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-   -   Different Helmholtz Slat Sizes (https://www.gearslutz.com/board/studio-building-acoustics/1314238-different-helmholtz-slat-sizes.html)

 Jeeuhmetrik 9th June 2020 08:39 PM

Different Helmholtz Slat Sizes

I understand the basics of a helmholtz array wall with one size on slats/slots and I can make calculations on that.

But in some studios I see helmholtz array walls with different sizes on both slats and slots. Is there any expert here that can explain how this works in more detail? (more than one cf obviously)

When every slat has a different slot on each side and every slot a different sized slat, how does this affect my calculations?

Basic helmholtz knowledge maybe, but couldn't find any good explanation online.

Hope someone understand what I mean and can elaborate a little further.

Best, M

 DPower 11th June 2020 08:53 AM

What you're seeing are most likely slat or binary amplitude diffusers rather than Helmholtz absorbers.

DIY Binary Amplitude Diffuser anyone?

If a truly sealed system as required for Helmholtz, and without dividers between the various sections, the peak of absorption would be an average of all the individual slat/slot combinations, which rather defeats the purpose of using this method to target specific frequencies.

 Jens Eklund 11th June 2020 05:40 PM

Allow me to disagree.

The ability to create a panel that offers both effective absorption in the modal region over a wide range and partial scattering is very useful, and I often use this method in my designs.

Quote:
 Originally Posted by Jens Eklund (Post 13503760)

 Jeeuhmetrik 11th June 2020 11:14 PM

Looks great Jens, well done and this is exactly what I had in mind!kfhkh
How do you make calculations when there’s more than one size of the slit and the slat?
From what I know the dampening occurs close to the openings and it takes into account the size of both slit and slat. Thats pretty straight forward with every calculator out there but when the slat size is different on both sides of the slit I get a bit confused.
Some kind of average makes sense like Dpower said but how can I control this if I want to battle 2-3 modes with one wall? Enlighten us please :)

 Jens Eklund 12th June 2020 04:16 PM

1 Attachment(s)
Performance of a variable slat configuration can be estimated by taking the average of the individual configurations:

https://www.gearslutz.com/board/atta...1&d=1591974876

 Jeeuhmetrik 12th June 2020 08:53 PM

Does that mean that you can put them in what order you like? (as long as the percentage of the wall is equal)

For example on the first pic you posted I can see 3 different configurations but they are not in 3 different sections but instead mashed up.
Not:
1-1-1-2-2-2-3-3-3
But:
1-2-3-1-2-3-1-2-3

1= 200mm slat, 5mm slit
2=100mm slat, 2mm slit
3=50mm slat, 3mm slit

Am I right assuming that these examples have the same average result?
The mashed up version sure looks cool on the wall but it’s still a bit confusing on paper when I try to understand how it really works.

Thanks for your time Jens, must be a lot of calculations and I bet these rooms are really well tuned.

 Kyle P. Gushue 12th June 2020 11:38 PM

Quote:
 Originally Posted by Jens Eklund (Post 14796348) Performance of a variable slat configuration can be estimated by taking the average of the individual configurations: https://www.gearslutz.com/board/atta...ions-slats.jpg

Is the idea to tune each panel section to the mode of highest pressure for the area its located, and use the averaged curve to see the resonator system as a whole overall ?