All the below very much AFAIK - I'm no wireless expert, so I stand to be corrected on what may be outdated info gleaned when I was working in stores. I've downloaded some info from
http://www.shure.com/ProAudio/Resources/us_resources_wireless, but don't know when I'll get to reading it. I'm especially vague on wireless monitoring as it came in a while after I last gigged.
Riaan C wrote:
wireless head microphone (is that the right term? One that hangs in front of your mouth a la Madonna).
They just call them wireless headsets, AFAIK.
Are there compatibility issues (eg. frequency clashes, etc)?
Yes. Any wireless transmitter tends to throw off a number of "side bands" where the same signal shows up in a number of frequencies, which can interfere with other wireless devices. Pro wireless audio systems have to be carefully selected to work together - you will notice that wireless mics, etc. are often colour coded (red, blue, etc.), and these colour systems guarantee that you can use any wireless items in the same colour code with different frequencies without interference. The good news is that it looks like many of the modern systems can be set to work in a number of different frequencies on a number of different wireless systems.
If both are Shure, eg, can they share the same transmitter module, etc?
They can, but not at the same time - that causes interference. You need a separate transmitter and receiver for each source, mic or guitar. Some receivers are dual channel, which means they are two complete receivers in one housing, so that they can accept two different incoming signals.
And what do you do when the 7-11 runs out of batteries just before the biggest gig of your life? ?
Smack yourself upside the head for not using rechargeable batteries in the first place. Seriously - they pay for themselves very quickly when you use wireless. Normal NiCad rechargeables don't last as long as alkalines (two hours vs. eight) and have a memory effect, but Nickel-Metal Hydride batteries also don't last long, but have no memory. Lithium-ion batteries are starting to appear now - still expensive, but have no memory, last longer (up to six hours) and a much longer lifespan.