Actually, it's a "perforated panel tuned resonator". The term "porous absorber" applies to things like mineral wool, fiberglass, acoustic foam, etc. It is very broadband, not tuned. And a "membrane absorber" or more accurately a "membrane trap" is a tuned device where the surface density and dimensions of the panel and the depth of the sealed air gap behind set the frequency. There's also a "limp membrane" absorber which is vaguely similar, can also be tuned, but the front "panel" really is a membrane, in the sense that it is not rigid at all. Things like tar paper (roofing felt), and MLV, and some types of plastic can be use to make limp membrane traps.I've read where lots of people will mount general store "peg board" (the perforated fiber board you'd use for a tool rack) to the front of their 703 panels. A porous membrane absorber, right?
But perf panel ("perforated panel") is different: it is a Helmholtz resonator, and is tuned. Mathematically, it is pretty much the same as a slot wall, and works on exactly the same principle. The "slugs" of air in the holes (slots) vibrate in sympathy with sound waves of the same frequency, and they are tuned by the size of the hole (width of slat), thickness of the panel (thickness of slat),, spacing between the holes (height of the slat), and the depth of the sealed air cavity behind (ditto). If all of the holes are the same size, and the same spacing, over the same cavity depth, then the whole things is tightly tuned to one very specific frequency. If you put porous absorber inside the cavity, directly behind the front panel and in contact with it, then it is a tightly tuned absorber for that specific frequency, with very high Q. That would be the case with pegboard over a panel of 703, for example.
On the other hand, if the hole size or spacing varies, or the depth of the cavity varies, then it acts more like a broad band absorber that covers a whole range of frequencies evenly, with a low Q... provided that the open area of the panel is greater than about 10%. If the open area is less than about 5%, then each hole acts on it's own, tuned to it's own frequency, so the device acts more like an array of small Helmholtz resonators, each tuned to it's own specific frequency, once again with a reasonably high Q.
So you can do that in many different ways, for different purposes, by making the holes, spacing and depth in different ways. You can even get micro-perforated membranes now, where the holes are really, really tiny, and the membrane itself is very thin, but when installed correctly they can be very effective. One advantage is that micro-perf panel can be transparent plastic, so it can be placed in front of windows: you can have a see-through tuned absorber!
But anyway, to answer the question: ".... Mmmmmm... maybe." Yes, you can put pegboard over a sealed cavity with insulation inside and get acoustic absorption. But once again, it ain't that simple! If you did that, would it be tuned to a useful frequency? Or might it end up sucking out frequencies that were already weak, while not touching the ones that actually needed it? And since perf-panel is mostly solid wood with only a small percentage of holes, in addition to absorbing the tuned frequencies, it reflects most others right back at you, except at the low end, which it allows through... If the holes / slots are large enough, then it can also provide some diffusion (slot walls do, for example).
So that's the situation. Pegboard night or might not be useful in your specific room. I'd suggest finding out the characteristics of the pegboard that you can get in your area, in terms of hole size, hole spacing (center to center) and panel thickness, then we can look at the REW data and see if there might be some way to use that.
Here's a perf-panel module under construction that I designed for one of my customers last year. It's part of a series of slightly different panels that went on the walls of the control room, each tuned slightly differently to treat certain small problems in the overall room response:
You can see the different hole sizes and spacings that I used to cover the range I wanted.
Well, yep, it can be done! But as usual with acoustics, it ain't as easy as it looks on paper! For example, Helmholtz resonators are pressure-based devices, not velocity based (like porous absorbers are) so you have to make sure that your device is placed at a pressure peak for the frequency you are wanting to treat. So if you are wanting to treat standing waves of some sort, the you can't just put it any old place that looks nice: it has to be where the pressure component of the wave is at maximum, or close to maximum. You also have to ensure that your device has enough air volume inside to be effective, etc. And you have to use the correct formula! That last comments sounds dumb, but there's an issue here: there are two equations that have been published in books for calculating Helmholtz resonators in slot walls and other types of perf panel: one of them is wrong; It has a "plus" sign where there should be a "multiplication" sign. It seems that at some point, many years ago, some careless proof reader missed that error, and the book went to print. Then nobody noticed! Other writers of other books then copied the wrong equation into their own books, and the error was propagated. For years, nobody noticed ...I had thought of using this method of cutting certain sized holes into hard faced panels to help tune while providing some broadband absorption but I didn't get very far because I couldn't find reliable info. Care to weigh in?
Until a few years back, a very smart, sharp-eyed acoustician by the name of Eric Desart saw the error, started investigating, notified the publishers of the books, as well as the Internet, and slowly the error is being corrected. But if you happen to have an older book, or even a newer one where the publisher didn't get the memo or didn't care, then you'll be using the wrong equation. Eric was a highly respected and very valued member of this forum, and posted on many threads here too over the years. He's also the guy who designed the very best isolated studio on planet Earth (Galaxy Studios, in Belgium). Unfortunately, he passed away earlier this year, and he is greatly missed. But his legacy lives on, and one part of that is his correction of the Helmholtz equations.So that's a long way of saying: make sure you use the right equation when you are calculating the tuning for your perf panel and slot walls!
What I do is to use the name block of each test to give me the most basic data, such as which speakers where on and what point in the series of tests I am looking. Like this:From the point of view of someone who knows the program, whats the best way to label the data so it makes it easier to understand?
I always start the name with a series of three characters to show which speakers were on, and filling in the other characters with a dash "-". So "L--" means only the left, "-R-" means only the right, "--S" means only the sub(s), "LRS" means all three, "LR-" means left and right but not the sub, etc. Then I add a very brief description of the series, such as "baseline" or "superchunks in" or "cloud in", to indicate what was the major change that happened just before this test was done, then I use the comment block at the bottom of each test to note down additional information that might be useful in the future.
That way I can see at a glance what test I am looking at, and I can easily flip back and forth between related tests to see what changed. So for example, if I want to see what effects the cloud had on the overall modal response, I'd probably look at the waterfall plots window, and flip back and forth between the "LRS - Baseline" and "LRS - Cloud in" tests, while concentrating on how the peaks changed, and how the decay patterns changed.
Etc.
(For 5.1 rooms, I use the notation "LCRlrS" to note the speakers that were on, where "C" of course is the center channel, "lower case "l" is the left surround channel and lower case "r" is the right surround channel.)
Thanks again for all the advice and criticism. I'm gonna gather some more data and post tomorrow and we can start sorting things out.
- Stuart -
The floor is porcelain tile. There is a 6x8 rug at the mix position/desk area, and another rug under the couch at the rear of the room. The rugs are almost exactly the same color as the tile so it looks kinda like carpet. Don't worry. Even though you totally reemed me last year when I told you I was building this room on top of a "kick drum" I took that into account and massed the crap out of this floor. It's about as close to solid concrete as I could get it. Nice and solid. 
Yep! There are reasons behind our crazy recommendations! 
But hopefully this will be a much clearer analysis of whats going on in my room.