# How to measure absorbers and bass traps



## sydney2013 (May 26, 2013)

I plan to build a few bass traps as described in attached LIMP MASS BASS ABSORBER.pdf
So I can tune this absorber's central frequency I would like to know if there is a way in which to measure my prototype absorber using a UMIK-1 and REW V5.

i.e. I don't want to build 3 or more such absobers, place in my room and find the frequencies absorbed are not in my target range.

So I don't want to measure the room + multiple absorbers but only one absorber.


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## JohnM (Apr 11, 2006)

*Re: How to Measure absorbers and bass traps*

Might find some folk able to comment on that in the Home Audio Acoustics forum or on the Gearslutz Acoustics forum.


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## Lumen (May 17, 2014)

*Re: How to Measure absorbers and bass traps*



sydney2013 said:


> I plan to build a few bass traps as described in attached LIMP MASS BASS ABSORBER.pdf
> So I can tune this absorber's central frequency I would like to know if there is a way in which to measure my prototype absorber using a UMIK-1 and REW V5.
> 
> i.e. I don't want to build 3 or more such absobers, place in my room and find the frequencies absorbed are not in my target range.
> ...


Technically interesting and money-saving project! If I understand you correctly, you're in a chicken-egg situation --> which comes first? As you said, you don't want to build a trap only to find it absorbs the wrong frequency.

So first you need to find your problem frequencies _without_ acoustic treatment. REW can help you with that. It sends test tones through your speakers which are picked up by the UMIK-1 mic. Then you can use it to generate graphs which tell you which frequencies need trapping (typically the deep troughs). 

If you just want general info about your trap, you can measure the room by itself, then measure it with the trap, and plot the difference. But if you want to test the absorber directly and accurately, you'll need a lab with specialized test gear as described in 
Alternative Test Methods for Acoustic Treatment Products.

This home-made test strikes a balance between the two methods.


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## Lumen (May 17, 2014)

To get more exposure and possible help, I've moved your thread to the Home Audio Acoustics Forum.


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