Quick Superchunk density question

[analog orange]

I'm building superchunks to put into the corners of my space.

I can easily get 8# rock wool.

I can get 4# rockwool, but it would have to be ordered and would actually be a bit more expensive.

Money not being an object, from everything I've researched on the forum it seems like 4# or less would be better for superchunking, no?

I'm fighting big nulls at 50 and 100hz.

[Glenn Kuras]

Originally Posted by analog orange

I'm building superchunks to put into the corners of my space.

I can easily get 8# rock wool.

I can get 4# rockwool, but it would have to be ordered and would actually be a bit more expensive.

Money not being an object, from everything I've researched on the forum it seems like 4# or less would be better for superchunking, no?

I'm fighting big nulls at 50 and 100hz.

Yes when filling the corner you are better off to use 4 pound.

[ektia]

Originally Posted by Glenn Kuras

Yes when filling the corner you are better off to use 4 pound.

Why?

[Brainchild]

If the thickness is too great for a given density (or vice versa, same thing) then the cumulative flow resistance within the material itself creates rapid pressure build-up, which then causes wave reflection back into the room instead of viscous and thermal dissipation.

CSR Bradford Fibretex 350 or 650?

Could someone help out interpreting material's gas flow properties

[Glenn Kuras]

Originally Posted by Brainchild

If the thickness is too great for a given density (or vice versa, same thing) then the cumulative flow resistance within the material itself creates rapid pressure build-up, which then causes wave reflection back into the room instead of viscous and thermal dissipation.

CSR Bradford Fibretex 350 or 650?

Could someone help out interpreting material's gas flow properties

spot on!

[trodsky]

What about a 2.8 lb density roxul product (AFB) over the Roxol Safe which is at 4.5 lb density..

The 2.8 stuff is HALF the cost of the 4.5 stuff.

This is for two superchunk bass traps. Floor to ceiling, 9' 6"

Thanks.

[avare]

Originally Posted by trodsky

What about a 2.8 lb density roxul product (AFB) over the Roxol Safe which is at 4.5 lb density..

The 2.8 stuff is HALF the cost of the 4.5 stuff.

This is for two superchunk bass traps. Floor to ceiling, 9' 6"

Use the 2.8 lb/ft3 for all the superchunk.

Andre

[trodsky]

Originally Posted by trodsky

What about a 2.8 lb density roxul product (AFB) over the Roxol Safe which is at 4.5 lb density..

The 2.8 stuff is HALF the cost of the 4.5 stuff.

This is for two superchunk bass traps. Floor to ceiling, 9' 6"

Use the 2.8 lb/ft3 for all the superchunk.

Andre

Yeah? cool, I guess I'm gonna trust you! thanks! thumbsup I"m not here much, so don't know individuals. But this place has better amount of crowd than some other studio construction forums.. at least people will answer here without yelling at me.

[trodsky]

Well well.

After some confusion and the place being out of stock of this and that, things changed.

actually the 2.8 stuff was 2.5.

However, they did have a 4lb rockwool 2". So they wrote out my order... warehouse people couldn't find it.. mistake in the computer or something, so they gave me the 4lb stuff at 4" at the 2" price. That's awesome customer service.

[boggy]

Originally Posted by Brainchild

If the thickness is too great for a given density (or vice versa, same thing) then the cumulative flow resistance within the material itself creates rapid pressure build-up, which then causes wave reflection back into the room instead of viscous and thermal dissipation.
.....

This behavior can be reduced if we build thick bass trap with layers of rockwoll and add air gaps between layers, thus keep layers of denser rockwoll reasonably thin. Gaps can be same dimension as rockwool sheet... for example. And... at end... all non-absorbed air flow will hit wall and reflect back into the room, through rockwool sheets ...

regards

Boggy

[avare]

Originally Posted by bozoel

This behavior can be reduced if we build thick bass trap with layers of rockwoll and add air gaps between layers, thus keep layers of denser rockwoll reasonably thin

Sorry, but that is completely wrong. At each air/layer interface there is an acoustic mismatch. This causes reflections. The more the impedance mismatch, the greater the reflection. Multiple dense layers create many reflections that are stronger than an homogeneous layer of lighter density material.

Please whip your physics teacher that taught you that with a light, wet mineral wool absorber (or 25% less dense fiberglass).

Andre

[boggy]

Originally Posted by avare

...........At each air/layer interface there is an acoustic mismatch. This causes reflections. The more the impedance mismatch, the greater the reflection. Multiple dense layers create many reflections that are stronger than an homogeneous layer of lighter density material.

This way we can reach same reflection coefficients like thick concrete wall with ceramic tiles, if we add enough layers... its obviously clear that this is impossible.

Originally Posted by avare

Please whip your physics teacher that taught you that with a light, wet mineral wool absorber (or 25% less dense fiberglass).
....

I can't

regards

Boggy

[TooManyToys]

This is the first time I'm seeing this. On some other sites when Superchunks were discussed some said you could use either 703 or 705, it didn't matter except for price. So now I'm learning a little more.

I've seen panels marketed as "Bass Traps" both in 4" and 6" thicknesses. So does the same principal apply to them as well? That maybe if you using 703 a 6" panel is ideal, but if 705 then maybe only a 4" or at maximum 2"?