PB+J said:
Wow, this is really contrary to my experience. Granted, I haven't performed with a lot of different systems, but I've been working with developing and fitting pickups and preamps with my local luthier and doing a lot of experimenting on my own, and there is a huge difference from one piezo pickup to another. Even two from the same company- the old Fishman BP100 and the Full Circle- are like night and day.
Most piezos are very low fidelity, with a very uneven, peaky response. The characteristic "piezo sound" is often, in large part, resonance in a poorly designed pickup, or a very bad impedance mismatch. Even most very well-regarded piezo pickups don't measure all that well. All piezos use, at their heart, an artificial piezoelectric crystal like Barium Titanate, but they use a tremdously wide range of crystal sizes and mountings.
The cheapest use an applied film on a brass plate, like the "benders" found in piezo buzzers. Better ones use machined pieces. The Realist appears to use two tiny cylindrical pieces, about 4mm in diameter. My pickups use larger pieces of around 14x10mm. Some encase the crystal in wood, some use plastic, etc. The BP-100 is deligned to repsonse to transverse waves. The Realist, K&K Bass Max, and the Full Circle work in compression. All have different response curves, different damping, different impedances.
A microphone is still the only transducer that will deliver exactly what the ear is hearing; everything else is really a compromise, because you can't use a microphone in every setting for one reason or another.
