Some experienced surround sound engineer who can shine me a light ?

marcel-gielen wrote on 1/22/2023, 1:38 PM

I am using Vegas pro (for personal use, mainly Holiday movie editing) I like to edit in 5.0 surround, however I am struggling with the levels.

In the living room we have a surround setup with all "full range" speakers. Level, phase and frequency adjustment done by the receiver with a mic at the listening position. When watching BD or DVD movies it sounds "balanced".

For editing I use a setup 4 identical full range speakers and one center speaker. Since the receiver used there, does not support level adjustment on its multichannel analog input, I used a sound level meter to adjust the levels. When using pink noise, level at the listening position for front and rear are comparable (within ~ 2dB)

When I edit a movie, and pan the sound primarily to the front (based on listening) and I play the movie in the living room, then the rear speakers sounds much louder (and the sound appears to come from the back instead of front).

Based on this experience, I created a test movie in Vegas using pink noise. (Level adjustment in the Vegas surround mixer, 0dB for all channels, during playback the level meters in Vegas show identical levels for front and rear)

For a first test, I took my sound level meter and switched on the test tone of the receiver. At the listening position front and rear level within approx. 2dB.

Then played back the movie created in Vegas, rear level more than 6dB higher than front (both the dB meter show, but it's audible as well)

Does somebody has any idea what I am looking ate here, why there seem to be such a big difference between front and rear ?

Thanks for any info/experience related to this.

Comments

fr0sty wrote on 1/22/2023, 1:56 PM

Not sure off the top of my head, but if you've already identified the amount that they need to be adjusted to balance that out (6db, you say), I'd just do that.

marcel-gielen wrote on 1/22/2023, 2:22 PM

That will work, but I like to understand why there is such a big difference. If I create a movie with equal levels at front and rear. Why do the levels then differ so much when playing back a calibrated setup.
I can dig deeper and perform some measurements at the audio line outputs, but it seems to me I am just missing something obvious.

fr0sty wrote on 1/22/2023, 2:27 PM

I agree, there's probably a checkbox somewhere that needs uncheckin'.

Howard-Vigorita wrote on 1/22/2023, 4:25 PM

@marcel-gielen I don't know if this is the theoretical answer you're looking for because my experience with surround is non-existent, but... when mapping dual mono to stereo, the panning law I use requires a 6db cut when panning the previously centered mono channels hard left and right. Might be the same deal panning previously centered mono signals hard front and back or converting the back 2 channels from dual mono to a single remapped stereo channel.

Musicvid wrote on 1/22/2023, 7:08 PM

Rear speaker output in a 5.1 arrangement should be sensed, not heard outright, except in the few instances that a sound originates LR/RR.

Set your LF/RF at a normal listening volume, back off the Center by -3dB or so, and slowly build you ambient rear volume until you can hear it, then back it off. Your goal isn't four discrete channels of equal volume.

fr0sty wrote on 1/22/2023, 7:18 PM

Rear speaker output in a 5.1 arrangement should be sensed, not heard outright, except in the few instances that a sound originates LR/RR.

Set your LF/RF at a normal listening volume, back off the Center by -3dB or so, and slowly build you ambient rear volume until you can hear it, then back it off. Your goal isn't four discrete channels of equal volume.

This is assuming film is the target, for music, this isn't always the case.