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Discussion Starter #1
First question, which material:


I'm a little cost concious, I only want to move up to a more expensive material if its effects are worth it, plus I'd rather go thinner than thicker to not lose room length if possible, but will spend more if I'd notice the difference acoustically. Which one should I pick? I was leaning towards the 2" OC703 or Roxul AFB 2":


Owens Corning 703 Rigid Fiberglass Board, 2 inch - $1.44 per sqft

ATS Acoustics Rigid Fiberglass Board, 2 inch - $1.23 per sqft

Roxul Acoustical Fire Batts, Mineral Wool, 2-inch - $0.75 per sqft

Linacoustic - 1 - $0.86 per sqft

Owens Corning 703 Rigid Fiberglass Board, 4 inch - $3.08 per sqft


Attaching the material to the front wall:


It has been suggested to me that furring strips be applied to the wall to minimize loss of room length, install the acoustic material between the furring strips, staple fabric to the furring strips (covering the staples with trim) and attach the screen mounting brackets to the furring strips over top of the fabric. The mounting brackets for my screen run vertically.


As most of the materials are 2' x 4', I was considering installing 2x4s horizontally to the wall (with the 4" side sticking out) spaced 4' apart to accomodate the 4' dimension of the OC 703 panels. I would use lag bolts thru the 2x4s screwed thru the existing wall board into the studs behind the wallboard. The 4' spacing will work well for the screen brackets as the screen frame is about 54" vertical and the brackets will be about this high also. The total wall height at the screen end of the room is 9'.


Will friction fitting 2 inch thick OC 703 boards between 2x4s 4' apart work or should each acoustic board be attached to the wall with adhesive or something else (suggestions?)? The 2x4s on edge have a nominal thickness of 3.5", so if the OC 703 was glued to the wall there would be an air space of 1.5" between the face of the OC 703 and the fabric. Is it better to put some sort of spacer behind the OC 703 so that the OC 703 surface is flush with the furring strips and thus the fabric will touch the OC 703 or have the OC 703 back against the wall and an air space between the face of the OC 703 and the fabric?


Should I use 4" thick OC 703 instead? If so, would probably use 2x6 furring strips instead of 2x4s.


Any other suggestions for attaching the OC 703 or alternative to the wall, and then the GOM material overtop?


Any suggestions on what type of trim to use to not be distracting?


Also, I will be making corner base traps. I'm guessing I can skip putting material behind those?


Thanks in advance.
 

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Quote:
Any other suggestions for attaching the OC 703 or alternative to the wall

A lot of folks here use roofing nails with plastic caps or washers, like this (except with longer nails):




Link: http://www.homedepot.com/buy/tools-h...ck-188795.html


Two-inch thick rigid fiberglass can also be attached with 3M spray adhesive:




Link: http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053

Quote:
The 2x4s on edge have a nominal thickness of 3.5", so if the OC 703 was glued to the wall there would be an air space of 1.5" between the face of the OC 703 and the fabric. Is it better to put some sort of spacer behind the OC 703 so that the OC 703 surface is flush with the furring strips and thus the fabric will touch the OC 703 or have the OC 703 back against the wall and an air space between the face of the OC 703 and the fabric?

Why not just use 2x2's and avoid the issue, altogether? 2x2's would also be cheaper and a whole lot easier to attach to the wall.

Quote:
Should I use 4" thick OC 703 instead? If so, would probably use 2x6 furring strips instead of 2x4s.

You might want to do some research on this forum about building a minimalist false wall. There is a thread (I believe started by BigmouthinDC) that describes the technique. Building a light 2x4 wall in in front of the front-wall acoustic insulation could be much easier than trying to attach 2x6's on edge to the wall.
 

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Discussion Starter #3
Aren't 2 x 2s really thinner than 2" and not allow enough space for the 2" acoustic material?


Thanks!
 

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Quote:
Aren't 2 x 2s really thinner than 2" and not allow enough space for the 2" acoustic material?

That's true. Shimming a 2x2 out with some plywood would still be easier than trying to fasten a 2x4 on edge to the wall, though. IMHO, of course.
 

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Quote:
Originally Posted by dwightp /forum/post/20861779


Two-inch thick rigid fiberglass can also be attached with 3M spray adhesive:

you do not want to coat the insulation with spray adhesive. OC703/equivalent is porous insulation and by coating the material with adhesive, you are covering the porous holes which will have unexpected results regarding absorption (and possible increase in reflection coefficient at higher freqs).


ive lightly sprayed 3M adhesive in the corners when combining batts to form thicker panels, but used very conservatively (just a dab in each corner to give some bonding between the two panels).
 

