Buyers Guide to Rigid Fiberglass

[Scottgman]

I've read John Sayers site. I've read Nathan Winter's site. I've read many posts on this forum and other forums. It's a lot of info and I'm not sure I understand (or care about) it all. But I want to make some absorption panels and bass traps and I want to make sure I'm getting the right material. If I have this all wrong... will someone please correct me?

Rigid Fiberglass (Owens Corning 700 series and other brands)

Desired Density: 2.5 to 3lbs per cubic foot. (more dense if you are specifically targeting high frequency absorption at the expense of low freq performance?)

Desired Thickness: More thickness = more absorption? Is this true for both bass traps and absorption panels? It's OK to stack rigid fiberglass boards? How do you stack them if there is jacket/coating/sheating on one side of each board?

Sheating/Coating/Jacket: Foil jacket or sheating will reflect some highs and high-mids? (You can alternate panels with the covering facing the wall/room to keep the room from sounding too dead?)

Mounting/Hanging: Should have space between wall and fiberglass panels (the more the better?).

Rockwool/Mineralwool/various other names

Basically the same performance and desired specs as the rigid fiberglass?

Thanks for your help!

 

[zbert]

PLEASE do a search on the subject. It's been covered over and over again.

 

[Scottgman]

Erm... the first sentence of my post explained that I have read most/all of the resources people suggest.

My point: I'm not looking for a PhD in acoustics. I just want to make sure that what I THINK I UNDERSTAND from the MANY PAGES of stuff I'VE ALREADY READ is, in fact, correct. So I don't spend money on crap that I don't need.

Is that so bad?

If I'm out of line, I apologize. But I don't see the big deal about compiling a short and sweet list of what to buy... just like the title of the thread indicated: A Buyers Guide. I'm certain it would help other people.

Instead of insulting me with the standard "do a seach, moron" reply, maybe you could simply verify whether the information I posted is correct?

I mean, if you actually read my first post, I think it would be clear that I have at least made an effort to understand this stuff and am just looking for some confirmation that what I think I know is correct.

Man, this place is more hostile than the mic forum

 

[HapiCmpur]

Man, this place is more hostile than the mic forum

That's not usually the case, and I'm hoping that someone knowledgable will soon respond to your questions because I'd like verification on the same set of info. Like you, I've been doing my homework here but am not sure I have understood everything correctly, expecially with all the jargon that the experts use.

I interpret all the postings on rigid fiberglass exactly the same way you do, Scottgman, except that I'm under the impression that it's best to go for something with even higher density -- perhaps in the 6 or 8 pcf range. I'd like to know which is preferred by people more experienced than I and for which applications.

By the way, is that Darwin you're using as an avatar?

 

[Scottgman]

That's not usually the case, and I'm hoping that someone knowledgable will soon respond to your questions because I'd like verification on the same set of info. Like you, I've been doing my homework here but am not sure I have understood everything correctly, expecially with all the jargon that the experts use.

Thanks for the support! I thought this was a perfectly reasonable thread to start since I had read and searched and read and searched and read and searched but still had questions. But apparently that's not good enough for some people.

I interpret all the postings on rigid fiberglass exactly the same way you do, Scottgman, except that I'm under the impression that it's best to go for something with even higher density -- perhaps in the 6 or 8 pcf range. I'd like to know which is preferred by people more experienced than I and for which applications.

The reason I posted those values for denisty is because (ahem, zbert) while I was searching/reading I found this:

http://www.homerecording.com/bbs/showthread.php?t=99482

"The best overall acoustic performance was achieved with a mineral-fiber blanket in the 2.5 to 3.0 Ib/cu.ft. density range. Densities above 3 lb./cu.ft. provide more sound attenuation at high frequencies, but low-frequency performance starts to suffer at higher densities. Mid and high-frequency performance goes down significantly as insulation density falls below 2.5 lb/cu.ft."

By the way, is that Darwin you're using as an avatar?

Yes.

 

[Son of Mixerman]

Desired Density: 2.5 to 3lbs per cubic foot. (more dense if you are specifically targeting high frequency absorption at the expense of low freq performance?)

