I will stick my neck out and explain what I know about the J&M sets and why the phrase 'powered mic' is a bit of a misnomer, and offer a more exact reason they are made the way they are. This little 'epic novel' might also help those of you that like to tinker around and have fun experimenting.
I think that the Voice II, like many other products, has some significant changes over the years. I have no special access to tech data on all the variations, and have really not been in the BMW arena very much, but we've fitted several 07 LT's that have Voice II with mics that work great, but Matt's system is obviously in need of something else, and bless his motorcycle heart, he's been working hard with me to figure out what that is.
I've been asking on this forum for some time for LT owners with Voice II to stop in for some testing and free goodies, and if anyone is local to Dayton OH, i'll make it worth your while to stop in my shop and let's figure this one out. It's kinda pricey to buy a BMW for 'testing' when I already have a small stable of bikes to support
Ok, to the point:
I wanted to clear up one thing that gets a lot of press, but inaccurately. J&M makes a headset similar to a Harley Davidson headset that actually has a microphone pre-amplifier built into the headset or possibly into one of the cables itself, using very small surface mount technology. I've attached a picture of this little amplifier from a Harley Ultra headset, which is nothing more than a 20x voltage gain single-transistor amplifier. My headsets do not include this preamp, and I'm pretty sure that's what Matt's bike and others like it need.
The interesting thing is that while J&M calls their mic a 'dual mode' mic or a "powered mic", it's only that because of the pre-amp, and not because of the actual mic cartridge itself. Both the Harley Ultra and J&M use almost identical 200-Ohm dynamic microphones (voice coil, magnet, diaphragm kind) similar to the ones we use on most of the Japanese bikes and even on the J&M CB2003 and many other systems like Garmin GPS etc, a 600-Ohm dynamic mic.
J&M and Harley do NOT use smaller the electret-condenser mics. Yes, that is the correct spelling, it's not 'electric' mic because it refers to a permanent static charge on a piece of material inside the capsule. Anyway, condenser/electret-condenser mics are what you find in virtually all other consumer electronics and even many motorcycle systems.
The dynamic mics (all of them) produce about 5-10mV when you speak into them, and in the J&M/Ultra scheme, that signal is boosted by the external headset pre-amp (operating on 3-5Vdc from the bike's mic lines) up to around 100mV, or about 20x gain, making it more of a 'line level input' than a 'mic input'. Remember how you had to use a special input on your stereo for the turntable vs a tape deck? Same idea, the turntable cartridge preamp is INSIDE the stereo, not hanging off the side of the cartridge. If you plugged a tape deck into the 'phono' input it distorted because the signal was 100x what it needed to be, and the phone was faint if heard at all when plugged into a 'tape' input.
Condenser mics of the kind that Matt has been testing produce similar signal levels on their own, using the 3-5Vdc for their own internal FET pre-amp. On all but Matt's system, which if I recall is an '07 model also, we've had good results with a standard condenser mic and the Voice II. Correct me if I'm wrong, but I assume you can use various models of the Voice II on the '07? Its all about the Voice II, and not the bike itself, I think.
I"m not sure what the logic is in building a system that requires external amplification, but I'm sure smart engineers have their reasons, tho I can't think of one other than market protection or forced loyalty. From a cost, performance and elegance standpoint, that kind of design makes no sense to this engineer.
I have plans to make a headset for the Ultra owners that have been asking for it, and I'm going to test it with Matt's bike when he visits here in June if characterization of his bike and system warrant it. I'll keep you all posted. I'm almost certain I'll just make the preamp as an inline plugin so that you can use a single headset is more than one application, because if I've learned anything in the last 10 years is that flexibility is golden in this arena! That way, I can include a variable mic 'boost' and switchable wind noise filter. If anyone has ideas, now is the time get your thoughts possibly into the final device!
Contact me 937-271-4077 or via "ed at edsets dot com" if you can come by Dayton soon.