Poly cylindrical diffusers aren't really that complicated. They are the poor mans solution to diffusion, and there is no formula per say, but it is nessesary to put some fluffy insulation behind them to dampen any resonances if you are sealing off the tops and bottoms. If you have the time and patience to build skyline diffusers they do a much better job at actual diffusion, rather than just scattering the reflections. I guess you could calculate the resonance of the diffuser if it is sealed, and tune it to trap a specific frequency as well. They do not have to be one half of a circle, they can be bent into a gentle arc as well. It it not recommended the two be placed side by side without any gap as they create a focusing parabolic effect. If you need to place them side by side some absorption between.

I'm not aware of any sort of calculations or formulas for diffusion, as there are for like absorbstion coefficients. I think it gets pretty complicated pretty fast, and I've never seen anything like that in any of the books I've read. Although I do believe there are requirements for the volume (physical room volume) for you to actually achieve a "truly" diffuse environment/diffusion. You really should check your local library d, and see if they have the master handbook of acoustics, by f Alton Everest. That's where I got it, and had it for a few years lol. It covers a lot of the stuff you've been investigating lately, and you don't need a PhD to understand it.

I'd really be more concerned about bass trapping, than management of the mids highs. What you have built already for diffusors is probably gonna be just fine, considering the size of the room.

There will be some absorption with the type of polys I have seen. The thin 1/8th plywood will allow bass to penetrate and be absorbed somewhat by the fluffy fibreglass,as well a consuming some energy while entering and exiting the diffuser.Mids and highs will bounce off, but who knows what the cut off frequency will be, and phase relationships at the the cross over point will have changed, due to the exiting waves starting at zero, and the reflected waves keeping the same relationship with themselves.

See https://recording.o… .. this is a new thread topic I have created to attempt to reign all of my other posts into one thread.

d/

Audiofreek, post: 415988, member: 45862 wrote: Poly cylindrical diffusers aren't really that complicated. They are the poor mans solution to diffusion, and there is no formula per say, but it is nessesary to put some fluffy insulation behind them to dampen any resonances if you are sealing off the tops and bottoms. If you have the time and patience to build

blah, blah blah. Read a book Audiofreak.

Heck read this PDF file on polys given link by Andre:
http://www.gearslutz.com/board/attachments/studio-building-acoustics/208284d1292187681-polycylindrical-diffuser-design-volkman-polycylindrical-diffusers-1.pdf

While I respect a persons attempt to make the complicated uncomplicated as you suggest AudioFreak, you have to know the complicated first:)

Donny,

check [[url=http://[/URL]="http://www.xix-acou…"]this[/]="http://www.xix-acou…"]this[/] out

Here is one for us - Do we even need to be this concerned at lower volumes?

you can't just mandatorially set a listening level and get accuracy. the human ear hears flat at or near 85dB. refer to[[url=http://[/URL]="http://www.google.c…"] Fletcher Munson curve [/]="http://www.google.c…"] Fletcher Munson curve [/]....

at lower levels of 60dB you will not hear a flat signal. the chart shows an astonishing attenuation @ 1 Khz. of 60 dB. we really should at least reference a mix at 85dB at least once in a while. we cannot compensate for bad rooms by simply turning down the volume. no magic bullet.

here's what a diffuser does according to Acoustic Ramps site;

In critical listening rooms, an array of (diffusers) make an ideal rear-wall treatment that helps to tighten the definition of imaging and clarifies the sound stage. In surround home theatres and group audiophile listening spaces, .... rear-wall treatment helps to create a sense of envelopment and immersion for the listeners.

The goal of an Acoustic Ramp diffuser is to control the existing acoustics of the room WITHOUT absorbing the acoustic energy. A reflection of sound off a flat hard surface can be disorienting and distracting. A reflection can mix with the source of the sound and cause comb-filtering which changes the timbre or tone-color of what you are hearing. People often describe the effect of comb-filtering as “hollowing out” the sound, making the sound “tinny”, or sounding like it is in a “garbage can.” Usually these are not the adjectives we want someone to use when describing our music!

You still need to have enough room for the sound to scatter and coalesce into something relatively even across the spectrum. I'm not aware of any way to calculate this, or to say type in the dimensions of the room, then the distance of the diffusors from the speakers/listeners, and estimate what you'll, get. If there is some sort of a thing it'd be really cool and I'd love to know about it. I'm honestly not being a smart a$$, I really would like to know cuz I haven't seen anything like that.

