specifications of "average" bookcase?

In my new design I count with some bookcases so I'd like to know what it does to room response... what does it absorb and how it diffuses? thanks a lot

Hmmm. I can't find any absorption data for a bookshelf. It would certainly depend on the average book height and depth, the average distance above and behind the books, etc. Might be difficult to come up with generic numbers that bears any meaningful relationship to a specific case. But I'll keep an eye out. Thomas

thanks, thats my problem too... there is no info around. I know there are many many variables, but let's make it for A4s - cca. 22cm deep. I think this would be valuable info for many home-studio owners....

I would think you would want to defy the normal approach to bookshelf population - namely, the organizing of books by height and spine depth. Rather, you'd want to mix the pocket guide paperbacks with the giant coffee table books, to produce a pseudo-random diffusion pattern. That's what I'm gonna do as I begin the book-fusor process in a few weeks.

And what about to make bookcase as a big quadratic difusser at the rear of the room and fill it with "random" books'n'things... could be nice'n'broadband ;-).

Matucha, that was the original intention of the "bookcase bandaid" diffusor idea - to come as close as possible to the effect of a QRD - It's NEVER going to be as RANDOM as an intentionally calculated and built diffusor, and if you had to go out and BUY all the books for a good sized "BSD" (Book Shelf Diffusor :? ) as well as buy the book shelf, it would probably be cheaper to just buy the real thing. The original point was to save money by using things that are already available, much the same as placing a couch at center rear of the control room to help with bass trapping. (Only the FRONT parts of the couch will do much good, since bass traps need to be away from the wall) Two other things that have NOT been brought up here - 1 - even an expensive commercial QRD won't get very low in frequency, so "nice and broadband" doesn't include low frequencies. A typical diffusor or bookshelf depth will only get down to about 400 hZ if you're lucky, unless it's several feet deep. 2 - Unless your room is large enough so that there is at least 10-12 feet from the back of your head to the rear wall (seated at mix position) then all of this is moot. Without that amount of distance, you should be absorbing the rear wall to avoid early reflections. To sum it up, if your room is small, a "BSD" would arguably be (a little bit) better than flat, non-absorbed rear wall but nowhere near as good as absorption. HTH... Steve

I know this discussion is mainly about small rooms, but still this is worth taking a look at. It's the main liveroom in a Belgian studio. Not sure if I could copy their foto's, so a link and short description will have to suffice. http://www.motormusic.be/showimageitems.php?studio=s1 A few nice pics of book shelf treatment there. :) Cheers, Sigert Hiphip hooray, my first post on this forum.

i think the link here is interesting but I'd wager the large room and high ceilings play a more critical role in the overall sound of the tracking space than the book shelves. part of the problem with diffusers in a small room is they need to be at least the a certain away from the listener to avoid acting as a flat wall in terms of incident angles for dispersion and combing effects. this means if you have a 7 1/2 feet, then people sitting right below them aren't likely to perceive "diffusion" as the person in the mix position will (assuming they're at least that far away...) and even so, any thing not diffused will reflect back at 15ms (at that distance) to the mixer - so reflection point absortion will still likely be needed... or the diffusers need have enough bandwidth to affect more than just a narrow range of frequencies - which usually means varying diffusers to cover a wider ranger... which means depth and coverage complexity.