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Quote:
Originally Posted by Roshy /forum/post/20859760


First question, which material:

first question - what is the goal you are looking to achieve?


Quote:
Originally Posted by Roshy /forum/post/20859760


Should I use 4" thick OC 703 instead?

2" with a 2-4" air-gap will give you close (if not the same) performance of 4" thick with no air-gap. this is porous insulation and it is a velocity-based absorber. placing it at areas of high particle velocity will increase effectiveness.

Quote:
Originally Posted by Roshy /forum/post/20859760


Also, I will be making corner base traps. I'm guessing I can skip putting material behind those?

how much real estate do you have in the corners?


for corner porous bass traps (if you have the room), you will get better performance using very thick traps of low gas-flow-resistivity material.

http://www.whealy.com/acoustics/Porous.html


eg., massively thick (16" minimum) traps of cheap, loosely filled pink fluffy attic insulation (low GFR) will perform very well - especially at lower frequencies. you can save the expensive OC703 for specular broadband absorption panels, and use the cheap pink fluffy stuff for bass traps (for LF modal issues).


if you have the room, super thick/deep traps of pink fluffy will perform better and save you a bundle.


you can build corner traps like you would OC703, or you can find some large plastic bags and loosely fill those, and then straddle and stack in the corners.
 

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Personally the only advantage I noticed when I tested panels on my front wall was it caught reflections from my surrounds and rears. I like my surrounds a little diffused but really with the distance to the front wall being so far the spl of the surrounds and rears isn't a factor by the time it hits my ears.


I really heard no real improvement. Of course we all know treating the reflections for the front 3 is where the wow factor is.


This is just my opinion. If your surround reflection off the front wall bothers you (youd have to sit close to your front wall ) then i'd say test it out with some other panels if you have the rest of your room treated with existing panels.


Also if your going to use some of the mounting methods mentioned, nails, glue etc. Youd be just find with ATSs semi-rigid material...good bit cheaper, same sonic performance and its what they use in their pre made panels, and I've used as well as two friends with Ht rooms.
 

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Quote:
Originally Posted by cdy2179 /forum/post/20862261


Personally the only advantage I noticed when I tested panels on my front wall was it caught reflections from my surrounds and rears.

there are also SBIR issues off the front wall (LF wave issues, not specular).


eg., if the distance between LF driver and front wall (or any reflection path off front wall or front/side walls) is 1/4wavelength of a particular frequency, then the total reflection path is 1/2wavelength and will combine back at the driver 180* out-of-phase, thus causing a null at that frequency (same for multiples of this frequency, but that becomes less of an issue as increase in freq becomes less omni-directional).


same thing with LBIR at the listening position: (1/4wavelength distance from the listening position to the rear wall; as total flight path (reflection off rear wall) will be 1/2wavelength = 180* out-of-phase and cause null at listening position).


this issues can usually be identified if one has a measured null at the listening position.

for SBIR: move driver closer to front wall (decreasing distance to front wall, pushing the 1/4wavelength null up in frequency)

for LBIR: move the listening position closer to the rear wall (decreasing distance to rear wall, pushing the 1/4wavelength null up in frequency)


if the null changes frequency accordingly, then you've identified SBIR or LBIR issues.


so, while the front wall may or may not need to be treated for specular issues, one may still require bass trapping on the front wall if one is experiencing SBIR.
 

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Discussion Starter #9

Quote:
Originally Posted by localhost127 /forum/post/20862015


first question - what is the goal you are looking to achieve?

I'm new to all this, just trying to do what most people seem to recommend. So I guess take away speaker reflections off the front wall. And Have the Bass traps in the corners. For the bass traps I was thinking of using:
http://www.atsacoustics.com/item--Ro...f-6--1006.html

Cut into 4's (so 24" along front and side wall), as long as having my front L and R about 6" from the trap is ok.. If not, then cut them into 8s and having 12" sides on the triangles

Quote:
Originally Posted by localhost127 /forum/post/20862015


2" with a 2-4" air-gap will give you close (if not the same) performance of 4" thick with no air-gap. this is porous insulation and it is a velocity-based absorber. placing it at areas of high particle velocity will increase effectiveness.

