Recording - January 2017 - 61

flexibility, each additional mic doubles the number of intermic phase relationships. Even with phase-fighting solutions
such as polarity reversal, directionality, EQ, level changes,
and mic repositioning, it quickly becomes impossible to
overcome all of the inter-mic combs. For this reason, a simple drum miking setup, with one to four mics, often sounds
better than larger configurations.
Polarity reverse
Because phase differences and associated comb filtering are always present when using multiple microphones, most experienced engineers experiment with
polarity when multimiking to ensure frequency response
is as desirable as possible.
Commonly found on mic preamps, consoles, and
processors, a polarity switch offers a useful solution
when combatting phase issues. In analog equipment,
reversing polarity inverts signal voltage from positive to
negative, which in turn reverses current flow. In digital
systems, reversing polarity overturns the waveform so
positive values become negative and negative become
positive. Acoustically, the effect flip-flops the pressure
wave so peaks become troughs, etc.
Polarity reverse is most easily visualized through a loudspeaker driver. Feed a kick drum through the speaker,
and you will see the sound first move the driver in one
direction. Next, flip the polarity by reversing the positive
and negative wires attached to the speaker. The kick will
now push the driver in the reverse direction. While you'd
think this might create a major change in sound quality,
it's surprisingly inaudible. Our ears and brains are simply
not fast enough to process the difference. Polarity reversal
is nearly impossible to notice under normal circumstances.
However, polarity reversal can cause major sonic
change in multimiking scenarios. The classic example
of this is when miking a snare drum from both the top
and bottom. The top mic excels at capturing the drum's
fundamental and the bottom mic more easily catches
the sizzle. The challenge is that when hit, the drumhead
flexes downward, away from the top mic. Oppositely,
the head moves toward the bottom mic when the drum
is played. Thus the two mics capture opposite pressure
waves and the resultant electrical signal is nearly 180˚
out-of-phase at the fundamental. When mixed together
at near equal level, the tone of the drum usually thins
considerably. Therefore polarity reverse is typically
required on one of the two mics to ensure the fundamental does not phase-cancel. The mics are still slightly
offset in distance and therefore a comb filter will still
exist, but the sonic impact is far less dramatic than
what occurs before polarity reversal.
Reversing polarity changes the phase of all frequencies by
180˚. This can be very beneficial when two microphones on
the same source are offset in time or distance and the perfrequency phase difference creates a comb filter. Inverting
the polarity of one mic changes the phase difference of all
frequencies by 180˚. While this does not remove the comb,
it changes the filter's summation and cancellation frequencies. Depending on the frequency content of the source and
the amount of time offset, the change might improve subjective sound quality. Therefore most pros experiment with
polarity whenever they use more than one mic on a source.
Are you double-miking a piano? Try listening in
mono and flipping the polarity of one mic. Are you
deploying multiple mics on a drum kit? Experiment with
a variety of polarity reverse combinations until the various drums are all as punchy as possible. Two mics on
an acoustic guitar or electric guitar amp? Definitely
play with the polarity switch.

1

2

3

Polarity vs. Phase
On many devices, polarity reverse controls are labeled "phase."
This has led to the common audio engineering expression "flip the
phase." Some in the audio industry argue that this is not a correct
use of the word "phase," as changes in phase other than 180˚
require a change in time. While polarity reverse changes the phase
of all frequencies by 180˚, changing the time offset between two
mics changes the phase of all frequencies by a different amount.
Phase shift and polarity reverse mean very different things, and
Figure 3 demonstrates the difference nicely.
As an audio educator, I strongly protested calling a polarity reverse
a "phase switch", but have softened my stance in recent years.
Reversing polarity does indeed change phase, albeit by a fixed
amount (180˚) for all frequencies... and besides, if Rupert Neve
labeled the polarity switches on his classic preamps "PHASE", who
am I to question that? That said, I do ask that my students call it
"polarity reverse," not "phase reverse."
Semantics aside, polarity reversal is a fantastic tool for solving
phase-related issues. It's not the perfect solution for all phase problems, but it is certainly one all engineers should experiment with
whenever using multiple microphones. This is especially important
when miking drums, as multiple microphones are typically in close
proximity and create numerous inter-mic comb filters. Whenever multimiking a kit, listen with all mics on and experiment with all possible
combinations of polarity reversal. You may find that reversing the
polarity of one mic improves the tonality of another drum.
Next time, we will continue to explore phase and its importance in
the recording studio. Stay tuned!
Eric Ferguson (ferguson@recordingmag.com) spent a dozen years
as a freelance audio engineer in Los Angeles, and is now on the faculty of the New England School of Communications (NESCOM) in
Bangor, ME.
RECORDING JANUARY 2017

