What should I do for treatments in a concrete room?

NBPK402

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In my new HT I am now unsure as to whether I should have treatments on the walls above the curtains. I originally was going to use Roxul panels all around the room with one layer above the curtains. One layer below the curtains, and then 1st reflection points. The curtains are a heavy velvet stage curtain, and go wall to wall on the wall behind where the speakers will go. I am also installing curtains on the side wall too... on the right side it will go to the fireplace, and on the left to the door opening.

As you can see the room is all concrete or stone so it is very live, and large. I cannot do any treatment above the 2nd French cleat other than we will have a curtain to cover the windows when we watch movies. I am planning on getting more Persion rugs to put in front of the front 3 channels to stop floor reflection.
I have used DIY RPG Diffusers in the past, and also made my own absorption panels. I have been told by some to use diffusers instead of absorption panels in this room.
What should I do? My wife wants me to start getting the room appearance completed...meaning get the frames up for the panels so we can at least display art work on absorption panels where ever we are going to use absortion. If I do absorption I will make blank panels for now, and then fill later since Roxul is $100 plus shipping a bundle here vs $55 in the USA.
Closing the curtains has def made an improvement in intelligibility of voices alone. I will be using YPAO to tune the room until I can get Dirac. This year is my audio build part, and next year will be projector, screen, and new AVP.

I will have 3 horns for the front channels, 2 horns for side channels just behind the mlp side walls, and 2 more horns in the rear corners of the room (in front of the bar, and where the coat rack is). The rears will be angled toward the mlp from the corners.
With the curtains in the front I will not be able to have corner traps unless I do not have the curtains go all the way to the wall...which would then mean I would have light leakage. Also the curtain direction is being changed to a single rail which opens and closes like a normal curtain. When the curtains are open I will have layers of material in the corners...especially with the side and front curtains all retracting into each corner. I can put panels down the center of the front wall though.

Room dimensions
Width 19' 7"
Height to center of the Boveda ceiling 32'
Length from below loft to front wall 21'
Length from hall way door to the front wall 46'
Length from kitchen bar to the front wall 31' 7"
MLP to front wall 18' 7"
 
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j.man1503

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If the walls and ceiling are concrete, you should prioritize bass traps in the corners. The more robust one's walls are in standard consumer rooms (not concert halls) the more difficulties it creates in the bass region.

The suggestion to put diffusion puzzles me, given the liveness that you describe the room. Diffusion is needed in any room. However, if the room is already live, this suggests that you'll need to prioritize absorption.

Concerning first reflection points, Floyd Toole in his famous book (Sound Reproduction...) argues from extensive research that first reflection points are actually desirable. Flutter echo between parallel walls are more sonically damaging.
 

NBPK402

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The only spots I can think of for bass traps are... the rear corners where the surround rears will go (bass bins would entirely block the panels unless I put that em just above the bass bins), and the corners on the loft wall facing the front of the room. I could put a 4' high one above the curtains, but it is going to look strange in the middle of the wall, and I do not know how much good it will do with the bottom of the panel being 13' above the ground. I was planning on having panels behind the curtains on the front wall outlining the windows, and also on the sides where we have wall (I do not want to cover the windows with panels).

Should I do absorption panels above the windows or just do first reflection? My last room we had absorption on the front and rear walls plus first reflections on the walls and ceiling. This time I can go to top French cleat only...above that the wall starts its curve.
 

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The more I think about it....the more I think I can put bass traps in the front corners (floor to the 2nd French cleat). I am thinking when I put up the new single curtain rail, I can shorten it by about 2', and I can make the curtain just overlap the wall by a few inches on each side. If I make bass traps the curtains would push against the bass traps there by eliminating any light. If I go this way I would be better off to have the curtains open from the center outward just like I have them now. My height channels will no longer be there either (Dolby, and Atmos want the fronts to be just in front of the seating area, and if I left them in the front they would be a long ways from the proper location) so there will be no interference with the mounts. My front left and right channel speakers would be right in front of the bass traps, but I do not forsee any problems with that other than the blocked part not working.

The rear channels I can make bass trap, but only on one side as the other side is at the bar, and I do not know how that would look... I will have to decide on that when I start to make the traps.

Can the Bass traps be made of pink fluffy or do I need something like Roxul? If pink fluffy will work I can start on them much sooner as that is readily available.
 

