Acoustical Treatments Master Thread - Page 367 - AVS Forum | Home Theater Discussions And Reviews
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post #10981 of 11010 Old 08-20-2015, 05:10 PM
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3d surfaces simply translate into higher cost than absorptive surfaces, but I find the results more pleasing.
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post #10982 of 11010 Old 08-21-2015, 05:17 AM
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Originally Posted by AXLCMT View Post
I plan on putting the usual OC703 on my side walls and front corners bass traps and the side walls up to 42" high (ear height).

The one side wall is 23 feet long and the other is 16 feet long.

Does it matter whether I buy the OC703 4' x 8' or 2' x 4'?

Does it make a difference?
The size does not matter as much as the thickness. Honestly if you can I would use no less than 4" on wall and get bass trapping in the corners.

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post #10983 of 11010 Old 08-21-2015, 05:26 AM
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Absorption is probably overused a lot in the dedicated theater builds because it's easily understood, cheap, and easy to do. It takes a little more to do diffusion well. But balance them is where you get the sparkle in a room.
I agree 100% on the diffusion, but what I mostly see is rooms with the wrong kind of absorption. Using just 2" fiberglass throughout the room is going to kill the upper frequencies, and leave the low end bouncing around. With the proper trapping the low end will become much tighter/focused. There is a reason we designed a lot of our trapping with limiters. It absorbs only below 400hz which is always welcome in smaller rooms or we use a built in scatter plate to diffuse/scatter the upper frequencies in the room.
http://www.gikacoustics.com/flexrang...ogy-bass-trap/
Many ways to skin a cat, but a lot absorption can be your friend, if used properly.

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post #10984 of 11010 Old 08-21-2015, 09:04 AM
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Originally Posted by myfipie View Post
I agree 100% on the diffusion, but what I mostly see is rooms with the wrong kind of absorption. Using just 2" fiberglass throughout the room is going to kill the upper frequencies, and leave the low end bouncing around. With the proper trapping the low end will become much tighter/focused. There is a reason we designed a lot of our trapping with limiters. It absorbs only below 400hz which is always welcome in smaller rooms or we use a built in scatter plate to diffuse/scatter the upper frequencies in the room.
http://www.gikacoustics.com/flexrang...ogy-bass-trap/
Many ways to skin a cat, but a lot absorption can be your friend, if used properly.
Would building a raised seating platform as a bass trap eliminate the need to have corner bass traps? Or I should say, could the platform trap perform the same way as corner traps?

My room is a closed 20Lx16W...just fyi.

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post #10985 of 11010 Old 08-21-2015, 03:05 PM
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Originally Posted by asoofi1 View Post
Would building a raised seating platform as a bass trap eliminate the need to have corner bass traps? Or I should say, could the platform trap perform the same way as corner traps?

My room is a closed 20Lx16W...just fyi.
Bass trap riser can help tame standing wave problems but you need to locate it and the vents near a boundary so it's not applicable for every room or situation.

You can also make your riser tuned to help at certain frequencies; it's called a helmholtz resonator. Think like when you blow across a bottle top... Except in this case you tune it to help at a certain place you need it. That's not acoustics 101 topic though.
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post #10986 of 11010 Old 08-21-2015, 03:07 PM
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Originally Posted by blazar View Post
3d surfaces simply translate into higher cost than absorptive surfaces, but I find the results more pleasing.
I'm generally not a fan of sensory deprivation chambers either . That's what a lot of diy theaters become when people go overboard with basics. Less is more. Same goes for killing light. I was in a theater that was pitch black, everything was black. It was awful.
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post #10987 of 11010 Old 08-21-2015, 07:34 PM
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Quote:
Originally Posted by Mfusick View Post
I'm generally not a fan of sensory deprivation chambers either . That's what a lot of diy theaters become when people go overboard with basics. Less is more. Same goes for killing light. I was in a theater that was pitch black, everything was black. It was awful.
So color grading rooms are painted 18% neutral grey. What would the acoustic equivalent be? For audio it seems like there are guidelines for reverb time, flatness of the room response and varying methods of getting there either through absorption, diffusion, room design, EQ, speaker placement, speaker design, etc. depending on personal preference. People don't typically listen or mix in an anechoic chamber.

Here'$ a live one!$$. No doubt it sounds great! And very pretty too!



Cheers,

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post #10988 of 11010 Old 08-22-2015, 04:13 AM
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That seems like a lot ^. Lol!

I think a lot of mastering studio tend to be a bit more on the dead side. But some reflections can add envelopment and spaciousness. You never want to kill them all; you only want to diminish the bad ones or the sound power to the point they are not a problem. If you listened to music in an anechoic chamber it would NOT sound good (natural).
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post #10989 of 11010 Old 08-22-2015, 04:31 PM
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Quote:
Originally Posted by Mfusick View Post
That seems like a lot ^. Lol!

