Roxul safe 'n' sound bass traps

  • Thread starter Thread starter guitaristic
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Never mind :) am going to trod this unknown path anyways, so I may be a guiding light to those like me who come afterwards!!

Bought the lumber today. Am going with the slightly more-fancy design shown over in this other thread--http://https://homerecording.com/bbs/general-discussions/studio-building-display/nicely-done-youtube-video-showing-one-way-build-your-own-bass-traps-361174/

Am planning to order the 12-pack of 4'x2'x3.5" Roxul tomorrow and should be able to pick it up within a week. Am going to double-up the panels for each trap, giving me 7" depth. All that's left now is to hit up my local fabric store with my awesome 60% off coupon, pick up the roxul, and consolidate the rest of the small stuff.
 
You did get my response to your PM to me, right?

I'm pretty sure the R value is important. Not sure if R-15 is enough for bass traps.
 
RAMI said:
You did get my response to your PM to me, right?

I'm pretty sure the R value is important. Not sure if R-15 is enough for bass traps.
Click to expand...

Yeah man! After doing some more research it seems r-values do indeed stack, so with my 2 pieces per trap the r-value will be more like 30. Although concerning r-values....I'm not actually sure if they matter or not. R-value is just how well it insulates. Maybe that relates to sound absorption somehow, but idk.

Would love to begin building my frames this weekend, but alas....work calls. Will start on those on Monday! :) pics will be included of course!
 
guitaristic said:
After doing some more research it seems r-values do indeed stack, so with my 2 pieces per trap the r-value will be more like 30.
Click to expand...

OK cool, that's good to know. I guess the only other thing to figure out is if you're spending more money for nothing by doubling up 2 less dense panels to make one trap. Other than that, good luck man. :cool:
 
Guys,

Yes, R values do indeed stack up... but absorption coefficients go a different route. R-Values really do NOT have anything to do with absorption coefficients. - I am sure that there is some correlation - but DON'T count on it. ;)
A good 'rule-of-thumb' for trapping is: Deeper traps = Lighter insulation.
* 2" - on the wall, use 3-4pcf rigid fiberglass or similar rock wool.
* 4" to 10" - on the wall, use 3-4 pcf rigid fiberglass (2") on the face and fill the back with attic blanket.
* 12" plus; use attic blanket.

There you have it.

Cheers,
John
 
jhbrandt said:
Guys,

Yes, R values do indeed stack up... but absorption coefficients go a different route. R-Values really do NOT have anything to do with absorption coefficients. - I am sure that there is some correlation - but DON'T count on it. ;)
A good 'rule-of-thumb' for trapping is: Deeper traps = Lighter insulation.
* 2" - on the wall, use 3-4pcf rigid fiberglass or similar rock wool.
* 4" to 10" - on the wall, use 3-4 pcf rigid fiberglass (2") on the face and fill the back with attic blanket.
* 12" plus; use attic blanket.

There you have it.

Cheers,
John
Click to expand...

Dude thank you so much for clearing all that up! Where have you been hiding the past 3 weeks? :D

Hmmm according to their website, Roxul has a pcf of 2.5! I'm not really a big fan of using blankets and such, so if I had a 5.5" thick trap with a 2-3" air gap, do you think that'd be good or would I need more?

Thanks again for your help!
 
Sorry for being 'away'.

If anyone would like my comment on their thread - PLEASE PM me or email. I've been busy on a myriad of projects the past few months, I hope you understand. - But I'll do my best to keep checking up on you guys here. ;)

Roxul AFB has a density of 2.5 pcf (45kg/m3), which is perfectly FINE for use in your 5.5" thick traps. With a 2-3" air gap, - Probably perfect. In situations like this, an air gap (space to the wall) that is up to equal the thickness of the absorption material can effectively double the absorption (average 90%) of the panel. This is free! - If you want 'better', fill the air gap with attic blanket.

Cheers,
John
 
jhbrandt said:
Sorry for being 'away'.

If anyone would like my comment on their thread - PLEASE PM me or email. I've been busy on a myriad of projects the past few months, I hope you understand. - But I'll do my best to keep checking up on you guys here. ;)

Roxul AFB has a density of 2.5 pcf (45kg/m3), which is perfectly FINE for use in your 5.5" thick traps. With a 2-3" air gap, - Probably perfect. In situations like this, an air gap (space to the wall) that is up to equal the thickness of the absorption material can effectively double the absorption (average 90%) of the panel. This is free! - If you want 'better', fill the air gap with attic blanket.

Cheers,
John
Click to expand...

All right awesome! :) thanks for your help! I will order my roxul today. Woohoo!
 
jhbrandt said:
R-Values really do NOT have anything to do with absorption coefficients.
Click to expand...

I see. You're obviously right since you are the authority on these things (along with only one or two other people here).

I think the reason I was under the impression that there was a correlation is because this chart seems to show that the higher the R value, the better the NRC, and the lower the frequencies that it traps: http://www.bobgolds.com/AbsorptionCoefficients.htm

Of course, there's always the possibility that I'm reading it all wrong.
 
RAMI said:
I see. You're obviously right since you are the authority on these things (along with only one or two other people here).

I think the reason I was under the impression that there was a correlation is because this chart seems to show that the higher the R value, the better the NRC, and the lower the frequencies that it traps: http://www.bobgolds.com/AbsorptionCoefficients.htm

Of course, there's always the possibility that I'm reading it all wrong.
Click to expand...

Well, idk as much as jhbrandt buuuuut I think there's an indirect correlation between r-value and absorption properties because both have to do with PCF. The denser the insulation, the higher the r-value and the PCF. And the higher the pcf, the better the NRC.

of course I could be reading it wrong too :D

p.s. bought some burlap for the back of my bass traps today!
 
Rami,

I don't see any 'R' values on Bob's charts... please show me what you are talking about. Thanks!

I'm sure that if one did a correlation chart R-value vs NRC that there might be some. but I don't look at that since it is a thermal rating.. EPS and Styrofoam all have 'R' ratings and they are useless for acoustic absorption. ;)
Cheers,
John
 
Sorry John. If you scroll down to ROXUL's listing, their products have the R values in their model numbers, MXR-40, etc.....

I actually thought that list was longer and had more details, like R values on every product.
 
Ah, I see what you mean.

Well, go to my publications page and download Absorption Coefficients spreadsheet. I put all of Bob's info in there ... and then some.
Click on the Roxul tab and look at the NRC compared to the model number... It's not very helpful. ;)

What you REALLY need is GFR! - Gas Flow Resistivity

THAT is what really determines the quality of absorption in any particular material. That is the reason that given densities of Rock wool will absorb sound differently from the same density of rigid glasswool (fiberglass) - it has to do with fiber diameter, etc., which adds up to GFR. I am currently gathering data on the GFR of many available products, however it may take me years to complete. Many manufacturers do not have the testing data.

Cheers,
John
 
I ordered my fabric today! Went with some sweet looking royal blue microsuede. I know it'll probably be pretty reflective of higher frequencies since it's not very breathable, but really I just need it for the bass absorption. I made some ghetto foam panels years ago for the mids and highs :laughings:

Insulation should be here this week!
 
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