Sure an audio compressercompressor will work .If If you can access the speaker wires you can place a small incandescantincandescent lamp in series with the speaker .When When the volume is normal the filament resistance is low .Choose Choose a small lamp with a dcrDCR of say 2 ohms approx .High High sound levels will heat the filament increasing DCR tending to soft limit the sound level .I I have used a standardstandard 6.3 volt 0.3 amp pilot lamp to make a poor mansman's compressor .