There are different kinds of mics and they all work very differently. You can sort them several ways. By active and passive, meaning active ones take batteries or phantom power while passive ones do not.

Another way to sort them is by polar pattern, meaning just what kind of shape their hearing response takes.

The first on the list is the unipolar mike, which hears pretty much the same no matter which way you point it. In short they hear what's in front of them and what's on each side. They hear pretty well from the back, too. These often get called karaoke mics or omni-directional mics and may be prone to feedback. The polar pattern is like a circle around the mic.

Next is the cardioid mike. These hear very well in front, pretty good on the sides and not very well in back. That is why they are called directional microphones. The polar pattern is like a circle that has one point pushed in towards the center, so if that point was at the top it would resemble the top part of a Valentine's day heart, the dip being the back of the mic.

The third type is bi-directional mics whose polar pattern is like a figure eight, hearing well on the sides, but not so much in front or back.

Multi-polar mics have switches built in that allow you to choose which mode to operate your mic in when doing a recording. I have a matched pair of mics that have swappable diaphrams that can be changed out to put them in omni or cardioid mode, the simplest switch of all. I have others that have switches on the side of the mic for all three modes, and the big boy has a couple spots on the dial in between each of the three major ones.

Buying a multi-polar is like getting three mics in one and all that extra utility into your audio toolkit. So, if the prices seem a tad steep, add up what it would cost to purchase a decent one each of the three types described above and compare the costs of the three to the one for a good rule of thumb.

Q: The Blue Yeti mic gets high recommendations at librivox. What kind of mic is that, and does it live up to the rave reviews?

A: The blue Yeti is a multi-polar USB mic. (Currently $129.99 at Musician's Friend, $119.99 at NewEgg and refurbished from $91.49 at BestBuy or $149.99 for a new one there.) As for the reviews, loan me one and I'll be happy to tell ya how it stacks up to the stuff in my mic locker. (They are made by Blue so they probably do.) You can pay twice as much, or more, for a 'regular' multi-pattern large diaphram studio condenser mic and still need phantom power and a mixer to jack it in to your computer and still not get better sound, according to the people lucky enough to own them. All I (Ric) can say is the specs sure look good!