Diffusion Questions

I would like to say this forum is fantastic! I am building a new studio in my home. I don't see much talk around here about diffusion in bigger live rooms. I'd like to talk about diffusion in general, and also hopefully draw some conclusions for my own benefit. Let's say you have a 1300sqft live room. The ceilings are between 18-20 feet. There are no parallel walls... Floors are wood. There are 8 superchunks bass traps in the corners. There will also be bass trap clouds hung from the ceiling. There are some slot resonators built in at alternating 15 degree angles to create a more diffuse slat wall. Sort of like in this thread:http://www.johnlsayers.com/phpBB2/viewtopic.php?t=7182&postdays=0&postorder=asc&start=15 I am very curious to learn about proper diffusion practices. How much diffusion needs to be on the wall? Does there need to be alot of diffusion hung from the ceiling? I've got bas traps and absorption down pretty well, I just can't find too much info about how much diffusion and where. I'd like not to go overboard with difussion. But I have calculated that I need somewhere in the neighborhood of 10-15% coverage and that would be roughly $15k for my live room. That's fine if I have to, but I really want to be smart about my diffusion purchases. Thanks Guys

Zero, I don't have a definitive answer for you, but I can tell you a story. :) I worked on a live room of roughly the same size a number of years ago. The existing room already had ample low frequency control and absorption. In other words, the "RT" was completely acceptable. The walls were gypsum wallboard; the ceiling was acoustical tile, about 15'-18' high; and the floor was hardwood. There were some nice built-in bass traps for LF control; some wall panels and hangings; some area rugs; the room sounded OK. The complaint the owner and recordist had was that they had to really work to get a good recording. Even though the room sounded OK, they had a hard time finding the best placements for microphones when recording just about anything in the room, be it a solo guitarist or a group of singers or a full drum kit. They would eventually "get there," but for what sounded like a decent room, it just seemed to take a disproportionate amount of time to "get there." What I suggested to them was replacing about 25% of the ceiling tiles with diffusers; then taking the equivalent area of removed ceiling tiles and adding that much absorption to the upper half of the walls. After doing this, it was determined that about a dozen or so more diffusers were needed on the upper walls, mixed in with the absorbers. (All treatment sizes were 2'x2'.) The end result was a room that sounded more or less the same, but much more uniform. Both the owner and recordist found that they spent about 1/4 the time miking up the instruments, thus leaving much more time to capture great recordings. I was fortunate enough to hear performances in the room both "before" and "after." It was apparent that, even though the general quality of the room was unchanged, the "after" version possessed a character that was more conducive to music recording. So, while there's no quantitative answer as to the amount of diffusion you should be considering, I think it's safe to say you will need some diffusion for the room. IMO, start with the ceiling, evaluate, then add more on the upper walls if you feel you need it. (At least, that's one approach...) HTH.

A great story. Thanks Jeff. Andre

Ouch! I am building a new room with similar size and proportions. Having never built a room of this size, I have probably underestimated the challenge of making such a large room sound great. I am coming close to the time where I am going to start to fit the room out acoustically, now I am getting super nervous. Maybe it's time for you to do some consulting with someone who can help you figure that out. I am going to consult with John on my final live room acoustics... but i am starting to think this is going to be a pretty daunting task.