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In last week’s Google hangout I was asked “Someone in a forum recommended that I buy a membrane bass trap. What do they do? Are they like your diaphragmatic absorbers? Why don’t you sell membrane bass traps? If they’re any good I would assume that you would.” We have updated this blog from its original posting on 12/14/19 to reflect changes in the science.

Well, the reason is a membrane bass trap is really the stepchild or cousin to diaphragmatic absorption. A membrane bass trap has a thinner front wall and has a lighter cabinet. Those are the two most important variables for performance. So a membrane absorber or membrane bass trap is a way to get less performance, less weight and less cost. They cover a narrow frequency range and are considered a tuned bass trap in some circles. They are tuned to a narrow frequency range.

Membrane Absorption:

We’re not about less, we’re always about more performance and with more performance comes more weight and more cost. We’re not a company that does band-aids. We don’t do solutions like that. Membrane absorbers do have their place but you need a lot of units to do the job. You might need four or five membrane absorbers to do the job that one diagrammatic absorber does. We don’t subscribe to that particular philosophy.


Membrane Absorbers

Membrane absorbers do have their place if you have to have low-frequency management within your room and if the weight of products is an issue then a membrane absorber will get you the frequency of absorption that your room will require, you just won’t get enough of the energy absorbed. They are lighter in weight but don’t go as low in performance as most small rooms require. You will need a lot of them and still may not go low enough to get your room issues and absorb enough at the frequencies you need. A membrane bass trap is a tuned bass trap but may not be tuned to your room needs.

Diaphragmatic Absorbers Are The Only Way to Go

So we like diaphragmatic absorption because it’s very powerful. It accepts our activated carbon technology very well and the performance speaks for itself. You’ll never get the performance we get in a diaphragmatic absorber in a membrane absorber. It’s just not physically possible and if a company tells you that that’s true, run as fast as you can!

Diaphragmatic Absorber

Diaphragmatic Absorber

Our ACDA-12 is the most powerful freestanding diaphragmatic absorber on the market. You can see the test results on this page.

Diaphragmatic Absorption:

Low-Frequency Energy Absorption

Absorbing low-frequency energy in a room is a very difficult thing to do. There’s a lot of band-aids in the marketplace, there’s a lot of products that say they do this, that or the other, there’s a lot of hype out there, there’s a lot of misconceptions and I just simply won’t tolerate that in our product line. So we work with diaphragmatic absorption because it will give you the performance that your small room requires. It’s expensive, it’s heavy but it works really well and we think those two trade-offs are worth it and most of our customers do also.

ACDA 12 Chart ver 2

Absorption Coefficient Vs. Frequency

If you’re going to compare a membrane absorbers surface area to the surface area of a diaphragmatic absorber, a diaphragmatic absorber will be three times as heavy but it will work five to ten times better. So that’s always been the trade-off I’ve been willing to make because I want to solve people’s problems in their rooms.

Form Or Function?

We’re not about band-aids and I would never develop a membrane absorber just to market another product in our line because I have a diaphragmatic absorber that has the largest rate and level of absorption that I’ve ever seen in any commercially viable products. So I wouldn’t add another product to our product line that did not work as well as a diagrammatic absorber. It’s just not the direction I want to go with low-frequency management because to me that’s just adding to the noise and the confusion in the marketplace today.

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In Summary

If you would like your room acoustic issues analysed for free by me then please fill in the form here and I will be happy to take a look for you.


Dennis Foley

I am an acoustic engineer with over 30 years’ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others.

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