61



Table of Contents for the Digital Edition of Recording - January 2017

Contents
Recording - January 2017 - Intro
Recording - January 2017 - Cover1
Recording - January 2017 - Cover2
Recording - January 2017 - 1
Recording - January 2017 - 2
Recording - January 2017 - 3
Recording - January 2017 - 4
Recording - January 2017 - 5
Recording - January 2017 - Contents
Recording - January 2017 - 7
Recording - January 2017 - 8
Recording - January 2017 - 9
Recording - January 2017 - 10
Recording - January 2017 - 11
Recording - January 2017 - 12
Recording - January 2017 - 13
Recording - January 2017 - 14
Recording - January 2017 - 15
Recording - January 2017 - 16
Recording - January 2017 - 17
Recording - January 2017 - 18
Recording - January 2017 - 19
Recording - January 2017 - 20
Recording - January 2017 - 21
Recording - January 2017 - 22
Recording - January 2017 - 23
Recording - January 2017 - 24
Recording - January 2017 - 25
Recording - January 2017 - 26
Recording - January 2017 - 27
Recording - January 2017 - 28
Recording - January 2017 - 29
Recording - January 2017 - 30
Recording - January 2017 - 31
Recording - January 2017 - 32
Recording - January 2017 - 33
Recording - January 2017 - 34
Recording - January 2017 - 35
Recording - January 2017 - 36
Recording - January 2017 - 37
Recording - January 2017 - 38
Recording - January 2017 - 39
Recording - January 2017 - 40
Recording - January 2017 - 41
Recording - January 2017 - 42
Recording - January 2017 - 43
Recording - January 2017 - 44
Recording - January 2017 - 45
Recording - January 2017 - 46
Recording - January 2017 - 47
Recording - January 2017 - 48
Recording - January 2017 - 49
Recording - January 2017 - 50
Recording - January 2017 - 51
Recording - January 2017 - 52
Recording - January 2017 - 53
Recording - January 2017 - 54
Recording - January 2017 - 55
Recording - January 2017 - 56
Recording - January 2017 - 57
Recording - January 2017 - 58
Recording - January 2017 - 59
Recording - January 2017 - 60
Recording - January 2017 - 61
Recording - January 2017 - 62
Recording - January 2017 - 63
Recording - January 2017 - 64
Recording - January 2017 - 65
Recording - January 2017 - 66
Recording - January 2017 - 67
Recording - January 2017 - 68
Recording - January 2017 - 69
Recording - January 2017 - 70
Recording - January 2017 - 71
Recording - January 2017 - 72
Recording - January 2017 - Cover3
Recording - January 2017 - Cover4
https://www.nxtbook.com/musicmaker/musicmaker/recording_202108
https://www.nxtbook.com/musicmaker/musicmaker/recording_202107
https://www.nxtbook.com/musicmaker/musicmaker/recording_202106
https://www.nxtbook.com/musicmaker/musicmaker/recording_202105
https://www.nxtbook.com/musicmaker/musicmaker/recording_202104
https://www.nxtbook.com/musicmaker/musicmaker/recording_202103
https://www.nxtbook.com/musicmaker/musicmaker/recording_202102
https://www.nxtbook.com/musicmaker/musicmaker/recording_202101
https://www.nxtbook.com/musicmaker/musicmaker/recording_202012
https://www.nxtbook.com/musicmaker/musicmaker/recording_202011
https://www.nxtbook.com/musicmaker/musicmaker/recording_202010
https://www.nxtbook.com/musicmaker/musicmaker/recording_202009
https://www.nxtbook.com/musicmaker/musicmaker/recording_202008
https://www.nxtbook.com/musicmaker/musicmaker/recording_202007
https://www.nxtbook.com/musicmaker/musicmaker/recording_202006
https://www.nxtbook.com/musicmaker/musicmaker/recording_20205
https://www.nxtbook.com/musicmaker/musicmaker/recording_202004
https://www.nxtbook.com/musicmaker/musicmaker/recording_202003
https://www.nxtbook.com/musicmaker/musicmaker/recording_202002
https://www.nxtbook.com/musicmaker/musicmaker/recording_202001
https://www.nxtbook.com/musicmaker/musicmaker/recording_201912
https://www.nxtbook.com/musicmaker/musicmaker/recording_201911
https://www.nxtbook.com/musicmaker/musicmaker/recording_201910
https://www.nxtbook.com/musicmaker/musicmaker/recording_201909
https://www.nxtbook.com/musicmaker/musicmaker/recording_201908
https://www.nxtbook.com/musicmaker/musicmaker/recording_201907
https://www.nxtbook.com/musicmaker/musicmaker/recording_201906
https://www.nxtbook.com/musicmaker/musicmaker/recording_201905
https://www.nxtbook.com/musicmaker/musicmaker/recording_201904
https://www.nxtbook.com/musicmaker/musicmaker/recording_201903
https://www.nxtbook.com/musicmaker/musicmaker/recording_201902
https://www.nxtbook.com/musicmaker/musicmaker/recording_201901
https://www.nxtbook.com/musicmaker/musicmaker/recording_201812
https://www.nxtbook.com/musicmaker/musicmaker/recording_201811
https://www.nxtbook.com/musicmaker/musicmaker/recording_201810
https://www.nxtbook.com/musicmaker/musicmaker/recording_201809
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201808
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201807
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201806
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201805
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201804
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201803
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201802
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201801
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201712
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201711
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201710
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201709
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201708
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201707
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201706
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201705
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201704
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201703
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201702
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201701
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201612
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201611
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201610
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201609
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201608
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201607
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201606
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201605
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201604
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201603
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201602
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201601
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201512
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201511
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201510
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201509
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201508
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201507
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201506
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201505
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201504
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201503
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201502
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201501
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201412
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201411
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201410
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201409
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201408
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201407
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201406
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201405
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201404
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201403
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201402
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201401
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201312
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201311
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201310
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201309
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201308
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201307
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201306
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201305
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201304
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201303
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201302
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201301
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201212
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201211
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201210
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201209
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201208
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201207
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201206
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201205
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201204
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201203
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201202
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201201
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201112
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201111
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201110
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201109
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201108
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201107
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201106
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201105
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201104
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201103
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201102
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201101
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201012
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201011
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201010
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201009
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201008
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201007
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201006
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201005
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201004
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201003
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201002
https://www.nxtbook.com/nxtbooks/musicmaker/recording_201001
https://www.nxtbook.com/nxtbooks/musicmaker/recording_200912
https://www.nxtbook.com/nxtbooks/musicmaker/recording_200911
https://www.nxtbook.com/nxtbooks/musicmaker/recording_200910
https://www.nxtbook.com/nxtbooks/musicmaker/nxtd
https://www.nxtbookmedia.com