Acoustic Panel Placement: Do You Need An Air Gap Behind Your Panels?

Hi; I've stumbled across this vid on YT, and was wondering whether there's any truth to it; all seems very scientific but it's this german's guy measuments after all, so he may be wrong ? (Summoning forum's guru @chervokas ) My panels have a 2¨ air gap between them and the wall, and in a nutshell, I'd be loosing over 10 db of absoption in th 1-2 khz area, and gaining some absorption in the adjacent lower frequencies 500hz-1Khz. So , better for vocals, worse for guitars (for those who don't wanna be arsed to watch the video)

 

This is good info, from Penn State, they are not trying to sell anything,
They show panels: flush, floating and spaced and their effectiveness. Spacing helps a lot for low freq. Hanging is by far the best.
Page 8.16

https://www.mne.psu.edu/lamancusa/me458/8_rooms.pdf

 

Wow, best post in ages, and no one is seeing it!

Thanks for the info.

 

Amen doctor fuse !!! thanks Pinhead for posting! I did not see it (somehow) until doctor fuse quoted it ...

 

I don’t think he’s wrong, the 2 inch air gap behind a 2 inch thick panel makes sense to me, but maybe I’m wrong too. I haven’t tried to find the software that he’s showing there but it all seems to make sense to me.

 

Those interested in room acoustics could do worse than checking out Acoustics Insider's (Jesco's) other videos, too. There is a goldmine of great information there.

 

I think the rule of thumb is if your panel is 4" thick, for best coefficient absorption efficiency, give them 4" thick of distance from the wall.

 

Thanx man ! Would love some more feedback, although the little I've had so far has been invaluable

FWIWYesterday I changed the panels-to wall distance from 4 to 2¨ and immediately noticed more absorption in the frequencies described in the video, so great info. Glad I came across it by chance. Common advice in the past has tipically been hang it as far from the wall as it is humanly possible, because the sonic waves that go through the panel bounce off the wall behind them and have to do back through the panel, so the air ¨cushion¨debilitates them. Maybe so, but at what expense !

 

There is a lot too it. An air gap isn't always helpful. It depends on the thickness of the trap.
The standard 2-4" traps, yes, a gap is helpful. As the trap gets thicker the need for a gap becomes less useful. A 12" thick trap will show no improvement at 40hz by adding a gap. I made a corner trap that is 40" across the face, and solid to the corner. It works great for bass. Added some thick perforated plastic to the face to reflect higher frequencies back into the room.

The spreadsheet found here will give you a real time visual of the effectiveness of different thicknesses, with and without gaps. As you play with that spreadsheet you may find an anomaly. Once you pass a foot thick the graph will show a loss of low frequency absorption. That is because the standard Roxul or fiberglass panels are too dense which causes the sound wave to bounce off rather than penetrate the trap. When you go thick, the trick is to reduce the amount of material per cubic foot in the trap. You can see how that works on a thick trap by reducing the Rayls value.

 

Thanks very much, but it doesn't run properly on (at least) my iMac with Office ... 11? even if I say to enable the macros (or not). Oh well. It does say something about Windows, maybe an up to date Excel will run it on Mac too.

OOPS, OK, 'rtfm' ... he talks about all this and how to download and install optional libraries ... nah, too much work for me but have at it. Office 365 will run it fine apparently, possibly with some extras installed. Interesting but not that interested! But again, a really cool tool if one wants to 'dive deep' into the tech and etc..

 

I signed up for things on his site, and looked at everything I could get (very nice array of tools for setting up home studios). He did respond via e-mail and said his stuff here is geared for home studios and not listening rooms (I answered a question about what the application was, there was a choice for critical listening in a home audio environment). He said he wasn't going to be covering that application, so 'unsubscribed' me from the newsletters, which is fine. He did offer of course to let me resubscribe if I wanted. Very nice guy, offers a LOT of free advice. I use several of his techniques anyway, especially in dialing in center image and soundstage. I'll try some of the listening tests (he also has .wav files with sweeps, pink noise, spot frequencies, etc. which are very useful).

One of the papers he wrote/provided mentions basically blasting absorbers over most of the room, then putting some diffusers 'on top of' some of them to ... subtract from the absorption effects? maybe to scatter higher frequencies as mentioned above. Errr, I don't think I'll be doing that! esp in a not-mixing-studio application. Oh well, some useful info for sure. Thanks for posting!

 

Go to gearlutz acoustic forum for advice by professional acoustician. the 4" thick= 4" space has been established a long while now!

 

Now, this is a useful on a more fundamental level when it comes to how to deal with the acoustics of your listening room.



I wish I had that knowledge when I moved into my then new listening room eight years ago. Although I may not have comprehended it. I suspect that one reason the video resonates (sorry for the pun) so much with me is that I have discovered it myself in a way too long process, with a lot of cursing and sweating.

 

I've used those dimensions for years with good results.

 

This guy really is the real deal. Thanks @The Pinhead for bringing my attention to him So much of what he says makes sense. Again, especially to someone who spent several years battling a difficult room. Here's another valuable video:


I have at times contemplated putting up an extra wall and shortening my room, which is also very long like the one in his example, but have sort of had a suspicion that it wouldn't be enough. This video puts words on that suspicion.