Home made Skyline Diffusors

Brent Jason · Post by **Brent Jason** » Wed Aug 04, 2004 1:06 am

great thread

does Balsa have sound-absorbing properties? i read the rpg skyline page and it shows an uneven absorption for the styrofoam versions they sell.

PVC won't burn by itself, it's self-extinguishing, or so i was told when remodeling part of the club i work with recently.

Rpro · Post by **Rpro** » Wed Aug 04, 2004 5:30 am

Here are some photos of my custom built rear wall diffuser.

Ptownkid · Post by **Ptownkid** » Wed Aug 04, 2004 11:34 am

oh my good word, that looks so rad.

How much did that beast run you?

Rpro · Post by **Rpro** » Wed Aug 04, 2004 11:36 am

It cost me close to $800.00 US.

AndrewMc · Post by **AndrewMc** » Wed Aug 04, 2004 2:29 pm

Whoa - that looks incredible. I bet you were relieved when you stuck in the last piece of wood !

Henrik · Post by **Henrik** » Wed Aug 04, 2004 5:52 pm

Ditto WHOA!

Are those based on the BBC prototype module, or how are they constructed?

Cheers,
Henrik

Rpro · Post by **Rpro** » Thu Aug 05, 2004 4:40 am

The diffuser was designed and constructed by me by lag bolting a 2" X 6" PT frame to the concrete wall then two 3/4" sheets of plywood were doubled up and attached to the frame. Next, Douglas Fir balisters were compound mitered to varying degrees and lengths to achieve diffusion.

I had to constantly adjust the balisters to give desired results read through my trusty Agilent 8594E 3 GHz spectrum analyzer. Once the desired configuration was found, I removed the diffuser from the wall laying it flat on the floor then glued and brad nailed each piece.

Be patient, the diffuser construction took about a month.

Henrik · Post by **Henrik** » Thu Aug 05, 2004 6:47 pm

It looks beautiful, great job! I've been in touch with a wood firm (or whatever they're called in English), that said they'd be happy to cut up all the pieces for me and sort them in different boxes. So I'm thinking of doing that, and then just trusting the BBC papers. It will surely be a lot better than the diffusing panels I can afford. I'm counting on cost being something like what you mentioned, 800 USD. That's for 14 BBC panels, 600x600 mm.

Cheers,
Henrik

hookiefree · Post by **hookiefree** » Tue Aug 10, 2004 7:27 am

[quote="Brent Jason"]i read the rpg skyline page and it shows an uneven absorption for the styrofoam versions they sell.
[quote]

Is this good or bad? I thought about doing this with styrofoam. Seems like it would be the easiest way to go.

Bassist_ · Post by **Bassist_** » Wed Sep 01, 2004 2:59 am

I think this is a nice little web site... does this help anyone?
http://www.mhsoft.nl/DiffusorCalculator.html

I would love to build some of these when the time comes...

Cheers
Steve

dudleylaw · Post by **dudleylaw** » Tue Jan 04, 2005 8:46 am

Please send information re: where you purchased the @" X 2" X 12" balsa wood blocks for $1.02 each. The best price I could find was in excess of $3.00 each. Also, have you made a "skyline" with the balsa wood yet? How did it turn out? I would like to do this for first reflections from the ceiling in an audio listening room. Thank you for you time to reply. Dudley Miller, Indianapolis

sverige_cruz · Post by **sverige_cruz** » Sun Feb 06, 2005 4:09 pm

Hello everyone, glad to join in on an old discussion. Hopefully I will not be kicking a dying horse (or whatever that expression is...

)

Regarding the BBC papers about building one of those diffusers, I had been thinking about a light and somewhat cheap material to build them...and the only thing that came to mind was EPS (extended polystyrene foam?) in large sheets from the local hardware store... but how to cut that stuff? I found some hobbyists on the web using hot wire cutting techniques to make semi-clean cuts by melting through the foam. I tried this, poured some glue on the pieces and came up with this:

I've only made one so far, as it's not so much fun building, but it may spark some ideas. I don't know if this stuff is a viable material for practical use (fireproof, density, etc...) but it was interesting putting it together. If this helps at all, cool - if I wasted my time (as in, the foam ain't good for diffusion), please let me know, so I don't go mad cutting foam in my garage.

Thanks to all here for all their knowledge. I'm just getting started with this acoustics thing.

Best Regards,
Jesus

tenkas · Post by **tenkas** » Mon Feb 07, 2005 10:43 am

I read the BBC paper, and I have to admit, my English is not good enough to understand everything. The plan shows that there are 4 or 5 different lenghts of wood or pvc pipe. Now, how do I know what length is (on the plan) the # 0 , the #1, the #2... I mean, how do I know that all #2 are 28mm (hypotheticaly)

thx

Jon Best · Post by **Jon Best** » Mon Feb 07, 2005 11:52 am

Henrik wrote:OK, cool. I'll try it myself some day. It DOES seem a bit tedious to make them out of 1156 17 mm wide pieces of wood...

That's why you see more of the 2D diffusors built for wider-band absorption- you know, the ones with vertical wells of different depths instead of the 3D ones with squares. If you've got a fairly absorptive ceiling, it doesn't probably matter if what hits it is diffused or not.

One thing that's interesting to me is the idea that when you make a *2D* diffusor without walls between the wells, it drastically reduces it's effectiveness: I wonder if it's true with the 3D versions?

sverige_cruz · Post by **sverige_cruz** » Mon Feb 07, 2005 2:55 pm

I just found this site, regarding the diffusers...

http://www.bobgolds.com/DifuserKgveteran/home.htm

I guess I didn't spend enough time searching the net before I sat down and though about this. I'm sure I'm not the 1st to do that... it's just proof that I'm new here...

tenkas: I just assumed from the BBC article about the lengths. I think they give a particular length as the deepest, and looking at the drawings, it looked to me like #2 would be half of that, and #1 half of #2, and #3...etc... (I think this is what you're asking, no?) Hope it helps.

-- Jesus

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