Surround 7.1 Routing Issue?

I may be having an issue but I don’t know if what I am experiencing is representative of normal behavior. In FMOD I’m using Standard Metering Channel Order. Just so there’s no question, my OS X system/interface output works just fine for other purposes (surround panning in a DAW, listening to a surround speaker output test), when set up in this standard order:
L-1, R-2, C-3, LFE-4, L Surr-5, R Surr-6, L Rear- 7, R Rear-8

When panning in FMOD, even restricting to only one speaker output, like this…
Screen Shot 2020-09-05 at 1.11.13 PM

…the meters clearly show that audio is only leaving the event on channel 5 (Left Surround). But my system output looks like this:

Obviously, the expected result is audio coming out of only output 5. But there’s a nontrivial spillage coming out of 1 & 7 as well.

If I pan to only Left Rear, I get this result:

Channel 5 is even hotter than 7, which is where 100% of the audio should be coming from. But there’s even spillage into channel 6 (Right Surround).

Also to note is that L, C, R work as expected in FMOD when audio is panned in their zones.

Actually, I just did some more probing and I realized that even if forcing my Master Bus to 7.1, having the Project Platform set to Desktop 5.1 caused this to happen. When setting to Desktop 7.1, panning worked as normal. But the behavior is still curious, especially when it was pushing a substantial amount of audio to channel 6 which was toward the opposite side of the pan. I am assuming that this was because the combination of the platform setting and the master bus setting was outside of intended use (i.e. incorrect). I also assume that if I’m mixing in 7.1 (and platform set to 7.1) but the user is in 5.1, the mixdown would be more expected than what I was experiencing.

Hi ,
If you work with 7.1 panning, and the studio project is set to 5.1, it will do a 7.1->5.1 mix even if your sound device is set to 7.1. Because of different speaker angles for 5.1 and 7.1, the downmix will spread a discrete signal into 2 different 5.1 speakers, so you will get sound coming out of 2 speakers in a 7.1 setup.

The best option is to use 7.1 as your project setting, then FMOD will mix down for every type of speaker setup the user has (ie stereo, quad, 5.1), if it is a flexible target platform (ie PC)

On consoles we stay in 7.1 and the console does the downmixing through dolby digital etc.

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