Multi-Source Pickup Systems
Because each type of pickup or mic has its own strengths and weaknesses, many guitarists use systems that combine two or more different kinds of sources, hoping that the strengths of one will offset the weaknesses of the other. For example, you might combine a magnetic pickup that has a strong bass and good feedback resistance, but a somewhat electricsound at higher frequencies, with a microphone that does a better job of handling high frequencies and detects sound from more than just the strings, but tends to feed back more easily. Multiple pickups can also help create a more complex sound that comes closer to capturing the way we hearthe guitar by mimicking the way different parts of the guitar produce different tones.
There are many ready-made commercial multisource systems that offer multiple pickups. The combination of an undersaddle transducer and microphone is one of the most common, but almost any combination is possible. One benefit of commercial multisource systems is that the components have been chosen to work together, and the systems may offer onboard electronics that optimize the sound. For example, the L.R. Baggs Anthem combines a UST with an internal microphone and electronics that include a crossover circuit that allows the UST to handle the low frequencies while the mic handles the high frequencies, using each sound source to its best advantage. Not surprisingly, multisource systems tend to be on the more expensive end of the pickup spectrum, with prices starting at about $200.
Excerpted from All About Pickups