masonary bass traps??

[randrohe]

Howdy
Would stones (round river stones) work as bass traps if they were mortared in place in the corners? I could leave an air gap behind it. I think they would be reflective but with the random sizes of the stone that may be alright. Would it be effective on the low end bass??
I'm thinking about 16" across the corner by 8" deep..
Any thoughts appreciated
Rand

[standup]

Rocks might do some diffusion, but not bass trapping. Bass traps, as I understand it, absorb energy, rocks reflect energy. Put the river rocks on a wall to break up reflections, look at fiberglass etc. for bass trapping in the corners. There are other people around here who actually know this stuff, look for their posts.

[norton]

If the air cavity behind the facia was filled with insulation, bass trapping should occur.

Probably not the most efficient, but my guess, is that it would be most effective at the extreme low end of the freq spectrum.

[Nick Sevilla]

I would not use smooth and dense stones or rocks for this purpose.

Study any George Augsburger design, there are many in pro studios.

He used more porous igneous rock pieces for his wall treatment, in order to make a good diffusion, combined with wood panels made of slat 1" strips arranged in a random spacing, to absorb as well.

Cheers

[GIK Acoustics]

Unfortunately, no, it would have no real effect on the room response. I see your reasoning is for the mass, but mass doesn't matter in sound absorption either. The important figure is the gas flow resistance of the porous material, along with the thickness. Any solid object is much too dense and rigid to be useful.

[randrohe]

Thanks for your knowledge..

[JWL]

You are getting good advice. One minor correction: mass doesn't matter for velocity absorbers, ie, broadband absorbers that most of us use. But for some types of pressure absorbers, ie, tuned panel absorbers, mass of the front absorbing face will certainly matter.