A QRD diffuser Idea

[cchord59]

I built this diffuser as a prototype to see how it will work. I used this calculator.
QRD Diffuser Well Depth Calculator

I didn't use the free acoustic calculator out there, because I don't have a windows computer.

I just used the rigid pink styrofoam that you can get at the Home Depot, and cut them to the required depths, and then glued them on their side onto a piece of hardboard.

I curious how much less effective this will be considering that their are no sidewalls to the wells, and the foam is not that dense.

These are just samples, so they don't look that good.

I'd love to hear your thoughts, how it could be better.

Thanks

[Nordenstam]

Looks good! IIRC, the pink is about 20kg/m^3 while the blue Dow styrofoam is 32kg/m^3. Look it up though, I'm not totally sure about that! Denser is better. As far as I've gathered from reading, the blue one is reflective down to about 4-500 Hz, while also giving some absorption down to about 150-200Hz. Good enough reflective properties for the application at hand, with the added low mid absorption as a bonus.

The build looks good. Using well dividers will make it quite a lot more effective. As it is now, the diffuser will only provide for the number theoretical performance for waves that hit the array in a perpendicular direction. Grazing angles will see an irrregular surface and something is still going to happen, but it won't give the nice spread in the energy that it could do with well dividers.

Lastly; invert the direction of the end cuts! Where there's a small bump going up above the surface of the well. Having it pointing inwards will be fine, as it is now, it's breaking up the pattern.


PS: in case you haven't noticed, there's a thread about the 2D diffusors I make out of styrofoam.

[cchord59]

Originally Posted by Lupo

Looks good! IIRC, the pink is about 20kg/m^3 while the blue Dow styrofoam is 32kg/m^3. Look it up though, I'm not totally sure about that! Denser is better. As far as I've gathered from reading, the blue one is reflective down to about 4-500 Hz, while also giving some absorption down to about 150-200Hz. Good enough reflective properties for the application at hand, with the added low mid absorption as a bonus.

The build looks good. Using well dividers will make it quite a lot more effective. As it is now, the diffuser will only provide for the number theoretical performance for waves that hit the array in a perpendicular direction. Grazing angles will see an irrregular surface and something is still going to happen, but it won't give the nice spread in the energy that it could do with well dividers.

Lastly; invert the direction of the end cuts! Where there's a small bump going up above the surface of the well. Having it pointing inwards will be fine, as it is now, it's breaking up the pattern.


PS: in case you haven't noticed, there's a thread about the 2D diffusors I make out of styrofoam.

This is great, thanks. I'll check out your thread.

[cchord59]

Is there an acoustic calculator out there like this one for macs?

mh-audio.nl - AcousticCalculator

[Nordenstam]

The same site offers a lot of goodies online: mh-audio.nl - Home

IIRC, this is the QRD calculator that's in the program: mh-audio.nl - Home
This one is slightly different in the input parameters, giving more control: mh-audio.nl - Home

If you wan't to go 2D, you're better off using a real calculator, like this one: Calculate a Two-Dimensional Primitive Root Diffuser (Skyline) - the one in MH-softs program is way simplified compared to what the real values are.