have a master thread on setting sound modes and other features such as Phase Matching Bass for manual calibration? A sticky or two explaining the intricacies of some of these functions would be helpful. I just got started and already Phase Matching Bass and Full Mono have caught me by surprise, as did the receiver losing its cal settings and getting confused in the sound modes when it loses power with the setup menu active and some channels shut off.