Acoustic Treatments, 2" inches or 4" inches thickness?

[Techlord]

I have researched materials just don't know how thick to go, I'm thinking about buying 2"-4" inches Acoustic Material (Roxul AFB 2"), just need to know if 2" inches is enough for my HT room measuring (D) 12' ft. x (W) 18' ft. and a ceiling height of 8 feet. I plan on at least six 2' x 4' foot panels, three on the front walls behind the speakers and three on the back walls behind the listening position. There's an attachment detailing my homemade 2' x 4' custom wood frame panels and would greatly appreciate any recommedations or better materials recommedations!







A look at my HT room below, thanks Techlord.

 

[mike c]

front and back, i'd recommend the 4"

for first reflection points on the sides and ceiling, 2" would do

 

[Techlord]

front and back, i'd recommend the 4"

for first reflection points on the sides and ceiling, 2" would do

If I go 4" inches couldn't I just have the material (very rigid type acoustic material) poke out 2" inches from the edge of the frames? I will be using microsuede fabric to pull over the acoustic material and staple it around the backside and hang it, am I correct in that I must install a piece of plywood on the back of the frame? As you can see I'm new at this... Nice looking kids you have there!

I appreciate the help Mike,

Techlord.

 

[mike c]

i dont think the plywood is necessary IMO, just the frame. and it's actually more effective with the sides exposed (for more absorptive material)

 

[Techlord]

i dont think the plywood is necessary IMO, just the frame. and it's actually more effective with the sides exposed (for more absorptive material)

I just found this YouTube video that shows you how to assemble the 4" panel without the plywood backing, it uses the fabric on the front of the frame then wraps the fabric around the acoustic material stapling it onto the back frame. I understand how to make it now, 4" it is! I like the idea of having the acoustic material exposed by 2" inches for extra absorption.

Thank you Mike again,

Techlord.

 

[oppman99]

I built some traps following that video a couple of months ago. Pretty easy and they work fine. I think it only took me about an hour and a half to put together 4 panels.

 

[Weasel9992]

If you can do 4" all the way around, then there's pretty much no reason to do 2". If we're talking about small-ish acoustic spaces the only reason to go with 2" panels is to save space for seating or something. 4" panels will do everything 2" panels will plus add low end control.

Frank

 

[Jack Hammer]

Just in case your plans don't account for this, IIRC, it helps to have an air space at the back of the panel where it meets the wall. So a 2" panel may be 3-4" thick, a 4" panel would be 5-6" thick. I forget the technical reasons but it had something to do with better absorbtion.

 

[Weasel9992]

Better low frequency extension...the panel will work better down lower, in other words.

Frank

 

[Bryce_H]

My home built panels are 4" deep, but use 2" acoustic fiberglass. It creates a 2" gap in the back to assist in a broader range of freq absorbsion. The front and back of the fiberglass is covered in quilting batting with speaker cloth over the front.

(Basically I followed Tom's guide to building acoustic panels)

 

[mike c]

remember though that a 4" panel flat to the wall is better than a 2" panel with a 2" gap.

 

[highfigh]

remember though that a 4" panel flat to the wall is better than a 2" panel with a 2" gap.

They both have their place, though. Depends on what needs to be absorbed.

 

[lsiberian]

front and back, i'd recommend the 4"

for first reflection points on the sides and ceiling, 2" would do

While it has been standard practice in the past to treat First Order Reflections it is only necessary if you have poor off-axis response. If you don't then treating them is a no-no. First order reflections from speakers with good off-axis response reinforce sound and provide more efficient use of amplifiers.

On the back you should only apply Rockwool directly behind your head. Behind the surrounds diffusing provides a better surround ambiance. The front wall is helpful, but not as critical as the back behind the head. Rear reflection leads to a poorer surround experience. I'd just fix up the back wall in most rooms. But if you want to do 2nd order and 3rd order reflections go ahead. 4" is about 4 times more effective than 2" So go with 4" if you can. for the back wall.

 

[Techlord]

While it has been standard practice in the past to treat First Order Reflections it is only necessary if you have poor off-axis response. If you don't then treating them is a no-no. First order reflections from speakers with good off-axis response reinforce sound and provide more efficient use of amplifiers.

On the back you should only apply Rockwool directly behind your head. Behind the surrounds diffusing provides a better surround ambiance. The front wall is helpful, but not as critical as the back behind the head. Rear reflection leads to a poorer surround experience. I'd just fix up the back wall in most rooms. But if you want to do 2nd order and 3rd order reflections go ahead. 4" is about 4 times more effective than 2" So go with 4" if you can. for the back wall.

I am commited to a 4" inch thick material, you mention Rockwool, what about 4" Owens Corning 703 behind my head rear wall? I need the material to be rigid rather than flexible! I am planning on installing three 2' x 4' foot panels with 4" inches of either Rockwool or Owens Corning 703, how does this sound? Also I have excellent off-axis response in my room, maybe that's because my room is wider than it is depth wise (D)12' x (W)18' x (H)8'.

Thanks,
Techlord.

 

[mike c]

I am commited to a 4" inch thick material, you mention Rockwool, what about 4" Owens Corning 703 behind my head rear wall? I need the material to be rigid rather than flexible! I am planning on installing three 2' x 4' foot panels with 4" inches of either Rockwool or Owens Corning 703, how does this sound? Also I have excellent off-axis response in my room, maybe that's because my room is wider than it is depth wise (D)12' x (W)18' x (H)8'.

Thanks,
Techlord.

as long as the rockwool and owens corning have the same density, they have the same effect.

that said, get the highest density available to you.

 

[Techlord]

as long as the rockwool and owens corning have the same density, they have the same effect.

that said, get the highest density available to you.

I found some Rockboard 60 that has 6 pounds per cubic foot compared to owens corning 703 with 3 pounds per cubic foot density. Also how does density play a role in determining what frequencies will be absorbed? I'm looking at taming down high to mid-range frequencies.

Thank you,
Techlord.

 

[mike c]

the higher the density, the more low frequencies it can catch.

 

[Bryce_H]

Quote:
Originally Posted by mike c
remember though that a 4" panel flat to the wall is better than a 2" panel with a 2" gap.

They both have their place, though. Depends on what needs to be absorbed.

The acoustics in my room were/are not bad to begin with. As I was able to build the room from scratch (started with bare basement - concrete walls and floor and joists), I could also build it with the fewest acoustical issues but altering my dimentions. I actually used an excel spreadsheet from Sound and Vision that calculated standing waves, nulls, and other acoustical issues based on room dimensions. I must have played with that spreadsheet for a week.

That said, my panels were built for moderate, but broad spectrum, absorption. So as quoted "Depends on the need." Mostly to handle first order reflections and decrease some of the bi-polar effect of my Def Tech speakers (reflections from the back of the speaker off the front wall were making it difficult to sometime clearly understand dialogue).

 

[Techlord]

the higher the density, the more low frequencies it can catch.

What about high frequencies, what is needed for the mid-range to high frequencies?

Thanks,
Techlord.

 

[mike c]

What about high frequencies, what is needed for the mid-range to high frequencies?

Thanks,
Techlord.

the rockwool/owens corning should do well in the upper frequencies, they're used for broadband absorption.