What type of Rockwool to use for Bass Traps?

[lanmonkey]

OK, So I need to build some bass traps.

As I am in the UK rockwool is the easiest available, most of which can be bought off ebay in varying thicknesses and similar prices.


Here is the datasheet for Rockwool:
http://redirectingat.com/?id=690X1299&url=http%3A%2F%2Fwww.sheffins.co.uk%2FLiterature%2FRockwool%2520Rigid_Semi_rigid_Flexible_slab.pdf

The listed densities are:
Rockwool RWA45 = 45 kg/m3
Rockwool RW3 = 60 kg/m3
Rockwool RW5 = 100 kg/m3
Rockwool RW6 = 140 kg/m3

I have read people on here say that 45 kg/m3 is good for bass traps, but according to the “absorption coefficients” section of the above datasheet, Rockwool RW6 with a density of 140 kg/m3 has the best low frequency performance.

What are peoples thoughts on this?

[RMJAZZ]

The basic rule of thumb is that the more dense it is...the better it will stop bass. I think it would also depend greatly on how you plan to build the trap. There are many ways to make a bass trap. Are you looking at a panel? Or a corner type bass trap? Or maybe some type of Holtz Resonator????

What frequency is causing you a problem?

Check out GIK acoustics...their site has a lot of useful info.

GIK Acoustics. Acoustic Panels and Bass Traps.

Rob

[lanmonkey]

Thanks for the reply.

I thought too that the more dense it is the better, but I think the 705 stuff that people rate so highly is only 45kg/m3 (?) and above all common sense tells me that there has to be a point at which it becomes so dense as to stop absorbing sound well.

I'm looking at both filled corner bass traps (so corner is packed with rockwool) and potentially also a 4(ish) inch thick basstrap on my back wall.

thanks

[ciro]

This is an interesting thread about thickness/density/absorption.

Ciro

[pkarpiozo]

Originally Posted by lanmonkey

OK, So I need to build some bass traps.

As I am in the UK rockwool is the easiest available, most of which can be bought off ebay in varying thicknesses and similar prices.


Here is the datasheet for Rockwool:
http://redirectingat.com/?id=690X1299&url=http%3A%2F%2Fwww.sheffins.co.uk%2FLiterature%2FRockwool%2520Rigid_Semi_rigid_Flexible_slab.pdf

The listed densities are:
Rockwool RWA45 = 45 kg/m3
Rockwool RW3 = 60 kg/m3
Rockwool RW5 = 100 kg/m3
Rockwool RW6 = 140 kg/m3

I have read people on here say that 45 kg/m3 is good for bass traps, but according to the “absorption coefficients” section of the above datasheet, Rockwool RW6 with a density of 140 kg/m3 has the best low frequency performance.

What are peoples thoughts on this?

here check out this thread:
http://www.gearslutz.com/board/gears...ml#post5044713

i use ROCKWOOL TECHROCK 80 in my abs, it is 80kg/m3 and works really great!!!!

[avare]

Originally Posted by ciro

This is an interesting thread about thickness/density/absorption.

+1. thanks for linking it. The short is the thicker the absorber, the LIGHTER the material. Up to ~4" thick 3 lb/ft3. At thicker than 12", regular insulation. Yes the cheap stuff!

Andre

[lanmonkey]

Originally Posted by avare

Up to ~4" thick 3 lb/ft3.
Andre

Thanks, can you tell me that in metric please?

[avare]

Originally Posted by lanmonkey

Thanks, can you tell me that in metric please?

Up to 100 mm thick, 48kg/m3 density glass fibre or 64 kg/m3 mineral wool type insulation. Yes there is a difference between glass and mineral type insulation.

Andre

[pkarpiozo]

Originally Posted by avare

Up to 100 mm thick, 48kg/m3 density glass fibre or 64 kg/m3 mineral wool type insulation. Yes there is a difference between glass and mineral type insulation.

Andre

Rockwool Techrock is 100mm, and weights 80kg/m3.

it is rock mineral wool.(maybe that is why it is so heavy)

[Glenn Kuras]

Originally Posted by avare

+1. thanks for linking it. The short is the thicker the absorber, the LIGHTER the material. Up to ~4" thick 3 lb/ft3. At thicker than 12", regular insulation. Yes the cheap stuff!

Andre

Agreed but still thick you are fien with 8 Ib at 6". That is what we use in our Monster trap and the numbers look pretty darn nice to me.

[peterscherr]

Are there certain materials to avoid for hanging panels? Fibers that tend to shed and flake down? Which fiber materials are preferred for hanging panels?

Thanks,

Peter Scherr

[SaSi_SiDi]

I'd like to point out that you should not give too much weight (pun intended) to the tabular data for various densities and depths, especially if the differences are small.

To finish a panel or bass trap you need some form of frame to stabilize it and some breathable cloth to cover it. However, some people have succesfully made good enough looking panels without a frame. I would guess it's possible with denser and more rigid material, though.

Browse through the "how I built my bass traps" sticky to get some nice ideas on how to make them.

[Steab]

Would it be risky to use 100kg density rockwool in 15-25cm traps rather than the suggested 64kg?
That's what I got, but I could buy some 50kg/m3 rockwool if it would perform better..
I'm talking about basstraps/broaband absorbers.

Thank's

[avare]

Steab:

For absorbers 15-25 cm thick definitely use the lighter material you described.

Andre

[Steab]

Originally Posted by avare

Steab:

For absorbers 15-25 cm thick definitely use the lighter material you described.

