qrd floor to ceiling without fins between the panels

jrp · 31st July 2011

I was wondering if it is possible to build a diffusor without fins.
Just wooden panels that go from floor to ceiling, the space between them being open.
Why am i thinking about this?
I got the wooden panels for free, it might look nice and is easy to build. It saves a lot of material and weight also.
The drawing shows it from the top.

Jens Eklund · 31st July 2011

Unfortunately, the fins of a QRD is there for a reason. Removing the fins will degrade the diffusion performance of a QRD, especially for random incident energy. It will still scatter some but not uniformly and especially if other incident than normal or close to normal. It is possible to make diffusers without fins (called “stepped” diffusers) but then the shape needs to be altered to ensure good scattering performance. This is usually simulated with BEM-math and my model, the “Optiffuser” is an example of this.

jrp · 31st July 2011

hm, i was somehow expecting this. It coold be turned into a very cool lamp when lit from behind and is an really easy build compared to the classic design. Still it´s a lot of work if the result is a failure.
Something makes me want to try this...

Mister Fox · 31st July 2011

Then why not combine the idea of a diffusor with an absorbtive wall.

Put rockwool (wrapped in dark cloth) behind the pannels, and still add light. You'd get "somewhat" diffusion, absorbtion, and you have a nice ambient light.

Depending on your desired sound and room specs of course. But if it's maybe just 1,5m wide on a 3m wall, it'd be both an eyecather and usable absorber/diffusor.

If everyting fails, you can still build it back - no?
If in doubt, build a smaller model (vertically) and do measurements first.

jrp · 1st August 2011

well, a smaller model might be interesting, but then it might be more work than the actual thing.
Also, i am not sure if i am able to measure the effect of an diffusor in my room with my equipment.
Filling the space behind the diffusor with mineral wool could be very nice, but it could just as well make the room sound to dead...
Maybe a bit much "don´t know" for building something like this.
There are known concepts that work and that can be used...

31st July 2011	#1
jrp Gear addict Joined: Oct 2006 Posts: 352 Thread Starter	qrd floor to ceiling without fins between the panels I was wondering if it is possible to build a diffusor without fins. Just wooden panels that go from floor to ceiling, the space between them being open. Why am i thinking about this? I got the wooden panels for free, it might look nice and is easy to build. It saves a lot of material and weight also. The drawing shows it from the top. Attached Thumbnails

31st July 2011	#2
Jens Eklund Lives for gear Joined: Oct 2009 Location: Stockholm Posts: 2,999	Keep the fins Unfortunately, the fins of a QRD is there for a reason. Removing the fins will degrade the diffusion performance of a QRD, especially for random incident energy. It will still scatter some but not uniformly and especially if other incident than normal or close to normal. It is possible to make diffusers without fins (called “stepped” diffusers) but then the shape needs to be altered to ensure good scattering performance. This is usually simulated with BEM-math and my model, the “Optiffuser” is an example of this.

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31st July 2011	#4
Mister Fox Gear maniac Joined: Jul 2011 Location: Berlin, Germany Posts: 157	Then why not combine the idea of a diffusor with an absorbtive wall. Put rockwool (wrapped in dark cloth) behind the pannels, and still add light. You'd get "somewhat" diffusion, absorbtion, and you have a nice ambient light. Depending on your desired sound and room specs of course. But if it's maybe just 1,5m wide on a 3m wall, it'd be both an eyecather and usable absorber/diffusor. If everyting fails, you can still build it back - no? If in doubt, build a smaller model (vertically) and do measurements first.

1st August 2011	#5
jrp Gear addict Joined: Oct 2006 Posts: 352 Thread Starter	well, a smaller model might be interesting, but then it might be more work than the actual thing. Also, i am not sure if i am able to measure the effect of an diffusor in my room with my equipment. Filling the space behind the diffusor with mineral wool could be very nice, but it could just as well make the room sound to dead... Maybe a bit much "don´t know" for building something like this. There are known concepts that work and that can be used...