Is this a suitable depth ( air gap ) for a panel absorber?

[thegreatindoors]

Hi!

I have made measurements of my rooms frequency response and found out the lower peaks to be at

60, 160, and 320Hz

Using the formula: Wave Length in Feet = 1130 / Frequency and dividing the result by 4 ( as suggested in Ethan Winers guide )

I get the optimum air gap depth for 160Hz at 1,7656 feet and half of that, 0,8828 feet, for 320Hz.

Of course I would like to save space and make the gap 0,88 feet + rigid fiberglass front. Would this give me good enough absorbtion at these frequencies?

These panels would then cover the front and back of the room. I already have corner basstraps (the meaurements were made with the basstraps installed.)

Am I on the right track here?

This is also something to consider from Ethan´s article:
"In practice, you don't necessarily have to measure wavelengths and calculate air gaps, and the first few inches of space yield the most benefit. Most people are not willing to give up two or more feet all around the room anyway, so just make the gap as large as you can justify. If you can afford to fill the gap entirely with material, all the better."

You can find the the thread for my project with more info here:

http://www.johnlsayers.com/phpBB2/viewt ... =2&t=13790

Suggestions?

[AVare]

What material are you using? If it is ~48 kg/m3 mineral wool, then 200 mm or more total depth is fine. Use material 100 mm thick.

Andre

[thegreatindoors]

Thanks! I haven´t bought the materials for the panels yet, but I´ll take that info to the seller. I used 100mm rockwool for the corner traps, not sure of its weight tough.. I guess I can add more of it and compress them to get more mass if needed.

If use the 100mm rockwool to fill the 200mm gap as you suggested, should I still put the rigid fiberglass slabs in front of the panel? So the the total depth would be 50mm fiberglass + 200mm rockwool = 25cm ?

I understand you agree with Ethan that a filled gap is better than an airgap? Also, should I make the panel airtight?

[AVare]

You have several things asked in your last post. Starting from what you did not ask, the best absorption is with the appropriate gas flow resistance at the right place. This can be achieved with a filled space of a given material, or one with greater gas flow resistance and an appropriate gap. Gaps of up to 2:1 are fine with the proper material.

With ~50 -64 kg/m3 material, thicknesses of up to 100 mm solid are fine for absorption down to ~125 Hz. For greater low frequency absorption with that material have a gap behind the material up to 200 mm.

For best with no gap at those depths use a lighter material to fill the space.



Good luck!

Andre