I wanted to start a new thread here, since I wasn't sure how long I'd go on with this.... I had more thoughts about the amplification issues that were again raised, and especially Ted's post about the Deagan instrument with mics inside each resonator. I had an idea about doing that when I was younger, and I never knew there was a production instrument made with such as system.
OK, first, let's totally separate the task of recording the vibes from the job of amplifying them. These are 2 different things, even though they both may use microphones. To get a pretty respectable sound in the studio is pretty easy - just put up 2 Neumann U87 or U47 mics (or the best large diaphragm condensers you can afford) spaced evenly a few feet above the instrument. Along with proper isolation, that's it. I saw Elliot Scheiner do a demonstration at Avatar Studios the other day, and he had some Royer ribbon mics for the drum overheads. I bet that would work on vibes. But otherwise, you can't go wrong with this overhead setup, unless there are other problems in the room.
Once you get onstage, however, there is a big drawback to overhead miking: it is much harder to isolate the sound, and lots of other stuff leaks in. This causes the output to be muddled or messy. What you need is much more control over "your" sound. The only time this may not be a problem is in 2 situations: (1) playing solo, where there is no issue of isolation, and (2) working with a good front-of-house sound engineer, who really knows how to make things sound good on stage with overhead mics. But most of us are in situations where the musicians are close together, and standard overhead mics don't work that well. The goal is to not have to play hard to be heard, and to maintain a full dynamic range despite the volume level of the band.
So, one thing you can do is to use pickups, which are very good at giving you this control, but come with their own set of issues. For one, they are often a drag to set-up - who needs to attach 37 or more mini-connectors after assembling a whole vibraphone, only to find that 3 have come loose and need to be glued back on right before the gig (I know some come permanently attached..)? But before all that, there is a whole difference in sound quality. Since you are banging directly on the bar attached to the pickup, the tone is much plunkier (for lack of a better word). It is full of attack characteristics that are not very natural, and that lack a certain "air." But it makes perfect sense. Look at an acoustic guitar using a similar piezo pickup - the pickup is on the BODY, not on the STRING! In that way, it can be more natural and effective. But since our bars are not physically attached to the rest of the instrument (and in particular, the resonators), there is nowhere else to attach a contact pickup that will do any good. In a general sense, "sound" is defined as waves moving through air. The natural sound of the vibes starts with a vibrating metal bar, and travels all around through air, being deepened and enhanced by the action of the resonators. When you use pickups, you are removing all of this, and the bar sound gets directly injected into the audio signal. None of the sound in the air gets amplified.
So now what? Well, look at acoustic piano for a minute. The best way that gets handled in a noisy stage environment is to mic it with the lid partly closed, and some moving blankets over the top for isolation. That seems like the best answer - good miking, more isolation. So for myself, I came up with the system of using mics from below in live applications, because that is where the sound is most concentrated, and the resonators act like baffles against outside noise. If you eliminate the pedal vibrations with elastic, you can clip these right to the frame and the setup is a breeze. But it still isn't perfect - the mics do pickup other stage sound, and the tone is not 100% ideal. But there is enough indirect sound from the instrument in the room that this added amplification usually gives me the control I need, and it all feels natural - so I can play at a dynamic level that I prefer. And another plus is that there are no mic stands in your way. If you would like an example, here is a Youtube video using this miking (there was a sound man here, but he just used my mic output and the results were great): http://www.youtube.com/watch?v=o6lK8SpnfnI
But.... when you take this idea further, it really seems that INSIDE the resonators would be a great place to put the mics! The sound is super-concentrated, and the isolation from outside leakage is optimal. In a larger venue, combining this with some overheads could also be very effective - using just enough from the overheads to perhaps dial-in more attack, with the resonator mics providing clear detail and a high level of discreet control. In addition, such a system can be permanently mounted, so there is no issue of setup. Just plug it in (we'd all love that..). I recently bought a Hammond 44 melodica, which has a similar type of built-in internal microphone (same as played by Spike in that video post with Behn) - the amplified sound is superior to anything else available.
So, I am not the guy who is going to build this, but I did order some inexpensive mic elements to experiment with. You can find some that have a pretty reasonable freq response for a few dollars each, so cost-wise, this is not impossible at all (here is such a supplier: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P9925-…). But, there are some definite challenges. Mostly, it will be about balancing out the sound over the range of the instrument. Putting a capsule about 10 inched down into a lower resonator should work well, but as you go up to the higher notes the tubes are so short that the mic will end up very close to the bar. The sound pressure will almost certainly distort the sound right at the capsule (not to mention that these notes cut through and need less amplification to begin with). So the system would need collector rails with adjustment pots (like K&K pickups), or some kind of special wiring with resistors to compensate. The upper notes may not really need a mic in every tube - I'm thinking a single mic underneath would be most natural & effective for the upper octave. The real challenge is designing good electronics, so that many mic elements can be wired together and there is no hum or buzz, and so the whole thing will run off standard phantom power. I definitely know some guys who could build it. Maybe if some of us experiment and come up with something that sounds good it might be worth pursuing? I think it really could be the way to go, if done right...