Acoustical Treatments Master Thread - Page 228

Linacoustic is the material I see used most often - nice because its black, has a coating on the face to keep fibers from floating about, and comes in rolls so fewer seams to deal with. Check the jm (Johns Manville) site for local distributors.

I couldn't find it locally myself for a decent price, so went with OC 703, and will cover with cheap fabric. Linacoustic was 5x as expensive locally for me, weird - although not too bad at fabricmate.com if the shipping costs didn't kill it.

Bass doesn't collect in certain places or avoid places around the room. It is everywhere, but does positively add and negatively cancel at certain frequencies at certain spots in the room based on room geometry. That is why "bass" sounds loud somewhere and can't be heard other places, but it is not all frequencies ... just certain ones. But if one is the frequency of a bass drum, it is easy to think that all bass is lacking somewhere.

If I read your bass trap dimensions correctly, I would not be able to consider them big enough to actually do much trapping. Effective bass traps are sizable. Click on the home theater link in my sig and look for the section on the traps I build and installed.

By moving the subs you can achieve smoother response, and traps and a good room correction technology can ice it.

Jeff

Thanks for your replies pepar, nice set up, I will add more/better bass traps and tinker with the subs placements.

I've heard several times from the usual suspects (gurus) that bass traps need to be at least 4" thick, 6" better - if those tri-corner traps are only 2" thick, and if the corner behind them is empty, I'd stuff those pockets with standard pink fluffy insulation.

For now, could I double up on some extra 1'X5'X2" thick panels? If I double up on the panels and place them along the back wall straddling the ceiling this should help correct?

John

studly, read the information here.

Nice, thanks again pepar.

I do like the looks of them and appreciate your input, I think I'll form some Roxul RXT 80 to sit in behind them and then put more RXT 80, 4 to 6" thick, along the front and back walls where they meet the ceiling. With this and possibly better locations for my subs hopefully I can get the sound that I paid for.

John

hey guys.

i've been toying with the idea of going with some acoustical treatment
in my room. i've been reading up, looking at the OC703 options for some
DIY style setup. the only problem is that my room isn't really traditionally shaped. i don't have closed walls on one side, and the other side there is a
door and a non flat wall.

i tried the mirror trick, but where i see the speaker reflection, i can't
really place a panel on the wall because there's nowhere to put it.

i've enclosed some pics of my setup, does anyone have some advice for
me for what i can do? bass traps, panels, etc.

thanks!





link to the whole gallery.

http://www.blu-ray.com/community/gal...mber=laychooba

Can't tell exactly where, but look up. The ceiling is a reflection point. And it wouldn't hurt to treat the right side wall above the piece of furniture there .. and then do a similar area on the left side for symmetry.

One big MUST DO to treat this room would be 4" of 703 on the rear wall behind the heads of people sitting on the couch (against the wall).

Just my $.02.

Jeff

Can't tell exactly where, but look up. The ceiling is a reflection point. And it wouldn't hurt to treat the right side wall above the piece of furniture there .. and then do a similar area on the left side for symmetry.

One big MUST DO to treat this room would be 4" of 703 on the rear wall behind the heads of people sitting on the couch (against the wall). Fallback would be 2", but bass will be very big for anybody sitting there ... and I mean "big" in a not good way.

Just my $.02.

Jeff

hi everyone, i wanted some advice as to the addition of rear bass traps for my room. take a look here for pics or what im talking about.

http://www.avsforum.com/avs-vb/showt...1164966&page=4


basically, my 2nd row is about 15" away from the rear wall and since the room already has 1" of OC703 4' high around the room, im wondering if adding superchunk bass traps behind the 2nd row seating. it won't be visible unless you look behind the seat and will probably be about 10' long x 2' high (off the floor). the trap will be spaced about 2' away from each side wall but will butt up against the lower portion of the rear wall. will this do anything for bass trapping?

Yes.

Hi Anthony,
Kevin in TO here. How are you? Did you ever get the Empire Epik subs we communicated previously about?

About your question, if you have only 15" between the back wall and the rear row of chairs, have you considered a diaphragmatic-type bass trap instead of the 'super chunks?' As you already are using 1" OC around the room I would hazard to guess that the RT60 is pretty low for the upper frequencies so the last thing you probably want is to reduce it further with more fiberglass super chunks. Moreover, fiberglass traps need to be thick to work really well - placement of a fiberglass trap out 15" from your back wall would work most effectively for a 226Hz wavelength (1130/226*12*0.25=15") as 15" equates to the 25% mark of the 264Hz wavelength where particle speed is maximized.

I'd be inclined to consider the diaphragmatic type trap that works where pressure is maximized not particle speed so this type of trap hangs right on your back wall and is about 4" thick. Check out RPG which makes them and you can order them here in Toronto.

Hope that helps somewhat. . .

hey guys, what type of fabrics do you get from JoAnnes to use for panels? thanks

The quick test is to see if you can blow through it. If you can, then it should be acoustically transparent enough to allow the sound pass to the absorption. Fabric from a fabric shop is NOT suitable to put speakers behind. For that some bona fide acoustically transparent cloth like from Guilford of Maine, a.k.a. GOM. Some of us use the GOM to cover panels as well, but there less expensive (!) alternatives for covering panels.

Jeff

Might you have a link to where you can order these from Toronto? I went to the RPG link and Canada is not an option. Thanks

I don't think RPG sells to consumers .. only through their distributor/dealer network. At least I can't find on their site where they do e-commerce.

