|
I would call that broad band.
It's really easy to kill hi frequencies - any old absorbant will do that.
The absorants get less effective on the mids, and almost ineffective on the lows.
If the absorbant is thick enough (in feet!), it can handle the whole range. Large air gaps are almost as good as total thickness, so foam with an airgap is basically a broadband absorber.
Think about wavelength. Picture a bass sinewave. Where is the air at minimum velocity (zero crossing)? At the wall. Where is it at maxium velocity? At 1/4 wavelength. (Half wavelength would be another zero crossing). Absorbants work by turning air molecules velocity into heat. Put it where the air is moving fastest.
Bass trapping is the hardest. One way to trap just the bass is to hide your absorbant behind a reflective surface. The hi's and mid's bounce off, and the low's get in and are absorbed. You can perforate this surface to make it more of a broadband absorber.
|