Bass traps with regular insulation advise needed

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

I'm in the same boat as you. I read through the post FOH linked. Here's a relevant snippet.


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.

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.

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...

Don't let that stop you; I don't.

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

A few better pics.

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?

$0.02

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.

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.
http://www.gikacoustics.com/video_basics.html
http://www.gikacoustics.com/news_081610.html

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.

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.

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

I thought the "shelving" was to provide support so as the bottom does not become compressed from weight above.

And you're right.

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

Oops..sorry typed my thoughts backwards .Thanks.

Correct.