Egregoros

Do Android devices actually transmit differing audio over Bluetooth?

I'm confused because I have a OnePlus Pad 3 and a Fairphone 5, both running e/OS/. But for whatever reason when I connect them to my speakers over bluetooth, both using regular old SBC and volume set to 100% on device (without adjusting speaker volume) somehow the sound from my Pad 3 sounds darker and contains more bass, while my Fairphone sounds brighter and less bassy.

Like wtf, I always assumed that unless your Android ROM tries to do some crappy Dolby or Virtual "Surround" shenanigans it'd just take the same bits of PCM, compress them to SBC and ship them out over bluetooth. Why does it sound different???

At first I thought I was going mad and this had to be some weird placebo-ish thing. But no. But when I leave the speakers are untouched and test both client devices with the same audio player (Finamp), same Android ROM, same Bluetooth codec and same audio file, for whatever reason they sound different. The only variable is the hardware, which shouldn't really matter when you never do a digital to analogue conversion.

Are there some real cursed hardware shenanigans going on here? Is there a difference in how the two SoCs compress bluetooth? Or is the audio -> SBC conversion done by some proprietary firmware blob and one of them contains some fucked hard-coded EQ?

I feel like I'm going mad, taking a lossless audio file, then playing it with the same app, and compressing it to the same codec using the same UI and shipping it off over the same wireless protocol should in theory yield the same result, no? Everything is (supposedly) happening digitally in software.