Covering entire walls with absorbing panels?

M

moves

Audioholic Chief
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95
#1
Is this a good idea? I don't have parallel walls and the room is large 14 X 30 or so. Plus.... I have concrete behind the drywall on the t.v. side. I bought some acoustic fabric today... 10 meters worth.
 
TheWarrior

TheWarrior

Audioholic Samurai
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#2
Is there a reason for doing this? Are you taking measurements? Without them, you're flying blind!
 
M

moves

Audioholic Chief
Ratings
95
#3
Is there a reason for doing this? Are you taking measurements? Without them, you're flying blind!
I didn't take measurements because I don't have the instrument but the back wall is concrete and that needs to be covered... just not sure about the side wall that has no concrete behind it.
 
highfigh

highfigh

Audioholic Warlord
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2,698 9 4
#4
Is this a good idea? I don't have parallel walls and the room is large 14 X 30 or so. Plus.... I have concrete behind the drywall on the t.v. side. I bought some acoustic fabric today... 10 meters worth.
No, you only need to cover the areas that cause problems. Also, without considering the height, treating the walls will only result in bad sound.

What kind of acoustic material?
 
M

moves

Audioholic Chief
Ratings
95
#5
No, you only need to cover the areas that cause problems. Also, without considering the height, treating the walls will only result in bad sound.

What kind of acoustic material?
This is the insulation that I was thinking of making the panels out of:

https://www.homedepot.ca/en/home/p....&bvrecipientDomain=yahoo.com#question/4471485

Also, many HTs as well as cinemas have their entire walls treated so not sure why this is a bad idea. I was thinking of something like this:

photo-of-high-end-home-theater-with-triple-band-acoustic-fabric-wall-finishing-using-brown-fab...jpg
 
KEW

KEW

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#6
The last thing you'd want to do is convert your room to an anechoic chamber!
There are some acoustic wall papers that I would suspect to be the equivalent of throwing a towel on a hardwood floor (but for the wall). This would help if you have a very (clap your hands and how strong is the echo) bright room.
1" thick fiberboard (like used for HVAC) wrapped in fabric (just to make it look good) stapled to the back is reasonable for cost and effort.
This is what RBH uses for setting up their systems for shows (and their own showroom). Acoustically you only need to catch the area right behind the speakers (go about 1 foot beyond the dimensions of the speakers in all directions),but if the the price doesn't bother you, I don't think covering your concrete/sheet rock wall with fiberboard is a bad idea.
 
highfigh

highfigh

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#7
This is the insulation that I was thinking of making the panels out of:

https://www.homedepot.ca/en/home/p....&bvrecipientDomain=yahoo.com#question/4471485

Also, many HTs as well as cinemas have their entire walls treated so not sure why this is a bad idea. I was thinking of something like this:
They may have a consistent covering, but that doesn't mean the whole space is absorptive- they would also have reflective and diffusive areas behind the cloth. The point is to make sure there are no major peaks or dips in the response and to make it allow speech to be intelligible, not to absorb any sound that hits the surfaces. Also, Rock wool is more for preventing sound transmission, rather than for in-room treatment. Rigid fiberglass is used for that more than soft, poofy materials.The first reflections should be tamed, with other areas allowed to reflect, to create a space that has even distribution of room modes (standing waves) and has a smooth, short decay rate. No audio track is mixed in hopes that the listening space will be acoustically dead- it's not a practical goal, nor does it sound good.
 
M

moves

Audioholic Chief
Ratings
95
#8
They may have a consistent covering, but that doesn't mean the whole space is absorptive- they would also have reflective and diffusive areas behind the cloth. The point is to make sure there are no major peaks or dips in the response and to make it allow speech to be intelligible, not to absorb any sound that hits the surfaces. Also, Rock wool is more for preventing sound transmission, rather than for in-room treatment. Rigid fiberglass is used for that more than soft, poofy materials.The first reflections should be tamed, with other areas allowed to reflect, to create a space that has even distribution of room modes (standing waves) and has a smooth, short decay rate. No audio track is mixed in hopes that the listening space will be acoustically dead- it's not a practical goal, nor does it sound good.

I don't feel comfortable using the fiber glass and having the risk of it getting into the air. If the rock wool that I linked to is no good for this purpose then what else could I use?
 
