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Microphones

Microphones for Small Studio Recording

Microphones are available in three fundamental types: dynamic, condenser and ribbon.
  • Dynamics (aka moving coil) mics are essentially sensitive speakers operating in reverse; sound pressure moves a coil of wire inside a permanent magnetic gap to produce a weak voltage for amplification. Their primary use is for stage work where rugged mechanical design is required though technology has blurred these lines.
    • Output (Level) is low as is the impedance. These mics require as much as 60-80 dB of gain which can test the limits of preamps. This also means that preamp noise can become an issue in studios when signals are much lower than live performances. One solution is to place and near-zero noise (EIN) "in-line" preamp near the mic to improve the SNR and thus require less from the preamp in the rack.
  • Condenser mics must amplify a weak signal derived from an electronic circuit which reacts to changes in capacitance (the result of changing the spacing between a thin metalized membrane and a metal plate). While more complex, the capsule membrane can be constructed with precision and the membrane can respond more linearly over a much wider frequency range. There are two types of condensers:
    • SCMs (Small Condenser Mic) which are generally 1/2-inch diameter or smaller and have built-in FET-based preamps to convert the capsule's high impedance to ~200 ohm line impedance for long cables. SCMs have higher noise, flatter response, greater dynamic range.
    • LCMs (Large Condenser Mic) which are generally 1+ inch diameter and have built-in preamps as well. LCMs have higher output, lower noise, less accuracy and less dynamic range and frequency response but more flattering. they are constructed in three flavors:
      • Transformer based: The capsule's high impedance signal is converted to a low (200 ohm) drive using a high-quality transformer. These designs have been generally phased out and replaced by FET-based preamps with wider frequency response.
      • FET-based: The mic's preamp (primarily for impedance conversion) is based of the Field Effect Transistor (a solid-state high-impedance version of the classic tube). These easily operate on the +48V phantom power supplied by most external mic pres. Some external preamps (like the VT-1B by Studio Projects) actually integrate a tube in parallel with a FET to "warm" the sound and thus gain the benefits of the classic "tube sound" without the dedicated mic supply.
      • Tube-based: Some "classic" LCMs still use vacuum tubes inside the mic housing. This requires a dedicated power supply just for the mic but tubes have a smoother distortion curve on the peaks which some prefer.
  • Ribbon "velocity" mic are constructed using a thin, corrugated aluminum (or similar) membrane suspended between the poles of a permanent magnet. They are generally not nearly as rugged as condensers and are often more expensive but they offer greater clarity (accuracy) in the upper frequency ranges. Their advantage is based on having very low mass in the membrane which allows greater transient sensitivity and fewer sonic artifacts.
Condenser Size
The most common choice for studio recording are condenser microphones which are generally classified by the size of the "capsule" which contains the membrane. Small condensers (SCMs) are up to about 1/2-inch diameter whereas large condensers (LCMs) are typically about 1-inch diameter.

[Note; there are actually two numbers used when referencing LCM size: a) the capsule diameter which is usually about 32-34mm and b) the membrane diameter itself which is usually about 20-25mm diameter. Two different LCMs might be listed as 34 mm and 24mm yet have the same size capsule; the specs just did not clarify. Generally, the capsule diameter number is listed.]

"The Best"
Selecting the "best" microphone for studio recording is, by definition, selecting 1) the best within budget, 2) the best for the specific source (voice, instrument, etc.) and 3) the best for the specific room acoustics. Mic placement can be critical and takes patience and testing. Room acoustics can make a great mic seem terrible so fight the urge to blame poor room acoustic on the mic; do not expect the mic to fix problems with the recording space. Below are some examples of studio microphones; primarily Large Condenser Mics (LCMs). There are many more available at a wide range of prices. The purpose of this list is to provide some examples of quality studio mics worthy of consideration for the small home studio. Expensive, but not beyond reach.

Neumann U47 and U87
The Neumann U47 and U87 are often referenced as industry standards -- very high quality multi-pattern LCMs, often described as "classic warmth" and providing superior vocal recordings. However, at over $3,000, they should be. While the small home studio is unlikely to own one, it is still helpful to know something of what other mics might aspire to become when they grow up. However, voices are so unique that even Neumann's are not necessarily the best choice and they are certainly not the only choice of superior high-end microphones. See more of the details on the Capsules page.

"Warmth"
The 300 to 500 Hz frequency range includes voice resonances which are described as "warmth". Recordings made with a mic whose sensitivity rolls off below 500 Hz may sound "lifeless". However, the response of an LCM is also dependent on distance; 6 inches, as opposed to 1-3 feet.

"Dry"
Roughly the inverse of "warmth", "dry" recordings can sound "sterile". Small studios need to kill as much of the bass reflections as possible and can leave a room sounding rather "dead". Recording with a "dry" mic will lead to "lifeless" recordings. The most likely cause of a "dry" mic is a limited low-frequency response.

"Proximity"
Mics with good bass response below 500 Hz can have added low frequency distortion and sound "boomy". So, "brighter" (broad peaking in the 3-10 kHz range) mics with 500 Hz roll-off, like the Shure SM137, work better for recording acoustic guitars. Accurately recording the acoustic complexity ("presence") is enhanced with such mics because they can be positioned closer to the source.

"Muddy"
This term often refers to a lack of clarity. However, it is usually a result of mic placement and room acoustic rather than the mic's performance. Usually there are multiple reflections and reverberations from the source with dynamically changing phase relationships; easily heard if an LCM is positioned in front of the sound hole of an acoustic guitar.

"Brittle"
The 1 to 3 kHz region is the center of most voices where they project the most volume. A "peak" in the mic response in this range could over-emphasize those qualities to disastrous effect.

"Pops & Hisses"
The 4 to 10 kHz range accounts for most of the 'esss's, 'pops' and breathing noises. The "pop" filters can't do anything about these frequencies. The filters are primarily there to protect the sensitive, and expensive, LCM from the performer's breathing moisture. "Swallowing the mic" is a bad habit from stage work and totally unnecessary in the studio.

Cardioid
Unlike the omnidirectional pickup pattern of the EMC-8000 measurement mic, the cardioid pattern is designed to reject sound from all but the source directly in front of the mic. As is obvious by the polar plots below, the rejection is only partial. However, the mic would sound unnatural if the pattern were too sharply unidirectional and the recording level would be difficult to control. The lack of side and back rejection is problematic in picking up unwanted sounds in the studio. A common (partial) solution is to position a broad-band absorber behind a cardioid mic. Low frequencies are difficult to reject this way because those waves easily refract around the sides of the absorber. However, mid-range absorption is still effective enough to be useful.

Hyper-Cardioid
This describes a much narrower cardioid pattern with much better side and rear rejection. These mics are more special purpose and their use is focused on isolation between sources when recording multiple instruments and voices at the same time or as additional support for isolation panels in the acoustic recording space. Not having to resort to these is still best.