Bass traps with regular insulation advise needed - AVS Forum
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post #1 of 24 Old 05-16-2012, 07:40 AM - Thread Starter
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I am now planning the sound treatment material list and need to know about corner bass traps when using regular fluffy insulation.

I know with super chunk traps folks are cutting the triangles and stacking them, but with the regular (R13-R30) insulation... do they need to be in triangles or a stack of squares?

FYI, my side corner trap space in limited to 15" on the front wall and 15" on the side wall (behind the AT screen). I think this works out to about 21.5" on the diagonal.

Thanks,

Scott
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post #2 of 24 Old 05-16-2012, 10:50 AM
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Quote:
Originally Posted by BroncoSport View Post

I am now planning the sound treatment material list and need to know about corner bass traps when using regular fluffy insulation.

I know with super chunk traps folks are cutting the triangles and stacking them, but with the regular (R13-R30) insulation... do they need to be in triangles or a stack of squares?

FYI, my side corner trap space in limited to 15" on the front wall and 15" on the side wall (behind the AT screen). I think this works out to about 21.5" on the diagonal.

Thanks,

Scott


Scott,

Dragon contributed a good, comprehensive post regarding this exact topic here. If you have any additional questions, fire away. You're already ahead of the game by understanding you need fluffy, SSC traps,....that's a good thing.

Best of luck

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post #3 of 24 Old 05-16-2012, 12:14 PM
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I'm in the same boat as you. I read through the post FOH linked. Here's a relevant snippet.

Quote:
Originally Posted by DragonFyr View Post

The easiest is to use three vertical trim strips. Two 2"x2"s ripped diagonally to provide three triangular strips affording a 45 degree front face is optimal.

These are installed in the apex of the corner and also ~ 24" on the side wall and ~30" on the front wall. Plastic orchard netting is then stapled to form 3 or 4 equally sized vertically divided sections. Strips of the 'pink fluffy stuff' is then maximally fluffed and installed standing vertically facing the trap's front.

I'm not sure I understand exactly how he's recommending you orient the netting and the insulation.

You frame it in with the 2x2 triangles. I get that. But which way is it with the netting/insulation?

My guess: The netting goes up vertically and parallel to the 45 degree face of the triangle. Behind that, about the depth of your insulation, another net, and then so forth. Then you cut your insulation the length of the floor to ceiling and stand it up between the netting.

I'm not sure.

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post #4 of 24 Old 05-16-2012, 03:25 PM
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It's funny Steve, I think you've read what he wrote correctly (though I agree it's not entirely clear), but I haven't seen (at AVS) anyone build a trap that way. Just for clarity, I doodled up some drawings. The design on the left is the one you described, and I think dragonfyr intends. It could be filled all the way to the corner, but may not improve much as a result. The sketch on the right is the way I have seen them built, but I'm not sure what influence the shelves may have, or how easy they would be to build compared to the first design.
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post #5 of 24 Old 05-16-2012, 03:40 PM
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That's exactly what I was thinking, nice work!

The idea of building it with triangular shelves sits better with me for no reason more than it seems easier to build, sturdier. Since Dragonfyr promoted vertical placement of the insulation, I could cut the insulation and set it up on the short edge and make the shelves 16" apart. This would keep it vertically oriented.

I also like his idea of using orchard netting, which I could simply staple to each layer/shelf to hold up the center pieces of insulation.

My good friend that I talk to about home theater stuff tells me I overthink and overbuild all of my stuff. I have a sneaking suspicion I'm doing it again...

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post #6 of 24 Old 05-16-2012, 03:55 PM
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Quote:
Originally Posted by stevegravley View Post

My good friend that I talk to about home theater stuff tells me I overthink and overbuild all of my stuff. I have a sneaking suspicion I'm doing it again...

Don't let that stop you; I don't.
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post #7 of 24 Old 05-16-2012, 04:41 PM
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I did these a while ago when I got bored. I tried it this way due to restrictions. Not sure if they would change much on a graph, but I could tell a bit (placebo?).

