Recording - February 2015 - 44

So you want a recording and mix that can translate to all of these potential
listening setups, and probably several I haven't thought of. Each of them represents a potential destination for your music-and a potential market for it.
You might try to simulate many of these listening environments. For example,
I check car stereo compatibility by burning a CD of a mix, bringing it out to
my car, and taking a spin on I-44. My car stereo is nothing fancy (basic Chevy
factory equipment), and with luck the sound I hear is representative of what
the average car listener will hear.
But it's impossible to simulate every possibility, so a reasonable compromise
is to monitor in a room designed to be as neutral as possible, on monitors that
are also as neutral as possible.
The shape of things
Almost everyone knows that the way to make a good control room is to construct it from scratch while the building is being built, using non-parallel walls and
a floor plan designed by an acoustical engineer. Nope, I can't afford that either.
In fact, almost nobody can; even the control room at our university's studio was
built into a pre-existing space, and the walls are resolutely parallel to one another. Most of us will work in a space that's rectangular, so let's talk about shapes
and sizes. And let's start at the bottom, with the worst possible shape-a cube.
What's so bad about a cubical room? To explain that, I need to take a short
detour through the annoying territory of standing waves. You can look up
standing waves online, and you'll get a lot of explanations (most of them
involving jump-ropes).
I'll cut to the chase: in a space with parallel walls, acoustical standing waves
develop at particular frequencies (usually low) that depend on the size of the
room. At each of those frequencies, there will be places in the room where that
frequency is exaggerated, and there will be places where it's barely there at
all. So a room with a standing wave at a bass frequency of 100 Hz will, if
you stand in the right place, have enough booming bass to rattle the fillings in
your teeth. Move a couple of feet, and the bass will be gone; any music you
pump into the space will sound like it has no bottom at all.
I've written a spreadsheet that calculates the frequencies of the most important
standing waves in a room: the ones that develop between parallel surfaces, like
the north and south walls, or the floor and ceiling. (For reference, these are called

When a frequency appears three times in the
table, that's triply bad news; such a "triple pileup" produces a triple-strong standing wave. In
this room, such a triple whammy appears at 282
Hz; that would be a problem frequency if you
tried to use this room for monitoring.
The problem is that the dimensions of the room
(8' x 10' x 12') are related to one another by
simple ratios (4 : 5 : 6), and rooms like that
almost always create problems. The worst, as I
mentioned at the start of the section, happens
when the dimensions are all the same (8' x 8' x
8')-a cube.
Try typing 8, 8 and 8 into line 3 of the spreadsheet. Oops; every frequency in the table appears
three times, a triple whammy across the board. A
room like that will have very uneven response, and
will be very hard to use for monitoring.
There are some room-dimension ratios that
audio engineers consider "golden", since they

Fig 2

There are some room-dimension ratios that engineers consider
"golden"; they produce rooms with few standing-wave pileups.
axial modes, but you don't really need to know that.) The spreadsheet is called
StandingWaves.xls and can be downloaded at http://is.gd/StandingWavesXLS;
it runs on every spreadsheet program I've tried, including Excel, Calc (part of the
free OpenOffice suite), Numbers, and Quattro Pro. Be sure to also download the
SpreadsheetReadMe text file that goes with it.
Let's look at one possible room, one with dimensions that are numerically
related to one another: 8' high, 10' wide and 12' long. Type those dimensions
into Line 3 of the spreadsheet; it will automatically calculate the frequencies of
the standing waves characteristic of that room, up to 300 Hz. (See Figure 1,
a screenshot.)
A good room will have an even distribution of frequencies, and each frequency will appear only once; if a frequency appears twice in the table, that
means there will be standing waves at that frequency appearing between two
pairs of surfaces in the room. As you see, 141 Hz appears twice, a double
whammy that's bad news; parts of the room will have a boom at that frequency, while at other spots it will barely be heard.
44

RECORDING February 2015

produce rooms with a good spread of standing
wave frequencies and no pileups. One example
is 1 : 1.14 : 1.39; for a standard ceiling height
of 8', that translates to a room 8' x 9.12' x
11.12'; type those numbers into line 3 of the
spreadsheet, and you'll see that the standing
wave frequencies are nicely distributed with no
pile-ups anywhere. Now you can use the spreadsheet to find out whether the dimensions of your
room are problematic.
Recycled remedies
So what do you do if you find that your chosen
room will have big standing wave problems?
One solution is to move; choose another room in
the house for listening/monitoring. For those of

http://www.is.gd/StandingWavesXLS

Recording - February 2015

Table of Contents for the Digital Edition of Recording - February 2015