With most of my speakers, the Sonos Amp has a nice flat frequency response, just a little rolled off after 15KHz which I can’t hear anyway. But some speakers can cause peaking in the frequency response (typical problem with Class D without post filter feedback). I think it happens with the Sonos Amp when speakers have a negative phase at high frequency. At least that is the difference I have with this problematic speaker (Carmody Overnight Sensations). Here is the frequency response (voltage measurement at amp’s speaker terminals). This might be why some people have reported that the amp sounds bright. I never really thought so even with these speakers, but still I would like to be able smooth out the peak with EQ, and the existing treble control doesn’t do so well. Please, please, you can give this to us!
edit: oops, previously I showed a curve that was generated after treble was turned one notch down.
