Update: confirmed this effect doesn't occur on an ancient Android 4.0.2 device, once I finally managed to get an audio player running on it. It sounds fantastic.
So whatever causes the compression is either hidden in Android 10 or the Sonim ROM.
On all Bluetooth devices? I'm not sure. Any audio "enhancements" enabled?
Nothing extra I'm running on top, this has been a problem since day one. No idea if it could be something installed in the base image or why that would be the case. Unfortunately there are no ROMs for this industrial phone and no root method.
I tried some aftermarket equalizer type apps and they also didn't help, uninstalled them all. The only thing I have running is "Bluetooth Codec Changer" which I installed for the testing.
Maybe a kind of audio normalization?
It really sounds like it, but is this a normal feature of Android 10 that can be switched? I've searched all over and can't find any documentation, I finally gave up and posted here in the hope that someone else had to deal with it.
I'm going to see if I can find an old phone and pair it with the same devices, confirm if it's this specific ROM
Maybe turning off absolute volume switch in dev options.
Missed your comment somehow. Unfortunately I tried that awhile ago as well as "Disable A2DP hardware offload" with no effect from either.
I'm actually considering calling the manufacturer and asking what they did to it
What brand it's your device?
It's a Sonim XP8, they're an ultra-rugged industrial manufacturer. I'm a farmer and tradesman so I'm kind of stuck with them, we can't get the ruggedized Samsungs here in Canada unfortunately.
Maybe you would like to check out the line BISON by a Chinese brand called UMIDIGI, I had used that brand and they are pretty neat.
A place to ask your questions and seek help related to your Android device and the Android ecosystem.
Whether you're looking for app recommendations, phone buying advice, or want to explore rooting and tutorials, this is the place for you!