Anyone have experience with or with using true pressure traps?

I am preparing to build a two channel listening room in my basement. Planned dimensions are 17’X23’X10’. Perfect chance to get it right since it is to be built from scratch. One chance if you will.

i have some experience with velocity traps (absorption), enough to know that when using typical absorption products, it is nearly impossible to effectively address room bass nodes without creating an acoustically dead room since fiberglass and rock wool traps are exceptionally efficient at absorbing mid and high frequencies and exceptionally inefficient at absorbing low and even mid-bass frequencies.

After checking out several companies online that specialize in room treatment, Acoustic Fields ( stood out to me because they design and build pressure traps that precisely target specific frequencies (vs the broad-band behavior of velocity/absorptive traps) based on mathematical modeling identifying exactly where and what frequencies of acoustic anomalies will occur in a specific room and matching frequency-specific pressure traps in the exact room locations that reduce/eliminate problem nodes at the listening position without affecting non-target frequencies as velocity/absorptive traps do.

This approach promises to get quite expensive. I am wondering if anyone here has any experience with Acoustic Fields (or installing/using pressure traps) that would provide helpful input regarding their experiences.



 Like you said it was a long time ago, but yes that sounds like the product that I remember.

 Wouldn't we all be better off with headphones? Ha! There are problems with making music any way that you have it. Still looking forward to your future experience with all this.

 The iso-wall is a technique that will get you most of the way there, but no doubt it would require some engineering advice. One thing that I like about it is that it is automatically out of the way from the beginning.

Usually the most optimal solutions are mostly passive control, with some active control layered on top.

  It does remind me of a product though that didn't go far for room correction. Must have been a financial thing because it made sense to me. I remember some company that used correction in the form of an anti-bass wave being used to cancel out the nodes in the room. Basically a sample was taken during every moment of the music and a microphone and amplifier/speaker combination produced the anti-wave. Seems this system was placed in the corner of a room. Didn't hear much more about it after its inception. 

And using that active control, following the passive bass traps.

@holmz it may end up that I have to go the passive trap route due to cost. I am beginning to realize that any method of optimizing the construction of the room, no matter how sophisticated or expensive, will leave peaks and nulls to deal with. The peaks are relatively easy: absorption and/or active equalization are well equipped to eliminate or at least moderate those, but it is the nulls that are the fly in the ointment. Even active equalization cannot help with the nulls. FF to 8:15 in the video below. It appears that speaker/listening room placement is the only way to minimize the effect of nulls?


... It appears that speaker/listening room placement is the only way to minimize the effect of nulls?

Correct, a null and a peak are destructive interference and a constructive interference respectively.

However the room dimensions will define the peaks that exist in the corners and parallel walls.

This is why I mentioned a microphone in post #2 and #4. One can calculate what they should be, and where. One can also measure what the peaks are at a variety of “where” positions. Knowing that, then you have a map of where the modes are high that need to be absorbed, and what freqs they are at.

We do not get pressure nulls in the corners as easily as we get them in the listening position(s). (We get velocity nulls in the corners and walls,) And your treatments will be located at the walls, so you have the problem constrained there at the wall, and only need to measure there. (But measurements at the listening position should likely also be done.)

As the long modes will be longer, they will be at a lower frequency… and at a lower freq than say the short wall distance modes. And if the traps are low-Q, then they will largely suck out what they should. if they can be made with a lower Q and tuned in-situ then it get easier to be closer to perfection, but the low-Q obviates the need for being “overly perfect”.

Treatments fix the peaks. And yes placement the nulls.
So focus on the peaks for the wall treatment.