More mic science talk--how does phantom power make a mic work?

I thought the thread about the physics behind proximity effect was pretty interesting, so I thought I'd ask why the 48 volts of phantom power that we all know a condenser mic requires makes it work. In other words, why does a condenser mic not produce any output without the external voltage, whereas a dynamic mic does? How does this relate to oddballs like the Blue Ball (the infamous phantom-powered dynamic mic)? I know I've heard the explanation before, but my mind is like a steel seive, so tell me again!

[dagosto]

Well. Dynamic mics create their volume through magnetic induction. The diaphram is attached to a magnet which it moves back and forth. The magnet is surrouded by a stationary coil of wire. As the magnet moves back and forth within the coil it creates an EMF (electro-magnetic flux) within the wire. The physics behind this is expounded upon in Faraday's Law.

Condeser microphones do not have a magnet attached to thier diaphrams. This allows them to be lighter and more responsive to quick movements in the air. To produce voltage the must be electrically charged. As it moves the distance between the diaphram and the fixed metal backplate causes a change in capacitance (or pull on the electrons in the metal back plate). This change creates a low voltage analougous to the soundwaves moving the diaphram. The charging of the diaphram is one of the two reasons condesor mics need phantom power.

Since the current created by the capsule itself (the diaphram and the back plate) there needs to be some sort of amplification stage. Because of this all condenser microphones have a small preamp built inside of them. These also require power most often supplied by phantom power.

Mics like the Blue Ball (the only dynamic that uses phantom power that I know of) create the initial voltage by way of Magnetic inductance. The difference is that this mic has a preamp built inside of it like a condenser. The purpose of this preamp is not to increase level as much as it is to isolate the transformer stage from whatever you are plugging the mic iinto. Input stages can vary greatly in impedance which will cause most dynamic mics to respond differently, usually altering the frequency response and adding low orders of distortion. The Blue Ball is mostly immune to this effect thanks to its internal preamp. I would be suprised if we didn't see some similar designs in the near future.

Thats nice to know about the blue ball. are they just as versatile as a sm57?

Originally Posted by DreamwaveMusic

Thats nice to know about the blue ball. are they just as versatile as a sm57?

hmmm this reminds me... would you say the sm57 is the best all around verastile mic? i been hearing this is so, just wanna make sure b4 i buy it

Yeah, an SM57 is so useful that you can't really afford not to have one, in my opinion. I'm surprised you don't already have one; they're most people's first seroius mic (well, either that or the SM58).

[dagosto]

Originally Posted by DreamwaveMusic

Thats nice to know about the blue ball. are they just as versatile as a sm57?

I've used it on a lot of different things. It has a more open sound than the 57 which can sometimes make it a little washy. I don't like it on percussion that much. It's my fav guitar mic and works well on some vocalists as well. Actually on just about any tonal source it usually does quite well. I think this is because notes really ring through over the percussive elements of a sound whereas other dynamic mics can peak out at frequncies where there is mostly enharmonic stuff going on. The internal preamp keeps its frequency response the same over the entire dynamic range.

It does certain things really well. others not as much. So to answer your question, no. I don't think it is as versatile. But I still use at almost every session.

[Nubus]

Originally Posted by DreamwaveMusic

Thats nice to know about the blue ball. are they just as versatile as a sm57?

I dunno about that. The Blueball is shaped in such a manner that it might be hard to fit into some of the places a 57 can go. That and the fact that it requires phantom.

Hey dagosto, have you ever used the Sennheiser e609 on guitar cabs, and if so, how would you compare it to the Blue Ball? I have the older black version--I guess there's a newer silver version that doesn't sound as good.

[dagosto]

Originally Posted by Whoopysnorp

Hey dagosto, have you ever used the Sennheiser e609 on guitar cabs, and if so, how would you compare it to the Blue Ball? I have the older black version--I guess there's a newer silver version that doesn't sound as good.

Suprisingly, I've never been in a studio while one of those was being used so I can't really comment on that. It's probably a good mic since Sennheiser is a very fine company.

[smopo24]

Originally Posted by Whoopysnorp

Hey dagosto, have you ever used the Sennheiser e609 on guitar cabs, and if so, how would you compare it to the Blue Ball? I have the older black version--I guess there's a newer silver version that doesn't sound as good.

i have used the silver version, which was great; but i think the blue ball was "truer?" somehow.....both were great in any respect, espically when combined with a 57!