Recording - November 2014 - 47

6" of their mouths, and the panelists'
chairs were 3' apart. But the Three-to-One
Rule only works when the sound sources
are comparable in volume-which Onion
and Tommy weren't, by a long shot.
Faced with these limitations of the
Three-to-One Rule, I invented a rule of my
own: the 10 dB Rule. According to this
new rule, if the signal produced by a
sound source that's bleeding into someone
else's mic is at least 10 dB lower than that
source's level coming from its own mic,
phase problems will be minimized. If not,
not. Onion's level in Tommy's mic was
about 4 dB less than it was in his own mic,
thanks to the boost required by Tommy's
softer voice, and we had troubles.
In the end, I suggested to the producer
that we move them apart; by putting
Tommy farther down the table, his mic
picked up less volume when Onion erupted, and the 10 dB Rule was observed.
Problem solved.
Following the Rule
How to ensure that the 10 dB Rule is
being followed? It requires a bit of messing
around during setup, as you're getting your
levels, and some cooperation from the
musicians. Let's say you're recording a jazz
combo, and you're deliberately using the
leakage between sax and trumpet. Place
your mics, set your levels, and pan both to
the center in your monitoring setup.
Then have the sax player quit playing.
Look at the level on the sax player's track
and the trumpet player's track; is the trumpet's bleed on the sax track at least 10 dB
down from its level on the trumpet track? If
it is, you're cool; have the sax player
resume while the trumpet player quits. Is the
sax bleed in the trumpet track at least 10
dB below its level in its own track? Still cool.
Don't just look at the meters; also listen
to both tracks, again panned to the center
and set to equal levels in the monitor mix.
No Phase Monster? Doubly cool; repeat
with other pairs of instruments. If all the
leakage signals are at least 10 dB down,
you should be okay; set up a reasonable
soundstage via panning and listen,
remembering to double-check the mix in
mono. If it sounds good, you're ready to
roll-you won't get bad comb filtering, but
there'll be enough bleed to create the
magic I talked about at the beginning of
this article.
If you don't have metering on each
channel, you can still do a bleed check.
With basic levels set, have the trumpeter
play while the sax player lays out. With
every mic on and routed to the center,
look at the meters for the mix as a whole.
Then mute the trumpet player's channel;
the level of the mix should jump down at
least 10 dB. Repeat with the sax playing
and the trumpeter laying out, and for
other combinations of instruments. Finally
unmute everything and record.

Can you use controlled leakage with
electric instruments? You bet! Sam Phillips
recorded Elvis's band that way for Sun
Records; it's on every record Chuck Berry
made for Chess, and plentiful leakage
was an essential ingredient in Phil
Spector's "Wall of Sound". Spector would
sometimes have six electric guitars, three
basses, and a drum kit playing in one
crowded and noisy studio. (If you try this,
you'll find that the drummer needs to exercise a certain amount of self-restraint, and
you'll discover why so many guitarists love
small Champ-class amps, which give
great tone at reasonable volumes.)
What if you find that you're violating
the 10 dB Rule-that the bleed signals
are less than 10 dB down from the direct
signals? Then it's time for corrective
action; you could take a hint from the
Onion-and-Tommy scenario and move the
problem players farther apart. You could
also use the directional characteristics of
your microphones; remember that cardioid mics have maximum rejection at
180° off-axis, while hypercardioids have
their maximum rejection at 120° offFigure 5

Figure 6

axis-and it's usually a sharper null than
most cardioids'. The sharpest nulls of all
come from Figure-8 microphones; a good
Figure-8 mic, or a good multi-pattern mic
in Figure-8 mode, will have a very deep
rejection notch at 90° off-axis.
Or, as a last resort, you could haul out
the gobos-but be sparing with them,
and use just enough to keep the leakage
within bounds, while not killing it completely. Remember Clips 1 and 2-that
controlled-leakage magic is valuable
stuff, and you don't want to lose it.
Next time, we'll discuss how the Phase
Monster can attack in sessions without
planned leakage, and what to do about
it. See you then!
Paul J. Stamler (stamler@recording
mag.com) is a recording musician, engineer, educator, and collector of bizarre
vintage recordings, living in St. Louis.
http://www.t-funk.com http://www.t-funk.com
Recording - November 2014

Table of Contents for the Digital Edition of Recording - November 2014
