Recording - March 2018 - 30

MAX OUT
YOUR
(and rooms) will also be pressed into
service to check the mix, as will different
types of headphones (studio phones,
earbuds), to help insure that the mix will
sound good wherever it's played.

The room

And that brings us to the room. Even
studio operators who understand the importance of flat response for the monitors
may not be experienced enough to realize
just how much effect the room itself will
have on the sound ultimately heard by the
engineer in the sweet spot. This is especially
critical for mixing-if the room alters the
sound too much, this will lead to the mixer
making choices in EQ, delay, and reverb
that only work when the mix is heard in
that specific spot in that specific room.
Mix decisions that compensate for
anomalies of the room can make the mix
sound worse in other rooms that don't
share those same colorations. The flattest
speakers in the world will still be subject
to room colorations, and so for a truly
professional production environment,
the room usually needs to be considered
part of the monitoring chain, and treated
with physical sound control treatments to
minimize any detrimental effects.
Room colorations are the result of
sound waves reflecting off the room's
boundaries-the walls, floor, and ceiling.
Reflected sound waves bounce off these

MONITORING

surfaces back into the path of the direct
sound waves traveling from speaker to
listener, and phase cancellations
and reinforcements alter the harmonic and
overtone balance of the sound, leading
to EQ choices that don't work in other
rooms. Additionally, delays and ambience in the room can give the mixer a
false picture of the overall ambience of the
mix, leading to dubious decisions about the
use of delay-based effects like chorusing,
echo, or artificial reverb. An overall loss
of detail from the room sound can result in
less-than-ideal choices made even in basic
aspects of the mix like level and panning.
Room sound problems can be
divided into two basic categories-lowfrequency and mid-/high-frequency
issues. I'll start with the low-frequency
issues, since these can be the most
severe, and are the most common
cause of mixes that don't "travel" well.

Don't stand for
standing waves

In any room, sound waves reflect off
room boundaries-I'll use wall reflections
as an example, but floor and ceiling
reflections are also part of the issue.
When the shorter wavelengths of mid
and high frequencies are reflected,
the resulting phase issues/colorations
are spread throughout the room (see
below). But the longer wavelengths of

FIGURE 4. A studio (the author's former room) with absorbers
on the walls and ceiling.
30

RECORDING March 2018

low frequencies are often as long as
or longer than room dimensions, and
these reflections produce cancellations
and reinforcements that are localized to
specific spots in the room.
There isn't space to get heavily into the
math/physics of it here, but these localized
areas consist of spots where the bass at certain frequencies is either cancelled (nodes),
for a loss of bass at those frequencies, or
reinforced (antinodes), for a boomy response.
This happens at frequencies whose wavelengths are related to the room's dimensions,
and typically a room will have several
for each pair of parallel surfaces (wall to
wall, floor to ceiling). These low-frequency
anomalies are called standing waves or
room modes. See Figure 3.
For example, there's always a buildup of bass at certain frequencies at the
walls themselves-that's why speaker
placement away from the walls is usually
recommended, as above. And since
the frequencies of standing waves are
based on wavelength and room
dimensions, room modes also occur
at harmonics of those frequencies-as
a result, the level and tonal balance of
bass notes in a typical room is different
at different locations in the room, as
different harmonics are either boosted or
sucked out in different listening positions.
The best way to deal with standing
waves is to utilize room treatments to
try and break up the worst of them.
This involves calculating the affected
frequencies (with a fairly simple formula) for
the several types of room modes, and
placing treatments in or at the walls that
will prevent them-these are generally
called bass traps, and there are various
types, including Helmholtz Resonators,
Diaphragmatic Absorbers, etc. Again,
there isn't room here to go into detail,
but there's plenty of material available
that does, including articles in Recording
available on our website.
Designing and placing cavities in
your walls may not always be an option,
but there are also surface-mounted
solutions available from a number of
companies that can be ordered and
positioned (usually in corners) to address
standing wave issues-some companies
will take room dimensions supplied by
the buyer and calculate the optimal size/
depth for a particular studio space. At
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