Fabrics & Rockwool Question

knightfly · Post by **knightfly** » Tue Jul 01, 2003 9:45 am

Guys, I'm hoping Eric responds to my PM and we can resolve this privately -

Charles, let's see if I can clarify a couple of things - you said,"7'5" high in the NW corner 8'5" in all the other corners" - does this mean that somewhere on the ceiling surface there has been a corner "chamfered" by the necessity of intruding roof framing or something? It's hard to picture a ceiling that has THREE of the four corners at the same height, unless somewhere there is either a LOT of water damage :=) or a beveled corner.

Second, does your floated floor have any insulation filling the cavities between the joists? (Please say yes...)

If that low ceilinged corner on the NW is one of your corners BEHIND the mix desk, would it be possible to duplicate it on the OTHER front corner? That would give you symmetry of mix position, and the rest of the problems could be handled other ways.

Carpeting helps impact noise between floors for second story situations, but only absorbs high mids to highs - you may find yourself wanting to take it out if it takes too much other absorption to tame early reflections and modal problems.

Your description of the space is a valiant attempt at penetrating the fog in my head, but a drawing would speed things up immensely - is there any chance you could post at least a rudimentary Paint .jpg of where things are? Visualization works MUCH better (for me, anyway) with PICTURES :=)

I know what you mean about the math, it's not one of my stronger suits either. I learned just enough about using spreadsheets to write one about 15 years ago for figuring out axial modes, now I just enter the dimensions and analyze the charts.

If I can get a better handle on your room from a drawing, I'll try to offer whatever suggestions for improvement I can... Steve

knightfly · Post by **knightfly** » Tue Jul 01, 2003 10:26 am

Charles, am I even CLOSE to what you have? This is a really rough dwg, but may help to clarify where things are. Also, I'm not clear on the actual SHAPE of the AC soffits - are they full length of the wall, or just recesses where vents are, or what?

Charles Dayton · Post by **Charles Dayton** » Mon Jul 07, 2003 6:37 am

Sorry its taken so long to get back. Been working. OK, yes there is insulation in the floor! Excrpt where the foley pits are in the recording room, and where the cable runs are in the controll room. Also your drawing is very close. There are two 35" doors, one is to the left of the window 12" from the south wall. The other is on the north wall, 16" form the NW corner. If you look at the ceiling line on the north wall you can see it angle down from 8'5" to 7'5" from the NE corner to the NW corner. If you look at the West wall you can see the same angle from the SW corner down to the NW corner. The South and East wall lines are level. The garage has a flat roof with a scupper at that NW corner, for rain runoff. My plan is to make a box 8'x4' with 3" of that 703 insulation and hang it level over the mix position on the west wall. Are you are suggesting I make it level? The sofits are rectangular. One at the top is 2'3" from the ceiling down, and then 16.5" in to the wall proper. The bottom sofit is also rectangular, 2' from the floor up and 16.5" in to the wall proper. Sort of like a bench. The bottom has the intake vents, the top the cooling vents. They are the full length of the wall. Also, what about angeling a panel on the North wall to offset the standing waves? I hope this is more clear. I don't have any drawing programs for my Mac, sorry.
Thanx again for the help,
Charles

knightfly · Post by **knightfly** » Thu Jul 10, 2003 12:44 am

Charles, no need for apology - I too am in need of some sleep so I'll try to get to this either later today, or tomorrow sometime. I'll try to redraw per your description, and answer your questions as well, at that time. Gotta go beddy-bye for now... Steve

Charles Dayton · Post by **Charles Dayton** » Sun Jul 20, 2003 10:05 am

I hope you havent forgotten this thread. I look forward to your advice. Particularly on angleing the sound board on the side walls.

Thanx,
Charles

knightfly · Post by **knightfly** » Sun Jul 20, 2003 4:36 pm

Hey Charles, guilty as (not quite) charged - Sorry about letting you fall through the cracks.

I'm working on a re-draw as we speak, should have it done in a few -

First, correct me if I've not followed, your South wall is about a foot closer to the North wall, full length of the room at bottom and top only, right? If so, what (if anything) are you using that "bench" for? Would it be too much percieved loss of space if you closed it in with 2x4's and sheet rock? If not, that would even out the room for mids/highs, giving you a foot deep panel-type bass trap. It would also even out the modal response of the room some, getting further away from square.

A 1/2" sheet rock layer over studs spaced out from the main wall by about 16" would resonate at around 32 hZ, which is right at the primary mode frequency of the long wall. Doing that would help acoustics in the room quite a bit, the only downside being that a panel resonance also weakens the Transmission Loss some at resonance. If you attached spun fiberglas insulation to the sheet rock panels themselves, it would dampen that resonance a little, smoothing out the response.

Your idea of a "cloud" over the mix desk is a good one - given the unevenness of the ceiling with that one low corner, there's no practical way to straighten that out with actual construction, so it would help a lot to use plywood-backed 703 suspended over the mix desk. I'd make the front (toward the window) LOWER, that will help flutter as well as improve the Reflection Free area at the mix position. In fact, a similar plywood-backed 703 treatment above the window, at maybe a 30 degree angle out at the top, would help imaging even more. I'll try to do an elevation to illustrate.

As to angling the soundboard on side walls, it won't make much difference. Only a slight change of refracted angle, and better low absorption where the panel is further from the wall. Sound goes through absorbent and reflects off the wall, coming back through the absorbent. There would be a slight angle change due to refraction, but it would have little effect overall.

