# Bass Traps that Don't Absorb Highs?



## mikie (Dec 9, 2006)

Hi All,
I did a quick REQ test of my family room the other day but didn't save the file :duh: Frequency wise things didn't look too bad, but the decay under ~200 Hz was not good (over 1000 ms). More bass traps are obviously in my future. The little lady is not thrilled with the idea of more fabric covered panels (already have superchunks in rear corners), and I want to avoid making the room too dead. My hope is that there's a paintable front membrame that lets bass through and reflects highs. I'm pretty handy, so if such an animal exists I might be able to figure-out something the little lady will accept.

Is anyone aware of the acoustic properties of painters canvas, thin cardboard, thin plastic, or other options? Any help would be appreciated. 

FYI: I'm away from home for a while & plan to fill time researching my accoustic challenges. :reading:

Thanks,
Mikie


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## hjones4841 (Jan 21, 2009)

Bryan (and Ethan Winer on his site) suggest that heavy paper (the brown type like grocery sacks used to be made of) on the surface of fiberglass reflect highs but allow bass to pass thru. I bought a 150' roll, 35" wide at Lowes this morning (it was in the paint department) for about $8 for some treatments I am planning.


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## bpape (Sep 14, 2006)

You can also build sealed wood front membrane absorbers that are good for about 2-2.5 octaves. You might need a couple different sizes but it's doable. If you play your cards right and the room allows it, you can build them down low on a wall and make them look like Wainscoating and a little shelf on top. 

Bryan


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## cinema mad (Jan 28, 2007)

hjones4841 said:


> Bryan (and Ethan Winer on his site) suggest that heavy paper (the brown type like grocery sacks used to be made of) on the surface of fiberglass reflect highs but allow bass to pass thru. I bought a 150' roll, 35" wide at Lowes this morning (it was in the paint department) for about $8 for some treatments I am planning.


 I made these Bass traps using the Brown paper membrane method so not to have BroadBand Absorbtion, it works very well ...

FWIW I posted the Bass traps with membrane Build in this forum...

Cheers....


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## mikie (Dec 9, 2006)

Thanks for the replies.

Paper is too thin for a room facing surface (dogs & kids would poke right through) - I was hoping that something like cereal box cardboard was doable.

Bryans idea about sealed wood membraine absorbers - I could probably get by with something that looks like wainscoating.

--Mikie


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## Kal Rubinson (Aug 3, 2006)

mikie said:


> Thanks for the replies.
> 
> Paper is too thin for a room facing surface (dogs & kids would poke right through) - I was hoping that something like cereal box cardboard was doable.
> 
> ...


Cover the entire trap, including the paper face, with GOM fabric.

Kal


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## bpape (Sep 14, 2006)

If you want to try to use cardboard, you can. Bond it to the absorptive material with spray adhesive. Just remember that the denser/thicker it is, the lower you'll stop doing any absorbing and the more peaky the absorption will become.


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## mikie (Dec 9, 2006)

Thanks Bryan. I'm thinking of building a simple test setup to measure reflected frequencies when readily available (aka cheap) membranes are adhered to a 4" absorber. Nothing fancy, just a speaker firing pink noise out the patio window at a panel. Mic a few inches in front of the panel to record what is reflected. I know this won't be lab quality, but it should give an inidication how various membranes reflect. If it doesn't reflect, then I assume it goes into the absorber. Let me know if you think this would be a waste of time.
--Mikie


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## bpape (Sep 14, 2006)

That's really tough to do but it might show you a little something. You could probably guess almost as close. I'd be more concerned with the efficiency of the absorption and the center frequency of the peak. Once you start getting into posterboard, etc. - you'll be down at least 50% absorption probably from around 350hz up if not more.

Bryan


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