This backwards? The higher the density the better LF performance. Mass/Density is requirted for LF attenuation, the less dense the more LF passes. At least to a point before the density is high enough it reflect LF too. But it depends alot on the trap depth and wall gap on top of it. This is tied to your mounting and hanging.

Desired Thickness: More thickness = more absorption? Is this true for both bass traps and absorption panels? It's OK to stack rigid fiberglass boards? How do you stack them if there is jacket/coating/sheating on one side of each board?

The perfect scenario would be something that is triple layered, in some regions nothing escapes in others some of everything is reflected.

I took and made some 2ft by 4ft corner traps where I have 4inch deep frame with 2inch Thk 3lbs density 703 and behind that 4 inch thick regular pink battings. The front of the 703 has 1inch Auralex wedge foam glued on.

I'm going to build more between the ceiling and wall and then a trap will replace the 4ich grey Auralex with matching traps. http://www.atomictoyboxstudios.com/images/IM003006.JPG


Here are the other ones 2ft by 4ft.
http://www.atomictoyboxstudios.com/images/IM003010.JPG

Sheating/Coating/Jacket: Foil jacket or sheating will reflect some highs and high-mids? (You can alternate panels with the covering facing the wall/room to keep the room from sounding too dead?)

Good. Faced or unfaced.

Mounting/Hanging: Should have space between wall and fiberglass panels (the more the better?).

Yup, can you add when sealed panel absorbers should be used.. Bandwidth data.

Rockwool/Mineralwool/various other names

Basically the same performance and desired specs as the rigid fiberglass?

Thanks for your help!

Lets add flammable dress-ups, this should be a sticky in at least 3 forums once your done.

Cool, I hate the search function alot of the time because you get 500 pages of discussions that never really answer the question quicky and effectively.

SoMm

 

[zbert]

OK then. The easy, answer best I can tell you (and I'm NO expert) is for absortion Owens 703 is a good start. You can always double up two sheets to make four inch corner panels. I covered the fiberglass with muslin material. Cost about a dollar a yard. Glued it on with Sobo fabric glue. Glued a thin piece of wood to the back of the panel and put picture wire across. I hang them like pictures. Four inches thick on each corner, paper side out. Yes you loose a bit of corner space but you get a good sound. Hang as many panels as you can. I mixed paper side out and fiberglass side out. The change in sound in my basment room is amazing. Really cleaned up the sound. This is the best non-technical expalination, and only one I can give you. Hope it helps.
Peace

 

[Scottgman]

Thanks for the reply, SoMm. Nice studio by the way. Is that Marshall a JCM 800?

This backwards? The higher the density the better LF performance. Mass/Density is requirted for LF attenuation, the less dense the more LF passes. At least to a point before the density is high enough it reflect LF too. But it depends alot on the trap depth and wall gap on top of it. This is tied to your mounting and hanging.

That's what I thought too. It seems counterintuitive. But the follwing thread discusses the topic (and Knightfly seems to know what he's talking about):

http://www.homerecording.com/bbs/showthread.php?t=99482

"The best overall acoustic performance was achieved with a mineral-fiber blanket in the 2.5 to 3.0 Ib/cu.ft. density range. Densities above 3 lb./cu.ft. provide more sound attenuation at high frequencies, but low-frequency performance starts to suffer at higher densities. Mid and high-frequency performance goes down significantly as insulation density falls below 2.5 lb/cu.ft."

My question regarding the facing/jacket/sheating (whatever you call it) is:

If you are stacking fiberglass boards (say I have 1" boards but want to make 2" panels) is it better to simply use fiberglass without any facing/jacket/sheating?

If you do have fiberglass boards with facing/jacket/sheating, how should they be stacked? (jackets facing each other? jackets on opposite sides?)

Yup, can you add when sealed panel absorbers should be used.. Bandwidth data.

Someone else will have to do that. I'm not at that level of understanding yet.

 

[Scottgman]

This is the best non-technical expalination, and only one I can give you. Hope it helps.
Peace

I guess you aren't understanding my questions. I've read how to assemble/cover/hang the panels once they are constructed. That's not what I'm after. I also understand-- after reading tons of information-- that rigid fiberglass is a pretty damn good start for absorption purposes.

I simply want a short and sweet guide on buying the Rigid Fiberglass.

