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In a recent Google hangout I was asked about the correct location for a bass absorber panel and whether they should be placed in quarter lengths along the side walls. And the short answer is no. Diaphragmatic absorption is a process that works on sound pressure. So does quarter length positioning in our rooms correspond to the correct sound pressure levels that we need for the diaphragmatic absorber to work? The answer is no and here’s why. Where are the highest pressure areas within your room? They’re against the room boundary surfaces, they’re at intersections where all the planes of the room, the vertical and the horizontal, planes intersect.

As you move out into the room, the pressure gets less. When we used to do our measurements at one foot from the wall, it was about 8 to 12% first variance. Another 6 inches out into that, it went another 10%. So there’s a gradual decrease in pressure from the wall surface. So the highest pressure is at the wall surface and once again just forget about acoustics, you don’t need any knowledge in acoustics, just stand against the wall in your room and walk all the way down it when you’re listening to music.

Put some low frequency stuff on and just walk the length of the wall and you’ll feel it, you’ll feel the pressure differences, you’ll hear what goes on in those modal areas. Sometimes its not much attenuation, sometimes its a lot. So we have exaggeration and attenuation.

Why do we want that in our rooms?

Well you can’t have areas in your room where one thing is going on that lets you hear too much of something and then one thing’s going on that won’t let you hear anything at all. You can’t have all that conflicting stuff going on in your room, so you have to reduce that and the biggest problem is room modes and the biggest room modal frequencies are frequencies below a hundred.

So you need to locate your diaphragmatic absorption technology in the higher pressure areas which are against the room boundary surfaces. Now, that said, there’s better locations to put them. Now that you realized that there’s better locations against the room boundary surfaces. Where’s the area of highest pressure in your room? Let’s use common sense. Forget about acoustics, where your speakers are. They’re the energy producing device. Without them, we don’t have a problem, the room’s a room, it’s not for music.

So the area between the speakers in the first boundary surface that’s closest in distance is usually the front wall. That’s a high pressure area, probably the highest pressure area in the room unless you’re looking at modal issues down the room but just in terms of just pure pressure that’s your highest area.

You want to really understand and hear the impact diaphragmatic absorption has. Put one behind each of your speakers, 12 inches and listen. You’ll just be amazed and then you’ll say, “well I’d like a few more of these” and that’s usually what happens. And the average room needs about 6 to 8 so that’s the process, the tuning process.

Once you understand how it works and put one behind each speaker, one in the corner of the front wall, then you’ll get it right away whether you buy it from us in the production unit, which is all pretty and shiny, or you build it yourself, which sometimes can be really rewarding and it doesn’t matter as the technology will create the changes in the sound quality that you’ll notice immediately.

Your bass will be defined, separated and defined.

Each note will occur and decay on its own volition. There won’t be any room sound in the decay. Well, you know, you’ll need some more units but what I’m saying is we have the technology to manage that so you get the initial fundamental sound but as the fundamental decays into its harmonics, you don’t hear room. That’s what kills our bass, the fundamental we know it’s a bass note that we’re hearing, we just can’t hear the life of the note. We don’t get to let it decay on its own volition, the room has to step in and put its own stink on the deal so you’ve got to get rid of the room. Well, that’s what we do with diaphragmatic absorption which will give you that attack and decay life in your low-end frequencies.

In Summary

So I hope this discussion on bass absorber panel placement helped you. If you have any questions at any time I am always on hand to help answer them. Leave them in the comments section or email me at If you would like to learn more about room acoustics please sign up for my free videos and ebook by joining the mailing list here. I send room tuning tips and things for you to test in your room every Wednesday. They are easy to follow and really help you enjoy more of your music. And 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.

Thanks and speak soon

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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