The increase in popularity of acoustic music in the last decade surely must be attributed to the advances in amplification technology. Acoustics instruments with pickups are seen with increasing regularity in high profile venue such as MTV Unplugged. It is fashionable to be Unplugged nearly all performers in the popular music field are plugging in their acoustic instruments.
The change in acoustic amplification started slowly in 1960's with the Gibson C-1E bridge-piezoequipped Classical Guitar as played by Charlie Byrd. In 1971 Ovation introduced the Ovation acoustic-electric which received huge exposure through Glen Campbell's playing on his weekly TV show. This began a virtual explosion of pickup designs by such as L.R.Baggs, Emg, Barcus-Berry, Fishman, and Highlander.
In the last decade, the acceptance and options for amplifying acoustic instruments have expanded dramatically. The options for transmitting the instrument sound to the amplification source now include:
Under-saddle pickups read string vibration transmitted through
the instruments bridge. Piezo-pickup design requires two
elements. Firstly the sensing device which records what
is happening in the bridge area and secondly a buffer pre-amp
which thanks to advances in technology are now small enough
to mount onboard a guitar and remain almost invisible. Highlander,
L.R. Baggs and Fishman are leaders in this technology. Another
advantage of this technology is the availability of MIDI
This pickup design responds to movement of the top. And although this design does not allow for high sound pressure levels as does the under saddle pickup it does offer rewards in the area of tone. Trance Audio produce excellent high-end pickups in this field.
A new generation has emerged which feature a wider frequency response as compared to the traditional electric guitar pickup. The industry standard for frequency response has been the Sunrise. Rare Earth from Fishman and the ACS from EMG also feature in this area.
Virtually all the big names in the pickup business, including Baggs, EMF, Fishman, and Highlander, offer such systems. One of the latest advances in acoustic instrument amplification uses a piezo under-saddle pickup and a mic, and blends the signals with either an on-board preamp or a stereo cable to an external mixing source. The result is a more open sound that includes more "air." This system is more susceptible to feedback because of the presence of the inbuilt microphone. Having said that, the problem is not as great for solo playing which does not generate high on stage noise.
With the introduction of a number of reasonably price condenser microphones this is a very viable option for the traditional concert gig.
High sound pressure levels can not be achieved but feedback is not a problem for solo or small ensemble performances and it does offer the best alternative for sit down audiences.
Once the initial sound source has been captured it remains to project this sound at an optimum volume to the audience. The alternatives for acoustic musicians are as follows:
Acoustic amp design, led by the Trace Elliot company, targeted the specific problems of amplifying the acoustic guitar. This early groundwork was picked up and taken to even greater heights by the German company AER Audio Elecrical Reseach. They introduced advances to the typical electric guitar amp design to produce a product that could accommodate the intricacies of the natural acoustic sound. They included:
Much wider frequency response. Dual channels, one is usually designed with a high input impedance for a direct piezo input, while the other may be used for a microphone or magnetic pickup.
Redesigned EQ Section tailored for acoustic guitar tone, usually including a notch filter and phase switches to help reduce feedback.
Inbuilt effects and effect loops Reverb or delay can be used to fatten your sound. One of their most significant features is that these amps can also serve as mini PA systems, handling a vocal mic in addition to the guitar.
With the advent of low-cost components by manufacturers such as Behringer it is an option consider a portable stage system to cover your amplification needs. A setup consisting of a small mixer hooked into a pair of powered speakers allows considerable flexibility for the performer.
Wider dispersion of sound. The Acoustic Amp disperses sound from one point in the room and often does not provide adequate coverage to all points in the room.
More Input alternatives. Additional instruments may be plugged in for ensemble performances. Stage microphones can be utilized for both on stage patter and condenser microphone for additional acoustic amplification.
Wider frequency response. A dedicated mixing board will give added fexability compared to the input section of an acoustic stage amp. Features such as effect loops that enable the patching of high-quality audio processors and a more comprehensive EQ section offer greater freedom of choice to the performer.
In summary under-saddle technology is hard to beat as far as complete frequency response and immunity from feedback go, although there is still that "wood and air" sound missing. Digital signal-processing advances will in the near future solve this problem.
Under bridge design appears to have become the most accepted method of producing acoustic guitar at reasonable levels of sound with remaining sticking point that of tone. This I believe will be solved in the near future by virtual acoustic solutions like the directions taken by the Line 6 Pod and COSM technology used by Roland.
Instruments by Takamine, Ovation, Yamaha, and Godin using this design offer the musician of today many reasonable price alternatives to explore.