Superchunk traps -- using Safe'n'Sound (Rockwool) 2.5ppsf?

[coyotekells]

Everything I've read here seems to suggest lower-density is best for the superchunk bass traps..

But 3lb or 3.5lb seems to the recommended optimum.

How will 2.5lb rockwool hold up in this scenario? I can get either, but the 2.5lb "Safe'n'Sound" from Roxul will be easier to get and cost less...

Thoughts?

[avare]

Originally Posted by coyotekells

But 3lb or 3.5lb seems to the recommended optimum.

How will 2.5lb rockwool hold up in this scenario? I can get either, but the 2.5lb "Safe'n'Sound" from Roxul will be easier to get and cost less...

The range you mentioned is used because it isreadillly available. The Safe'n'Sound will be fine, if not better.

Andre

[Glenn Kuras]

Originally Posted by avare

The Safe'n'Sound will be fine, if not better.

Andre

It would be fun to see how it would come out in with lab testing.

[avare]

Originally Posted by Glenn Kuras

It would be fun to see how it would come out in with lab testing.

Agreed. It was fortuitous that testing for both the SSC (Studiotips Super Chunk) and SCA (Studiotips Corner Absorber) was able to be arranged at Riverbank Acoustical Laboratories. For other people, Riverbank is THE most famous reverb chamber in the world. Having such test data for a purely DIY design is unheard of. Absorption testing with reports cost $1k at the NRC labs. I don't know the rates at Riverbank, Orfield, etc.

Naturally that is disregarding the fact that almost all reverb chambers in the world are too small for creating diffuse fields below 125 Hz, the range that we are interested in. Vibro Acoustics has a chamber twice the size of what has been the standard for decades (20,000 ft^3 vs. 10,000 ft^3). Their facility is NVLAP certified for testing down to 50 Hz. When I approached them about doing absorption testing, the response was that they are not very interested in that sort of testing.

A more realistic, at least financially, option is to use an impedance tube. B&K and Bruel make them usable down to 50 Hz, but the sample size is quite small and the results are for normal incidence. RPG has one for larger samples, but is their internal lab equipment.

If anyone has an extra $20k to help DIY testing, I could make one. I would even provide that person with free testing for their product.

Andre

[Glenn Kuras]

If anyone has an extra $20k to help DIY testing, I could make one. I would even provide that person with free testing for their product.

you could build it for $20k? If so YOUR ON!!!

Glenn

[nosebleedaudio]

Sound is air movement, if you increase the resistance to passing thru a material that means more will reflect off going back into the room.
And yes I know there are 2 things at work here...
From the specs I've seen over the years the 3lb is better, you use more(thickness) for more absorption in the lower frequencies...
I use ONLY 3 lb for several reasons.

[Driller]

Originally Posted by nosebleedaudio

Sound is air movement, if you increase the resistance to passing thru a material that means more will reflect off going back into the room.
And yes I know there are 2 things at work here...
From the specs I've seen over the years the 3lb is better, you use more(thickness) for more absorption in the lower frequencies...
I use ONLY 3 lb for several reasons.

The cotton I used for my 34" face superchunks is 2lbs and seems to work fine. Anyway, it's not going to be a case of working vs not working at all, it's a question of degrees surely?

[avare]

Originally Posted by Glenn Kuras

you could build it for $20k? If so YOUR ON!!!

Glenn

I was referring to making an impedance tube measuring system, not reverb chamber, in case there was ambiguity there.

I did some cursory research on this after reading your post. The $20k figure looks very realistic actually. I was looking at differential mic designs, to provide almost real time results, as opposed to using sine waves and physically moving one mic on a probe. The most expensive part would be the software. Using generic lab software as a base, it is $2k plus application development costs. The tube itself is trivial in comparison to the other costs.

Interestingly regarding cost, I found one document on the net at prices ranging from free to $37! It is a thesis, so fairly techy and probably of little interest to most people here, but I'm including the link to the free site just so I can say that I have given away thousands of dollars of knowledge on Gearslutz. The number is based on everyone reading the thread having the opportunity get that information, at $37 a person.

Construction and Testing of a Modern Acoustic Impedance Tube

Financially generous in my own mind,
Andre

[1320 P.]

I just finished treating my live room using Safe n Sound and it is great. I could not find any 703 or 705 in my area. I did find some John Mansville, but decided to go with the Roxul. (Cost)

3" should be fine for most applications I think. I did build some 6" (2 pieces) but when you walked in the room, it felt as though you were getting your brains sucked out.

My live room is now +/- 10 from the worst reading in the room. The best was +/- 7. Perfectly acceptable for the chosen application.

[Glenn Kuras]

Originally Posted by avare

I was referring to making an impedance tube measuring system, not reverb chamber, in case there was ambiguity there.

I did some cursory research on this after reading your post. The $20k figure looks very realistic actually. I was looking at differential mic designs, to provide almost real time results, as opposed to using sine waves and physically moving one mic on a probe. The most expensive part would be the software. Using generic lab software as a base, it is $2k plus application development costs. The tube itself is trivial in comparison to the other costs.

Interestingly regarding cost, I found one document on the net at prices ranging from free to $37! It is a thesis, so fairly techy and probably of little interest to most people here, but I'm including the link to the free site just so I can say that I have given away thousands of dollars of knowledge on Gearslutz. The number is based on everyone reading the thread having the opportunity get that information, at $37 a person.

Construction and Testing of a Modern Acoustic Impedance Tube

Financially generous in my own mind,
Andre

Andre,
We may need to take this off the public forums, but I may be VERY interested in talking with you. My plate is pretty darn full with other projects this year, but keep me in mind for maybe first of next year.

Glenn