Calculating 2D QRD diffusor

[FirstLoveStudio]

When calculating well width for 2D QRD, how do you factor in the width of the dividing pieces? do I add the extra width between the wells and keep well width constant? Also, using MDF, what is the optimum thickness for both dividers and back pieces?

Thanks!

[Nordenstam]

Originally Posted by FirstLoveStudio

do I add the extra width between the wells and keep well width constant?

AFAIK, yes.

Originally Posted by FirstLoveStudio

Also, using MDF, what is the optimum thickness for both dividers and back pieces?

As thin as possible, and, thick, respectively. You want the dividers to be very thin - but not so thin as to let sound through. What that is in MDF is beyond me. The back pieces should reflect as much as sound as possible (down to the lower design limit of the QRD).


Not much help, I know, but perhaps it can get better answers rolling from other posters..

[Clueless]

Originally Posted by FirstLoveStudio

When calculating well width for 2D QRD, how do you factor in the width of the dividing pieces? do I add the extra width between the wells and keep well width constant? Also, using MDF, what is the optimum thickness for both dividers and back pieces?

Thanks!

I have received advice that the dividers between the wells can be infinitely thin (i.e. non-existent). If you check out George Massenburg's Studio C at Blackbird, you will see that his 2D QRDs use the "infintely thin" well dividers, and nobody has said his QRDs don't diffuse.

[jayfrigo]

In the same way that a perforated panel absorber will still work without subdivided cells behind each opening, a 2D diffusor can still diffuse without well dividers. 2D is more forgiving than 1D in this aspect. However, a perf trap will be easier to calculate and perform to tighter tolerances with dividers, and one might say something similar for some 2D designs.

The design, sizes, and depths involved will influence how well they perform without dividers. The original omnifussors (with the recognizable QRD pattern) need the wells more than the newer skylines, and the newer ones like divider-less skylines, and also hemis and Berger's designs with dividers, diffuse more uniformly, especially in arrays of multiple units. So technically, the well-dividers are a required part of technology, but practically, for some combinations of element sizes and design, you really don't need them.

[FirstLoveStudio]

Originally Posted by jayfrigo

In the same way that a perforated panel absorber will still work without subdivided cells behind each opening, a 2D diffusor can still diffuse without well dividers. 2D is more forgiving than 1D in this aspect. However, a perf trap will be easier to calculate and perform to tighter tolerances with dividers, and one might say something similar for some 2D designs.

The design, sizes, and depths involved will influence how well they perform without dividers. The original omnifussors (with the recognizable QRD pattern) need the wells more than the newer skylines, and the newer ones like divider-less skylines, and also hemis and Berger's designs with dividers, diffuse more uniformly, especially in arrays of multiple units. So technically, the well-dividers are a required part of technology, but practically, for some combinations of element sizes and design, you really don't need them.

thanks a lot everyone

[FirstLoveStudio]

This now has been thinking...

Could I aske the same question in reference to a 1D QRD?? i.e. whats the ideal thickness of MDF for the dividers between wells?

Thanks a bunch

[jayfrigo]

As was said by someone above, as thin as possible without "crosstalk" into adjacent wells, and without warping. However, you can think about your design frequency and effective bandwidth (f max and f min) and think about the wavelengths involved. If you have a 1/4" wooden divider, it's going to be high frequency that simply reflects off the face of that. Frequencies within your design bandwidth will still diffuse, but indeed there is a high limit to its effectiveness.

Also interesting to consider that RPG started with aluminum dividers between wells to keep it as thin as possible, but they moved to wood, which while thicker, offered other advantages without adversely affecting the design bandwidth.