Recording - September 2014 - 64

The forgotten Room Surface

-The Ceiling!

Figure 5. RotoFast Cloud Anchors screw into 703
fiberglass so it can be hung from a ceiling.

Alternatives to fiberglass
There are other absorbent materials that you can
use if fiberglass is not your cup of tea due to handling-safety concerns. One of them is called
UltraTouch from Bonded Logic, which is made from
recycled blue denim and other textile fibers
(www.BondedLogic.com). This makes it very Earthfriendly and non-irritating. The manufacturer has pictures of children playing with it, and I personally have
rubbed my face in it with absolutely no problems.
This material is also available as Quiet Liner, which is
a denser material available exclusively from
Acoustical Surfaces (www.acousticalsurfaces.com).
This version performs better, but costs more. Note that
this material is not self-supporting like the O-C 703 is,
so you'll need to attach it to some backing like
Masonite, 1/8" or 1/4" plywood, or even pegboard.
The contractors I know who have worked with it say
it's not nearly as easy to work with as 703.
Another material is ReCore from Fabric Mate
(www.fabricmate.com). It is made from recycled
beverage bottles, so it's also very Earth-friendly and

non-irritating as well. It comes in a variety of thicknesses and densities, but I
recommend using 2" thick with a 3 lb. per cubic foot density. This comes in a
uniform white color, so you can actually install it uncovered if white works in
your decor. Fabric Mate also makes finished fabric-wrapped panels, if you
want them covered but don't relish the prospect of doing the work yourself.
The one cautionary note about ReCore is that the acoustical information on
it is not very complete, so it's hard to really understand how well it performs
and if it has any peculiarities that should be accommodated. That being said,
I've worked in some rooms that have it installed, and it has performed fine in
those cases. So if you don't need the reassurance of extensive data, and you
want an absorbent that is Earth-friendly and can stand up on its own (literally), this is an excellent choice.
You can also use the popular sculpted foam products, but as much as
you'd think the uneven surfaces would help things, in my experience sculpted foam products just don't work as well as the materials I've mentioned.

X marks the spot
So you have a lot of good choices, but whichever you select, placement is
very important. Whether you choose diffusion or absorption, it needs to be
positioned so that it covers every point of first reflection from each of your
speakers to each of your listening positions. If a sound wave bounces off the
ceiling and gets to your ears, it should hit the treatment while trying to do so.
How much space does the treatment need to cover? Width is easy; two
thirds of the width of the room is a good rule of thumb. But how long must it
be? Where should it start and end?
The easiest, roughest technique is to measure the distance from the front
edge of your speakers to the front wall of your room. Put the front edge of
the treatment right above the front edge of your speakers, and the rear edge
double that distance from the rear wall. So if you have a room that's 14 feet
long and the front edges of your speakers are 2 feet from the front wall, you'll
need an 8-foot ceiling treatment that starts 2 feet from the front wall and ends
4 feet from the back.
If your ceiling is so large that a single device doesn't cover this area, you
can use multiple diffusors or absorbers. If you choose multiple polycylindrical
diffusors, my secret tip of the day is that it's good to vary the width of each
one-it gives better, more random diffusion.

Don't Forget...
I'll close with a very important reminder. Ceilings have one annoying and
even dangerous ally in defying your attempts to treat them. I refer, of course,
to gravity. Whatever we do to our ceilings is going to be an issue that's left
hanging over our heads-literally!
When hanging anything from the ceiling, be sure it is firmly attached. It is
far better that it be too well attached, rather than not attached well enough.
I live in earthquake country, so I pay a lot of attention to these things!
So there you have it. Your ceiling is now neither overlooked nor underloved, and you now have the tools you need to take your critical listening
space to the next level.
Bruce Black (black@recordingmag.com) is a recording and post-production
engineer now working as an acoustics consultant with Media Rooms Tech in
Ventura, CA. Learn more at mediaroomstech.com and read Bruce's blog at
manofacoustics.com. All photos by the author.

Figure 6. Alternatives to 703 fiberglass for ceiling-mounted absorption include (left to right) UltraTouch, Quiet Liner, and ReCore.
64

RECORDING September 2014

http://www.BondedLogic.com http://www.acousticalsurfaces.com http://www.fabricmate.com http://www.mediaroomstech.com http://www.manofacoustics.com

Recording - September 2014

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