Ed,
> Lot's of science to discuss here! Where do you want to start? <
Yessss!
> As I recall, 12 degree's will eliminate standing waves. <
You're thinking of the minimum angle needed to avoid flutter echo between parallel surfaces. While that does affect "standing waves" at higher frequencies, it does nothing for the stuff below 300 Hz which is the real problem in most rooms.
> Personally, I don't care much about what is happening at the back of the room Ethan. It is what I hear at the mix position that counts. <
I agree 100%. But what many fail to understand is peaks and dips at the mix position are caused by reflections off the walls, floor, and ceiling. This is why bass traps are always put in the corners and often along the rear wall. That's where the damaging reflections occur. Reduce or eliminate reflections off the back wall, and you flatten the response at the mix position.
> Explain to me how a 12' room can have standing waves at 100Hz and below! <
Easy. First, the real culprit is acoustic interference, which is a more general case. The reflections I just mentioned happen at all room boundaries. There is always a null 1/4 wavelength away from every boundary. For 100 Hz that's about 34 inches. There's a corresponding peak at 1/2 wavelength away, which is about 5-1/2 feet. There are other peaks and dips at the wavelength multiples - a null at 3/4 wavelength, a peak at 1/1, and so forth. This happens at all frequencies in all rooms. So for small rooms in particular, where you're within 10 feet of the back wall, the low frequency response is a continuous roller coaster of peaks and dips that skew the response by 20 dB typically. If you have a room in that size range in your house, play a 100 Hz sine wave and walk toward and away from the walls. You'll immediately see what I'm talking about, and realize the importance of bass traps in small rooms.
> I seriously doubt your bass traps are going to do much for that either except to add a bit more density to the walls. <
I can tell you for certain that bass traps make an enormous improvement at 100 Hz in small rooms. Here's a plot of my partner's 10x16x7 control room showing the response with and without wood panel bass traps:
But I think you're missing something important. When my partner and I started RealTraps last year, our main products were wood panel bass traps. In April we started selling MiniTraps, which are an entirely different product and work on a completely different principle. Now this is pretty much all we sell. If you get a chance, stop by our site and look at the MiniTraps page. In particular look at the specs, the explanation of how we measured them, and the comparison to other product.
> people in small acoustical spaces suffer more from blurred transients from hard early reflections at their mix position. <
I don't know if they suffer "more" from early reflections, because a response that varies by 20 dB continuously throughout the low end is about as damaging as it gets. But I surely agree that early reflections are a big problem. And as with low frequency peaks and dips, most home studio owners have
no idea they even have this problem!
> What I read little about from people with DEGREE's in acoustical design is bass traps. <
Have a look at any book on recording studio design and you will find entire chapters on bass traps.
> these walls are going to let lower frequencies pass right on through, and even if they hit a super rigid surface a few feet later, you now have an air pocket and the wall again to act as a bass trap. <
Yes, a wall that's not massive can serve partially as a bass trap, but that's never a complete LF solution. Unless the wall is very thin, like 1/4 inch plywood, the resonant frequency will be too low to be useful. The biggest problems are from about 80 Hz and above, and a sheetrock wall resonates lower than that. More important, suich absorption is fairly narrow. What's really needed is broadband absorption across the entire bass range, and no standard wall construction can do that.
Since you seem to need convincing that bass traps are even necessary at all, I strongly urge you to play various sine waves and walk toward and away from the walls. I am certain that will change your opinion very quickly.
> I just find it troubling that your bass traps are about the only acoustic treatment I see you suggest, even when you don't know a thing about the person's room. Always the link to your website that sells these things. <
There's another misconception. First, I truly believe that broadband absorption is what
all smallish rooms need more than anything else. I've been on this bandwagon for nearly 30 years. I've been selling bass traps for less than one year. I don't need to know anything about the room to suggest bass traps. If it's a room, it needs them! Now, they may need other things, and how many traps and where they go may vary. But the core requirement for broadband trapping is absolutely universal.
Your real misunderstanding here is my advice and links. It is very rare for me to refer people to my company's site. I post here and about 20 other groups every day, and what I always link to is my Acoustics FAQ. This is an unbiased and totally non-commercial article that explains acoustic treatment. Much of the article explains how to build your own treatment. My partner complains that I shouldn't be so free with DIY help because he worries folks will build their own rather than buy. But I feel
so strongly about the importance of acoustic treatment that I'd rather see people make their own than go without. You can verify this easily by searching on my name here and in all the other popular newsgroups and web forums.
> It would be interesting though to compare yours with the RPG brand ... It is impossible to argue which is the better performance vs. price unless they can be directly compared. <
That's what absorption specs are for! Again, please go to the RealTraps site and read up a little bit. I suspect you will be very surprised.
> I was just thinking about how speaker box compression, crossover designs, amplification ... What about temperature control <
Yes, all of those are important. But first you have to get rid of the 20 dB LF response variations that are far more damaging!
--Ethan
