guitarist said:
What are the differences like in audio quality & maximum sound levels, etc? Does it depend on what they're being used for? Right now I'm using a dynamic mic for a guitar amp & some vocals, but it doesnt seem to handle the guitar amplifier.
Well, you ask for it! (a deep breath and...)
Condenser mics differ from dynamics in that they capture the sound via a “capacitor” that changes its value (capacitance) in proportion to the sound waves vibrating it. To do this, the “capacitor” needs to be electrically energized and its output immediately amplified to “drive” the preamp input. Since the signal from a condenser has been electrically amplified, it can be pretty “hot”.
Think of it like this: Go to your local favorite fast food joint and get a “water” to go and a clear straw. Poke the straw through the lid and seal up the hole around it with putty, play-dough, or something so that it is airtight. Once it’s all sealed up, squeeze the cup and notice the water moving up the straw. Release the cup and notice the water moving back down the straw.
In this analogy, the cup is the capacitor and it capacitates water. In a condenser mic, the capsule is the capacitor and it capacitates voltage (which it gets from the phantom power supply). When the diaphragm (represented above by the outside of the cup) is vibrated via sound waves, the voltage charge on the capsule moves up and down like the water in the straw. This is a very, very tiny change in voltage, but it can be measured with a good Field Effect Transistor (FET). This measurement is then amplified into a good strong signal before being sent down the line to the preamp. Besides supplying a voltage source to the capsule, the phantom power also supplies power to this pre-preamp built into the mic.
Dynamic mics, on the other hand, work like this: Long, long ago, some dead scientist discovered that if he took a piece of wire, wound it into a coil and passed it through the magnetic field of a magnet, current flowed through the wire. Likewise, if the coil was moved in the opposite direction, the current also flowed in the opposite direction. (Remember doing this in grade school science and wondering, “what am I learning this for?”)
Later, another scientist (probably dead too) discovered that if he made a lightweight coil out of very fine wire, attached the coil to a very lightweight membrane, and mounted it so that it moved freely back and forth across a magnet, it would generate currents proportional to the sound waves “felt” by the membrane.
Thus, a dynamic mic captures the sound by moving a coil through a fixed magnetic field in proportion to the sound waves vibrating it (backwards from a speaker). This MECHANICALLY produces a small electrical signal, which is sufficient to drive the preamp input. Trouble is, even though it can “drive” the preamp input, its interaction with the preamp depends on the mic’s output “impedance” (resistance at every frequency) and the preamp’s input “impedance”. This can change all over the place, depending on things like whether the pre’s input is transformer or capacitor coupled, type of transformer used, type of mic, etc, etc.... In addition, since the signal is “mechanically” amplified, it most often is not as “hot” as a condenser’s electrically amplified signal.
What does this mean? Well, to me it means that:
1. The preamp design has more to do with the sound of a dynamic mic than that of a condenser mic.
2. Dynamic mics are generally going to be noisier then condensers because they need more gain due to the weaker signal. Actually, it’s the preamp that’s noisier. The mic itself is actually very quiet.
It is for these reasons that I believe condensers are generally better for use with cheaper mic pres simply because their interaction is going to be more predictable and quieter.
Now, having said all that (whew!), one thing you ask was what are the differences in audio quality & maximum sound levels? Well, I just covered the sound levels, but as far as quality goes the best I can tell is that dynamics come very close in audio quality to condenser mics, DEPENDING on the preamp you’re running them through.
Your next question was “Does it depend on what they're being used for?” I would not only answer “yes”, but also add “...and who’s using them”. I don’t mean to sound like a broken record because this gets repeated on this forum time and time again, (maybe because it’s true?
) but you really have to experiment and decide what’s right for you.
Lot’s of people have great success micing amps with dynamics (SM57 comes to mind) and others with ribbons and still others with condensers. Depends on the musician’s pick, the musician’s picking method, guitar, guitar pickups, guitar strings, guitar cord, guitar electronics, (the guitar strap probably doesn’t matter
), guitar amp, speaker cabinet, speakers, room, MIC, mic cable, mic pre, recording medium, song context, other instruments, vocals in the mix, etc, etc. You see, in the BIG picture the mic is but one small part.
Now... what do you mean by “it doesn’t seem to handle the guitar amplifier”?