DanDan

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Hola Negatron. Pink Fluffy is ideal for deep bass traps. But for flat panel traps you need to use denser material with higher Gas Flow Resistivity. At 8" let's just say 3 pcf 48KG. 6" let's say 60-80KG. The common commercial 4" traps have traditionally been 100KG 6pcf.

DD
 

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Hola Negatron. Pink Fluffy is ideal for deep bass traps. But for flat panel traps you need to use denser material with higher Gas Flow Resistivity. At 8" let's just say 3 pcf 48KG. 6" let's say 60-80KG. The common commercial 4" traps have traditionally been 100KG 6pcf.

DD
Hi Dan, I am thinking of a 2' wide corner trap that would be about 13" deep at the deepest part, and 2" deep at the sides of the triangle. So that would still be a shallow trap due to the side depth, correct?
 

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It looks like I will need 9 bundles of 2" @ 6 to a bundle to go 16'high on 2 walls, and another bundle could do my center wall with 2" too. Then I can get a little more for the loft wall corner, and all that I will have left is the fireplace unless I need to do it up to the mantle...yes, or no on the fireplace?

I am assuming from what you said I need to do the corners like this, and a 2" piece with pink fluffy stuffed behind it would not be as good for my corner traps. I ask this because this would be signicantly less expensive for the corner traps.
 

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I will leave the practical build details and stick to the Acoustic. The original TESTED StudioTips SuperChunks were 32" wide. About 17" deep at the apex, but let's note, thinner everywhere else. They work well, just as the tests show. I have tried 24" wide SSCs a few times. They were very disappointing. I strongly suspect a Corner Straddling 6pcf trap may well perform better due to it's 70-80 Hz resonant absorption peak. As a wild generality, I don't think it worth the framing to trap less than 4" fibre plus 4" air gap. Or 8" +
DD
 

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I just came up with an idea. Would a 24" half round absorber sealed to the corner work better than a superchunk since it would have a cavity behind it?
 

DanDan

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A cavity is not better than fibre, it is a sort of free lunch though. i.e. Nearly as good as fibre for no money.
A rigid fibre batt straddling a corner floor to ceiling is a very particular scenario. It has a resonant 'drum head' absorption peak. I have no idea what a half round would do. It places probably thinner fibre, further from the boundaries. Probably quite good, but I would fill it with fluffy to be sure. Which would eliminate any resonant bonus! LOL.
I have seen other 24" traps deployed, Lenrds I think. Framed fluffy is the best. My favourite Studio Builder Boggy uses 24" DEEP on all boundaries. Note, big fibre traps can be any shape, square, like GIK SoffiTraps, Rectangular or angled to suit your space. Some people just stack up rolls of attic insulation in corners hidden by curtains or whatever.
DD
 

NBPK402

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A cavity is not better than fibre, it is a sort of free lunch though. i.e. Nearly as good as fibre for no money.
A rigid fibre batt straddling a corner floor to ceiling is a very particular scenario. It has a resonant 'drum head' absorption peak. I have no idea what a half round would do. It places probably thinner fibre, further from the boundaries. Probably quite good, but I would fill it with fluffy to be sure. Which would eliminate any resonant bonus! LOL.
I have seen other 24" traps deployed, Lenrds I think. Framed fluffy is the best. My favourite Studio Builder Boggy uses 24" DEEP on all boundaries. Note, big fibre traps can be any shape, square, like GIK SoffiTraps, Rectangular or angled to suit your space. Some people just stack up rolls of attic insulation in corners hidden by curtains or whatever.
DD
So make a 24" wide half round, and bend a 2" piece of rockwool to the half round shape, and then fill the cavity with fiberglass?
2: Make a chunk style of half round pieces of rockwool stacked up like a corner chunk...leave the cavity behind or stuff with fiberglass?
3: Make a half round and stuff the corner , and half round with fiberglass?
 

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I would guess that square would be a lot easier to do than round. GIK SoffiTraps test data is pretty impressive.
They are 17" squares I think, but 24" would be much better. Concrete reflects strongly all the way down to the lowest LF.
That curves ceiling may cause problems also.
DD
 

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Yes...the curved ceiling is going to be a big problem. I am thinking I can take the 2 front corner traps up to the point where the ceiling starts to curve. That is at about the height of the top of the lights on the side wall. I am also trying to decide if I should make flat absorption panels for the row right below the French cleat or make them all 1/2 rounds (maybe 10 or 12" half rounds). And then make flat absorption panels down to the floor back to the left side of the room where the door opening is closest to the windows. What do you think?
 

