Using Multiple Amp Mics
Guidelines for employing multiple mics on your next recording
This month, let’s take a look at using more
than one mic when recording an amp. Yes,
that classic Shure SM57 will do the job just
fine, but by using several mics, you’ll give
yourself far more options at mixdown.
Using multiple amp mics isn’t hard, but there
are a few things you need to think about
before the red light goes on. First, decide on
the kind of mic that will work with its partner.
For simplicity’s sake, we’ll assume the first
mic is a dynamic cardioid like the above
mentioned SM57, simply because this type of
mic is so common and you can always rely on
it to deliver the goods.
That said, the strength of a 57 lies in capturing punchy midrange frequencies, so you
might think about putting a second mic with
different sonic characteristics on the cabinet.
A perennial champ in that department is the
Sennheiser 421, which paired with the 57, provides a nice bottom end and a smooth top.
Or you could turn to a ribbon mic. Ribbon
mics are known for their smooth, natural
sound, and they can easily handle the low
end of a speaker cab. Some great ribbons
for recording guitar are the Royer 121 or
122, Beyerdynamic M160 or M88, AEA R84,
and even the $100 MXL 990. Most modern
ribbons can easily handle the high sound
pressure levels that can come from a loud
cabinet, so don’t worry about turning up.
As nice as ribbons are, you don’t have to
break the bank just to pick up a second
mic—just about anything will work as long
as it has a different character than the first
mic. Also, make sure to record each mic on
its own audio channel, which is usually not a
problem with the high track counts of today’s
DAWs (Digital Audio Workstations).
When placing mics next to each other, try to
make sure the sound from the speaker hits
each mic’s diaphragm at the same time. This
helps avoid any phase-cancelling issues. Also,
if your mic preamps have phase switches, be
sure to confirm that the two mics both have
the same phase settings. More than once
I’ve heard an unusual sound when recording
an amp and realized the phase switch was
reversed on one of the preamps. That’s not
to say you shouldn’t try using an out-of-phase
mic, but to begin with, I’ve always found it a
good practice to first record with everything
in phase. Once you know how that sounds,
you can start experimenting.
A little side story on phase: A good friend
of mine, engineer John Holbrook, told me
a story of the first time he recorded Brian
Setzer. John said he couldn’t figure out what
was going on with the guitar sound after
he set up the mics, but didn’t have time to
analyze the problem before Brian wanted
to roll. Only after the session did he realize,
thanks to Brian’s tech, that one speaker in the
cabinet was wired out of phase. John said it’s
actually a very cool sound.
With the two-mic technique, you should also
try placing one mic on axis and one off axis.
Off axis simply means you’re changing the
angle of the microphone in relation to the
speaker. Instead of pointing the mic straight
at the speaker (on axis), turn it slightly to the
side (off axis). This angled position alters the
tonality. The only way to understand what
it sounds like is to try it. If you’re working
alone, record a minute or so of various axis
setups and compare the results.
If you’re using two mics, consider mic’ing the
back of an amp. Open-backed cabinets offer
some nice tones when you mic them from
behind. But be sure to flip the phase on one
of the mic preamps, because the speaker will
be pushing and pulling, and you want the mics
to correctly capture that dual movement. That
said, perhaps having the mics out of phase will
create exactly the sound you’re after.
If you have extra mics and the urge to
explore sonic options, try placing a third
mic a few feet in front of the amp. This can
impart a nice sense of space to the recording.
It’s common to use a large diaphragm mic in
this situation, as they tend to capture a good
balance of lows, mids, and highs. But again,
any decent mic will get the job done.
Once you’ve got all the mics from your guitar
part recorded, it’s time to mix. This is where
the effort you’ve invested in a multi-mic setup
will pay off. With one mic, you can reach
for the EQ if the sound lacks something frequency-wise. But with multiple mics, you’ve
got many more options. By panning the different mic tracks to the same basic position
and raising and lowering each relative to the
others, you’ll hear a range of different and
unique frequency blends. Obviously, the song
will dictate what’s needed, but you may now
have everything you need in front of you—
meaning, you can possibly skip that EQ.
To create some extra space, try panning that
third room mic to the opposite side of the
main mics. This will open up the guitar sound
and provide extra depth. Room mics don’t
always work though, as they sometimes can
“cloud” the upfront sound of the guitar in a
mix. Do a quick pan and trust your ears to tell
you what’s working and what’s not.
So, if you haven’t explored this technique,
think about recording with two or more mics
in your next session. Just take the time to set
it up correctly, check your phase, and make
sure you’re not overloading the signal to
“tape.” This is certainly one of those cases
where more is truly more.
Rich Tozzoli is a Grammy-nominated engineer and mixer who has
worked with artists ranging from Al DiMeola to David
Bowie. A life-long guitarist, he’s also the author of Pro Tools
Surround Sound Mixing and composes for the likes of Fox
NFL, Discovery Channel, Nickelodeon and HBO.