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[dean70]

The level trim function under room correction appears to have a limited range. The slider maxes out to +10db, but after about +4db it stops having any effect on the spl level.

I have a surround channel that requires and extra +2db to line up with the other channels (big channel imbalance, I know!) & cant quite get there because of this limitation.

[Scolex]

Clipping protection may be interjecting which is why you don't see an increase in SPL after +4
What you could do is cut the other channels by 2db to balance the system as a whole.
What are you using as a reference signal and how are you measuring output.
 

[dean70]

BTW this is using the -20db generated files under Tools\Advanced options with the volume slider set to -10db. I see 73db on all channels except the 1 surround which I cannot adjust high enough. The reference front left is set to 0db on the trim.

[Scolex]

Well using a -20db signal pretty well rules out clipping protection.
I have some questions mainly due to my own curiosity.
Any idea why that particular channel has such a large dip in SPL.
Have you swapped the speaker with the other surround or swapped amplifier outputs to determine if it is an amp or speaker issue.
Have you altered the location of said speaker a little to see if room acoustics are causing a dip.
Which files did you create pink noise, narrow band pink noise, or series of tones.
Is the dip present across the audio spectrum or just a certain range.

What make me so curious is that seems like one heck of a dip for a single channel when you consider a 3db increase is in effect doubling the wattage being output by that channel.

[dean70]

I have figured it out. It behaves more like a balance control than volume level. If you increase one side, it reduces the opposite channel by that amount. Guess it prevents clipping, but makes it hard to get the relative levels right if using more than 2 channels.  ?

[mwillems]

I have figured it out. It behaves more like a balance control than volume level. If you increase one side, it reduces the opposite channel by that amount. Guess it prevents clipping, but makes it hard to get the relative levels right if using more than 2 channels.  ?

If you use the "adjust the volume" filter in the parametric EQ module you can make arbitrary volume adjustments to any channel(s) you want.  That said, to avoid clipping, you'd be better off reducing the volume of the other channels.

[mojave]

I have figured it out. It behaves more like a balance control than volume level. If you increase one side, it reduces the opposite channel by that amount. Guess it prevents clipping, but makes it hard to get the relative levels right if using more than 2 channels.  ?

If you measure all speakers first using an SPL Meter, then you can get relative levels correct. If you make changes on a speaker by speaker basis you will be chasing your tail.

Room Correction's volume level makes sure that there is always zero net gain in the digital signal. It sets the relative levels accordingly. For example, if your side surrounds need to be +4 dB and the rear surrounds need to be +2 dB, then it will do the following:

L, R, C, Sub:  -4 dB
Side Surrounds:  0 dB
Rear surrounds:  -2 dB

The new "Set levels from decibel meter" feature makes it even easier. Use Tools > Advanced Tools > Audio Calibration > Volume Calibration and measure the SPL at each speaker.

At the bottom right of Room Correction, click "Set levels from decibel meter" and enter in the SPL from each speaker. Now all levels will be set correctly.

[dean70]

Thanks I will give that a try. I initally used the Set levels from decibel meter function which is where the 0db Front Left reference came from. Maybe it needs to be a bit smarter and set the 0db on the lowest channel instead and adjust the others down like the example you gave?