Anyone have experience with acousticfields.com or with using true pressure traps?

... 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.

@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?
 

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.

 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.

Dlcockrum, here you go...

"The Iso-Wall construction technique solves the three main problems with listening rooms: 1) it greatly reduces wall shudder; 2) prevents sound inside the listening room from getting out; and 3) absorbs excess bass energy by virtue of the flexible walls, turning them into giant membrane bass traps."

I participated in a call with Dennis @acousticfields.com this afternoon. He was friendly and helpful and came across to me as one who knows what he is talking about. The bottom line is that he offered his room design services for a substantial fee (which is completely credited toward a subsequent purchase of goods) and suggested that I go the DIY route, buying only the carbon and foam from him, due to my limited budget. It appears it will take a lot of carbon to build the complement of pressure traps (around 70!) needed to completely treat a room this size (17’X23’X10.5’).

Two things look to be a problem: 1) he said he is backlogged 2-3 months for design services and 2) the cost. I could possibly swing (at the high side of my budget) the number he quoted if the pressure traps were turnkey, but adding labor (and the cost of wood) for my carpenter to build 70 of the pressure traps would make the cost way beyond my means.

@arsh I briefly reviewed the description of the ASC ISO system on their website and it appears that it primarily intended for soundproofing. That is not a concern for me since the new room will be the only room in the basement and the exterior walls are cinder block and mostly underground. I am 100% focused on optimizing the sound quality inside the room itself. Did I misunderstand the ASC ISO system’s benefits? BTW I really like the concept of the Stillpoint Aperatures and hope to work four into my room budget.

@4krowme I recall there was a product from Billy Bags some time ago that used a microphone and an amplified bass speaker wired out of phase that was hung in a corner from the ceiling to cancel room bass nodes. I thought it was interesting but it was long discontinued by the time I discovered it. Would that be what you are remembering?

I am also about to build a dedicated 2 channel listening room, about 31 x 23 x 14. I am wary of  building a lot of treatments into the actual structure that I cannot reverse. So, instead, I am planning to use the ASC ISO wall construction methods and then add treatments inside the finished space as needed based upon listening and measurements. Consulting with ASC.  I also have many Stillpoints Apertures, which I will try to incorporate if possible and appropriate. Best of luck!

 Starting from scratch will give you the possibilities that most of us won't have. I couldn't be more interested in the outcome.

  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. 

Get a mic and REW and do some measurements in the space.

Are you thinking of the mass loaded membrane traps?
Those are somewhat modellable, but I think you need to have the target freq, and then tune it by adding or taking away a bit of mass at the end… much like a passive radiator.

There are also the round bass traps, which could be added later, as well as active bass “traps”. But starting with the in-wall resonant ones makes a lot of sense.

Once you know the low frequency decay, then just treat the higher freqs so that their delay is similar. (I.e. don’t go overboard with super short ring down times for high frequencies, if the low notes are taking forever to decay.)

The resonant freq on the various places will likely be different along the walls… !

Lowest in corners, then long walls, then short walls.

@holmz my thought was to try to design the construction of the room such that the acoustic treatments would be built into the walls, so I am attempting to find someone who can mathematically model the room before it is built. Currently the basement is unfinished and one very large room (1900+ sq ft total) and the existing walls are cinder block. The basement is divided in half lengthwise by a staircase so I have 20 feet max on each side and length is limited to 27 feet due to a tankless water heater installation.

I can keep you apprised of my findings as I learn more about which acoustical treatments and construction techniques will work best.

Not yet, but I am super interested.

Do you have a way to excite the room and measure the pressure (frequencies) in the corners?

You probably need ^that^ to get the traps built to address the frequencies you want to suck up.