How would you make a 2" air gap behind the insulation in the wall? I'm a total newb to any type of construction. BUT, my father will be here helping me, and he redid his whole basement, so knows most of the basics at least, but has never done anything with acoustics... so dumbed down to a newb level would be great if possible


Quote:
Originally Posted by localhost127 /forum/post/20862015


how much real estate do you have in the corners?

Here is the current plan... the wall between the AV area and the room will probably be extended to run the whole way though.



Quote:
Originally Posted by localhost127 /forum/post/20862015


for corner porous bass traps (if you have the room), you will get better performance using very thick traps of low gas-flow-resistivity material.

http://www.whealy.com/acoustics/Porous.html


eg., massively thick (16" minimum) traps of cheap, loosely filled pink fluffy attic insulation (low GFR) will perform very well - especially at lower frequencies. you can save the expensive OC703 for specular broadband absorption panels, and use the cheap pink fluffy stuff for bass traps (for LF modal issues).


if you have the room, super thick/deep traps of pink fluffy will perform better and save you a bundle.


you can build corner traps like you would OC703, or you can find some large plastic bags and loosely fill those, and then straddle and stack in the corners.

Not sure if I have the room for that...


If I was going with the triangle cuts method. How do you go about securing the fabric to it, and the whole thing to the wall? I've seen lots of pictures of people in intermediate stages, but can't determine how to then attach it all to the wall and make it look nice..


Also, on fabric material, would either of these work:

Stretch Velvet from Joanna's
http://www.joann.com/joann/catalog/p...DID=xprd768914

OR

Micro velvet black from Hancock:
http://www.hancockfabrics.com/Micro-...VVviewprod.htm


Joanna's is WAY cheaper... anyone used both of these?


Would these work well for side first reflection panels as well?


Thanks!
 

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Quote:
Originally Posted by Roshy /forum/post/20862646


I'm new to all this, just trying to do what most people seem to recommend.

before jumping the gun, i'd take a few moments to get an understanding of the inherent issues that one is generally trying to solve in small acoustical spaces. another requirement is to gain an understanding of just how porous absorption 'works', such that you know how to make your absorber and where to place it in order to be most effective.


ethan w. has written a nice article that can be easily digested by the newcomer. i highly suggest reading it a few times. you'll notice that we are dealing with two different issues in small acoustical spaces: 1) low-freq modal issues (where the energy functions as waves). 2) specular issues (where energy functions as 'rays' - and can be modeled like light (eg., billiard balls bouncing around a pool table).


porous absorption works by converting kinetic energy (from the sound wave passing through the insulation) into heat. there are 2 components of a sound wave, pressure and velocity, and they are inversely proportional (where pressure is maximum, velocity is zero; and vice-versa). therefore, the porous insulation/absorber must be placed at areas of high particle velocity in order to maximize absorption/efficiency.


read on (better to link than to retype and reinvent the wheel).
http://www.ethanwiner.com/acoustics.html


let us know if you have any additional questions!
 

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Discussion Starter #11
Just read through this. So have slightly modified what I'm planning. Please let me know if this sounds good or not.


Either place 2x4s with the 4" side facing out or build fake wall with 2x4s. Inside this frame place strips of 1x2s that are used to space the insulation from the wall(would these just go directly beside the 2x4s? Or put in middle?). Put the OC703 in the wall and secure into 1x2s with the screws and washers linked way above. Then cover this in material which is attached via nails or staples.


Would this work?

How do you cover up staples or nails?


For bass traps, put OC705 up against a corner as shown in the link, so not triangles as I said before, attaching it to 1x1s and covering with material. Is attaching with screws good? How do you cover up staples or nails from materials?


Any comment on the materials I listed?


Thanks!
 

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Discussion Starter #12

Quote:
Originally Posted by dwightp /forum/post/20861779


A lot of folks here use roofing nails with plastic caps or washers, like this (except with longer nails):




Link: http://www.homedepot.com/buy/tools-h...ck-188795.html


Two-inch thick rigid fiberglass can also be attached with 3M spray adhesive:




Link: http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053




Why not just use 2x2's and avoid the issue, altogether? 2x2's would also be cheaper and a whole lot easier to attach to the wall.




You might want to do some research on this forum about building a minimalist false wall. There is a thread (I believe started by BigmouthinDC) that describes the technique. Building a light 2x4 wall in in front of the front-wall acoustic insulation could be much easier than trying to attach 2x6's on edge to the wall.

For the screws and washers, would that only work with the rigid fiberglass? Would it work with the roxul mineral wool stuff ats sells? If not, any ideas on how to attach that stuff?


Thanks
 
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