how to treat a ceiling?

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dobro

dobro

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After treating the corners of my room with various pieces of stiff fibreglass, I've got six pieces of 2'X4' fibreglass left over for the ceiling. It's a pretty small room - about 12 X 8 X 11, I think. I can't angle it over where the wall joins the ceiling (don't ask...) so how should I apply it to the ceiling? Flat? Or would angling it work better? By 'angling', I mean attaching it to the ceiling so that one edge is lower than the other.

And if I attach it flat, is there any advantage in suspending it down a bit from the ceiling so that there's some space behind it? No good for bass frequencies, right?
 
Flat, centered over the mix desk (at least 3 or 4 of those pieces for a 4' x 6' minimum "cloud") space the material (without backing) so that its face is 8" from the ceiling, and it will work down to about 400 hZ. That should pull a lot of the "boxiness" out of the room; if you have the space, 12" will work even better... Steve
 
Excellent. 'Cloud cover'. Yeah. Love ya, Steve.

Why over the mixing desk instead of along the edges of the ceiling? And yeah, with an 11 foot ceiling, there's lots of space for a one foot space between absorber and ceiling.

By the way, I've got 6 pieces of 2'X4' and each one's 2" thick. If I doubled them, would it pull the absorption range down lower than 400 Hz? By enough to make it worth doing? Or would I do better to put all six pieces in separate places 12" from the ceiling?
 
I'm gonna use two or three bamboo poles and suspend them from the supports for the ceiling tiles - bamboo's really cheap here - and just lay the sheets of fibreglass on top like toast on a rack.
 
Unless your ceiling is already absorbent, you need to eliminate early reflections between speakers and ceiling - you do this by putting up a "cloud" whose front-to-back center is halfway between you and your speakers, and center it left-to-right. Typically this needs to be at least 4 x 6 feet to catch any possible reflections. This is necessary until your ceiling is at least 10-12 feet higher than your head (while mixing); beyond that distance, reflections will be late enough NOT to smear the stereo image. At that point, diffusion could also work.

You already have your corners treated, although ceiling/wall corners wouldn't hurt. However, it's nearly impossible to get specific without pix and drawings of the exact space - see this thread for an example -

http://www.homerecording.com/bbs/showthread.php?s=&threadid=114785

BTW, doubling your panels isn't cost effective if you're already standing them away from the surface - you'll get more benefit by covering a greater area. What controls the lower frequency range is the distance from the wall to the OUTER surface of the absorber - peak absorption occurs at the 1/4 wavelength point.

You can figure out the peak absorption distance from facing of the absorbent to wall with the formula
D=3390/F, where
D=distance in inches
F=frequency

This is the 1/4 wavelength frequency for those particular conditions, above that frequency you'll still get absorption. Below it, absorption will fall off sinusoidally, reaching roughly 70% at 0.75 F. In plain english, if you set your face-to-wall distance to peak at 400 hZ (8,475") then you'll get 70% as much absorption at 300 hZ, which is still pretty usable. All this is at 90 degree incidence (straight on, not angled)

I'm sitting here wasting beautiful weather with a crapload of outside "honey-do's" waiting, so that'll have to do for now - I'll check back tonight to se how much chaos I've caused, and see if I can straighten it out... Steve
 
Okay, I understand the relation between distance between absorbent and reflective surface and the frequency it kills. 8.75" for 400 Hz, 16.95" for 200 Hz, and hang the stuff just over my head for 100 Hz LOL.

I suppose the rule of thumb for which frequency to kill primarily is 'the lower the better'. Or does it depend on the room size?

I can do diagrams for this thread if I can get the software for it. I'll ask Cap'n D.
 
The smaller the room, the more bass problems (since modes are spaced further apart frequency-wise, they are more obvious) so yeah, the lower the better. Corner bass traps help a bunch too - any and all corners if possible. For side walls and ceiling though, main thing is around 300 hZ and up. Even 400 and up is a major help for stereo imaging... Steve
 
What is the greatest advantage of membrane traps in corners over suspending rigid f/g in the corners. Is there a huge difference in low freq. absorption?

Is effectiveness at louder volume levels a consideration between the two, or is it only a matter of absorption and wider bandwidth of frequencies?
 