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highfigh

highfigh

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#9
I don't feel comfortable using the fiber glass and having the risk of it getting into the air. If the rock wool that I linked to is no good for this purpose then what else could I use?
Rigid fiberglass is bonded with resin and won't become airborne unless it has been disturbed and there's nothing covering it- Rock Wool can be an irritant, too. If you don't know what an MSDS (Material Safety Data Sheet) is, read this.-

http://www.americanrockwool.com/_docs/rwpp/RockWool Premium Plus SDS.pdf

The materials needed depend on the effect needed and the only real way to know this is to measure the room's acoustical characteristics- this isn't done by professionals using guesswork. Any material will have certain abilities to block, absorb, reflect or diffuse sound and they have been measured- it's the only way for someone to recommend something as a remedy to an acoustical problem. If you look at the specs for different materials, you'll see NRC (Noise Reduction Coefficient),STC (Sound Transmission Coefficient) & other acronyms and they come with graphs to show their effect at specific frequencies but mainly, they're used for frequencies above the low end because that range is harder to absorb- they'll often prefer to isolate the object that causes the noise, to stop structure-borne transmission. When you look at the graphs, you'll see that their effectiveness falls off as the frequency drops- many are almost useless at frequencies below 150Hz.

There are three ways sound can be transmitted; direct radiation from the source to the listener/mic through the air, structure-borne and modulation, which means that something is made to vibrate and re-radiate the sound- the last two are likely the cause of problems like the one in the thread about the projection screen that rattles.

This leads me to the question- what problems with the sound make you believe you need to treat the room? If you hear fast echo from percussive sounds or you hear sounds that seem to come from the left of the left speaker or the right of the right speaker, the rock wool in the walls won't help. If you hear the drywall 'ring' (vibrate with a specific frequency) from certain notes or you have problems with sound passing through walls and ceiling, it will help.

You don't need millions of dollars of test equipment- a laptop with a decent mic and a program like RoomEQ Wizard will tell you a lot. You can also find out how reflective the room is with a smart phone and an app like ClapIR but first, I would recommend reading about sound control- there's more info than anyone would want to read but having a good foundation in this makes the solution easier to find.

BTW- I'm not saying the rock wool is useless, but again, the actual problem and problem frequencies need to be known. I measured a room and found that it had a bad problem with cancellation around 80Hz and a smaller one at around 150Hz. Normally, this is caused by reflections from more than one surface that meet in places where the energy from one cancels the energy from another, so I made some panels and found that they didn't make much difference. Out of frustration, I gave the side wall a moderate thump with my fist and found the problem- it hadn't been insulated, as intended. I went to the backside of the wall and loosened the drywall to look inside- empty. We told the homeowner to have his guys insulate it and when we went back, the problem was gone and that wall was as dead as the other walls and the ceiling. Ironically, the homeowner owns an insulation supply/installation company. The outer surfaces of the walls and ceiling have no treatments- the floor is carpeted and the corners where the walls and ceiling meet have a small, angled soffit, with a larger vertical column that's similar at each side of the screen, which frame the screen and contain the L & R main speakers and the subwoofers below them.
 
M

moves

Audioholic Chief
Ratings
95
#10
Rigid fiberglass is bonded with resin and won't become airborne unless it has been disturbed and there's nothing covering it- Rock Wool can be an irritant, too. If you don't know what an MSDS (Material Safety Data Sheet) is, read this.-

http://www.americanrockwool.com/_docs/rwpp/RockWool Premium Plus SDS.pdf

The materials needed depend on the effect needed and the only real way to know this is to measure the room's acoustical characteristics- this isn't done by professionals using guesswork. Any material will have certain abilities to block, absorb, reflect or diffuse sound and they have been measured- it's the only way for someone to recommend something as a remedy to an acoustical problem. If you look at the specs for different materials, you'll see NRC (Noise Reduction Coefficient),STC (Sound Transmission Coefficient) & other acronyms and they come with graphs to show their effect at specific frequencies but mainly, they're used for frequencies above the low end because that range is harder to absorb- they'll often prefer to isolate the object that causes the noise, to stop structure-borne transmission. When you look at the graphs, you'll see that their effectiveness falls off as the frequency drops- many are almost useless at frequencies below 150Hz.

There are three ways sound can be transmitted; direct radiation from the source to the listener/mic through the air, structure-borne and modulation, which means that something is made to vibrate and re-radiate the sound- the last two are likely the cause of problems like the one in the thread about the projection screen that rattles.

This leads me to the question- what problems with the sound make you believe you need to treat the room? If you hear fast echo from percussive sounds or you hear sounds that seem to come from the left of the left speaker or the right of the right speaker, the rock wool in the walls won't help. If you hear the drywall 'ring' (vibrate with a specific frequency) from certain notes or you have problems with sound passing through walls and ceiling, it will help.

