Positioning Acoustic Treatments Sound Absorption Panels in Apartment

Okay, I'm nearing completion of my Apartment Home Theater, Operation: Acoustic Absorption, and thought I'd better clear it with the experts before I go further. I've been scouring website and forums to learn as much as possible about DIY acoustic panels, and would like to do a little webpage detailing my lessons, but I still have a couple questions before I finish that I think this group could help withmany thanks in advance.

(Please see attached pictures and diagrams below. Any picture requests will be speedily honored.)

The pictures show the panels in my messy living room just lying around before being mounted (screws and drywall anchors). The diagrams show where I'd like to mount the panels (in blue). The only panel not shown will be mounted on the ceiling at the first reflection point. More in my Gallery.

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My questions are numbered for convenience in referencing.

1) Would you change anything with the positioning of the panels, especially on the front wall? Is the number too great on any one wall, should they be moved to a different wall or the ceiling? Is the ceiling worth the trouble of hanging a panel?

2) I need to cover the panels with fabric yet. I've heard light weight, natural fibers, non-shiny. I want to do muslin, but am having a hard time getting it past the aesthetics committee. Anything else to look for? I'm worried about keeping the fiberglass face acoustically un-obscured, especially with the layer of poly fill on there already.

3) For horizontal mounting, though these are pretty light, I'm thinking I should run a 24 dowel across the middle as a brace. They will be mounted at a single point in the middle of the 48 dimension. Anyone have problems with frames warping?

Note: I currently have no sub but am planning on getting an Athena AS-P300 very soon (unless someone want to sell me an AS-P400 for around $160 shipped.)

4) For the frames straddling the wall corner as bass traps, am I wasting my time using only 2 703? Should I instead move those panels to a location on the wall to further help with flutter echo (I'm still failing the clap test)? I could try to tame bass nulls and peaks with a Behringer Feedback Destroyer instead.

5) On another corner bass trap note, should I load the empty space where the bookshelves meet in the corner with something (fiberglass/cinderblocks)?

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Misc info:

The panels are 2x24x48 unfaced OC 703 with a thin layer of poly quilt batting on the front/back in a 3/4x2.5 frame.

Speakers are JBL Studio series (s38ii and S-center). JBL N24ii surrounds. No subwoofer, yet, looking to buy an Athena AS-P300.

Room is approx 14x15', 8' ceilings, medium-thick carpet on floor.

To measure effect, using a Radioshack Digital SPL Meter w/ Room EQ Wizard and built in laptop soundcard.

I have one panel I'm going to hang about 2 inches from the ceiling at the first reflection point, that is, if most people think it will be more valuable there than hanging at another point on a wall or in a corner.

The two bookcases are just cheap staples bookcases and are not attached to the wall. They make a nice column behind them, so I could stuff it with something, I just don't know if the bass waves would actually reach it or just bounce off the cases/books.

I will get pics of te process in my gallery soon, and I'll post in this thread when I do, butI'd actually like to putup a quick webpage, or maybe just another thread to help others learn as I go.

Never been to basstraps.net, I'll have to check it out.

JUst moved to NY actually, haven't updated the profile. Never met Emeril, but Fall River did have great food.

Since my room is so small, the smearing is really bad, and I'm afraid diffusion won't help much as the reflections will come so quickly. I really think I need panels at the first reflection points behind the seating (though I could be wrong, convince me?)

I only have two usable corner that I can bass trap (not counting ceiling/walls). The back left corner is the staris, and the fron door opens into the back rigt corner. I could move the bookcase upstairs I guess, but that would take out the media storage from the room.

4" is recommeded for bass traps, but I only had 12 panels worth of OC 703. Should I put the panels double thick, and only half te height of the wall?

The window actually isn't too bad since I can set a panel in it easily. Since my room is so small, my LCR 1st reflection points only span about 2 feet, and can easily be handled by a single panel. I plan on draping the windows soon to help with other room reverbs.

When you say treat the ceiling reflections, are you talking primarily about the front wall/ceiling? I may be able to pull that off.

I'll have to play around with room arranger. I think I'm going to have a hard time getting this past the committee.

I went horizontal so that one panel would cover all the reflection points. Going vertical didn't leave a lot of absorption for off axis seating, and might have put a chunk of wooden frame in the middle of the area I wanted to absorb. The wall between the window and door is also less than 2' wide, so a panel won't fit, and it'snot at a first reflection point. My diagram is probably a little off, sorry.

You're thoughts on 2" 703 from floor to ceiling in a corner versus 2-frames (4" 703) covering only 4' of a corner?

Should I still treat a small area right behind the listening position at ear level so speech doesn't bounce off the back wall and hit me in the ears?

Did you mean "Reflections make speech unintelligible ? I didn't understand how reflections could make speech more clear.


See previous post comment on "the committee". I'm going to play with room arranger and see what I can do. What about putting one of the tall bookcase in each corner? Could I put cinderblocks or concrete behind to make an effective bass trap?