The main advantage of membrane traps is lower frequency absorption in less space. They need to be placed flat against walls for best efficiency, where absorbent fiberglas traps are better diagonally across corners. Membrane traps absorb much less at higher frequencies, so help keep a room more "live" - so it helps to know the specific application before you can decide which will work better in what location... Steve
 
I just ordered four 4X8 rigid f/g sheets, and one 2X4 sheet.
(It's all me wifey would let me spend right now) :(

Should I cover my corners first and then maybe build a membrane with what's left over?
 
Nuthin's free, CD - until I know what you're doing and where with what, I'd just be fartin' in the wind (not that that's a BAD thing :=) but you'll need to post some kind of layout info with all 3 dimensions, where your stuff is, etc, before I'd have a snowball's chance of coming close on treatment... Steve
 
dobro said:
.....I can do diagrams for this thread if I can get the software for it. I'll ask Cap'n D.
Click to expand...

I'm using Microsoft Publisher, but it doesn't export to a graphic file so I'm not sure if that's what you're gonna need. As you noticed, I had to print out the diagram, then snap a digital pic of the page to upload to this site. Got the job done, though!

If I find a useful program, I'll let you know.
 
In Publisher;

File -> Save As -> Windows Bitmap(*.bmp)

works for me.

Kevin.
 
Print Screen - Paste in Paint - Resize Vertical and horizontal - JPeg or BMP.

Works for me!
 
Along the same line... if I attach some 1" 703 wrapped in fabric to a couple of boards/straps/rc... whatever from a ceiling, what are the chances of it sagging over time? Any experienc there?

For example:

703.gif


Thanks
Kevin.
 
Not sure but I believe it will sag without the right support. You need a backing of 1/2 inch at the least to accomodate stapling fabric. Take a 4x8 sheet of plywood and rip it (cut with the grain) length wise in two pieces( ripping the wood in that direction makes the board stiffer and won't sag). You should be left with 2 - 2'x8' pieces.. The remaining two should then be cut into two equal pieces both 2'x4'. Makes four baffles

What I have depicted below is not written in stone. But I believe this is the best way to do it when it is on the ceiling and there is only one person doing the work and no one elso to help.

This way you do not have to glue it down.

1.Mount the 2x4's on the ceiling( if you cannnot find a stud use toggle bolts). Then screw the plywood to it. One screw in each corner.

Bore a hole half way through the fiber. The hole has to be big enough to accomodate a 1/8 - 1/4" fender washer. Screw 3" coarse thread screw through the center of your bored hole then through plywood and then into 2x4. see diagram

Staple and stretch fabric one side then the opposite side into the side of the plywood, folding the fabric under as you go along. This will create a finished look. Staple the remaining sides and the job is finished and you can tell all your friends you did it.

Remember there are other ways to do it. This is how I will do it
if ever decide to.

Later,
Casenpoint
 

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longsoughtfor said:
In Publisher;

File -> Save As -> Windows Bitmap(*.bmp)

works for me.

Kevin.
Click to expand...

Sorry. I have an older version of Publisher (97) and it doesn't export to any graphics protocols. Not sure about the current version.

Anywho, I think dobro is looking for something free, which I am trying to locate also.
 
I found what I was looking for Cap'n. Knightfly steered me towards Paint in Windows, which I've never used for anything before, but which does straight lines and boxes and text, so it should work for simple diagrams I post here. I've been too busy for the last few days working on the studio and recording to work out a diagram and post it here.
 
I know I should probably do a new topic, but Im getting some good ideas from here. I have a couple of questions along the same thing as far as the cloud goes. I have 7 1/2 foot celling, which kinda sucks, my room is about the same size as dobro's. Its like 11x10. My mixs are always off, I just spent a grip of $ on a new mic and padding up a closet for a booth. But I feel I could do some room treatment w/o spending a lot of money. Would the cloud thing work for my situation, I mean the celling is pretty low, but would it help? What kind of foam padding could I use? Like I said, I dont have a lot of money, but could I do a cheap version, LOL, I know that isnt the way to go, but would it help if I got some of the foam insulation from a local hareware store to do a litlte treatment, or would I just be wasting time? Thanx, sorry to interupt your thread dobro, pm
 
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