Awesome work, Hans!?
Perhaps the low-frequency issue could be partially addressed by a variable highpass filter or, taking it further, a graphic equalizer of some kind.??
You might also look into preprocessing the audio through an allpass filter; this is done in AM broadcasting to help in reducing peaks: ?
I am looking forward to updated firmware incorporating this work.
Thanks and 73, Don N2VGU
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Donald S Brant Jr