new mixing room (john manville vs OC 703)

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foreverain4

New member
well, i left my dedicated 1500 sq ft facility in indiana :( to finish up my education in music business in orlando fl. needless to say, i am in the need of creating a room for myself, mostly for mixing, but i will probably be tracking a bit in it to. i am in need of bass traps, as this is a pretty small room compared to what i had before. i searched and found a local company that stocks 2" thick john manville 817 for $1.60 a sq ft. OC 703 would be a special order, and a bit more pricey. the 817 comes already cut in 2' x 4' panels. it has a foil backing, but this could easily be removed if i need to. the room is 11ft 10in wide, by 13 ft deep, with standard ceiling height (which is about 8.5 ft???)

what i plan on doing:
auralex foam for early reflections (i already own a mass of this, i may as well use it)
JM 817 for bass traps on front wall over corners where wall meets wall (two 2x4ft pcs, 8 ft tall total)
JM 817 over corner where ceiling meets wall in front of mix position (will cover 2x4 ft pc)
JM 817 over corner where ceiling meets wall left and right of mix position (2x4 ft pcs)

questions:
is the 817 a good substitute for OC 703?
should i put bass trapping in the back of the room too?
will the 2 in thick pcs be thick enough straddling the corners, or should i double the thickness to 4 in?
do i have to remove the foil backing, or can i just turn it toward the wall?

drawing to come....
 
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what are the thick yellow block on the side? best bet is to make the corners of the room deep and wide where possible to get the most bass trapping. wall-ceiling/floor-wall/vertical corners work for bass trapping with tri-corners being the most effective spot (in most cases). then add a front absorber, side, and ceiling at first reflection points. 2" or 4" with 4" being a better choice in most cases. on the back wall add another absorber or two to reduce reflections off the back wall.
 
the big yellow things are the top view of the ceiling/wall corners being straddled by a piece of 817. thanks for the input. maybe this view will clarify..
 

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I bought certainteed condensed f'glass for my studio, and I was assured at SPI that it was the equivalent to 703. It's a matter of the pounds per cubic foot or something, not the brand name. I say buy the JM stuff and get on with making your traps. :)
 
817 I believe is a substitute for OC705. JM 814 is the sub for OC703. The 3lb (703 or equiv) will be about half the cost of the 705 or equiv. ie - 6" of 703 will be 75% of the price of 4" of 705 and work better in the bottom end due to increased thickness.

Gulfo is right on about the corners and the rear wall being 4" thick - or more.

Bryan
 
cool, thanks for the info guys. i will at least double them up to 4in. is it ok to just leave the foil backing on and just put it toward the wall? here is another drawing, sorry so small, there is a file size limit on here.


google sketch up rules!!!!
 

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foreverain4 said:
do i have to remove the foil backing, or can i just turn it toward the wall?
Click to expand...

The foil will actually make it better as a bass trap, but it will obviously reflect high end. Having it facing the room is supposed to be best, but maybe turning it toward the wall will be a good compromise. A little better low end absorption and it would absorb some highs too.
 
i built mine using 2in Roxul Rockboard 60 from ATS Acoustics. I doubled them into 4in baffles. The Rockboard 60 is equivalent to OC 705 (6 pcf) and is about 2/3 the price ($55 for a box of 6). It made a huge improvement to the sound of my room.

and at the 4in depth, works really well both as a bass trap and as movable gobos for isolating off performers, amplifiers, drums, etc. I've got a couple "changes" in mind for design ideas for the next time around, though.

in the end, though, i did a cost-benefit analysis of how much the raw materials ran me (wood, screws, fabric, roxul) combined with the time spent per panel, and found that i essentially paid myself $18/hr to build these things. for that sort of money (and the time committment involved), I decided that for me, it's more cost-effective just to buy the panels already built and save myself some time and effort.

i'm in the market for some more....so i think it's about time to give Glenn a call.


cheers,
wade
 
If you're going to use FSK, have it on the side facing the room for non-reflection point applications. Peel it off the other layers. Having it on the back side facing the wall will give you no benefit.

Bryan
 
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