To make it easier... check out this page:

http://www.spi-co.com/rfq/show_product.mv?id=8&nChart=getinfo

OK, right off the bat, I've got several decisions to make before I ever get my hands on any rigid fiberglass.

Do I want/need All Service Jacket, Foil Jacket, or plain boards?

Do I want/need 3# or 6# density?

Do I want/need 1", 1.5", 2", 2.5", or 3" thickness?

Anyway, I think I've got my answers. Thanks for everyone's help. I'm going to get plain boards (maybe a few with foil jacket if I can) with 3# density. I think I'll also get 3" thickness just to make life easy and because there doesn't seem to be any drawbacks from using thicker boards (besides losing space in the room). I think I'll also go with the rock wool if it's cheaper.

Cheers!

 

[Innovations]

I've read John Sayers site. I've read Nathan Winter's site. I've read many posts on this forum and other forums. It's a lot of info and I'm not sure I understand (or care about) it all. But I want to make some absorption panels and bass traps and I want to make sure I'm getting the right material. If I have this all wrong... will someone please correct me?

Rigid Fiberglass (Owens Corning 700 series and other brands)

Desired Density: 2.5 to 3lbs per cubic foot. (more dense if you are specifically targeting high frequency absorption at the expense of low freq performance?)

Desired Thickness: More thickness = more absorption? Is this true for both bass traps and absorption panels? It's OK to stack rigid fiberglass boards? How do you stack them if there is jacket/coating/sheating on one side of each board?

Sheating/Coating/Jacket: Foil jacket or sheating will reflect some highs and high-mids? (You can alternate panels with the covering facing the wall/room to keep the room from sounding too dead?)

Mounting/Hanging: Should have space between wall and fiberglass panels (the more the better?).

Rockwool/Mineralwool/various other names

Basically the same performance and desired specs as the rigid fiberglass?

Thanks for your help!

Here is where my information is different than yours.

More thinckness = broader absorbtion, not necessarily more. For example a 2 inch panel will absorb all of the highs and mids that will hit it. You can't absorb more than all. But the 2 inch panel will not absorb all of the bass that hits it. 4 inches will absorb close to all the bass that hits it, to the point of there being not a whole lot of point of going to 6. In other words even for bass you are better going with six four-inch traps than four six-inch traps.

Sheeting helps slightly in the bass at the expense of mids, but so little as to not be really worth the expense. Just buy the unfaced stuff as it gives you more flexibility in how to use it.

It is perfectly OK to stack the boards. you would want the facing to be at or near the back for panels. However if you save the money and get unfaced panels this is not an issue.

Yes you want to mount them with a space behind. this does two things, first It gives the sound the ability to be attneuated through the absorber, bounce off the wall, and then be further absorbed on the return trip. The other thing it does is to allow sound from the room to get around behind the panel and be absorbed. The distance from the wall is limited by practical consideratons. Two inches or so in usually fine.

 

[Scottgman]

Thanks Innovations! That helps!

Cheers!

 

[Innovations]

OK, right off the bat, I've got several decisions to make before I ever get my hands on any rigid fiberglass.

Do I want/need All Service Jacket, Foil Jacket, or plain boards?

Do I want/need 3# or 6# density?

Do I want/need 1", 1.5", 2", 2.5", or 3" thickness?

Anyway, I think I've got my answers. Thanks for everyone's help. I'm going to get plain boards (maybe a few with foil jacket if I can) with 3# density. I think I'll also get 3" thickness just to make life easy and because there doesn't seem to be any drawbacks from using thicker boards (besides losing space in the room). I think I'll also go with the rock wool if it's cheaper.

I get plain boards, 3 pound density, and one inch thickness. The reason for the one inch thickness is that I can just layer them up to make any thickness I want and the price per cubic inch is essentially identical.

 

[Ethan Winer]

Folks,

> Do I want/need All Service Jacket, Foil Jacket, or plain boards?
> Do I want/need 3# or 6# density?

I just completed a round of tests to settle these questions for once and for all. The short answer is 705-FRK is the best for bass trapping. Less dense, and therefore less expensive, 703 is fine for mid/high frequencies. Here's a link to the complete report:

www.ethanwiner.com/density/density.html

--Ethan

 

[Son of Mixerman]

Thanks for the reply, SoMm. Nice studio by the way. Is that Marshall a JCM 800?

