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Optimizing Tone with Effects
A Look At Acoustic Amplication
By GuitarGearHeads
15 Nov 2004
Amplifying the acoustic guitar as been a
ongoing dilemma for both manufacturers and producers and players alike. In
live situations, you may sacrifice a bit of sound quality for tonal
consistency. However, in recording situations you may rely on microphones
that reproduce the guitar with outstanding fidelity, but are prone to
feedback and ambient noise. In this lesson, we review your options and help
you decide which is the best option for your needs.
Piezo – Piezo pickups are the most popular for acoustic-electric
guitars. These are also sometimes referred to as “under saddle transducers”
since these pickups are typically installed in the bridge, usually directly
below the bridge. These pickups use crystals that resonate in response to
string vibration. These kinds of pickups are typically ideal for stage
situations because of its resistance to feedback problems that manifest in
uncontrolled environments (such as a live gig). Although makers such as
Fishman, Dean Markley and L.R. Baggs have been innovative in developing
great sounding piezo pickups, it is still widely viewed that these pickups
do not give a clear representation of a guitars natural sound. Specifically,
piezo pickups often cited as sounding “quacky”, which references a
characteristic sound resulting from frequency compression. Therefore,
although great for the stage, it is more likely that a good sound engineer
will forego the piezo pickup for a microphone (or several) during a
recording session.
Magnetic – Magnetic pickups have been the mainstay for electric and
semi-hollow body guitars from the beginning. However, although some makers
experimented with magnetic pickups over the years (e.g., John Lennon’s
famous slope shoulder 1962 Gibson J-160E used in Beatles recordings from
1962-64) they never became widely available for acoustic guitars.
Nevertheless, there has been recent trend over the last decade during which
magnetic pickups are becoming a more recognized option for acoustic guitar
amplification. This can be largely attributed to the release of the ProMag®
sound hole pickup line from Dean Markley as well as other manufacturers
following Dean Markley’s lead. Magnetic pickups are advantageous in that
they do not suffer from the “quack” associated with piezo pickups and they
tend to offer superior reproduction of mid-range tones. Since these pickups
are also resistant to feedback problems they are also ideal for stage
situation. Magnetic pickups also typically offer one of the easiest options
for retrofitting a pickup to an acoustic guitar that does not already have
one installed since most are simply attached to the sound hole.
Unfortunately, like piezo pickups, magnetic pickups are not typically used
in recording situations because they tend to introduce a pesky 60 cycle hum.
This unwanted noise is typically inaudible in a stage mix, but can be much
more pronounced in a studio controlled studio environment. Because magnetic
pickups sense the vibration of metal strings, they do not work with nylon
strings.
Contact – Contact pickups have probably been the most revolutionary
development in acoustic amplification techniques. The most vocal proponents
of this pickup style are L.R. Baggs and B-Band. These pickups are typically
directly attached to multiple points on the underside of the guitar’s top,
allowing for a more complex, multi-tonal sound. Evolving from both piezo and
microphone technology, contact pickups are highly acclaimed for their
ability to reproduce and amplify the acoustic guitar sound while faithfully
maintaining its natural timbre. This, of course, offers tremendous
advantages in recording situations. Due to their direct contact with the
guitar top, contact pickups are often register more frequencies in the bass
range. Contact pickups are often not preferred in live gig situations
because of their potential for feedback. However, this disadvantage has been
mitigated by newer designs (e.g., Taylor’s Expression System) and by
feedback reduction units.
Condenser Microphones – The condenser microphone is widely considered
to be the holy grail of acoustic amplification in professional studios
around the world. Typically sited brands are those made by Shure and AKG
(with the Shure SM57 being the age old standby and preferential standard);
however, many quality brands have made inroads into this market. They are
without a doubt the best representation of the guitars natural complex
sound, even when compared to contact pickups. Although some types of
condenser microphones can be built directly into the guitar as an internal
pickup option, the most commonly used method is to externally record the
sound emanating from the guitar using one or more condenser microphones.
Debates rage among sound engineers and producers as to the best placement of
these microphones to collect both direct and reflected tones. The downside
to condenser microphones is their inherent likelihood to cause feedback in
an uncontrolled environment. Furthermore, they are also a hassle to set up
and place, suffer from sound quality variations in the guitarist’s
orientation to the microphone, and can magnify sound check difficulties
during live situations. Many well known artists do continue to use condenser
microphones in live shows, but they have the benefit of a capable and
competent sound crew. For the rest of us, the piezo and magnetic pickups are
probably still the easiest option.
As a final note, the most recent trends seems to be moving toward
combinations of two or more kinds of pickups, either separately or
manufactured into one pickup system. This approach tends to take advantage
of a pickup type’s best properties while minimizing the worst. Nevertheless,
the combinations may yield types that are still best for heavy gigging
situations and those that are best for recording and playing smaller venues.
Written by Gary Allen and Dan Halberg
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