Unfortunately, I'm about $300 into room absorption already, and I haven't even bought fabric to cover them yet (another reason I want to go with muslin; it's cheap? ANy sources for dyed muslin, something in a blue?) I also need to buy a subwoofer I think (Athena AS-P300). More absorption may have to wait.



Any recommended brands?



Already done. I'm thinking of putting a wooden dowel accross the front and middle of the 2' dimension to prevent sagging of the 703, covering the whole mess with natural colored muslin (a little darker than theceiling color) and suspending the panel abot 2 inches from the ceiling using thin, white chain. I think it will look pretty nice, but it is a lot of work if the results won't be worth it.

Thanks for all your help, past, present, and future.

The listening position is about 3-4 feet from the back wall (I've been playing with moving my viewing distance a little closer).

I'm setting up an imageshack account right now. I'll post some construction pics, as requested by Joel, and also my sweeps from Room EQ Wizard (measured response and waterfall is what I should post, right?). I don't know how much help they'll be though, since my low frequency performance will change with the addition of a subwoofer in the next couple weeks.

True, I've got a wicked peak at 30hz, and a null a little north of that. See below post of graphs. I'm thinking I could take them out electronically wth a Behringer Feedback Destroyer. Any experience with that? I see a lot of manufacturers are using a similar and vastly more expensive system built into their subwoofers.

Okay, Here's the quick and dirty construction run down. This is not necessarily what you should do, just what I did.

Step one: For each frame you'll need 2 pieces of wood 4' long, and 2 pieces of wood 2'1.5" long (for 3/4" thick wood). Makes the interior dimensions 4'x2'. You'll also need a drill and some screws.

Word to the wise, the 4' lengths sold at Lowes are more like 3'11.5". I had to do a lot of squeezing, but at least the fiberglass is in there solid.



Drill starter holes 3/8" in from the end of your 2' pieces using a bit appropriate for your screws. I also used a larger bit to indent the starter holes a little so that the screw heads fit flush. Wear glasses or goggles.



Using the holes in the 2' pieces,drill starter holes into te 4' pieces. Careful not to snap your drill bit by letting the boards slip (yep, that's me). Screw them together to make a frame.



After all your frames are made, open up your fiberglass.



Yes, I'm working with fiberglass in my kitchen, and without gloves or a mask. Not bright, but I wasn't cutting it, so there wasn't much mess.

If you are concerned about fibers getting out (ironic, based on my care up to this point), you need some thin poly quilt batting. I bought the 90" variety which was more than stretchy enough to cover my 48" panels times 2 sides without cutting.



Cut a pice of poly 90"x 28-30", fold it in half, and put a piece of fiberglass inside



At this point, I wrapped the edges in tape to keep the poly in place while I squeezed it into the frame.


With the frame face down, squeeze the poly/fiberglass into it, starting with the narrow ends. If your frames are too small (me again), this will take a little breaking down of the edges.

Once it's in, flip it over and you have a perfectly faced panel.



Now, to find som suitable fabric to cover it with...

Here's some graphs from Room EQ wizard. As you can see, my symmetry isn't too bad until I get down below 300 HZ.

W/O Panels - 1/3 octave smoothing

W/Panels

Waterfalls - 300ms

L W/O Panels

L W/ Panels

R W/O Panels

R W/ Panels

Sorry for not just doing a before after overlay, but I did a full compliment w/o panels, saved that set, and then did a newset w/ panels. Even after importing measured responses and impulse data, the imported data does not match the initial data set. Can anyone help me, am I doing something wrong w/ REQWizard? Should I just post them anyway?

I've finished a panel!!





Man, covering these things takes a lot of time and staples.

So, I found 40 yards of fairly loose woven cotten fabric at Wal-Mart for $1/yard. They only had 20 yards of each, so I had to get two shades. The Darker one above, and a lighter blue (approximated in the diagrams below).

Considering aesthetics, here's what I'm thinking for placement.



I also added an Athena AS-P300 Sub and Behringer BFD 1100P. Here's the before and after results.

Ran audio out from my laptop to the aux in of my receiver. Set the crossover in my receiver. Recorded the response in REW Left channel. Set filters, send to BFD. Record into Right channel, tweak, Record into center channel, compare, and on, and on.

After I got everything how I liked it, I recorded the results into the right channel, and showed the measured responses, 1/3 octave smoothed, for left (before) and right (after), then snapped a jpeg.

REW is very awesome.

As Ethan has noted hundreds of times, BFD didn't do anything for ringing, in other words, according to my waterfalls, my 40hz frequencies still bounce around the room twice a longs as the others. However, since they aren't nearly as loud as they were before BFD, I don't notice it as much.

Alright, back wall is done (man these tings are taking for ever!)

Here are the painted cleats I used to hang them:



Here's a single panel, showing the gap from the wall:



Here's the final back wall:



It looks great. With the cleats painted, the panels appear to float 3/4" off the wall, just kind of hanging in mid air. The panels actualy look very arty, especially glad I went with multiple colors and got a little creative with the placement.