Using the where to buy feature, I see only BC and AB vendors listed.

thanks jeff,

GOM is just too expensive for my budget. i am looking for cheaper alternatives, and have heard folks here using fabrics from jo-ann, not sure what exactly.

anyone use this speaker cloth from jo-ann, looks a bit on the high end of cost.

http://www.joann.com/joann/catalog/p...2a&supercatId=

Hi Studlygoorite (nice name by the way!):
Try calling Martin at Pilchner Schoustal in Toronto or visit their site here:
http://www.2psii.com/

They have a close working relationship with RPG and they may order stuff on your behalf.

Thanks pal.

hey kevin, good to hear from you. still haven't decided on adding an epik or not, but i did get another sub (svs pc12 plus). im still craving midbass punch so that is why im trying to first try out some more room tweaks and then assess the situation. the only place i can add the bass traps (at the rear of the room) that will blend in with my room is directly behind the second row of seating. since that row is about 15" away from the back wall i thought to place some traps behind it that won't be visible. i don't want to hang anything on walls, etc. can you tell me which, specifically, rpg trap you're suggesting?

thanks.

You might consider this one for your floor/wall corner:
http://www.rpginc.com/products/modexcorner/index.htm

or this one that hangs on the wall and likely could be painted black to match your wall colour so as not to be noticable:
http://www.rpginc.com/products/modexplate/index.htm

Cheers,
Kevin

I have attached some pics of my room as well as a drawing of the room with dimensions, and where I plan on putting the treatments. The purple rectangles are the treatments. for the corner traps I want to build a trapezoid shaped treatment using 2 layers of O.C. 705 (4" thick total) one being the FRK, this one goes on the back correct? The side wall panels I want to use O.C 703 2" thick but I think I want to make them about 3ft wide by 5ft high. Is it okay to use a 2 x 4 panel and then cut one in half length wise and put it next to the other and then put the other piece on top to make a 3 x 5 panel and then frame it? The ceiling panels will be the same thickness but I don't know what size yet. the drawing is not really to scale that is why I have only one panel on each side of the wall towards the back of the room. I think this will be proportionally correct based on the dimensions of the room. My surround speakers are inside the columns and are dipole (Paradigm ADP-590's). Will putting side wall panels fairly close to the surrounds effect there sound too much? The panels will probably be about 2feet from the speakers based on where my rack is and then the same on the other side, and towards the back of the room. the back wall panel will be between the 2 surrounds, should this be 2" or 4" thick. My seats are about 2.5ft from the back wall. I know this is a lot of questions but any help would be greatly appreciated.
P.S next post will have the rest of the pics
Thanks,
Jay

More pics of room.

Thanks

 

HT sketch.pdf 16.1044921875k . file

 

HT sketch 2.pdf 13.89453125k . file

No, the front. The idea is to not absorb too much high frequency. The FRK reflects high frequencies rather than absorbing them.


This is probably too much absorption. Use the mirror method to find the first reflection points for the front speakers. They likely won't be spread up/down 5 feet. Focus the panel size on the actual reflection points. And consider increasing panel thickness an inch or two, even if it's just an air gap, to help broaden the frequency range being impacted, for a more natural effect.


Same advice: thicker is better, but less coverage as long as you hit the first reflection points is the ideal.

There have been a few threads on the norwegian AV forums about tuned resonators as bass traps. Basically sonotubes, closed inone end, open in the other, and very little to no damping. From measurements, when tuned correctly (cut to length) they are VERY effective at killing nodes. They are also dirt cheap and very quick and easy to make.

Any thoughts on these compared to other tuned resonators?

Would 4" thick 705 unfaced be sufficient enough for the bass traps, or does the FRK backing make a difference.

I thought that 2" thickness would be enough for the mids and highs.

I want to keep the ceiling treatments as thin as possible due to fairly low ceilings.

Thanks

Looking at what material I have onhand for covering my side wall/ceiling acoustic panels, I have 3 yards of this speaker 70" wide cloth from PE.
Holding it over the OC703 appears no issue, is there any thought about why NOT to use this as my acoustic panel covers?
http://www.parts-express.com/pe/show...number=260-335



I've made 1 prototype 2' x 4' frame boxe from 1 x 4 pine, routered a 1/4" deep x 2" trench 1/2" from one side (the front), then I'll use bumpers to provide a gap to the wall side.
I'll wrap the 2" OC703 with the speaker cloth (front side only) and the pine box will be outside, nesting the 2' x 4' nicely.
This pict is wrong position of my HT, but you can see the black speaker grille will match my black speakers and go with the dark green walls fine, while I feel using the pine and staining will keep the rustic look going as well.


So, simply, using speaker cloth as shown above ok or not good for these panels?

In general, the goals are:
1) Control reflections, but don't go too far and lose all of them.
2) Absorb across a wide range of frequencies, typically by having thicker panels.

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The reason for the FRK, mostly, is that you want as much bass trapping as possible, BUT you also don't want to absorb too much of the mid and high frequencies. The FRK acts to reflect the mid and high frequencies, so you don't "overdamp" your room (make it sound lifeless and inert).

So if you use the FRK, it doesn't really help with bass trapping, but it prevents problems with other frequencies.

That said, you can probably be okay without it in your scenario, if you need to not put it on/use it.

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2 inch thickness is better than 1 inch, but not as good as 3" or 4" in most situations. In fact, getting too thin arguably causes more harm than good at some point, since it only absorbs a very limited range of frequencies and the other frequencies are inconsistently tamed. If you can do 3" or set the 2" panels off the wall with an air gap, that's better than just a 2" panel on the wall. But a 2 inch panel on the wall is better than no panel at all.

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I understand room limitations. Most of us have those issues. So if you have to compromise on the ceiling because of that, don't sweat it. Just remember to be judicious with how much surface area you cover. Hit the key points, and don't just swath it around everywhere.