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Post by yves on May 20, 2013 8:14:17 GMT -5
(Any advantage/disadvantage to setting these slightily out from the corner? If so by how much?, or if not, should they be pretty much right up against the baseboard?). Yes, since you will be lining the exterior to keep the air gap in the middle, allowing some air to flow between the exterior and your walls will likely help to improve bass absorption. Another trick that will also help to improve the bass absorption is to cover the exterior of the corner bass traps with kraft paper, which you can glue directly onto the batts using spray glue. Don't use too much glue or you will risk soaking the batts. Don't use kraft paper inside the air gap in the middle. Once dried, you can then apply that 'sock' you mentioned. |
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Post by The Mad Norseman on May 20, 2013 12:35:56 GMT -5
(Any advantage/disadvantage to setting these slightly out from the corner? If so by how much?, or if not, should they be pretty much right up against the baseboard?). Yes, since you will be lining the exterior to keep the air gap in the middle, allowing some air to flow between the exterior and your walls will likely help to improve bass absorption. Another trick that will also help to improve the bass absorption is to cover the exterior of the corner bass traps with kraft paper, which you can glue directly onto the batts using spray glue. Don't use too much glue or you will risk soaking the batts. Don't use kraft paper inside the air gap in the middle. Once dried, you can then apply that 'sock' you mentioned. Thanks for the advice yves!, but never heard of the 'kraft paper' trick before, (I would think that would prevent the frequencies from penetrating the bass trap and being 'absorbed'?). The outer 'sock' covering will be removable so for starting out anyway I'll leave the kraft papaer off and provide for a vertical cavity up the middle as you and a couple others have suggested (but with a middle layer applied at the top & bottom as well), and try it that way first. It will be 'absorptive' on all three faces - including those facing the two nearest corner walls. maybe struggle with the wire mesh tonight!  |
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Post by yves on May 20, 2013 13:45:28 GMT -5
Thanks for the advice yves!, but never heard of the 'kraft paper' trick before, (I would think that would prevent the frequencies from penetrating the bass trap and being 'absorbed'?). The 'FRK' in Owens Corning 705 FRK is kraft paper and metal foil, but kraft paper without the metal foil will also get the job done nicely. As Ethan explained, it will deflect mid and high frequencies, but Ethan also provided a link to some measurements he did, which clearly show that it helps to improve bass absorption. The curved surface will cause it to act similar to the curved deflector shown in the first photograph of the article, as far as mid and high frequencies are concerned, while at the same time also giving you improved corner bass trapping. www.gearslutz.com/board/studio-building-acoustics/610173-acoustics-treatment-reference-guide-look-here.html |
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Post by The Mad Norseman on May 20, 2013 18:11:07 GMT -5
VERY interesting - thanks for the links yves! Much to learn and understand there... Just to keep the thread going, here's a photo of the 'short corner' where the left bass trap will go behind the left front speaker & subwoofer... You can see that 45" tall corner/wall segment that leads up to (yet another!) plant collection area! But actually, I like lots of plants (and a virtual full size tree!) in our HT's area as they also make great sound diffusers! Attachments:
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Post by yves on May 21, 2013 2:03:33 GMT -5
Don't thank me for it – thank Ethan Winer instead!  Speaking about diffusion, here's an interesting video on that. www.youtube.com/watch?v=4nzmBhkR4JQ(The GIK Acoustics website also contains a wealth of information on room treatments, BTW.) |
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hemster
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Post by hemster on May 21, 2013 2:54:59 GMT -5
Ethan knows a lot about acoustics and is a decent fellow but just pick an argument with him about this subject... I know who I'm wagering on! |
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Post by The Mad Norseman on May 21, 2013 13:06:58 GMT -5
Fore-warned is fore-armed hemster! (Thanks!  ). |
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Post by The Mad Norseman on May 21, 2013 17:54:21 GMT -5
Just ordered the 'Roxul Acoustical Fire Batts, Mineral Wool, etc.' & 56" wide Black Burlap acoustically transparent fabric - both from ATS Acoustics (on line). So we're on the way! I've also been toying with the idea of drilling three 1.5" diameter holes up through the base so that sound waves near the floor, or that find their way under the 'trap', can go up into the base trap...any real value in doing that? Or shall I just leave the base solid - like the top? Now is the time to do that if I'm going to...  |
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Post by The Mad Norseman on May 25, 2013 14:11:55 GMT -5
Its progress photo update time! The ATS Acoustics insulation & black fabric covering has arrived, and the 1/2" wire mesh bass trap surrounds are now in place, (to contain and conform the insulation). I left one side 'open' to receive the insulation of course...but frankly, I'm somewhat surprised I didn't close it all up and then find that out when I went to fill them...  Next step will be to fill in the countersunk screw holes in the top plates, sand, and spray paint the enamel satin black...then begin stuffing! Attachments:
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Post by The Mad Norseman on May 25, 2013 14:12:34 GMT -5
Here'a another shot closer up,... Attachments:
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Post by deltadube on Jun 22, 2013 21:06:21 GMT -5
like to see some pics with the insulation going in.. are you going to fill fully? laying the pieces flat...
lots of cutting..?
im using the afb as well 3 in x 23in x 47.. for the corner trap i was going to build 6 .1 ft x 25.75in 2x4 frame.. put in 2 sheets cover back and cover front wrapped to back with accoustically transparent fabric cotton sheets.... the electric staple gun is very handy for this.. stand in the corner on an angle.
works great.. 6 inches traps a ton of bass.. its simple and very effective..
the size make it ez to use the material 96in 2x4 - 22.75in gives you the 6.1ft . 47 and 23.5 1.5 sheet afb.. 22.75 piece is nailed on the inside of the ends flush.. everything just fits snug..
thanks for the peek Mad..
cheers..