Andre

Thank you.
I thought so.
The closest available densities are 40kg/m3 and 75/m3. The traps' depth are gonna be aproximatelly 28-30cm.
Should I go for 40kg?

[DanDan]

May I ask what type of Traps are you building?
There are practical considerations.
For Superchunks go light, 40KG sounds good to me.
However panel traps made with 40KG Rockwool will be very floppy, and will need framed support. For perspective up around 100KG panels are quite stiff and will stand without any frame.
Also their response is quite nice sounding, there is a touch of HF air about it which I and singers in my little vocal room like a lot.

Note OC705 is around 6 pcf. Equivalent would be Roksil 140 I guess.

Rules of thumb to find equivalence.
Imperial/US to Metric multiply by 16.
FibreGlass to Rock add around a third.

DD

[Steab]

They are going to be bass traps/broadband absorbers on the back wall. Im going to use a modded ikea bookcase for framing, but I'm not concerned about that.
Since 50kg/m3 -which seems to be ideal for fat traps- isnt availiable, I guess I should go for 40kg (just cause it's closer) rather than 75kg, unless 40kg just doesnt cut it. That's my dillema, and I'm interested in opinions.

[lucey]

Originally Posted by avare

+1. thanks for linking it. The short is the thicker the absorber, the LIGHTER the material. Up to ~4" thick 3 lb/ft3. At thicker than 12", regular insulation. Yes the cheap stuff!

Andre

If cost was not a factor ... is an 18" rear wall trap of all 705/Roxul 60 going to be a lot better than pink fluffy ... especially at the lowest frequencies?

thanks,

[DanDan]

Well, you can be very sure that Andre has substance behind his short statements.
Brian, I don't know the density of the pink stuff, but at that thickness I would want to be down around 2 pcf. 705 would certainly not be a good choice.
Expensive heavy, and not the best performer at that thickness.

However, for Staab's traps one might consider 10cm of 100KG with a 10cm airgap behind. One wonders would that perform better or be cheaper than a full fill of 40KG. I suspect the latter, but Andre?

Staab, apart from the theoretical questions, rest assured, it really is not critical, and 40KG will definitely work if you just want to get on with it.


DD

[avare]

Originally Posted by lucey

If cost was not a factor ... is an 18" rear wall trap of all 705/Roxul 60 going to be a lot better than pink fluffy ... especially at the lowest frequencies?

Pink fluffy is cheaper AND BETTER FOR LOW FREQUENCY ABSORPTION at 18" thick.

Andre

[avare]

Originally Posted by DanDan

However, for Staab's traps one might consider 10cm of 100KG with a 10cm airgap behind. One wonders would that perform better or be cheaper than a full fill of 40KG. I suspect the latter, but Andre?

Staab, apart from the theoretical questions, rest assured, it really is not critical, and 40KG will definitely work if you just want to get on with it.

The 40kg/m3 would definitely be better, the air flow resitivity 100 kg/m3 is significantly higher than 40 kg/m3 material. The resistivity increases much greater than a linear relationship.

Andre

[lucey]

Originally Posted by avare

Pink fluffy is cheaper AND BETTER FOR LOW FREQUENCY ABSORPTION at 18" thick.

Andre

That's so interesting. Well, I had 100 sheets of 705 at $1 a sheet, so I've made it all 705 and Roxul 60.

Does the 705 wall have more isolation from the room next door? Is there anything I gain in any category !?

[Steab]

Originally Posted by avare

The 40kg/m3 would definitely be better, the air flow resitivity 100 kg/m3 is significantly higher than 40 kg/m3 material. The resistivity increases much greater than a linear relationship.

Andre

Thank's Andre, I was lucky enough to finally find 50kg/m3 rockwool and i'll go with that.
Also, would you suggest 100kg or 50kg for first reflection absorbers? I'm thinking about 10cm max in these ones..

[avare]

Originally Posted by lucey

That's so interesting. Well, I had 100 sheets of 705 at $1 a sheet, so I've made it all 705 and Roxul 60.

Does the 705 wall have more isolation from the room next door? Is there anything I gain in any category !?

It has no advantage in walls for isolation. You can use it 2" thick (you did not indicate what thickness you have) spaced up to 4" for absorbers.

Andre

[PaulP]

Originally Posted by lucey

That's so interesting. Well, I had 100 sheets of 705 at $1 a sheet, so I've made it all 705 and Roxul 60.

If that isn't supposed to be $1 a square foot then you got the best price on the planet.

Paul P

[lucey]

Originally Posted by PaulP

If that isn't supposed to be $1 a square foot then you got the best price on the planet.

Paul P

Oh no, it was $1 per piece. Any size I could pull from this pile....

I got 100 pieces, it filled a cargo van. 24 were 20" x 8'. 20 were 2x4'

[avare]

+1 on Paul's "best price on the planet."

Andre

[johndykstra]

it's official....I'm a dork. I actually got excited when I saw that huge pile of insulation

[lucey]

Originally Posted by dykstraster@gmai

it's official....I'm a dork. I actually got excited when I saw that huge pile of insulation

So was I, until an hour later when I REALLY and TRULY realized that the T shirt I was wearing was not appropriate for digging through that pile.

[The MPCist]

Originally Posted by lucey

So was I, until an hour later when I REALLY and TRULY realized that the T shirt I was wearing was not appropriate for digging through that pile.

Well worth it though! 1 buck a sheet.... wow!