703, 705, or?... for between studio wall and concrete wall...?

[666666]

My stud / sheetrock dual studio wall is about 2 feet away from a basement outer concrete wall on two sides. I'm concerned about the low end going through the sheetrock walls, hitting the bare concrete and then bouncing back into the sheetrock walls, possibly creating additional resonance in the sheetrock and worse yet, possibly bouncing back into the room effecting internal acoustics.

The space between the studio sheetrock walls and concrete walls is unfinished area... generally dark, damp and dusty... it would not make sense to use expensive high-end bass traps there. I'll get the pretty stuff (RealTraps or GIK, etc) for INSIDE the studio room itself... but for between the sheetrock and concrete, I am looking for a relatively low cost solution for a material that will eat low-end frequencies well, need not look pretty at all, no frame needed, can suspend in whatever crude manner works... no one will ever see it.

I am unfamiliar with 703, 705 etc... in fact I am unfamiliar with any insulation that is not sold at Home Depot. Could someone please recommend a material for use in my situation here. From everything I've read in the past, I believe 703 (or 705?) might be what I'm looking for... or...? Mineral wool, Rockwool, etc...? Need not be rigid. Also, in my situation, it will only get hit with lower-end frequencies... I'm concerned only with low-end absorption, not concerned with upper frequencies or uniform reflections, etc.

If 703 is what I need, what are the typical dimensions of this stuff? Weight per panel? Approximate cost in the U.S.? I guess I'd go to a specialty lumber yard / construction supply to have it ordered.

EDIT: I just found a few places online that sell 703 / 705... I see it apparently comes in 2'X4'X2" sheets typically for about $80 for a pack of 6. Is this a decent price? If not, what is a typical price at a local lumber yard?

Thanks

[Ethan Winer]

For large cavities between walls the best material is also the cheapest: plain pink (or yellow) fluffy fiberglass. Fill the gap, but don't pack the fiberglass too tightly. Just enough thickness to fill the gap.

--Ethan

[666666]

Originally Posted by Ethan Winer

For large cavities between walls the best material is also the cheapest: plain pink (or yellow) fluffy fiberglass. Fill the gap, but don't pack the fiberglass too tightly. Just enough thickness to fill the gap.
--Ethan

Thanks Ethan!

Thing is, the gap I have behind the wall is about 2 feet, but I cannot fill the entire 2 feet with insulation... this 2 foot space also serves as a service gap, I need to walk through this gap occasionally to inspect / service pipes etc... I was hoping to add insulation not wider than about 6 inches so that I still have 18" of space to walk. Will 6" of typical "pink" fiberglass stuff be enough, or, because I wish to keep the thickness to only 6", would I benefit from the 703, 705 or mineral wool? In other words, will typical "pink" batt insulation offer enough performance (limited to just 6 inches thick) verses the more expensive stuff? Again, I am trying to cut down on the possibility of low frequencies going through the studio sheetrock walling, hitting the outer concrete walling and then bouncing back into the studio sheetrock walling.

Thanks -

[avare]

Use the cheapest insulation. 6" is fine.

[slaveern]

Originally Posted by Ethan Winer

For large cavities between walls the best material is also the cheapest: plain pink (or yellow) fluffy fiberglass. Fill the gap, but don't pack the fiberglass too tightly. Just enough thickness to fill the gap.

--Ethan

Ethan,

Just curious - is there a reason not to pack them too tight? Also, what is the 'impact' of filling the cavities with denser materials like 703/705? Is it just about cost/effectiveness?

[666666]

Originally Posted by slaveern

Ethan,
Just curious - is there a reason not to pack them too tight? Also, what is the 'impact' of filling the cavities with denser materials like 703/705? Is it just about cost/effectiveness?

Good question.

This question relates to a new problem I have... I was about to simply add 4" or 6" of the "pink stuff" behind the walls as discussed above, but now that the walls are complete, I am finding that I just don't have enough room behind the walls for 6" or even 4" of batt insulation. Remember, the space behind my walls is a "service gap", I need to be able to walk through there... it's a lot tighter than I thought... I guess I need to lose a few pounds ...

Anyway, looks like I can only get about 2" of stuff along / behind my wall. I see that 703 / 705 is sold in 2" thicknesses... I am going to guess that, because I have only 2" to work with that 703 / 705 WILL be the best option at this point? Yes? Or should I get 3.5" R-13 batt insulation and compress it to 2"? Which will offer better performance in this application or perhaps they'd be the same?

Also... WHAT is the difference between 703 and 705??? Which one is preferred for general sound absorption? Is one "better" than the other in terms of absorption? Does each have a different "favorite" absorption frequency range?

Thanks

[Ethan Winer]

Originally Posted by slaveern

is there a reason not to pack them too tight?

If it's too tight it becomes dense enough to conduct sound. But mostly it's about not paying more than needed to do the job. Fluffy fiberglass works fine when it's very thick. Rigid fiberglass is better when it must be thinner.

--Ethan

[Ethan Winer]

Originally Posted by 666666

WHAT is the difference between 703 and 705???

See this:

Density Report

--Ethan

[Glenn Kuras]

Also... WHAT is the difference between 703 and 705??? Which one is preferred for general sound absorption? Is one "better" than the other in terms of absorption? Does each have a different "favorite" absorption frequency range?

Preferred is kind of a hard question to answer. The best bang for the buck is going to be 703, but the best is going to be 705. I will say though that 6" of 703 will work better then 4" or 705 and cost less, but will take up more room. See everything is a trade off.

Glenn

[666666]

Great info!

Glenn and Ethan, your help is much appreciated!

[woofhead]

Hey double 666 man,

I've gotten 703 a few times in Queens from this place:

J&S Supply Corp, Distributors Of Roofing Materials and Fiberglass Insulation Products - New York City Metropolitan area , New Jersey, Connecticut

It's in long island city near the border of greenpoint brooklyn and lic queens.Probably your best bet in nyc.They also have the johns manville equivalnt-either would work.Ask them for a better price if you get alot and they may give you a discount.It's just a small warehouse and you go into the office to speak to a person and pay.One guy in there is a character and makes corny jokes-pretty friendly place for a building supply place.You may want to attach the 703 to the concrete walls as opposed to the outside of the walls of the studio_i would at least try it out both ways to see if it makes a diff or ideally I would get the 1 inch and cover both surfaces.Another suggestion:Get a roll of torch style roofing rubber at lowes($38 for 100 sq ft and about 100 lbs.) and cover the building wall(not the outside of the studio wall) completely with this-you could hopefully glue it with caulk and throw a couple of screws with washhers into the masonry(go for joints ), then attach the 1" 703 to that with staples and cheap caulk.This may achieve your goal but if not add the layer of 703 on the studio wall as well-total depth 2 and 1/8 inches so no need to cut back on beer and bagels. Not scientific but I've used the rubber\703 combo in my old studio and in the one I'm building now and it seems to work quite well.Differenet application in my place(I used the rubber to float the subfloor on the rafters of the house and used 703 and a sheetrock chamber between the rafters)but my gut tells me to try this-I'm no expert though.Good luck,

Mike