I think a lot of mastering studio tend to be a bit more on the dead side. But some reflections can add envelopment and spaciousness. You never want to kill them all; you only want to diminish the bad ones or the sound power to the point they are not a problem. If you listened to music in an anechoic chamber it would NOT sound good (natural).
Here's a better pic, I think someone at Blackbird Studios likes skyline diffusion.


It's Blackbird Studios and I would guess calculate that those skyline diffusion ( http://www.mh-audio.nl/DiffusorCalcu...iffuser#result) go down to around 300Hz. A lot of work, a lot of weight if they're solid wood.

Cheers,

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post #10990 of 11010 Old 08-23-2015, 09:19 AM
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That is really cool, but has negative wife acceptance factor. ;-)

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post #10991 of 11010 Old 08-24-2015, 09:36 AM
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I'm asking questions that I'm sure are asked elsewhere here, but considering there are nearly 11,000 posts I've got little hope of finding an answer. I've recently moved into a new house and have my first real dedicated theater. I'm thinking that acoustical treatments are going to be my next upgrade and I'm trying to figure out where I want to start. My research has lead me to thinking bass traps might be the way to start (along with treating the first reflection points). With bass traps how much is that going to change ability to hit the ULF? Right now I've got dual SVS subs (corner loaded) and have usable bass to just north of 12hz. I don't really want to lose my ability to play that low by taming room modes. On the subject of bass traps, my initial plans would not have floor to ceiling bass traps. Right now I'm looking with some interest at the GIK room kit 3, which would give me 4 traps, one for each corner plus make some headway on those first reflection points. Are traps still worth it if I'm not going to have floor to ceiling. Finally with bass traps, how much do they help control peaks and nulls? I assume the end game here is a flatter response, I just am not sure what I should be expecting.

In terms of treating the room, my only other concern is using my bipole side surrounds. Those speakers depend on reflections to work, so wouldn't treating the room render them pointless?

Again, I know that most of these question are pretty basic, but acoustics is an area of this hobby that I'm really still clueless on.

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post #10992 of 11010 Old 08-24-2015, 01:04 PM
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If your room is untreated, there is a big chance that you have big nulls and/or big peaks at one or more frequencies, no matter if your system goes to 10 Hz or not. That's the whole point of bass traps, to smooth out those dips and peaks. DRC cannot cure nulls. More traps = more (useful) bass

I am sure more knowledgeable folks will chime in.

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post #10993 of 11010 Old 08-24-2015, 01:57 PM
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Quote:
Originally Posted by erwinfrombelgium View Post
If your room is untreated, there is a big chance that you have big nulls and/or big peaks at one or more frequencies, no matter if your system goes to 10 Hz or not. That's the whole point of bass traps, to smooth out those dips and peaks. DRC cannot cure nulls. More traps = more (useful) bass

I am sure more knowledgeable folks will chime in.
This is true.

You generally don't have problems at 10hz either.

It's worse than that, cause you have them in the more audible midbass regions where you can clearly tell difference because it's audible.
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post #10994 of 11010 Old 08-24-2015, 03:15 PM
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...I've got dual SVS subs (corner loaded) and have usable bass to just north of 12hz. I don't really want to lose my ability to play that low by taming room modes.
That's fine. As the others said, there will be no measureable change in that regard.
Quote:
Originally Posted by AllenA07 View Post
On the subject of bass traps, my initial plans would not have floor to ceiling bass traps. Right now I'm looking with some interest at the GIK room kit 3, which would give me 4 traps, one for each corner plus make some headway on those first reflection points. Are traps still worth it if I'm not going to have floor to ceiling.
Yep. The more traps the better, so some is better than none.

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Finally with bass traps, how much do they help control peaks and nulls? I assume the end game here is a flatter response, I just am not sure what I should be expecting.
Controling peaks and nulls is all they do - how much is reasonable question. The answer, as always, is "It depends." I wouldn't expect to take more than 3-5dB off of most peaks with a basic assortment of passive standard absorbers. Nulls should come up by a similar amount. Good before and after data on this is hard to find, but it is out there.

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In terms of treating the room, my only other concern is using my bipole side surrounds. Those speakers depend on reflections to work, so wouldn't treating the room render them pointless?
If those speakers require reflections (which I find a little dubious, but I'm not well-informed) then you should figure out where those reflections happen and endeavor not to place absorption there. Other than that, have a good time.


