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Polys in QRDs: Glenn, care to share some tips?
Old 16th September 2011
  #1
Lives for gear
 

Polys in QRDs: Glenn, care to share some tips?

Before, Glenn's Poly-QRDs were just awesome eye-candy to me. But now that my woodworking skills have greatly increased, I'm considering trying them. Just for the fun of it heh

With the acquisition of several Hammond organs, I've decided to make my apartment living room into a live-ish room instead of a control room kind of thing. So I'm considering some polys/diffusers to augment my bass traps, get rid of some flutter, and make the walls look less... wall-ey. Plus I need something to do on the weekends


So, a few questions...
1) Do the mini polys need to be a certain arc to be effective? I never really paid much attention to polys before, but I seem to have "1/3 of a circle" stuck in my head. Is this a good angle/starting point? I can't really tell from Glenn's pictures, but it looks like a smaller arc than 1/3 of a circle.

2) Will the mini polys detract from the performance of the QRD? And if so, will they add enough to make the difference worth it?

3) Do the mini polys have to be a certain thickness to be effective? Probably basic poly knowledge, but like I said, I don't really know.

4) Will this just become a funny looking QRD or will it actually be helpful in a live environment?



Thanks for the inspiration Glenn. Hopefully I can actually make something. Then you won't be the only one hogging the poly-QRDs!!!
Old 16th September 2011
  #2
Gear Guru
 
Glenn Kuras's Avatar
Your welcome.

Actually the person that come up with the idea was Dr Jason Jones. I am going to email him to see if he has time to give any insight on them. But with that said without a full blown work (CnC and so on) shop I really can not see doing these as a DIY project
Old 16th September 2011
  #3
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Jens Eklund's Avatar
Quote:
Originally Posted by Torea View Post
2) Will the mini polys detract from the performance of the QRD?
Probably.


Quote:
Originally Posted by Torea View Post
And if so, will they add enough to make the difference worth it?
I don’t think so and I think a higher order normal QRD will perform better but I need to model it in Reflex do be sure, perhaps later this month.
Old 16th September 2011
  #4
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Quote:
Originally Posted by Glenn Kuras View Post
Your welcome.

Actually the person that come up with the idea was Dr Jason Jones. I am going to email him to see if he has time to give any insight on them. But with that said without a full blown work (CnC and so on) shop I really can not see doing these as a DIY project

Well, I've got a lot of time on my hands at the moment. If it seems possible, I'll give em a shot. They look pretty awesome heh


Quote:
Originally Posted by Jens Eklund View Post
Probably.


I don’t think so and I think a higher order normal QRD will perform better but I need to model it in Reflex do be sure, perhaps later this month.


If you don't mind modeling them out, that would be great! Even just for all the other folks who've been curious.
Old 16th September 2011
  #5
Gear Addict
 

I remember playing around with poly-topped wells in AFMG Reflex Beta several months ago.

I didn't keep the data but I remember being quite disappointed with the result, compared to flat-bottomed wells.

If I recall correctly, there was a small gain in very high freq scattering but the mid frequency scattering and diffusion was significantly worse. I played around with varying the size of the curves as well and couldn't find a happy medium. Tried with and without well dividers.

The principle is that QRDs work via destructive/constructive interference of sound waves reflected from wells of different depth having travelled different path lengths. Simple QRDs like N7 have reasonable mid-freq performance but run out of puff at higher frequencies. The intention when curving the tops of the wells is that for mid-frequencies, a slight curvature of the well shouldn't affect how the sound wave is reflected as sound at that wavelength can't "see" the well as curved, but the curvature should be effective at extending the frequency range at the upper end of the range of the QRD.

If curved-well diffusers were to be effective then they could be very cost-effectively produced from high-density expanded polystyrene block. I would like to see Jens have a go at some REFLEX models (when he has the time) as when I tried I was quite unsuccessful at it (but then it appears he might have the knack for this sort of thing - certainly more than me).
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