Portable Diffuser / Absorber

Just thinking about treatment for my "live room" - which also doubles up as a bit of a gym, so I can't have any perminant treatment in there. I was thinking about making about 3 of the attatched picture. Basically your average diffuser, but with an "open" back, which is filled with rockwool. I figure if I wanted more of a "live" sound I have the rockwool side against the walls, dead and the diffuser side goes against the walls. The room is a about 3 x 5 meters. I'll probably be mostly recording more "acoustic" music - guitars, drums, vocals etc. Just wondering if its a good idea or not? Cheers, Gareth

the QRD depends on the the reflection from the back of the cavity to do its work. besides the diffusion, QRD also have absorption properties. you could set the diffuser (or diffusers) into an absorption treatment wall which allows bass into corner traps and provides some mid-high absorption, and has the diffusion...

Thanks for the response! I don't mean to be rude, but I'm not sure if you've understood the design as I intended (more than likely my fault with my explanation!) I understand that diffusion needs a hard surface to work - the idea of the "gobo" was to have one side diffuser - one side absorber. Here's a cross section. However I was reading up on some threads over at gearslutz and there was a lot of talk about being too close to diffusers, and for this type you'd want to be about 9ft or so away? If thats the case maybe its not such a great idea as these would probably be no more than 5ft away from a drumkit at least. Would probably just make 9ft if it was a single guitarist. Maybe making some slat absorber gobo's would be a better idea to keep the liveness of the room - I don't want to fill my room with absorbers and have everything dead dead dead! Cheers Gareth

ok, gotcha! filling the back with rockwool is fine - from an isolation gobo perspective through, you might consider a layer or two of MDF or drywall to beef it up internally. as far as proximity, a 2D QRD is probably a better choice, otherwise i would tend to keep them further away - and i'd probably keep them away more for the purpose of shaping a given space than purely isolation (which is what i'm assuming you're also looking to do).

gullfo wrote:

ok, gotcha! filling the back with rockwool is fine - from an isolation gobo perspective through, you might consider a layer or two of MDF or drywall to beef it up internally. as far as proximity, a 2D QRD is probably a better choice, otherwise i would tend to keep them further away - ****and i'd probably keep them away more for the purpose of shaping a given space than purely isolation (which is what i'm assuming you're also looking to do)****.

Good idea - Yeah an inner "wall" would probably be better. A 2D QRD is along the lines of an Auralex Space Array if I'm not mistaken? Hm - that would be a lot harder to make so I'll have to give that some thought. What do you mean by the last bit? [in asterisks] - probably just me being stupid? Do you mean they'd do a better job of "creating a better room sound" rather than as "isolation gobos" - if so - yeah - this was the intended idea (room sound!). Cheers Gareth

What do you mean by the last bit? [in asterisks] - probably just me being stupid? Do you mean they'd do a better job of "creating a better room sound" rather than as "isolation gobos" - if so - yeah - this was the intended idea (room sound!).

Your interpretation of Gullfo's statement matches mine, FWIW. :)

Great idea! In addition to what Glen wrote, the distance guideline is 3 times the wavelength of the lowest frequency diffused. If you want to 3/4 of width usable without lobing, go for a wavelength of 1/4 m, or about 1 kHz. Enjoy! Andre

AVare wrote:

Great idea! In addition to what Glen wrote, the distance guideline is 3 times the wavelength of the lowest frequency diffused. If you want to 3/4 of width usable without lobing, go for a wavelength of 1/4 m, or about 1 kHz. Enjoy! Andre

Thanks! Just trying to avoid sucking all the "life" out of my little room :D 3 times the wavelength..? So that would mean for example, if these were going to be positioned 3ft away from the source, the lowest frequency would have to be around 1k? (Just checking to make sure I understand this properly). So according to this calculator: http://www.mhsoft.nl/diffusor.asp#calcul With the numbers: Width: 150cm Theoretical Depth: 12cm Prime Seed: 19 I get a bandwidth calculation of: Low - 1017Hz High - 2657Hz It appears that I'd need quite a high prime seed in order to start the diffusion at around 1kHz? Wondering whether it would be easier/better to make one of Johns helmholtz gobos..? Cheers Gareth

You have the idea right. You seem concerned about the high prime number. Why? You are dealing with high frequencies, so dimensions are small. John's diffusors still absorb lows. Nothing wrong with that, but a different acoustical effect. Your choice, soup or consume. Andre

AVare wrote:

You have the idea right. You seem concerned about the high prime number. Why? You are dealing with high frequencies, so dimensions are small. John's diffusors still absorb lows. Nothing wrong with that, but a different acoustical effect. Your choice, soup or consume. Andre

Only because it would be a lot more work to make something with so many wells. I'll have to have a think about it :? I actually completely forgot to upload the dimensions of my room. Its in this post now. As you can see, the room isnt huge and will double as a gym. Mostly this is concerning drums, as everything else should be workable. The drums would have to go to the left of the room. I'd then put one of these gobos on the back wall (the longest one), one infront of the window, and one at an angle across the corner where the room gets smaller. I'd then put some corner bass traps and some 703 panels wherever possible, and some form of ceiling cloud. What do you think would work best in this room? I quite like the idea of diffusion, since I don't really want a very dead sounding room - I feel it just sounds quite tubby with no life. However, I would like quite a controlled sound - I'm not expecting the "big rock drum" sound here. Do you think the diffuser idea would make a nice drum sound, or would it be better to use johns design and directly absorb as well? Cheers Gareth

It depends on how bass trapping you will be putting into the room. If there is not enough, then John's design. If you do, then the Schroeder diffusor, to the option of a bit more low end when tracking. Again, sort of, chowder or stew. :) Andre

or just treat the room and make it a nice sounding exercise/live room... http://img175.imageshack.us/img175/1844/garethhreessr3.th.jpg http://img174.imageshack.us/img174/3479/garethhreesrenderem0.th.jpg

gullfo wrote:

or just treat the room and make it a nice sounding exercise/live room... http://img175.imageshack.us/img175/1844/garethhreessr3.th.jpg http://img174.imageshack.us/img174/3479/garethhreesrenderem0.th.jpg

Glenn thats absolutely beautiful! As its in my parents house they don't want to modify the room - but to be honest if I can make it look like that.. they might be convinced! However, for now I don't really have the cash for something quite as extensive as that, and more of my work seems to be location recording and mixing at home at the moment. Definately something I'll pester them about though :D Again, I forgot to upload the plan of the room in the last post some how! Here it is, just for reference: Cheers Gareth

maybe like this then