And finally - if you are trying to smooth the bass response, the first move should be locating the subs themselves (As well as considering changing the seating positions). Corner loading tends to result in the highest peak output, but least smooth response. Having two subs (in different corners, obviously) should help to smooth some of the variation corner loading produces, but it can't smooth all of it. Opposing wall midpoints might give you a smoother response and less seat-to-seat variation, which would render DSP more effective.
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post #10995 of 11010 Old 08-25-2015, 12:02 PM
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question...if im building corber bass traps with roxul...but cant go floor to ceiling due to a sub in that corner or other obstruction.. ...will that still be better than no trapping at all?

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post #10996 of 11010 Old 08-25-2015, 01:41 PM
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Originally Posted by Brian Fineberg View Post
question...if im building corber bass traps with roxul...but cant go floor to ceiling due to a sub in that corner or other obstruction.. ...will that still be better than no trapping at all?
It's going to depend on how much area you are able to cover. There's going to be a point where it's probably not really worth the effort. I'm not sure what that is, but I'd say between three and four feet would maybe be a minimum. Less than three feet, I'm not sure if it would do a whole lot.

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post #10997 of 11010 Old 08-25-2015, 04:05 PM
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Originally Posted by Brian Fineberg View Post
question...if im building corber bass traps with roxul...but cant go floor to ceiling due to a sub in that corner or other obstruction.. ...will that still be better than no trapping at all?
Probably yes, cover as much of the corner as you still can. How much coverage can you do? Have you built panels before?

Here's some other thoughts. I have 2'x4'x4" floor set bass traps for the 4 corners of my room. I wanted to treat the side wall but couldn't because the bass trap was in the way so I simply angled the bass trap to have it cover more of the back wall so I'm now able to hang a diffuser on the side wall. I also have 12"x12"x18"x24" triangle traps that I use where the larger ones won't fit due to wall hung speakers, doorways and headroom limitations.
Good luck.

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post #10998 of 11010 Old 08-26-2015, 07:22 AM
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Originally Posted by dnoonie View Post
Probably yes, cover as much of the corner as you still can. How much coverage can you do? Have you built panels before?

Here's some other thoughts. I have 2'x4'x4" floor set bass traps for the 4 corners of my room. I wanted to treat the side wall but couldn't because the bass trap was in the way so I simply angled the bass trap to have it cover more of the back wall so I'm now able to hang a diffuser on the side wall. I also have 12"x12"x18"x24" triangle traps that I use where the larger ones won't fit due to wall hung speakers, doorways and headroom limitations.
Good luck.

Cheers,
Yes I've built panels. My entire Ht is treated with wall panels etc. now looking to make bass traps. But in the front behind the screen the speakers I stands are in the way. In the back the left corner has a sub in it. And the other corner is free but near a walkway (would obstruct the walkway)

So back corner with the sub would be about 5' of bass trap above the speaker. That's really the only option
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post #10999 of 11010 Old 08-26-2015, 02:10 PM
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Quote:
Originally Posted by Brian Fineberg View Post
Yes I've built panels. My entire Ht is treated with wall panels etc. now looking to make bass traps. But in the front behind the screen the speakers I stands are in the way. In the back the left corner has a sub in it. And the other corner is free but near a walkway (would obstruct the walkway)

So back corner with the sub would be about 5' of bass trap above the speaker. That's really the only option
Yes, the 5' of treatment will make a difference.

The side that you can't treat the vertical corner on because it's a walkway...Can you treat the horizontal corners with bass traps in that location? If so that would help.

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post #11000 of 11010 Old Yesterday, 08:44 AM
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Hi all acoustic treatment experts, need your advise & help!

Today I have free time to take REW measurement of my dual subs with UMIK-1 post Audyssey XT32, FYI subs placement and seating positions very limited and I'm sitting 1-2 feet from rear wall, there are 3 huge dips/nulls around 55Hz, 70Hz and 85Hz, any ideas what's the culprit and how to eliminate those huge dips/nulls? is it because of reflections (rear wall/floor?) and can be solved by building few very thick bass absorbers/traps? or adding few more subs will smooth the nulls?


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post #11001 of 11010 Old Yesterday, 08:50 AM
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Would 1 mil plastic be considered acoustically transparent? I am putting up 5.5 inches of ultratouch behind my screen. Was going to buy fabric to cover everything, but it will not be seen. The plastic is very cheap at Home Depot. Thought I could use this instead.

Thanks
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post #11002 of 11010 Old Today, 06:46 AM
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I took a measurement of my theater last night. This is of my treated theater without the back wall treated (Sides, Front + corner bass traps in front)

Can someone please tell me what I am looking at? / Give an analysis

It looks like my SPL is pretty good (1/3 smoothing)
It also looks like I have big problems under 45hz and a null at 100Hz, is this correct?

