Emulator

Are you sure that the game isn't just using the low-pass filter on those effects? Have you compared recordings to console to make sure? Dolphin didn't emulate the Low-Pass filter in old builds in HLE audio. If you try LLE audio in the old builds, does it sound like HLE audio in the new builds?

Just tested LLE on 5.0-16177 (pre-regression) and it sounds the same as HLE, so I doubt it's that.

Tested both HLE and LLE on 5.0-17021. LLE sounds fine, HLE still sounds filtered.

Sounds like HLE is busted in its low pass filter in some way. I remember this game being mentioned in the long, long ago.

That'd explain it, then. LLE audio is a workaround in the meantime, at least.

The HLE LPF was re-enabled in 5.0-14712, but Super Monkey Ball 2 doesn't use it. The main suspect is probably https://dolp.in/v5.0-16434 which is a change related to DPL2 mixing. Can you check? (For Windows you can just download old builds from the website.)

I'm stuck on Linux at this point, but I can probably compile it to make sure assuming no big dependencies break.

I've tried to reproduce this but I'm failing to hear a difference. Can someone else bisect please?

https://github.com/dolphin-emu/dolphin/commit/855dbf88cac56541162ed038127276f7177bec59 alters the output, though it's still different from LLE.

That's https://dolphin-emu.org/download/dev/27c6731a660fb301ec43db31b87d69ae6e66568a/ (5.0-16434) for reference, previous build https://dolphin-emu.org/download/dev/256e3b071e5807a9ff8c264491f82b775b345fe0/ (5.0-16431).

I'm aware of the LLE vs HLE differences. LLE presumably uses proper DPL2 matrix encoding while HLE just mixes the surround channels without any phase shift. But according to OP there was an HLE regression which is what I'm failing to repro. How does the HLE audio compare before and after the DPL2 mixing change?

And yes, checking, that does match the output of 5.0-16177, which is the version indicated by our reporter as pre-regression -- once you factor out the dumping audio rate changes from https://github.com/dolphin-emu/dolphin/pull/10762.

fwiw I suspect this is actually a 'more accurate emulation reveals problem' kinda thing, in this case the fact that our HLE does not properly handle the Dolby Pro Logic stuff.

Just tested both on my end and I can confirm 5.0-16434 is the first broken version.

Two observations from earlier today:

• old HLE is identical to LLE downmixed to mono
• new HLE is identical to the left channel of LLE
  (Can someone confirm just to make sure I'm not misremembering?)

So either that's the effect of the missing phase shift and to be expected or we're doing something wrong with the right channel.

(Can someone confirm just to make sure I'm not misremembering?)

Yep, that's what the waveforms look like to me.