Best density?!?

filete · Post by **filete** » Sat Dec 17, 2005 3:12 am

Hi there!
With so many options, I am really confused!
I need to make 10 broadband absorver and 6 bass traps.
I will be using Rockwool, but want to make sure to get the best density.
So, questions:

1 - What density should I get for the Broadband Absorver?
And for the bass traps?

2 - Its 100mm for the bass traps and 50mm or 40mm for the broadband
a good thickness?

Hope to have an answer soon,
Thanks

bpape · Post by **bpape** » Sun Dec 18, 2005 4:23 am

For reflection points, use the 4lb density. The denser materials tend to let sound skip off at shallow angles of incidence.

For bass absorbers, you can use the 8lb at 4" thick (or thicker) or you can use more 4lb a little thicker for less money and similar (or better) performance)

knightfly · Post by **knightfly** » Sun Dec 18, 2005 9:13 am

In fact, if you can get 3 PCF it's even closer to ideal, since very few sound waves strike at exactly 90 degree incidence... Steve

filete · Post by **filete** » Sun Dec 18, 2005 11:56 am

knightfly wrote:In fact, if you can get 3 PCF it's even closer to ideal, since very few sound waves strike at exactly 90 degree incidence... Steve

3 PCF for the bass traps too?!

knightfly · Post by **knightfly** » Sun Dec 18, 2005 3:17 pm

3 or 4 - 4 PCF will leave just a bit more "sheen" in the room response; IOW, it will not absorb quite as much high frequency because of the tighter weave of the insulation. I doubt you'd hear much difference, but nearly all plans, etc, for traps assume 3 PCF (as in Owens Corning 703)... Steve

bpape · Post by **bpape** » Sun Dec 18, 2005 3:25 pm

If you can get the mineral wool in 3lb, that's great. 4lb and 8lb are the most common.

As for bass absorbtion, I'll take 6" of 3lb over 4" of 6lb all day. It's a combination of density, thickness, and mounting distance from the boundary (within reason).

I have some people who like the best of both worlds and layer 3lb and 6lb (or 8lb) where there is 3lb on the front and back (2" layers each) with 6 or 8lb in the center for a 6" thick sandwich that works very well.

filete · Post by **filete** » Sat Jan 07, 2006 5:48 am

I finally received my panels today,
and because in my country there´s only one factory that makes semi-rigid rockwool,
and buying small quantities can take almost 2 months to deliver,
I had to choose from what was ready in stock.

So, I´ve just got:

12 panels of 3.5 pcf (56 kg/m3) with 1.5"/40 mm of thickness.
16 panels of 4.4 pcf (70 kg/m3) with 2.3"/60 mm of thickness.

Now, some questions for you, gurus

1. Should I use 2 panels of 4.4 pcf (70 kg/m3) to make each bass trap
with 4.7"/120 mm of thickness or one panel (60 mm) should be enough?

2. My idea is to use the panels with 3.5 pcf (56 kg/m3) for the first reflection
points. I was not able to get 2"/50 mm of thickness, so using just 1.5" will
it make much difference?

3. Is there any problem to join these 2 panels beside having
different densities?
Lets say, for instance, to make a bass trap with 4"/100 mm of thickness.

Also I would like some help with links, where I can see some pictures, of other members building rockwool panels...
I only find rigid fiberglass pictures, that seems more easy to build, there´s even members who dont cover the back of the panel,
but like I wrote on the start of this reply, I believe with rockwool is another story...
because of the irritate skin danger and fibers can floating around...

Thanks in advance!