One day back in 1985 , we were working in the studio, when Dallas came in with something brand new. It was a fire engine red Guild Acoustic 6 string with a Baggs saddle/pickup installed in the bridge. We thought it sounded just great!! Actually, it was more of a convenience than a good representation of tonal quality!! Those were the early days in a new era of great acoustic electronics. We still have that guitar in it's primitive form.
Now there are so many great systems available to choose from. I'm using the Highlander IP-2 on my own CHEROKEEAcoustic. It's a dual source (stereo) system with the piezo cable pickup in the bridge and a Joe Mills mic at the soundhole. This is a personal favorite, mainly because I helped in the design of the original Highlander IP-1!!!
I've installed hundreds of pickups in acoustic
guitars, but each installation requires a short consultation
with the owner to find out just what that particular player is
wanting his guitar to sound like. This helps determine the brand
and style of system to use. Now for some info!!
Magnetic Pickups
Piezo Pickups [Transducers]
Top-Sensitive Vibration Pickups
String-Sensitive Vibration Pickups
Electronics for Piezo Pickups
Amplifiers for Acoustic Instruments
Microphones Installed for Live Performance
The single most requested customizing job we are asked about here at Neely Guitars is, "how should I pickup or amplify my acoustic guitar?" We'd like to explain all of the trade-offs involved, and suggest several of our favorite options which fall into three distinct price ranges.
First, you need to determine what the end purpose is of picking up the sound of your guitar. If this is primarily for recording, then a good (probably more than $250.00) condenser microphone is your best bet. The true sound of an acoustic instrument is a composite of sound emanating from all over the soundboard added to by the sound from the air resonance of the chamber with the reflected sound from the underside of the guitar top. This is a complex blend of sonorities which comes together somewhat away from the instrument in the air; hence the best sound is captured by a microphone.
If your primary need is for live performance acoustic amplification, there are three types of systems you might consider: a magnetic pickup mounted in the sound hole, a piezo (pee-ay-zoh) pickup mounted either under the top or in the bridge and one or two mics mounted in or on the guitar. There are tradeoffs with any of these types of pickups as well as practical limits to how loud you can get before feedback.
Beware of manufacturers' claims that their pickups will not feed back; once you attach the pickup to the guitar, it most certainly will. If you need to play really loud, and require an acoustic-like sound, you might consider an instrument like the GIBSON CHET ATKINS CE (nylon string) or CHET ATKINS SST (steel string). These are solid-body instruments which simulate acoustic ones, and they are quite good. For adding a pickup to your acoustic, read on......
Magnetic pickups for acoustic guitars work just like the pickups in electric guitars: the vibrating strings disturb a magnetic field which generates a current in a coil of very fine wire. These pickups are generally high impedance devices, and thus have a limited frequency response made worse by running long lengths of cable from the guitar to an amp or board.
Typically, response starts dropping off at around 5,000 Hertz (cycles per second) measured right at the guitar output; 20 feet of cheap cable can drop that figure to 2,500 Hz. The result is that the upper harmonics are lost.
The better acoustic guitar magnetic pickups can sound amazingly good under the right circumstances: short runs of high quality low capacitance cable and a system which has good frequency response. Feedback suppression is reasonably good as the pickups are not picking up vibrations directly from the top, and the partial blocking of the sound hole cuts down acoustic coupling between the guitar's air resonance and the amplified sound field.
A magnetic pickup's output will sound much like the guitar it is mounted on, rather than a Strat or Les Paul, because the sound of the guitar is reflected in how the strings vibrate. Conversely, the same pickup mounted on a solid body will sound like a solid body guitar pickup.
Magnetic pickups are relatively inexpensive, convenient and moveable between instruments. You can do the installation yourself, though if you want a permanent installation including an output jack/end pin, you should have us do the work.
Piezo pickups are based on types of crystals (quartz, barium lead, barium titanate, and others) which put out a voltage when they are stressed in various ways. Electrodes are attached to specific surfaces of the crystal so when the crystal, packaged as a pickup, is subjected to vibration the output is sent on down the line.
Frequency response of piezos is typically from near DC (below audibility) to 100,000 Hz or beyond; the commonly accepted limits of human hearing are 20 Hz to 20,000 Hz, so there is no problem with frequency response. There are a number of different ways to mechanically connect the crystal to the vibration source; this is the art of piezo pickup design.
The main problem with piezos is that they are extremely high impedance devices. As such, the frequency response you can practically use is greatly affected by where the piezo output is sent. It takes a very high input impedance to match the high output impedance, in order to prevent severe low end roll off. Otherwise the result is that typical, honking 'cardboard' sound of guitars with piezos with no matching preamplifier.
We consider it absolutely necessary to match the output of a piezo pickup through a high impedance buffer preamp before sending the signal on to an amplifier or PA. Such a preamp should have an input impedance of at least 2 MegOhms (2,000,000 Ohms). More is better.
Cable length to the preamp should be minimal, in order to avoid high frequency roll off; therefore, if practical the buffer preamp should be mounted inside the guitar. Unfortunately many manufacturers claim that no preamp is necessary with their product, in order to not scare off potential customers - and in fact, preamplification is not needed to amplify a weak signal.