My dual 15's are behind the seating. Tonight I'm going to make some above the subs from ceiling, down 4 ft. 30"x24"x24". I had all materials in the garage.

In the front I'm just using the curtains to cover and making a fabric frame for the back. This room is all trial and error since this house isn't permanent.

Not sure if the pic attached...

Attachment 246823
LL
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post #8 of 24 Old 05-16-2012, 04:43 PM
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A few better pics.
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post #9 of 24 Old 05-16-2012, 05:41 PM - Thread Starter
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I read through his lengthy post and kinda got lost. With the added drawing, it now makes more sense. Thanks for that!

Now IF I make the frame and place a vertical piece of insulation in between the mesh (as described).... the question remains of which R value insulation would be best.

Also, I can't quite seem to understand IF there is a noticable difference between the shelves with fluffy triangles or the suspended vertical piece.

Thanks,

Scott
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post #10 of 24 Old 05-16-2012, 06:38 PM
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I'm not fully versed in the "why" of any of this, but my understanding from dragonfyr's post (and there is some disagreement on this point, but I trust dragonfyr in this regard) is that the lowest gas-flow resistivity (read lowest density) is usually the best choice for very low frequency absorption. As porous absorption is velocity-based, the areas nearest the wall provide the lowest benefit - for that reason, the smaller triangle in the deep recess of the corner provide very limited additional benefit. Given that, the "fluffiest" insulation will be best (lowest "R" value, right?) and I bet (personally, but with your money ) that the two methods I sketched are identical - so which is easier to build properly, and which costs you less time and money?

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post #11 of 24 Old 05-16-2012, 08:16 PM - Thread Starter
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Yes ...but, utilizing the vertical method would allow for any variable of R value insulation. The density of the various R values are very similar per square inch. R13 for example, is just as "fluffy" as R19. Only difference is the thickness of the insulation (3.5" to 5.5"). I would assume that the thickness would have some effect on the dampening, so what thickness is recomended? Also, would this be using faced of unfaced insulation?

The stacked triangle (fluffy insulation) method would have the same thickness from the corner to the middle of the long measurement of R30 to R60 insulation.
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post #12 of 24 Old 05-17-2012, 04:22 AM
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Quote:
Originally Posted by BroncoSport View Post

R13 for example, is just as "fluffy" as R19. Only difference is the thickness of the insulation (3.5" to 5.5"). I would assume that the thickness would have some effect on the dampening, so what thickness is recomended? Also, would this be using faced of unfaced insulation?

Ah, right. sorry (I haven't installed insulation, yet, so I have trouble remembering those details... anyway). Thicker is better, as usual, but I don't know where the diminishing returns kick in.

The facing relates to your particular high frequency needs. Without measurements I wouldn't know where to begin - even with measurements I wouldn't know how to give a competent recommendation. I suspect that measurements show that most DIYers could use more high frequency input back into the system because all the porous absorption tends to suck it out. Assuming that suspicion, 6mil plastic or some paper facing would probably result in benefit - in fact I understand that even heavier facing can not only reflect high energy content (keeping the room from going dull sounding - maintaining the brightness of your speakers) but also enhance the low frequency absorption of the trap, allowing it some additional resonant absorption as the trap begins to approximate a tuned absorber.

*please note that I am just reiterating what I have understood from other people's ramblings - I have no first hand experience with this at this point, and easily could have misunderstood something along the way.
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post #13 of 24 Old 05-17-2012, 08:08 AM
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The point of bass trapping in corners is based on really 2 things. The size of the bass trap and how much area you cover. Both are important but if the size is standard 2' across the corner (either totally filled or a panel straddling that is 4" thick) then focusing on covering as much corner area should be your priority. Put simply, the more area you cover the better the response will be on the low end.
As far as density, if filling the corner (24" across, with 17" sides) you can use fluffy but to make sure I would recommend 3 pound if possible.
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post #14 of 24 Old 05-17-2012, 08:23 AM
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Quote:
Originally Posted by HopefulFred View Post

........ Assuming that suspicion, 6mil plastic or some paper facing would probably result in benefit - in fact I understand that even heavier facing can not only reflect high energy content (keeping the room from going dull sounding - maintaining the brightness of your speakers) but also enhance the low frequency absorption of the trap, allowing it some additional resonant absorption as the trap begins to approximate a tuned absorber........

