A project log for Feedbass! (microphone in loudspeaker)

Using a microphone in speaker cabinet as feed-forward, to extend low frequency range of audio system

DeepSOICDeepSOIC 03/23/2018 at 19:510 Comments

I've been using my feedbass-equipped speaker for a little while, and I noticed two good things.

++ Good tradeoff between bass and loudness.

If I were to extend frequency response down to say 50 hz perfectly, the speaker will only be ok at very low loudness, as a lot of bass boost is required (approximately 14 times). Feedbass makes only a 4.5 times boost, which seems to be enough to make the bass very audible, yet leaves much more room to increase the volume.

++ Good overload behavior

As the amplifier clips, the positive feedback is broken, and the system almost instantly leaves the overload. In contrast, a pre-filter based design would remain overloaded until the transient is finished, letting no sound through for that period.

This results in a very soft overload behavior of feedbass, where the bass is distorted, but the sound is not interrupted. With filter-based correction, as soon as some subtle overload begins, the music is completely ruined by the intermodulation. With feedbass, there is almost no intermodulation, and moderate overload sounds OK.

That makes me reevaluate the results: the project is an EPIC SUCCESS!!!, even though it's a bit accidental. And I plan making a few more feedbass speakers soon!