Recording - November 2015 - 26

from the highest peak to the deepest null. All small (meaning
smaller than, say, a basketball court) rooms will exhibit a
response like this, meaning there will be peaks and nulls this
severe in most untreated rooms. The difference between rooms
will be in where the peaks and nulls occur. In other words, all
untreated rooms do not sound the same.
This is the the hidden presupposition in this myth, and it reinforces the idea that all treated rooms are "perfect" and all
untreated rooms are identically bad (see Myth 13 below). The
fact is, a treated room will have a much flatter frequency
response, therefore at any given frequency it will be much closer to the frequency response of each listener's room.
To illustrate the point: imagine a single frequency of, say, 41
Hz. In the mix engineer's room, there is a null of -25 dB at 41
Hz, but in a listener's room there is a peak of +10 dB at 41 Hz.
This means that for a song in the key of E, the root bass note of
the song (which happens to be 41 Hz) will be 35 dB softer in
the mix engineer's room than the listener's room!
However, if the mix engineer had treatment in the room to get
rid of the null, the difference would be only 10 dB, an improvement
of 25 dB-equivalent to over 300 times more
power, or going from a 10W amplifier to a 3162W
amplifier! And this is just for one (albeit very important for many songs) frequency.
In short, a properly treated room greatly
improves the accuracy of the mix environment,
which means that mixes done in that room will
always translate better to any other audio system
for reproduction. This means a mix engineer can
work faster, with more confidence, and produce
better results. These are all good things.

the question at hand is, do they differ much from regular household
rooms finished in drywall, concrete, or even linoleum? This question
is polarizing, and there are well-known audio people I respect on
both sides of this question. One side says that if a wood room
sounds really good, it probably doesn't have much to do with the
wood itself. The other side will undoubtedly observe that there are
a lot of great-sounding rooms with a wood finish. Who is right?
There's no way to tell. The only definitive test would be to build
two absolutely identical rooms-same size, dimensions, layout,
and equipment-with wood and non-wood walls. This isn't likely to
happen any time soon, so we're left with three less-than-scientific
arguments: anecdotal evidence ("Wood sounds good because the
acoustic guitar room at my local store is wood, and it sounds amazing in there"), argument by authority ("Wood sounds
good because Expert So-And-So says it sounds
good"), and tradition ("There are quite a few goodsounding wood rooms in the world").
But we're not done yet. The "wood finish" in many
of these good-sounding rooms is part of the acoustic
treatment! For example, slat absorbers are custombuilt treatments that have decades of proven use, and
can perform very well-but the visible fronts of
absorbers like this often use wood slats, and many
people may not realize they are acoustic treatments.
Then there's the fact that wood is a critical part
3. Bookshelves are diffusors
of the design of many acoustic instruments. We
Here's another common misconception. It arises
know that well-made resonant wood structures are
from the design of a one-dimensional QRD Diffusor,
essential to violins, guitars, etc., so we assume that
with its uneven build with wells of various depths, as
this must be true of wood surfaces. But damped
shown in Figure 2.
wood, such as a parquet floor over concrete, defIt does kind of look like a bookshelf, stuffed with
initely doesn't sound much different than other
books of various sizes, doesn't it? And it is true that
reflective surfaces such as drywall or concrete.
a bookshelf will help to break up sound waves a litSee realtraps.com/art_surfaces.htm for details on
tle bit, as well as absorb a bit of sound. Books are
these properties of damped wood relative to other
similar to wood in the sense that they do have a tiny
materials, with some test data.
amount of absorption, relative to smoother/stiffer
I was discussing this myth with a friend of mine,
materials such as concrete or drywall, though the Figure 2. A one-dimensional who is a well-known studio designer for whom I have
QRD-style RealTraps
amount of absorption is nowhere close to that of a
great respect. He is convinced that wood sounds betdiffusor with wells of
soft blanket, much less a real acoustic panel.
ter than drywall. He told me to alternately hold a
varying depths.
However, breaking up sound waves from an
piece of wood and a piece of drywall up in front of
uneven surface is not the same thing as diffusion. A Photo courtesy RealTraps. my face and speak into them each in turn. The difdiffusors scatters sound evenly in all directions across
ference, he assured me, would be easy to hear.
its effective plane, which for diffusors of this type are left/right,
I tried his test, with a small, 16" square scrap of plywood, and
unless the diffusor is installed horizontally in which case it will be couldn't really discern much difference. Of course it wasn't a douup/down. To achieve this even scattering, the sequence of well ble blind test, so it could have been plagued by expectation bias
depths is critically important. The well depth pattern isn't random- or other prejudices, but in my case my only prejudice was to see
it is a specific mathematical sequence that must be calculated and which one sounded better! In other words, I'm not attached to any
precisely constructed. If the calculations or the craftsmanship is off, particular outcome, I just want to know the truth of the matter.
When I told him my results, he said that the 3/4" plywood I
then the diffusor won't work in terms of providing actual diffusion.
I should add that diffusion has a specific sound to it, one that had used is much more damped than a board. He's quite right,
most people who haven't worked in rooms with diffusion haven't of course, which brings up another issue: what kind of wood?
experienced. It's really difficult to emulate the sound of diffusion How thick? What density? Just to be sure, I repeated the test
without actually using diffusors. That said, given the choice both with the plywood, and a scrap of a pine 1x10 I had, with
between a bookshelf and a bare, reflective wall, in most cases similar results. I just didn't hear much difference.
If you or someone you know has tried building two identical
I'll take the bookshelf if I can't use real acoustic panels.
rooms, one with wood and one without, to test this theory,
4. Wood sounds "warmer" than other reflective materials
please let me know-I'd love to see the results! Until then, feel
This "myth" might be the most controversial of all these, and free to use wood in your rooms if you like the way wood looks.
also it may be the least myth-worthy. Perhaps I should call this Maybe a wood room might sound better, but using wood finish
is no substitute for properly treating the room to begin with.
one "as-yet-undetermined" rather than definitively a "myth."
In general, I find rooms with a natural wood finish to be gor- Perhaps most importantly, if your room is other than wood, you
geous, and definitely conducive to creativity in my mind. However, can still get a great sound (see Figure 3 on the next page).
26

RECORDING November 2015

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