You don't need millions of dollars of test equipment- a laptop with a decent mic and a program like RoomEQ Wizard will tell you a lot. You can also find out how reflective the room is with a smart phone and an app like ClapIR but first, I would recommend reading about sound control- there's more info than anyone would want to read but having a good foundation in this makes the solution easier to find.

BTW- I'm not saying the rock wool is useless, but again, the actual problem and problem frequencies need to be known. I measured a room and found that it had a bad problem with cancellation around 80Hz and a smaller one at around 150Hz. Normally, this is caused by reflections from more than one surface that meet in places where the energy from one cancels the energy from another, so I made some panels and found that they didn't make much difference. Out of frustration, I gave the side wall a moderate thump with my fist and found the problem- it hadn't been insulated, as intended. I went to the backside of the wall and loosened the drywall to look inside- empty. We told the homeowner to have his guys insulate it and when we went back, the problem was gone and that wall was as dead as the other walls and the ceiling. Ironically, the homeowner owns an insulation supply/installation company. The outer surfaces of the walls and ceiling have no treatments- the floor is carpeted and the corners where the walls and ceiling meet have a small, angled soffit, with a larger vertical column that's similar at each side of the screen, which frame the screen and contain the L & R main speakers and the subwoofers below them.
Thank you so much for the reply.... This seems like I need to know what I'm doing in order to get this done properly. I guess I'll look for some Room EQ to test the frequencies. I am assuming the miniDSP with mic would do? I would need this as well for when I get the subs.

So basically, I shouldn't build anything until I test the room... I guess another question is what am I looking for in the graphs but I guess that will wait until I actually get the mic and the miniDSP.
 
highfigh

highfigh

Audioholic Warlord
Ratings
2,698 9 4
#11
Thank you so much for the reply.... This seems like I need to know what I'm doing in order to get this done properly. I guess I'll look for some Room EQ to test the frequencies. I am assuming the miniDSP with mic would do? I would need this as well for when I get the subs.

So basically, I shouldn't build anything until I test the room... I guess another question is what am I looking for in the graphs but I guess that will wait until I actually get the mic and the miniDSP.
MiniDSP works fine, but RoomEQ Wizard is free and it works very well. Even if your computer's mic is a cheap one, I wouldn't worry about being accurate at the highest extreme.

Listen to the system in the room- take some time to position your speakers first- it makes a huge difference and can negate the need for some treatments. THEN, listen carefully and find the problems (if any). Sometimes, it doesn't take much to turn a room into a good place for music.
 
M

moves

Audioholic Chief
Ratings
95
#12
MiniDSP works fine, but RoomEQ Wizard is free and it works very well. Even if your computer's mic is a cheap one, I wouldn't worry about being accurate at the highest extreme.

Listen to the system in the room- take some time to position your speakers first- it makes a huge difference and can negate the need for some treatments. THEN, listen carefully and find the problems (if any). Sometimes, it doesn't take much to turn a room into a good place for music.
Thanks for the feedback! The room I was in before was a lot smaller and had some heavy bass issues with some music.

Now, the room is a lot deeper and I feel the music is just not as powerful enough and I am sitting 7 feet away. I find myself listening at -6db for some tracks where as compared to the old room, -6db was unheard of. It would blow my ears off.

I have Totem Wind Towers and am powering them with the McIntosh MC302 so I am not worried about the power. The speakers are I believe 87db sensitive so that is also an issue. What I might do is run a curtain somewhere around 3 feet behind my listening position to see if that tightens things up a bit. I will def try the free room EQ Wizard that you suggested. I was thinking of hanging the wall panels that I already have and finding the first reflection points and then maybe run that EQ.
 
M

moves

Audioholic Chief
Ratings
95
#13
OKay so I DLed REW and now just thinking about if I can use the mic that came with my Pioneer Elite for MCACC Room EQ? If so, do I just plug this into the headphone jack on the back of my MAC desktop?
 
M

moves

Audioholic Chief
Ratings
95
#14
NVM I got the minidsp USB mic second hand. It should arrive shortly. I forget now what the model is but I am sure you know what I mean.
 
highfigh

highfigh

Audioholic Warlord
Ratings
2,698 9 4
#15
Thanks for the feedback! The room I was in before was a lot smaller and had some heavy bass issues with some music.

Now, the room is a lot deeper and I feel the music is just not as powerful enough and I am sitting 7 feet away. I find myself listening at -6db for some tracks where as compared to the old room, -6db was unheard of. It would blow my ears off.