On the other hand, if there is a hard boundary also at the new angle, (like plywood, or gypsum) then the sound that doesn't get absorbed would reflect back at a supplementary angle, only being slightly warped first in one direction and then back the other way, so that the resultant reflective angle would be almost identical with or without absorption covering the reflector (the plywood backing) - in that case, the absorbent would still help flutter echo, and having the plywood backing angled toward the rear would help achieve a better Reflection Free Zone to mix in.

Another possible way to use the area between air plenums would be to put your angled "abflectors" (plywood faced with 3" of 703) between the upper and lower plenum. This wouldn't give you much low bass absorption, but would improve imaging overall. In order to maintain symmetry, you would need to do that on the North wall also.

You could always trap the ceiling corners, plus the couch should provide some small amount of bass trapping especially being out from the wall like that. Whatever amount of trapping the couch provides should go down to about a 5 foot quarter-wave, which is 20' full wave, which is around 56 hZ.

I re-did the one drawing and drew an elevation so you could see what I've been blathering about - Let me know what you think, and which way those doors actually swing... Steve

knightfly · Post by **knightfly** » Sun Jul 20, 2003 4:40 pm

And here's the elevation...

knightfly · Post by **knightfly** » Sun Jul 20, 2003 4:44 pm

The reflections shown are a crude ray-trace done by hand, with an accuracy of about 1-2 degrees. Close enough to illustrate sound paths... Steve

knightfly · Post by **knightfly** » Sun Jul 20, 2003 5:44 pm

Charles, here's a way to get cheap drawing capabilities for your Mac -

http://www.directdeals.com/ProductDetai ... 01-360-002

I also checked out actual Mac drawing programs for download, wasn't very impressed but you're welcome to look -

http://download.com.com/3120-20-0.html? ... ch=+Go%21+

If it were me, I'd get a copy of Virtual PC and download a trial copy of smartdraw from

http://www.smartdraw.com

Then, you could upload all kinds of kinky ideas for ridicule :=) or, maybe just save a bunch of posts clarifying where/what/how, etc... Steve

Charles Dayton · Post by **Charles Dayton** » Mon Jul 21, 2003 4:16 am

You have an accurate picture of the room. The doors open in and out because they are double doors. That bench area is quickly filling up with cabinets for storage, so... I don't know what that means, but the wall is becoming flush. I've already angled the panel over the window, so we're on the same page there. Didn't think about angleing the cloud. Great idea! I'm not clear as to whether you think angleing the side panel was worth it or not.
Just as a side note; I mix T.V. shows at a network here in L.A., and I noticed they were rebuilding the sound control room for the soundstage. I took a look in and saw they were mounting 1" of 703 directly on the walls! I mentioned to the head tech about some air space behind the 703 and he said it wasn't necessary. Just goes to show you, people with a lack of knowledge making important decisions. That's why I always bring headphones! Then again, work in a room long enough and you can adjust to most problems. It's just a pain.

Charles

knightfly · Post by **knightfly** » Mon Jul 21, 2003 5:11 am

Charles, I'm not sure what you mean by "angling a panel on the North wall" - if you meant something like I drew, yes - I think both north and south walls should be done. This will improve imaging at the mix position. If you meant tilting a panel out from the wall (so it would either lean on the wall, or fall into the room if not supported) I wouldn't do that. Rotating panels to the angles I show on the floor plan drawing would accomplish much more.

I know what you mean about ignorance (only 1" 703, NOT stood off) - I built a room into my barn about 20 years ago (I live on 10 acres in the country, STILL have noise problems) and was amazed that my wife could tell what I was playing on the piano, from INSIDE the HOUSE 100 feet away - (sigh...)

Since then, I've commandeered (then lost again) one of the bedrooms (kid left) which wasn't very quiet but acoustically I made it work - Now working on same for the OTHER kid's room as a temp fix while designing a separate facility (about 2200 sf, with minimum 16' ceilings) which I hope to break ground on in the next year or so - been studying acoustics in spare time for the last 20 years, because I have no intention of making ANY mistakes this time.

I just traded a neighbor (about 125' away) with a lawn-mower fetish and a (real) psychopathic 40-yr old son (convicted felon, likes knives) for a really nice couple who build hot rods/race cars - can you say, "floated EVERYTHING"...:=(( - The other side neighbor can't figure out how to train his (chained up) large dogs not to bark all the time (hint: you need to be smarter than the dog) - Guess that explains my preoccupation with isolation (I refuse to use the term "sound proof" - it's all relative)

When I finally get this project ready for prime time, sound for pix and TV is just one of the areas I'm going to pursue. Maybe at that time I can turn the tables and pick YOUR brain a bit... Steve

knightfly · Post by **knightfly** » Mon Jul 21, 2003 2:43 pm

Sooo, Charles, have you gotten a chance to check out any of those Mac drawing pgms? Man, I can't believe the Mac OS doesn't at least give you a rudimentary drawing pgm, like Paint... Steve

giles117 · Post by **giles117** » Mon Jul 21, 2003 8:56 pm

There is a simple drawing program called iDraw For OS X

I believe you can find it at the apple/osX/downloads site.

Bryan

Charles Dayton · Post by **Charles Dayton** » Thu Jul 24, 2003 3:06 pm

I wasn't planning on just leaning them against the wall, I was gonna use some scotch tape too! (Joke) Although attaching them has been interesting. I've been using 2" furring strips and velcro.(in case I want to move a panel) and o.k. o.k. I'll get a drawing program.
Steve, anything you want to know about post sound ask away, any time. I'd be glad to help.
Charles

knightfly · Post by **knightfly** » Thu Jul 24, 2003 5:38 pm

"o.k. o.k. I'll get a drawing program" -

Why, Charles, whatever led you to believe anyone thought you needed a drawing program

"anything you want to know about post sound ask away" - Cool, now all I need to do is lose enough ignorance to know what questions to ask... Steve