The "Depot Diffusers"
A very easy to build, very inexpensive but good performing wideband
sound diffuser design, effective from 400Hz to 8kHz or wider.
Optimized to use off-the-shelf dimensions of inexpensive firring strips
(sold in large hardware centers in the USA, such as Home Depot,
Menards, or Lowes). Size is 34 inches wide, about 4.5 inches
deep, and as tall as you want to build (easiest is 8 feet tall).
The Depot Diffuser is a 1D type diffuser, usually the best type to use
in listening room to adjust ambience.
These can be a nice one-day project and would almost certainly
make more of a change to a system’s sound than changes to
electronics or wiring, maybe even than changing speakers. Best placement is usually 5 feet or more behind the listening chair, but reflection points or behind speakers are other options.
Diffusers
are a less often used, usually too-expensive type of room treatment.
Absorbers are the more common type. Absorbers remove energy from sound
waves that hit them, effectively smoothing responses and reducing
specular reflections, and are usually the first choice. But after a
point too much absorption starts to make the room seem dead or even
downright uncomfortable to sit in. Diffusers break up specular
reflections but don't absorb the energy. Instead, energy at different
frequencies is scattered over a wide area and range of time delays.
Diffusers don't kill the lively-ness of a room but can make it sound
much richer and seemingly larger. Placed at reflection points or behind
the listening chair, they make a dramatic and immediate effect, not one
of those "I think I can hear it" kind of things.
These
ultra-easy, wideband, inexpensive diffusers perform well from about
400Hz to 8kHz. They are 1D "step” type diffusers, optimized using
the diffusion simulator “AFMG Reflex”.
They simulate well, even compared to the usual QRD diffusers you might
be familiar with. Credit for the assembly concept and instruction on
optimizing step diffusers goes to Tim Perry at Arqen Sonic.
The
total cost of wood for one 8ft tall diffuser should be around $92 for
one 8ft diffuser, with left over plywood. Two would cost about $152,
three would be about $212.
WAF
might be a factor choosing to install these, but I think if they were
near floor-to-ceiling sized and painted to match the wall colors they
could look pretty nice, or at least inoffensive. I like the way they
look, even without any finish at all (though I'll probably sand and
urethane them sometime).
The
first step is to get the wood, enough to build the height you want to
make. Try to pick mostly un-warped, decent looking pieces if you can.
Here is what you'd need for one 8ft (96", minimum wood cutting), 34.5"
wide diffuser. Alter as needed for other heights or quantities:
_____________ Wood List _________
*Qty 12 of 96" pieces of nominal "1x3" (~0.7"x2.4" actual) furring strips, about $2 each.
Part numbers are 164704 at Home Depot, 13PFUR.8 at Lowes, 1031528 at Menards.
*Qty 4 of 96" pieces of nominal "1x2" (~0.7"x1.5" actual) furring strips, about $1 each.
Part numbers are 160954 at Home Depot, 128218 at Lowes, 1031515 at Menards.
Plywood,
from Home Depot 577138, or Lowes 12232 , or Menards 1251061; about $32
per 48”x96” sheet (you'd need two sheets to make one
diffuser, or three for two diffusers). Home Depot cut mine to these
sizes at no additional cost. You need:
*Qty 2 of 12.25"x96" plywood
*Qty 1 of 34.5"x96" plywood
______________
To
assemble, first lay the big piece of plywood down, ugly (unsanded) side
facing up. Take one of the 1x3 pieces and set it on the plywood,
aligned all the way to one (long) side. Then set one of the narrower
pieces alongside the 1x3, for positioning. Move the 1x3 back and pencil
mark the big piece at the four corners of the narrower ply (4 places) -
also run the mark down the edge (thickness) of the big ply.
Repeat for 4 more marks, starting this time with the 1x3 aligning piece on the other long side of the big ply.
Then,
mark and draw 4 full lines the length of the large ply, spaced about
half the thickness of the 1x2 wood pieces (~0.35”) away and
inward from the previous marks – that is, toward the centers of
where the narrow ply pieces had been positioned. The full lines
indicate where to nail or drive screws to connect the 1x2 wood to the
large plywood piece.
Line
up all the 1x2 pieces narrow side down and about 7 inches apart, then
put the large ply piece on top of them, ugly side up. Pull one of the
1x2s over so that its end is along a short line you marked and so that
the full line is about in its center. Align both ends to those lines.
Then
drive a 1” nail or brad through the ply into the 1x2, along the
long line. Repeat at the other end, and about every 8 inches or so
between. Repeat for all 4 boards, when done it should look like the
photo above.
Move
the large ply out of your way and lay down a narrow ply board
“pretty side” up. Use one of the 1x3 boards to set spacing
from one long edge of the ply, as before. Align another 1x3 next to it
and nail that second one in place. Remove the spacing board. Align
another 1x3 alongside the last one (toward the inside of the ply) and
also nail it in place, then another one on top of that. Choose better
looking 1x3 pieces to be the ones on top, where they will show, and use
less nice ones as the covered-up pieces. Repeat with the other ply,
remembering that these two ply pieces will be mirror images of each
other.
Now,
lay down the large ply assembly, pretty side up and place the narrower
ply pieces on top of it. Align the edges of the narrower assemblies as
well as possible on top of the 1x2s of the large ply, with the 2-high
stack of 1x3s toward the center, and nail the assemblies in place.
Lastly,
nail a stack of three 1x3s on the narrow plywood pieces at the edges
toward the center. And you’re done. That's it!
