Choosing a Microphone
by Fenris Wulf, KDVS Studio Tech
The best-sounding microphones have a neutral capsule that doesn't hype the bass or treble, smooth off-axis response, a simple circuit with little or no negative feedback, and a good output transformer. Ignore "specs"; the most important aspects of a microphone's sound are phase response and transient response, and there is no standard way to measure these. Ignore price as well; a cheap Russian mic with a few mods can sound better than a "famous name" mic costing ten times as much.
The most versatile type of microphone, and the best for vocals, is a multi-pattern large-diaphragm condenser. These microphones use dual diaphragms to obtain different polar patterns; you won't get the same sound with a single-diaphragm cardioid-only mic.
Classic tube microphones such as the Neumann U47, AKG C12, and Sony C37 have a natural, three-dimensional sound that has never been surpassed. (Most of the sound comes from the capsule design and the output transformer; the tube is only part of the equation.) Modern microphones are harsh and muddy in comparison. Even so-called "reissues" seldom equal the originals. Microphone construction is a high art, and very few people have the expertise to do it right. NOS microphone tubes are very expensive, unless the mic is designed around a lesser-known tube. (See my article "Guitars, Amps, and Tubes" for more information on tubes.)
"Vintage reissues" made by the original companies are often the least authentic. In some cases, the original company doesn't exist; its name and trademarks have been purchased by a larger company in order to sell cheap mass-produced equipment at inflated prices. This is true of other recording equipment as well.
To obtain a great tube microphone, you have to spend $5000 and up for one of the better reissues, or take your chances with a vintage mic. (Make sure it has the original capsule and tube!) Some of the early transistor mics have a similar design to the classic tube mics and sound nearly as good; you'll have to do some research to find out what they are. Other mics can be improved by modifying them: removing the high-frequency resonator over the diaphragm, upgrading the output transformer or other components, damping resonances in the headbasket or body, or having the capsule re-tensioned by an expert. Some microphones cannot be modified, because they use surface-mount circuit boards or mass-produced capsules.
Even dynamic mics are not as good as they used to be. Certain models that sound wonderful on kick drum, guitar amps, or vocals haven't been made in decades. The "new and improved" versions usually sound worse. When a microphone (or other piece of equipment) becomes too expensive to manufacture, the company re-designs it to be cheaper and uses "specs" to convince you that it's an improvement.
Ribbon mics are a different story, because of their simplicity. There are many excellent models on the market, both reissues and modern designs, and they don't cost a fortune. (Avoid the cheap Chinese ribbons; they have resonances in the headbasket and other design problems.) The ribbon is somewhat fragile, but a blown ribbon can be repaired much more easily and cheaply than a dynamic or condenser capsule.
Every microphone has a resonant frequency that is determined by the mass and tension of the diaphragm. The audio will "ring" slightly at this frequency, which can ruin the sound if the resonance isn't damped properly by the designer.
Condensers have a resonant frequency in the treble and sound "zingy." Some capsule designs are excessively bright and are compensated electronically in the microphone circuitry.
Dynamics have a resonant frequency in the midrange and sound "honky." The diaphgram has a hump-shaped frequency response, which is flattened out by using resonant chambers behind and in front of the diaphragm to boost the bass and treble.
Ribbons have a resonant frequency in the subsonic range that doesn't affect the audio. When used as intended (three feet or more from the source), they have relatively flat response without the need for electronic or acoustic compensation. A ribbon is darker than a condenser, but it takes high-frequency EQ very well. Its inherent figure-8 pattern has the ability to make an instrument "present" and "roomy" at the same time, without the phase cancellations of multiple mics. A ribbon mic comes the closest to reproducing the sound in the room, and is a favorite choice for drum overheads, guitar amps, and acoustic instruments.
On distorted guitar amps, a ribbon can be too smooth. A good condenser or dynamic has more "bite" and brings out the "crunch" in way that a ribbon cannot, even with EQ.