Recording - March 2015 - 22

One of the hallmarks of a superior recording is mastery of the
sense of audible space. There are certainly a variety of techniques a recordist can use to achieve space, and the particular
techniques each engineer chooses to use will largely shape his
or her style as it develops.
One of the best ways is to take advantage of the space in the
room where the tracking takes place. Capturing a sense of space
can be done through a combination of instrument placement,
microphone technique, and an understanding of the room
acoustics at play in the room. This can give the recordist a bulletproof formula to record tracks where the sense of space can be
precisely manipulated during the mix, to achieve exactly the right
amount of space and ambience, with or without external effects.
This article will discuss a few strategies to accomplish exactly that.

away from the sound source, with a wall 8' away, then the early
reflections will be about 16 ms delayed in time, and about 18
dB softer, than the direct sound from the instrument.
Early reflections like this will interfere with the direct sound
from the instrument to the microphone, which produces comb filtering. This interference will create severe peaks and nulls in the
frequency response of what the microphone hears. The farther
away the reflective surfaces are, the less severe the interference
will be, in terms of its volume being softer and delayed further
in time. These kinds of peaks can be challenging to overcome
during the mix; much of the mix work will be about compensating for these problems, as opposed to a creative or artistic
expression of getting a great balance and an exciting mix. A
larger room directly minimizes these effects.

Of course, the ideal scenario for capturing space in recordings is to record great musicians playing great instruments in a
great-sounding room! Recording under these conditions almost
feels like cheating, in the sense that the recordist has fewer challenges to overcome under these ideal circumstances. It becomes
a simple matter of setting up the mics, getting levels, and capturing the players doing their thing.
But what are some characteristics of a great-sounding room?
We first have to understand a few of the technical details of
great acoustics, so that if they are not present, we will have
some idea of how to overcome these limitations.

2. A great-sounding room will have a good reverb time, and
even more importantly, the reverb time will be even across the frequency spectrum.
Reverb time is typically measured in seconds as RT60, which
means the amount of time it takes for the sound to decay 60 dB
from the initial attack. Most rooms should be somewhere
between 0.5 and 1 second of RT60. Like many audio parameters, however, RT60 is frequency-dependent. It is common for
some frequencies to linger longer than others. This is often called
"ringing" and is a sign of an untreated (or undertreated) room.
Sometimes, the ringing is at a narrow enough bandwidth that
a single note from an instrument can cause the room to resonate
audibly at that note. This phenomenon is at the root of the "onenote bass" phenomenon where different notes are difficult to pick
out, and it sounds almost like the same note is being played. We
often think of reverb as being mostly a midrange or a treble phenomenon, but reverb exists throughout the frequency spectrum,
and if it is out of control anywhere, that will greatly affect the
quality of recordings that are made in that room. We want reverb
that is controlled and relatively flat in frequency response.
Understanding these parameters will help the recordist better
understand how to overcome the limitations of the space so that
the best quality recordings can be made. We'll now discuss how
to work with these parameters, to maximize recording quality
and flexibility in any room.

What makes a great-sounding room?
1. A great-sounding room will have enough physical space
for all the musicians to set up comfortably, with no nearby surfaces to cause early reflections.
In a small room, where walls or ceilings are close to the performers and the microphones, the early reflections from nearby
surfaces will be both stronger and earlier in time, which means
they will be more problematic for the mix. Sound waves take time
to travel, so the further away the walls and ceilings are, the later
they will be delayed in time, by about 1 millisecond per foot. In
addition, the further sound has to travel, the weaker it gets; every
time the distance between a sound source and the microphone is
doubled, its level drops by 6 dB. If a microphone is about 1'
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RECORDING March 2015

Recording - March 2015

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