Thanks And yes it's a Mid 80's JCM800 2205 Channel switcher lead series with Groove Tubes, 6550 power tubes instead of the stock El34's.


SoMm

 

[Scottgman]

Thanks And yes it's a Mid 80's JCM800 2205 Channel switcher lead series with Groove Tubes, 6550 power tubes instead of the stock El34's.


SoMm

NICE! As a guitarist, I feel strangely aroused when viewing such a nice amp.

 

[Scottgman]

Folks,

> Do I want/need All Service Jacket, Foil Jacket, or plain boards?
> Do I want/need 3# or 6# density?

I just completed a round of tests to settle these questions for once and for all. The short answer is 705-FRK is the best for bass trapping. Less dense, and therefore less expensive, 703 is fine for mid/high frequencies. Here's a link to the complete report:

www.ethanwiner.com/density/density.html

--Ethan

Thanks Ethan! That's good to know. Your website is invaluable in my opinion!

 

[Son of Mixerman]

NICE! As a guitarist, I feel strangely aroused when viewing such a nice amp.

Well it's good you didn't see that the back is off and I have speaker cab covered up


Yes sir...... I exposed her... Tubes


If looking is strangely arousing.... are you jealous I get to plug-in anytime I want?



with Monster Cable


I wonder if I could make my millions opening a pay-per-view Studio Porn site?


SoMm

 

[Innovations]

Folks,

> Do I want/need All Service Jacket, Foil Jacket, or plain boards?
> Do I want/need 3# or 6# density?

I just completed a round of tests to settle these questions for once and for all. The short answer is 705-FRK is the best for bass trapping. Less dense, and therefore less expensive, 703 is fine for mid/high frequencies. Here's a link to the complete report:

www.ethanwiner.com/density/density.html

--Ethan

Interesting test Ethan. I am guessing that the reason the FRK performed better at the very low frequency is that the surface caught the low frequency air movement and transfered the mechanical energy into the fiberglass and then the stiffer 705 did a better job of absorbing the mechanical energy. All-in all from a bang-for-the-buck (or no-bang since we are talking about trapping) I am likely to stick with the unfaced 703.

Your tests also confirmed my thinking that past a certain thickness it was better to use the fiberglass to make more traps rather than thicker traps.

 

[knightfly]

Guys, the mis-understood quote about 2.5 to 3 PCF fiberglas - this is true, researched by Mr. Stanley Roller of USG some years ago - however, in light of the fact that it was probably me that posted it, it has likely been taken OUT OF CONTEXT...

That particular study was about insulation density INSIDE OF WALLS, Not for acoustic absorbers; and, inside a wall, insulation tends (apparently, from the quoted study) to balance out TL IN A WALL when the insulation density is around 2.5 to 3 PCF; lighter than 2.5 tends to (slightly) improve BASS TL (seems backward, I know) and heavier than 2.5 (again, according to the study by Mr. Roller, a degreed engineer) tends to help higher frequency TL, again this is INSIDE A WALL.

My half-assed theory as to WHY this happens - it's possible that the heavier the insulation, the more it can act as a THIRD LEAF in a wall; a third leaf of mass in a wall will definitely cause better TL at mids, but at the expense of low frequency TL - so possibly (just my thoughts) what happens is that the denser the insulation, the less it acts as an absorbent and the more it acts like a board -

Other than taking things out of context, you're doing fine... Steve

 

[stayouttamalibu]

Folks,

> Do I want/need All Service Jacket, Foil Jacket, or plain boards?
> Do I want/need 3# or 6# density?

I just completed a round of tests to settle these questions for once and for all. The short answer is 705-FRK is the best for bass trapping. Less dense, and therefore less expensive, 703 is fine for mid/high frequencies. Here's a link to the complete report:

www.ethanwiner.com/density/density.html

--Ethan

very interesting and informative article. thanks for taking the time out! so a quick question, you showed that the 705-FRK is clearly the best for bass trapping. now, would that be with the foil paper facing out from the walls and into the room, or facing the walls? i know you said in your acoustics article that it definitely makes a difference in terms of the higher frequency reflections, but what about for straight bass trapping?