well divider width in qrd?

[djjohnnybravo]

hi! all i'm going to build a QRD for my studio using mhsoft calculator , and i got one question what should be the width of well divider? becosue all other numbers are easy to generate by calculator but this value are missing , it seems like important thing in projecting this qrd for accurate 1000hz range



thanks for help

[FastlanePro]

The width of the wells corresponds to 1/2 wavelength of the highest frequency you are attempting to diffuse.

Cheers,
Lane

[djjohnnybravo]

so following this what You have said, usging 3649,6 hz as the highest frequency i get these numbers :



dividing this 9,4 centimenetrs for 2 is 4,7 and this witdh for slat is to high em I right?

what do You think?

[FastlanePro]

Maybe I'm missing something, but isn't 4.71cm exactly what the QRD calc told you?

Unless I'm missing the point (or my cold medication is turning my brain to mush), I think you just proved the calculation worked...

Either way - the well depth of 4.71 appears to be correct for the upper limit of bandwith you are talking about.

Also note that the bandwidth isn't a "hard line". There will be diffusion well above the BW - but it may be degraded somewhat in the uniformity of pattern. Similarly, the pattern won't likely be perfect right up to your theoretical upper limit either. Think of it as being a bit like a microphone polar pattern. There will be variability dependant on frequency.

If I've said something incorrect I'm sure one of the resident experts will chime in. They're good that way - and many are way smarter than I am.

Cheers,
Lane

[djjohnnybravo]

Lane all my infos are based of that calculators that screens i have put above

thanks

[FastlanePro]

Hah! My brain *is* mush. I just realized you were talking about the width of the physical divider between wells, not the well itself.



I've never actually seen a guideline for allowable "divider width". Intuitively, the divider with should be significantly less than the well width - otherwise it would become significantly reflective with respect to the wavelengths you are talking about.

This is really more of a "construction" issue rather than calculation - though I definitely understand your concern. My best advice is to look at either commercial products or other DIY threads to see what others have done. What method/materials were you planning on using?

Clearly the construction has to be substantial enough to be ridgid, etc. But again - the dividers should be "significantly" thinner than the wells. In fact, many are made with no divider. It all depends on how you build it.

Anyone else out there have a concrete number?

Lane

[djjohnnybravo]

yeah , Lane we Was talking of two different tings hi hi hi

i'm tying to use chipboard or MDF as the frame of QRD , dividers of well will be made of slat/plywood - (i'm not shure if the name is correct,= very tinny piece of real wood , not mixed or not from scratch )

and i'm going to fill the acuurate lenght for each well by the fiberglass just like in REALTRAP's QRDs

[Lonely Raven]

You could also try QRDude


QRDude: Quadratic Residue Diffuser calculator

It gives you quite a bit more information to get you started on your QRD.

[djjohnnybravo]

thanksa Bro this software is nice and will be helpfull mary x-mas

[SaSi_SiDi]

The well dividers (fins) need to be as thin as practically possible. Ideally they should have zero width and infinite rigidity. And since this is impossible, we need to settle for as thin as possible and as stiff as possible.

Among lumber varieties, chipboard would be unsuitable as at low thicknesses it just breaks, MDF is stiff but fragile and plywood seems to be the best match as it's pretty solid even at 3-4mm widths.

Plexiglass has also been used. Harder to work with than plywood but can be even more rigid at 2-3mm widths.