Room is approx 17' long by 12' wide
Measurements are from main listening position 6 ft from back wall and 6 foot from side wall
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Hi all acoustic treatment experts, need your advise & help!

Today I have free time to take REW measurement of my dual subs with UMIK-1 post Audyssey XT32, FYI subs placement and seating positions very limited and I'm sitting 1-2 feet from rear wall, there are 3 huge dips/nulls around 55Hz, 70Hz and 85Hz, any ideas what's the culprit and how to eliminate those huge dips/nulls? is it because of reflections (rear wall/floor?) and can be solved by building few very thick bass absorbers/traps? or adding few more subs will smooth the nulls?

Can you hear those nulls? They look like cancellations due to reflections, and they may be narrow enough that you don't hear them.

Nulls are always some kind of cancellation, and that can - in theory - be resolved with absorption. All of the above is a potential solution, but you need more data to know up front. You also need to decide what you're looking for at other seating positions. XT32 measures at multiple seats, doesn't it?
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post #11004 of 11010 Old Today, 07:14 AM
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Originally Posted by raynist View Post
Would 1 mil plastic be considered acoustically transparent? I am putting up 5.5 inches of ultratouch behind my screen. Was going to buy fabric to cover everything, but it will not be seen. The plastic is very cheap at Home Depot. Thought I could use this instead.

Thanks
Ray
If you are installing 5.5" of absorption purely for the bass absorption capability, then thin plastic is adequately transparent. However, behind a screen there is often a comb filtering of sorts that happens with high frequency reflection between the rear surface of the screen and the wall - 1mil plastic may not be adequately transparent to address this concern.
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post #11005 of 11010 Old Today, 07:18 AM
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Quote:
Originally Posted by batlin27 View Post
I took a measurement of my theater last night. This is of my treated theater without the back wall treated (Sides, Front + corner bass traps in front)

Can someone please tell me what I am looking at? / Give an analysis

It looks like my SPL is pretty good (1/3 smoothing)
It also looks like I have big problems under 45hz and a null at 100Hz, is this correct?

Room is approx 17' long by 12' wide
Measurements are from main listening position 6 ft from back wall and 6 foot from side wall
The dip at 100Hz doesn't show up with 1/3 octave smoothing, so I would forget it. There's a good chance it is related to a standing wave between the floor and ceiling and will be tough to treat anyway. The ringing below 45Hz is unclear, since we don't see it tail off in your plot. If you can extend the time in the diagram, you may find that this is just your room's noise floor.
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post #11006 of 11010 Old Today, 07:25 AM
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Quote:
Originally Posted by HopefulFred View Post
If you are installing 5.5" of absorption purely for the bass absorption capability, then thin plastic is adequately transparent. However, behind a screen there is often a comb filtering of sorts that happens with high frequency reflection between the rear surface of the screen and the wall - 1mil plastic may not be adequately transparent to address this concern.
Thanks.

I ended up using 0.31 mil plastic.

As a non scientific test I covered one of my headphone (just left side) with this and could not hear a difference.

I have some 2.5 inch acoustic foam I was thinking on putting on the front of the traps behind the screen to help wih high frequencies.
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post #11007 of 11010 Old Today, 07:50 AM
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Quote:
Originally Posted by raynist View Post
As a non scientific test I covered one of my headphone (just left side) with this and could not hear a difference.
It could also be that, probably like me, you don't hear much above about 15KHz.
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post #11008 of 11010 Old Today, 08:05 AM
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Quote:
Originally Posted by HopefulFred View Post
Can you hear those nulls? They look like cancellations due to reflections, and they may be narrow enough that you don't hear them.

Nulls are always some kind of cancellation, and that can - in theory - be resolved with absorption. All of the above is a potential solution, but you need more data to know up front. You also need to decide what you're looking for at other seating positions. XT32 measures at multiple seats, doesn't it?
Thanks for your opinion, FYI that Audyssey XT32 calibration was done at one middle seat only (my couch have 4 seats), I also suspect those 3 huge nulls due to cancellation which caused by reflections especially rear wall since I sit so close to rear wall.

what additional data to know? speaker & subs placement? dual subs placed right below my screen, with center speaker placed in between dual subs, LR on both sides of subs
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Originally Posted by HopefulFred View Post
It could also be that, probably like me, you don't hear much above about 15KHz.
This is true, I can't hear 16khz tone at all.
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Originally Posted by WereWolf84 View Post
what additional data to know? speaker & subs placement? dual subs placed right below my screen, with center speaker placed in between dual subs, LR on both sides of subs
What are the room dimensions - a diagram is often easiest/best.
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