Audio Monitoring Basics: Part One
Burning the Midnight Monitor Oil
© 2000 by Eddie Ciletti
Speaker components have improved considerably over the past twenty years.
Distortion is lower, power handling is higher and bandwidth is wider. Despite
the improvements, however, monitoring systems are still the weak link when
compared to any electronic hardware, digital or analog. The obstacle is
not the lack of progress but that the largest collection of variables ever
thrown at transducer technology is called "a room with stuff in it." This
obstruction can make it difficult to assess the health of your monitoring
In the February 2000 issue of MIX, Bob McCarthy wrestled that thorny
beast known as "room tuning." This article focuses on monitor health and
channel balance issues, including troubleshooting tips — from the console
to the drivers — for both live and studio applications.
There’s plenty of talk about the sound of "outboard gear." From converters
to mic preamps, equalizers to compressors, these are devices that can be
abused without fear of destruction — appreciated for what can be rather
subtle nuances. There is nothing subtle about monitoring systems. A cabinet
at the near-field position will sound much different on a bookshelf, on
the floor or next to an identical system. All this before we drive ‘em
hard, blast ‘em with feedback or accidentally remove the reference clock
from a piece of digital gear. Ouch!
Have you ever wondered how much abuse a monitor system can take before
its performance is degraded? Precise evaluation requires test equipment
as well as a test environment (an anechoic chamber), not to mention a level
of technical expertise that goes well beyond the scope of this article
and the green in your wallet.
To proceed with a basic investigation requires minimal electronic tool
kit plus a bit of comparative analysis. Next
to the "Tools" Sidebar, Table-1 lists
the necessary electronic accessories including alternatives for those of
you with more cash. More extensive troubleshooting techniques will be detailed
in Part Two: Audio Basics and Troubleshooting Procedures.
For example, with an oscillator and a voltmeter it will be possible to
confirm signal integrity from source to destination. Additional tools include
a pink noise generator, a sound pressure level meter and your earplugs
Whether built-in or freestanding, large speaker systems have to ability
to move more than air. Using a continuously variable oscillator, start
at 1kHz and sweep downward into the bass region. You might be horrified
to hear how easily walls, floors, racks and light fixtures can be coaxed
into a cacophony of sympathetic vibrations. It is not necessary or recommended
to go beyond a "comfortable" listening level for this test.
Other "room interaction" issues will reveal themselves when panning
any sound source from left to right (or right to left, in some parts of
the world). Try this test with kick, snare, vocal, crunchy electric guitar
or pink noise. If differences were noticed, especially at low frequencies,
would you suspect the monitors or the room? You can swap power amp channels
easily enough — crossovers and drivers require a little more effort. Be
sure to exercise every connection between the console and each speaker
component. If nothing changes, it’s back to "thornsville," a.k.a., the
room and/or cabinet placement.
Near-field monitors minimize room interaction, improving mid- to high-frequency
accuracy (imaging), yet many fall short of providing adequate low-frequency
information. Subwoofers may seem to be a gimmick that are admittedly tricky
to set-up, yet the two octaves below 80 Hz are important enough to encourage
everyone to experiment. Satellites with less than an 8-inch woofer may
need help in the octave above 80-Hz.
Absolute (coarse) polarity is critical — an out-of-phase subwoofer will
create a "hole" at the crossover region rather than a smooth transition.
Most times you simply want the subwoofer to pick up where the satellite
rolls off. For greater flexibility, get a subwoofer that includes a crossover
for itself as well as the "satellite" speakers. There will always be phase
shift in the crossover region — it’s the inherent nature of the filters
— so look for the ability to fine-tune the phase (in addition to polarity).
Hearing and feeling the bottom helps the listener/engineer create better
mixes. Cleaning up sub-sonic slop makes room for the "real" bass instruments.
Reducing the guesswork and using less EQ will improve mix compatibility
— no more bottom-heavy mixes. All of the aforementioned items serve a dual-purpose
by reducing the stress on Chihuahua-sized woofers.