I am considering giving this an attempt. This is a little dated but sound waves have not changed sence 02. Inflation and some material avalibility probably has though. Does anyone have better guide or clearance on premade treatments?
DIY ACOUSTIC TREATMENTS Updated last 6-6-2002
by Jon M. Risch,
jrisch@strato.net
Many audiophiles don't know it, but for the price of one not so fancy
interconnect, or about $150 dollars, you can acoustically treat your
room with excellent absorbers, including 4 wall panels AND a set of
4 bass traps. A full blown acoustical treatment with floor to ceiling
bass traps in front, and 6-8 wall panels, along with some basic
diffusion for the rear wall will run around $470, with a significant
chunk of that in the retail bargain diffusors.
Equivalent cost of the minimal retail options exceed $1,400, and
may not work as well. A full blown treatment using retail options may
reach $2,700 or more, and will not work any better. Read on for
details.
Sonex vs. Fiberglass
An equivalent thickness of fiberglass (building
grade) will perform similarly to Sonex, but with slightly better low
frequency absorption. Since fiberglass comes in thicker versions,
such as 6 1/2" and 8" thick, you can get correspondingly better LF
absorption than 4" of Sonex. So far, so good.
But when I tried to find a suitable covering, then I ran into problems!
It seems most all fabrics are woven way too tight to allow the sound to
readily pass through to the fiberglass! Even some velour that was being
sold as "sound absorbent covering" had a large amount of reflectance
at high and middle frequencies. It is not just a matter of allowing the
sound waves through the cloth and into the fiberglass, but how much
of the sound reflects off the surface of the cloth, and back into the room.
At middle to high frequencies, many cloths have a fair amount of
reflectance, even some speaker grille cloth's..
I eventually found a solution and recipe for do-it-yourself sound
absorbing panels/coverings:
A rock wool panel (these run about 1" thick) for the very back, spaced
off the wall/ceiling as much as 6-8 inches (or as much spacing as can
be spared, the more the better the LF absorption), then a thickness of
fiberglass of any brand (the thicker, the better, use 8" thickness
if budget and space permits), then a layer of fairly loose polyester
batting (available at fabric stores and Wal-Marts for use in blankets)
to provide a protective layer that doesn't adversely affect the
absorption of the fiberglass (the entire absorptive layer COULD consist
of this material, but it would be cost prohibitive, on the other hand
no itch!), and then a layer of burlap as an outer covering. Colored
burlap is available in 36" widths from fabric stores and most
Wal-Mart's. Light colors work well with the layer of white poly
batting just underneath the burlap, although the darker colors are OK.
In actual anechoic testing, I found the burlap to have the least
reflectance and allow the most absorption by the fiberglass.
Practically speaking, it works best if a simple, minimal wooden frame
is constructed from 1X2's or 1X4's (depending on the thickness of
fiberglass), with the rock wool panels glued/stapled to the rear of
the wooden frame, with vertical frame members spaced about
14" apart (the width of the fiberglass) and the fiberglass WITH
PAPER BACKING stapled at the edges to the middle side edges of the
vertical frame members (I usually ran a 10" strip of poly batting down
the middle of the strip {roll} of fiberglass between the paper and the
rock wool panel, in order to prevent possible flapping paper noises
against the rock wool). Then staple the poly batting over the
fiberglass, stapling to the vertical frame members (hence the need to
adjust the wood depth dimension to the fiberglass), and finally, using
brass tacks every 6" to affix the colored burlap along the vertical frame
members, and across the top and bottom. These can be on the back
along the top and bottom, so brass is not necessary, and cheaper
tacks, nails or staples could be used there.
If you want to be sure the wooden frame does not reflect too
badly, wrap the bonded fluffy polyester batting around and along the
side of the wooden frame, and cover this all with burlap too. Some
adjustment of spacing between frames may be needed at the two
sidemost sections to accommodate this, depending on how you have
laid out the burlap and polyester.
When this is all finished, you have a nice looking sound absorbing
panel with scallops every 14" or so that run vertically, that can be
semi-permanently located, but can leave with you as needed. Portable
versions with sturdier frames can be built of course, and put on
rollers or wheels for adjustable studio or listening room use.
DO NOT double up on the burlap layers, as performance suffers! Also,
remember to treat the burlap with fire retardant, wear gloves and at
least a cheap respirator mask when handling/cutting the fiberglass,
and to lightly vacuum the outer burlap surface to get up any loose
fiberglass particles. Once covered in burlap with the poly batting
layer to prevent fiber or particle escape/contact, these panels provide
excellent performance at minimal cost and no health hazard.
I have been asked about the need for the rock wool/series 700 panels
on the rear of the fiberglass and frame. Are they absolutely necessary?
No, but a typical absorbing panel, using 6 1/2" fiberglass AND the
rigid panel glued to the rear will be effective down to below 100 Hz.
Using only the fiberglass will result in a panel that is good down to
around 200 Hz. Wall spacing is important too, if the panels are placed
flush against the wall, then effectiveness in the LF can be halved
compared to even just 4" of spacing.
Recent checks on 700 series pricing and availability has lead to the
discovery that, to the consumer, the only size that is readily available
is a 2' by 4' panel, in 1", 2" or 3" thickness's. In some area's of the
country, rock wool panels are still available, but not everywhere.
Due to the cost associated with these smaller panels, I now
recommend straight 8" fiberglass for maximum effectiveness at LF,
without the rigid panels glued to the back of the frame.
If you use at least 6" thicjness of fiberglass, then the rock wool/OC
panels are not necessary to obtain adequate low frequency
absoprtion.
+++++++++++++++++++++++++++++++++++++++++++
Rough Costs:
Fiberglass (faced) - 6" thick, 15" by 39 feet at $12.50 roll
Burlap - Dyed, with minimum levels of insect and fire protection,
available from Wal-Mart, $1.48 a yard by 36" wide.
1" X 2" white spruce 8 foot long, 92 cents each
1" X 4" white spruce 8 foot long, 98 cents each
Polyester batting, bonded fluffy loose pile, approx. 1/2 to 3/4
thickness, 45" wide, $2.17 yard
Brass plated nails, approx. 50 for 86 cents
#9 Brass Upholstery Nails, 30 for 81 cents
Tube Liquid Nails 29 OZ, $4
Tube RTV Silicone Rubber, 10 OZ, $4.50
Staples: $2 for 1,000, 9/16"
OPTIONAL: Owens Corning 705 semi-rigid fiberglass panels,
2' by 4', by 1", 12 to a carton for approx. $92, not including S&H.
Rough Total for a 4 foot tall by 30" panel: $12.50 each, minimum
investment of materials for 4 panels, for $50 total.
4' X 45" panel: $17 each, minimum investment of 4 for $68.
Some materials left over.
ASC Wall Panels are $398 for eight 2" thick by 8" wide by 48" tall
panels, good only down to about 500 Hz.