Rods book, basically doesn't get into it because a typical home studio is too small for diffusion to be practical, so I'm guessing it's either too expensive/time consuming, ineffective, or some combination of the two.

Those things sure do look pretty tho :)

not an expert but i really don't think a small room precludes diffusion. i've seen many booths and small control rooms in very nice studios that included diffusion. if you deaden the room with absorption then diffusion may not be necessary. but no one likes a completely dead room. the cool thing about the ramp is it is broadband. somewhere along the ramp are depths that will apply to almost any room ... my dream C/R would be almost all diffusion with very little absorption and large enough to negate the need for bass trapping.

Maybe this link is helpful

that is the one drawback ... as of yet, no one had designed a cost effective solution. diffusion is expensive. sounds to me like opportunity.

I'm not an expert either, for from it. How I've interpreted it is that, if the room isn't large enough for "true diffusion" for lack of a better phrase, then there are issues on how to predict its effects. But I dunno if I am thinking about it correctectly.

my dream C/R would be almost all diffusion with very little absorption and large enoug to negate the need for bass trapping.

Would it look like this ?

That's George massenburgs place. Pretty cool huh? I'm equally jealous of, and glad I'm not, the carpenter who had the tedium of this job.

There's plans for QRD and the diffusors similar to top what Donny made, in some books and on the web, I'd be curious to know how much he spent on the lumber.

Definately ain't cheap either way, but they are significantly more expensive when buying pre made stuff. Same thing for acoustic doors. Very very expensive pre fabbed. About 3-5x the cost, according to my research, comparing overly doors, to something like in build it like the pros.

We have saw mills around here, this would be pretty simple to get but what a PITA to instal it indeed! Looks like it would feel pretty ugly to be in. I would like to walk in there, just to hear what it sounds like.

kmetal, post: 416130, member: 37533 wrote: There's plans for QRD and the diffusors similar to top what Donny made, in some books and on the web, I'd be curious to know how much he spent on the lumber.

Definately ain't cheap either way, but they are significantly more expensive when buying pre made stuff. Same thing for acoustic doors. Very very expensive pre fabbed. About 3-5x the cost, according to my research, comparing overly doors, to something like in build it like the pros.

plus shipping. A case of RealTraps cost $800 to ship.
My Acoustic Amp box cost $650 to ship. Shipping it the setback for this stuff. But those in the youtube I posted, look like they are really simple and very easy to ship.

Man, I didn't even ask them how much it was to ship the doors. Probably in the 500-1k price range. Those things just looked like plywood strips w some screw holes drilled in them. When your talking reflective properties of wood, the amount of coats of poly you put on them, has a significant effect on its frequency response. I've heard of a couple of studios that put up wood panels, then poly-ed them one coat at a time till they were happy.

The DIYer in me, would just try to find the dimensions of something like this, and just build it myself. But I've been like that my whole life. Lol I build a half pipe skateboard ramp in my back yard when I was 10. Lol I had a scale model made out of cardboard and everything.

I hope someone(s) could post some reading material about diffusion, and the implementation/calculation of it. In this area, of acoustics, I personally feel like one of the people who post the "best LDC for under $200" type things. Any info would surely be welcomed.

http://www.xix-acoustics.com/wp-content/uploads/2011/12/AcousticRampManual-V1.1.pdf

I hope someone(s) could post some reading material about diffusion, and the implementation/calculation of it. In this area, of acoustics, I personally feel like one of the people who post the "best LDC for under $200" type things. Any info would surely be welcomed.

do you have a copy of [[url=http://[/URL]="http://www.google.c…"]F. Alton Everest's [/]="http://www.google.c…"]F. Alton Everest's [/]book? there's a ton of stuff in it on just about everything relating to acoustics .... including bass traps and diffusion.

Space and Andre both recommended this book to me as well. I'm going to pick this one up this week, along with Rod's book too.

try to get the 6th edition. this book has been around for a long time. 6th edition is the latest update.

Thanks for the heads up Kurt. I'll look for the latest edition.

[[url=http://[/URL]="http://www.google.c…"]F. Alton Everest's [/]="http://www.google.c…"]F. Alton Everest's [/]book? there's a ton of stuff in it on just about everything relating to acoustics .... including bass traps and diffusion.

yea its a good book. my interest has been sparked specifically in the realm of diffusion lately, cuz its the area i know the least about.