This may be a reason for building the traps vertically. I've read a few designs that call for 6mil plastic between vertical layers of insulation in the bass trap to help with high frequency response of the room. Laying the insulation flat would not allow you to do that.

Just a thought.

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post #15 of 24 Old 05-17-2012, 08:53 AM
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Quote:
Originally Posted by J_P_A View Post

This may be a reason for building the traps vertically. I've read a few designs that call for 6mil plastic between vertical layers of insulation in the bass trap to help with high frequency response of the room. Laying the insulation flat would not allow you to do that.

Just a thought.

I would not put them between the layers as the front layer will absorb to much upper frequency. I have actually tried the layer between, in our test room and did not see any more absorption on the lows. Now if you put it on the front you will.

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post #16 of 24 Old 05-17-2012, 09:31 AM - Thread Starter
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Quote:
Originally Posted by myfipie View Post

I would not put them between the layers as the front layer will absorb to much upper frequency. I have actually tried the layer between, in our test room and did not see any more absorption on the lows. Now if you put it on the front you will.

Very interesting and good information, thanks. Would there be any benefit to straddling the corner with thicker insulation...say R19 instead of R13?
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post #17 of 24 Old 05-17-2012, 09:39 AM
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Quote:
Originally Posted by BroncoSport View Post

Very interesting and good information, thanks. Would there be any benefit to straddling the corner with thicker insulation...say R19 instead of R13?

If you did you would want to make them thick (over 6"). For panels that are 6" or thinner I recommend some density as it gives stiffness to the panel which can give it a bit of a spring action around the 70 to 80hz area. That with a limp membrane really helps. If you look at our testing, in the lab of the 244 and Monster panel you can see the increase in absorption in that area.
http://www.gikacoustics.com/absorption.html
Other things are going on with the product but you can get that effect if DIY'ing yourself.

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post #18 of 24 Old 05-17-2012, 09:45 AM
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Quote:
Originally Posted by myfipie View Post

I would not put them between the layers as the front layer will absorb to much upper frequency. I have actually tried the layer between, in our test room and did not see any more absorption on the lows. Now if you put it on the front you will.

Gotcha! Now that you mention it, I think that is the sort of design I'm remembering. Front wall, not in the corner traps.

Carry on

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post #19 of 24 Old 05-17-2012, 06:42 PM
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I thought the "shelving" was to provide support so as the bottom does not become compressed from weight above.
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post #20 of 24 Old 05-17-2012, 06:51 PM
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I thought the "shelving" was to provide support...

And you're right.
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post #21 of 24 Old 05-23-2012, 10:13 AM
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Quote:
Originally Posted by myfipie View Post

I would not put them between the layers as the front layer will absorb to much upper frequency. I have actually tried the layer between, in our test room and did not see any more absorption on the lows. Now if you put it on the front you will.

So are you saying the 6mil plastic dragon mentioned on the front showed now effect in testin?
Just want to make sure I got it clear
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post #22 of 24 Old 05-23-2012, 10:35 AM
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Quote:
Originally Posted by calimark View Post

So are you saying the 6mil plastic dragon mentioned on the front showed now effect in testin?
Just want to make sure I got it clear

No, there's an increased effectiveness with the plastic adhered to the front face of the trap. He was explaining not to place the membrane between layers in the middle of the trap.

This has been the result of testin



Good luck

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post #23 of 24 Old 05-23-2012, 10:38 AM
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Oops..sorry typed my thoughts backwards .Thanks.
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post #24 of 24 Old 05-23-2012, 12:32 PM
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Quote:
Originally Posted by FOH View Post

No, there's an increased effectiveness with the plastic adhered to the front face of the trap. He was explaining not to place the membrane between layers in the middle of the trap.

This has been the result of testin



Good luck

Correct.

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