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Post by yves on Jun 23, 2013 8:56:30 GMT -5
The problem with these types of corner bass traps IMO is they don't absorb very much below 100 Hz if you don't make them preposterously big (like say, more than 3 ft wide at the front side) and use fluffy pink Owens Corning fiberglass or similar low density insulation to fill them up completely. In a small room, Ethan recommends covering all four wall to wall corners and all four wall to ceiling corners with corner bass traps, but I am seriously looking into VPR bass trap panels made with Caruso Iso Bond instead now, as they take up alot less space and they can be made to absorb down to 50 Hz or even lower.
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Post by The Mad Norseman on Jun 23, 2013 16:35:53 GMT -5
Finally getting around to posting some progress photos! The 2" Mineral wool batt insulation cuts easily, but will tear if you're not careful. Getting it into the trap and around/conforming to the curved front took some doing to nudge it in, bit by bit, but the second one went easier. I left a central small cavity, but also stuffed some insulation at the top and bottom as well. This insulation is much denser than typical fiberglass batts, and not as irritating to the skin. (Wear a face mask and gloves anyway to avoid irritation when manipulating this stuff. (BTW - That's a yard stick for scale in the photos). Anyway, both bass traps are 'stuffed' now, and sealed up awaiting their coverings which is next. Attachment DeletedAttachment Deleted |
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Post by The Mad Norseman on Jun 23, 2013 16:40:42 GMT -5
Here's a couple more - these are painted now you'll notice (black to annoy boomzilla! ), and the spray enamel satin black went down smoothly - I applied two coats, (did some minor sanding between coats to get rid of some minor imperfections). Here's a couple more photos: Attachment DeletedAttachment Deleted |
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Post by The Mad Norseman on Jun 23, 2013 16:44:30 GMT -5
And the last two, these showing more close ups. The black finish came out really well, and the insulation went in a bit tough here and there, but ended up covering all the ground I needed it to. I've still got a couple whole 2' x 4' pieces left over for a couple future wall panels!  Here's the last two for today (next up is putting on the black acoustically transparent coverings which I still need to decide on a 'fastening around the back method'...): Attachment Deleted |
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Post by yves on Jun 23, 2013 18:00:23 GMT -5
(black to annoy boomzilla! )  |
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KeithL
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Post by KeithL on Jun 23, 2013 18:24:54 GMT -5
If you don't feel like working with fiberglas, high density polyester fill (like for upholstery and pillows) should work - just make sure to stuff in a lot of it. If you want more absorption, commercial felt comes in sheets of various thicknesses (they sell it for carpet pads and upholstery), and then there are old favorites like long-haired lambs wool (rather pricey if you can still get it at all). For the most absorption, and a reasonable cost, I would say line the inside with 3/4" felt padding (in sheet form), then stuff the rest with cotton padding or "bulk felt" (the stuff they put in couch cushions). I assume you can get it where you would buy upholstery supplies.
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KeithL
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Post by KeithL on Jun 23, 2013 18:31:25 GMT -5
Another interesting thought.....
You can make a very interesting and flexible "tunable trap".
Start with something hard but workable (like those Sonotube 12" cardboard tubes they use to cast concrete in).
Cut it lengthwise so it has a very wide slot (cut about 1/4 of it away.)
Now stuff it and cover it.
Because bass frequencies are not very directional, the bass will find its way into the opening, but by turning the opening into the room or towards the corner, you can adjust whether mid and high frequencies are absorbed (if they hit the slot) or reflected (if they hit the outside wall of of the tube). This way you can sort of tune the frequency response of the trap by turning it around.
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KeithL
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Post by KeithL on Jun 23, 2013 18:40:41 GMT -5
Just an FYI for other would-be bass trap makers...... Bass traps are used to absorb excess bass if certain frequencies are "piling up" at standing wave nodes (which will make the room sound boomy at those frequencies which correspond to those nodes). Where the optimum places to put bass traps are located up will depend on your room, and your speaker location; they sort of need to be placed where the peaks (nodes) are located. While the corners may indeed often end up being where the bass traps should go, DO NOT automatically assume that putting bass traps in the corners of your room will be necessary - or will make an improvement. (Room treatments, including bass traps, are NOT an "everybody needs them, and one size fits all" type of system tweak. If you need them, and put them in the right places, they certainly will help. But, if you don't need them, or put them in the wrong places, then they will probably make things worse.) The problem with these types of corner bass traps IMO is they don't absorb very much below 100 Hz if you don't make them preposterously big (like say, more than 3 ft wide at the front side) and use fluffy pink Owens Corning fiberglass or similar low density insulation to fill them up completely. In a small room, Ethan recommends covering all four wall to wall corners and all four wall to ceiling corners with corner bass traps, but I am seriously looking into VPR bass trap panels made with Caruso Iso Bond instead now, as they take up alot less space and they can be made to absorb down to 50 Hz or even lower. |
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Post by deltadube on Jun 23, 2013 19:02:45 GMT -5
And the last two, these showing more close ups. The black finish came out really well, and the insulation went in a bit tough here and there, but ended up covering all the ground I needed it to. I've still got a couple whole 2' x 4' pieces left over for a couple future wall panels! Here's the last two for today (next up is putting on the black acoustically transparent coverings which I still need to decide on a 'fastening around the back method'...): View AttachmentView Attachmentgreat job Mad.. they look real good .. are stacking them ? i just made my 6 x 2 ft trap 6 inches thick afb. took about 1 hr do to 1 and about 100 staples.. looks good. i can finish off the top with a corner triangle.. afb has great stc ratings at 6 inches think.. and being angled to the corner wall almost doubles the thickness.. cheers |
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Speaking about diffusion, here's an interesting video on that. 
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