I have been left wondering about diffusers, base traps, and absorption panels.
In laying out a room, with too many variables it makes me wonder how would you know what, where and how many? You have your reflection points, but getting rid of them will effect the sound stage and bring your lively Axiom speakers to sound like a studio. But too much and you loose the definition of what you want to hear in garble.
I hear about these base traps, but do I need one in each corner of the room, or can I put one into a corner where I have some protruding piping that I'd like to hide anyway?
if you diffuse a wall, does it need to be the back wall? Or if you did a side wall, would it be negative if you didn't do the opposite wall too?
That is before you start throwing back into the mix, optimal speaker placement as that might change as soon as you hang your room treatment up. The room starts spinning and it's time to get off.
I've been following the acoustical treatment thread over at AVS for a few years and it is, honestly, VERY complicated when throwing everything into the mix. There are definitely guidelines that help to tame every room, but getting those to be optimal is difficult for the DIYer. That is why a number of people focus just on the "biggest bang for your buck" approach while doing the most simple application of treatments that they can. That is just absorption. Corner bass traps are large absorption pieces, front wall treatments are pretty much just really tall/wide absorption pieces, and then stopping the first reflection points with absorption panels, and you get (my made up number) 80% there. WAY better than nothing in the room, but still room for improvement. Then the old 80/20 rule kicks in...
You can spend 20% of your time/money/effort to get 80% of the desired result, but to get that last 20% of the desired result, will cost you 80% of your effort. In other words, to get any further will take 4 times the time/money/effort than the other pieces. That has a lot to do with getting it right and not just slapping things up, and getting it right really takes someone that knows what they are doing (money), and for the diffusion panels it takes more money to buy them, or time and effort to make them.
I have my entire front wall treated (behind my screen and false wall). Floor to ceiling bass traps, and then 3.5" of absorption everywhere else on that wall. I have a thick carpet and pad (counts towards high frequency absorption more so than a thick rug on a hard floor), and I have 6 large (24"x48") acoustical (absorption) panels on my walls - 3 on each wall, plus an extra thick 24"x48" panel on my back wall above my rear seats. I didn't want to make the rear wall completely dead like the front as most advise that you have a dead-live setup with the front wall dead (absorption) and the rear wall live (reflective or maybe diffusion) but I was able to really get some good taming of lower frequencies when I added that 5.5" thick panel to the back wall.
I've been in a home theater that was fully tested and designed by an expert acoustician, and it was absolutely amazing, but that room cost $800 for the room analysis and acoustical plan (actually cheap, but because the expert had the homeowner take the measurements with equipment that they shipped him to save on flying the expert out to Iowa), and then they worked up a ton of DIY acoustical panels specifically designed for his room. It took the guy about a month, he said, of working every night after work and a bit on weekends to get all of those done (again, lots of time). It was a small price to pay for him though. I mean, he put in a separate $15,000 or so HVAC unit just for his home theater so that he could pump in cold air in winter when the rest of the house was getting heat, and so that in summer, the rest of the house wasn't an ice box just to keep the theater cool.
For more info on it, and even a 21 minute video done by the acoustician in post #5, go here (16 minutes 40 seconds into the video shows the left side wall with the fabric panels removed and the many, but not all, DIY treatments that were designed specifically for that room):
The Savoy Theater In that same post (#5) it shows the slides that David (the homeowner) used for the get together that I was at. There are some slides showing the plans for the acoustical treatments as well as general construction.
Oh, and to accomplish this, he lost something like 2 feet of space for each side wall and the rear wall, the front screen is something like 4 feet from the actual real wall.
