Multiband EQ degrades audio on iOS

I added the multiband EQ DSP to some ChannelGroups in my FMOD-powered iOS music-generating app, but I noticed that the audio quality suffered when I did so.

The following audio files were captured with 0, 1, or 2 multiband EQs in the chain. No parameters were passed to these DSPs, so (I assume) they are totally flat.

No EQ in the chain:

One EQ on the master ChannelGroup:

Two EQs, one on the master ChannelGroup and another on one of the “buses”:

:inbox_tray: Download all three files

I tried the “Three EQ” DSP and it did not have this issue; quality was identical with or without that DSP on the chain. But I was hoping to use the multiband EQ…

Note, I have not tested this out on other platforms.

Using the Core API, the default for a multiband EQ is for band A to be enabled and set to a 12dB lowpass with a cutoff of 8kHz and a Q of 0.707, all other bands are off. This is probably what you are hearing.

You can see the defaults for all DSPs in our docs, here are multiband defaults.

Ah, I’m sure it is! What a peculiar design choice… anyway, now I know I can just override that band with my own settings. Thanks!