The preamp is necessary to buffer (match) the electrical characteristics of the pickup with the outside world, so that it can sound as good as possible. The difference between a buffered pickup signal and an un-buffered one, using no gain or EQ, is like that between night and day.
There are two major approaches to piezo pickup design for acoustic guitars. The first method is to pickup the vibrations of the top; such a pickup can be referred to as "top sensitive".
The second method is to pickup string vibrations from the bridge saddle, before the vibrations even get to the soundboard. Therefore such a system is said to be "string sensitive", as it is more sympathetic to the vibrations of the strings than the top.
TOP-SENSITIVE VIBRATION PICKUPS
Typical of the "top sensitive" pickups are BARCUS BERRY and FRAP. They are small pickups encapsulated in epoxy blocks, with a lead wire coming out one end. Unfortunately, it is very difficult to find the perfect spot for these pickups. The best of such systems we've heard is a double (stereo) FRAP installation on one of David Crosby's Martin D-45's.
The pickups are mounted under the saddle area of the bridge; it sounds great. The kicker is that an identical installation on another of his D-45's sounds terrible and feeds back at a much lower volume level! These pickups tend to exaggerate any response variations of the guitar on which they are mounted. Our feeling is that such top-sensitive pickups were modern in 1972, and deserve to be retired today.
We have found that the best type of pickup to use is the "string sensitive" style typified by MARTIN'S THINLINE and our favorite, the L.R. BAGGS bridge saddle/pickup.
The MARTIN THINLINE II pickup (made by Fishman) is a slim unit which mounts under the saddle in a Martin style bridge. It works just fine if the saddle does not fit too snugly into its slot. The pickup depends on even pressure applied between the bottom of the saddle and the six micro-crystals embedded in the unit.
If the saddle slot bottom is not perfectly flat, or if the
saddle rides up and binds in its slot, the saddle loses contact
with one or more crystals and you lose one or more strings' output.
We have a modification to the bottom of the saddle in a THINLINE
equipped guitar, as well as a method of lubricating the saddle
to keep it from binding. Both of will help you get the most out
of your guitar, and cost only $25.
We've put them in Martins, Gibsons, Guilds, Dobros, Rodrigues
- you name it. We're even putting one into a Deering six string
banjo bridge! Installation must be done by a qualified repairman,
as the fit needs to be good to get top performance and longevity
from the pickup.
[We have special fixtures and router bits for doing a top
quality job. We have seen and re-done installations made by other
repairmen in the area. We also know that we do the best job of
them all.]
As we previously stated, you should not expect top performance from any piezo pickup without a buffer preamp. Many factory installations of pickups include the preamp with some sort of EQ built right into the guitar. Too many of these are long on the bells and whistles, but short on true quality.
One can still get acceptable performance with an external preamp if you keep cable length to a minimum. Look for a unit which has high input impedance--5 MegOhms to 10 MegOhms is a good range. Go for low noise, listen for the right sound and don't get carried away with more features than you need.
We prefer simple tone controls or parametric equalizers over graphic EQ. This protects the integrity of the sound. We have had very good luck with the TC Electronics units. Remember, in most situations what you are plugging into will have tone controls, and cascading electronic functions only adds to system noise.
Working with Wolstein Labs and with some of our most demanding clients, we have developed our own buffer preamps which are the finest available. Bob Wolstein served his apprenticeship with George Massenberg and is a consultant for Gibson Guitars. He's also one of the best audio designers and engineers in the business. His design philosophy is to make equipment which has the most uncompromised signal path possible, and thus needs the least correction down the line.
Our buffer preamp can be easily mounted in your guitar or in an external box. For internal installations, we mount the preamp circuit card and the battery clips on a block of 1/2" mahogany which is attached to the guitar back with two layers of double stick foam tape. This shock mounts the electronics and allows mounting with no screws or glue.
WESTWOOD/WOLSTEIN LABS BUFFER FEATURES:
Internal or external mount
Two nine volt batteries for extra headroom
All discreet audio stage
10 MegOhm input impedance
Ultra-low noise
Flat response from 5 Hz to 100 KHz
Trim pot to adjust output level (great for matching to wireless
transmitters)
AMPLIFIERS FOR ACOUSTIC INSTRUMENTS
Do not expect to get a great acoustic guitar sound through an electric guitar amp. They are designed for adding their own sound to the sound of an electric guitar, not for accurately reproducing the sound of an acoustic one. If you plan to have your own monitor amp on stage, use something like a small PA or a rugged studio monitor speaker with a good power amp.
We've had very good results amplifying keyboards, acoustic guitars, and even a concert harp using the BARBETTA self powered speakers. These units have two-way active crossovers with separate power amps for the bass driver and tweeter. They are rugged, very portable, convenient and also sound good.
MICROPHONES INSTALLED FOR LIVE PERFORMANCE
For a number of years we have been installing miniature electret condenser microphones such as the SONY ECM-30 inside guitars to capture the air chamber resonance which magnetic pickups and piezo pickups miss. This mic was particularly well-suited to internal mounting due to its size and wiring configuration, but it is no longer being manufactured.
We have found a source for very similar bare mic elements, so we are making our own mics for much lower cost than the Sonys were. The mic capsule is mounted in a block of soft foam for vibration isolation, and is attached to the top-right underside, just below the sound hole.
© Neely Guitars 1998. All Rights Reserved.