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This is the only one I have been able to find in Mexico...
http://www.knauf.mx/

I just measured, and my traps can be about 18' tall, I am thinking of extending the trap out about 6-8" from the corner. Since the curtains will need to seal against it I am thinking it will end up being almost a triangle outwards too. I will draw up an image to make this clearer.
 

NBPK402

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Here is what I am thinking of in the post above... Does this make sense? Please excuse my drawing... I was on my last piece of paper and had no eraser. I am not sure, but maybe I can even get away with the recess entirely(or am I better off keeping 4" inside the corner with 4" more on the outside), and extend the trap material the full 25" for a 4" thick panel, and just let the curtains go over the bass trap until they stop... I have about 5" of clearance from the wall to the curtain for sound panels calculated in to the curtain rod installation for the sound panels above the window to clear the curtains.
I goofed on the dimension for the depth... it is 18" from the corners to the back of the corner NOT from the front to the corner.

20190121_140011.jpg
 

j.man1503

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The only spots I can think of for bass traps are... the rear corners where the surround rears will go (bass bins would entirely block the panels unless I put that em just above the bass bins), and the corners on the loft wall facing the front of the room. I could put a 4' high one above the curtains, but it is going to look strange in the middle of the wall, and I do not know how much good it will do with the bottom of the panel being 13' above the ground.

I agree, it might look strange. Although, I believe it will still help you in the bass region. However, if you're going with the corner traps, you might not need this anyway.

I was planning on having panels behind the curtains on the front wall outlining the windows, and also on the sides where we have wall (I do not want to cover the windows with panels).

I definitely would not cover the windows. Although ultra purist will insist to put the panels over even windows.

Should I do absorption panels above the windows or just do first reflection? My last room we had absorption on the front and rear walls plus first reflections on the walls and ceiling. This time I can go to top French cleat only...above that the wall starts its curve.

Great idea to have the front wall and rear wall full of absorption.
 

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We covered our last HTS front, and rear wall, and it worked great. Last time we used 2" on the front and 12" on the rear I believe. This time I cannot cover the front and rear as much as before.

I can cover the front wall from the windows up...about 6', and then down the center behind the curtains, plus about 16' on the front corner traps.
On the rear I am unsure what I can do other than the one corner. Beyond that I am in my wife's
territory. I can put up treatment on the loft area which would get me one layer on the back wall, and another layer on the loft balcony wall...both of which can be 2" or maybe 4". I also can do a trap on the balcony wall, but not on The loft corner as that is my wife's dance floor, and I already put my rack on the loft.
 

j.man1503

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You might have to do some experimentation with the treatments elevated so high above the listening environment. Since it is will only contribute to bass region and reverb and not flutter echo first reflections, I would start small and then add. I would do all the corners you can for bass and some broadbands at the listening level (I know you said you can't do many of these). Then, I'd measure the rooms reverb and bass response and see where you are. If you need to reduce the reverb and squash some huge bass peaks, then you could add more above the listening level as you have suggested.
 

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You might have to do some experimentation with the treatments elevated so high above the listening environment. Since it is will only contribute to bass region and reverb and not flutter echo first reflections, I would start small and then add. I would do all the corners you can for bass and some broadbands at the listening level (I know you said you can't do many of these). Then, I'd measure the rooms reverb and bass response and see where you are. If you need to reduce the reverb and squash some huge bass peaks, then you could add more above the listening level as you have suggested.
So take the bass traps up to the upper french cleats, and then work on panels from the curtains down only for a start?
 

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You may also consider any 90 degree angle in the room not just corners... For instance floor to wall and wall to ceiling... Another material to look into is also activated carbon/charcoal for a low frequency DYI absorber...
 

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You may also consider any 90 degree angle in the room not just corners... For instance floor to wall and wall to ceiling... Another material to look into is also activated carbon/charcoal for a low frequency DYI absorber...
I was planning on going from the floor in the corners, but not along the whole floor with traps. We have a cat, and I can most likely stop him from clawing the bass traps, but if I did it all along the floor... not likely to stop. I have seen articles about the activated carbon, but I have never seen anything about a DIY or what the parts are to buy. Do you have a link by any chance?
 

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