I have Totem Wind Towers and am powering them with the McIntosh MC302 so I am not worried about the power. The speakers are I believe 87db sensitive so that is also an issue. What I might do is run a curtain somewhere around 3 feet behind my listening position to see if that tightens things up a bit. I will def try the free room EQ Wizard that you suggested. I was thinking of hanging the wall panels that I already have and finding the first reflection points and then maybe run that EQ.
How high is the ceiling?

One reason it's not as loud as before is the fact that you're sitting farther from the back wall and the reflected sound was able to augment what was coming from the front of the room. That sound path is now close to 60 feet- even if the wall is totally reflective, the reflected sound level is far below that of the direct sound. Also, you might want to move your chair- where you sit relative to the speaker position makes a difference but a curtain will absorb sound, not reflect it. You don't have a problem with reflection, you have a problem with attenuation. This is similar to taking speakers outside and being disappointed because you expect them to sound the same as when they were inside- it can't happen unless you're in a space that's similar and in the same position.
 
Mikado463

Mikado463

Audioholic Chief
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331 3 28
#16
nice size room, if it were me I'd start with corner bass trapping and first point of refection, have a listen and go from there.
 
M

moves

Audioholic Chief
Ratings
95
#17
How high is the ceiling?

One reason it's not as loud as before is the fact that you're sitting farther from the back wall and the reflected sound was able to augment what was coming from the front of the room. That sound path is now close to 60 feet- even if the wall is totally reflective, the reflected sound level is far below that of the direct sound. Also, you might want to move your chair- where you sit relative to the speaker position makes a difference but a curtain will absorb sound, not reflect it. You don't have a problem with reflection, you have a problem with attenuation. This is similar to taking speakers outside and being disappointed because you expect them to sound the same as when they were inside- it can't happen unless you're in a space that's similar and in the same position.
Thanks for the feedback and the makes sense... I also ran the MCAAC Room correction on the speakers and have them 3 feet from the wall and they sound much better now. I no longer have to play them at -6db.... but I just want to get the best that I can since I invested a lot of money into this equipment.. might as well get the most from them. I'll try the new mic that I ordered and see what happens. I am also not sure of the side wall is insulated. I know the ceiling is not... It's a drop ceiling at about 7 feet. high and underneath is not insulated.
 
highfigh

highfigh

Audioholic Warlord
Ratings
2,698 9 4
#19
When looking at the acoustical performance of a product @ 125 hz... what does the number mean? It says at 125hz the 3 inch safe and sound yields 0.52... is a higher or lower number better?

The 3 inch rock wool omfortboard 80 is rated at 0.75 at 125Hz.

https://www.rockwool.com/products/safensound/
That's the NRC, or Noise Reduction Coefficient and the higher the number, the more it's doing to help. If you look at the higher and midrange frequencies, you'll see that the number is larger. Doubling the thickness increases the effectiveness, as does increasing the space between the wall and the absorptive material, but only for frequencies higher than bass. That requires more material.

Three things can happen when sound energy hits a material:
-It reflects, more or less energy, depending on the hardness and smoothness of the surface and the density of the material. Lightweight materials are made to move, dense materials just sit there.

-It scatters, more or less, depending on the roughness/jaggedness of the surface.

-It passes into or through because the material is porous. If the material is dense enough, it will slow the motion of the energy- sound is caused by an alternating increase and decrease in air pressure, so the energy causes the air to move forward and backward. Whenever something is moving and it hits some object or material and it loses energy, heat is produced. It's not a lot, but the amount is directly related to the energy loss. High frequencies don't require much to reduce the energy, but low frequencies do- that's the reason heavy, thick absorptive material is needed, or something that's dense and able to move when the sound hits it.

https://svetlanaroit.files.wordpress.com/2009/11/visual_values2.pdf
 
M

moves

Audioholic Chief
Ratings
95
#20
Yes makes sense! I've been reading a bit here:

https://www.gearslutz.com/board/stu...panels-roxul-safe-n-sound-rockboard-60-a.html

I learned a lot and It all coincides with what you just said. Do you think ,52 and ,75 is a significant difference? Why would something like the safe sound be less dense and effective as something that is not meant for sound?

I've looked on the Roxul site and couldn't seem to find density information... that's odd because the other site I linked to, the people are talking a lot about density.

I also have the drop ceiling with no insulation that I am thinking of doing. I also have 2 concrete walls surrounding the left front channel with an opening to the right of the listening position.I think insulating may help with noise getting through the ceiling and losing energy. I am also concerned about the reflections passing through the insulation and reflecting off the concrete walls. It might be wise to cover those walls with a 2-3 inch gap........ Not sure. I've ordered the mic so I will play around with it once it arrives.
 
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