Hollow Quadratic Diffusor

[Rutgar]

Hello Everyone,

I have a bank of RPG Diffractals across my back wall. The upper frequency benefit is apparent. However, when looking at the back side, they are hollow, creating a cavity when they are mounted on the wall. I have some 1" thick rigid fiberglass left over from an ancient project, and my automatic thinking, is that I should use it to fill in these back side cavities of the Diffractals. Although, I believe this won't hurt anything... I'm not really sure if it will actually help anything. I do have some bass buildup where these are positioned, and was thinking that the fiberglass, might be beneficial. Anyone here have any thoughts, or opinions?

Below is a photo of the back side of one of the Diffractals off of the wall. You can easily see how much of a cavity space there is:

 

[Ethan Winer]

Yes, adding absorption is a good idea. It might give a bit of bass trapping, and it might reduce resonance. Worst case is no difference, and best case is a small improvement.

--Ethan

 

[Rutgar]

Yes, adding absorption is a good idea. It might give a bit of bass trapping, and it might reduce resonance. Worst case is no difference, and best case is a small improvement.

--Ethan

Yeah, that was sort of my thinking as well Ethan. Plus, the price is right, since I already had the rigid fiberglass.

 

[Bruce B]

Yeah, that was sort of my thinking as well Ethan. Plus, the price is right, since I already had the rigid fiberglass.

rigid insulation? I put Roxul bat insulation in mine.

 

[Rutgar]

rigid insulation? I put Roxul bat insulation in mine.

Ah, okay. But, I didn't have any Roxul bat insulation (also, I don't know what that is... ).

Basically, I cut the 1" rigid fiberglass to fit into the individual wells from the back. But, in the future, it would be easy enough to use something else, if it would provide more benefit.

 

[Bruce B]

Ah, okay. But, I didn't have any Roxul bat insulation (also, I don't know what that is... )..

Roxul Insulation

 

[microstrip]

I also have six RPG diffractals in the front wall of my room. I have considered putting a rigid fiberglass plate behind them, even got the proper thickness and at the last minute decided not to do it. Nowhere in the RPG literature they advise to do it, and I preferred to assume they know what they do. Much less stressing ...

 

[DonH50]

They sell absorbers too, why undercut their business?

I am surprised they do not offer a combination diffusor/absorber panel.

Roxul is modern mineral wool.

 

[Rutgar]

I also have six RPG diffractals in the front wall of my room. I have considered putting a rigid fiberglass plate behind them, even got the proper thickness and at the last minute decided not to do it. Nowhere in the RPG literature they advise to do it, and I preferred to assume they know what they do. Much less stressing ...

I can't find where RPG advises NOT to do it either. They don't appear to address it either way. So is it possible you are working on a false assumption?

 

[microstrip]

(...) I am surprised they do not offer a combination diffusor/absorber panel. (...)

Don,
Although it will depend of the values of coefficients and frequencies you are targeting, the RPG Diffractal has absorption and diffusion. On some of their devices RPG advise to use or not rigid fiberglass plate behind them, and supply data on both conditions. However they do not refer to it using the Diffractal.
http://www.rpginc.com/product_Diffractal.cfm

 

[microstrip]

I can't find where RPG advises NOT to do it either. They don't appear to address it either way. So is it possible you are working on a false assumption?

Surely. But on other type of acoustic devices they advise to do it and supply data on its effect. To make it clear - I am not an expert and could not foresee what would be the effect of adding the fiberglass. So I mounted them in the way they suggest in their application notes.

 

[Rutgar]

Surely. But on other type of acoustic devices they advise to do it and supply data on its effect. To make it clear - I am not an expert and could not foresee what would be the effect of adding the fiberglass. So I mounted them in the way they suggest in their application notes.

LOL! I know what you mean... obviously I'm not an expert either. I have had them hung up for years, without thinking about putting anything inside of them. It only occured to me when I was having to move one to a different location.