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This page: Noise and Dynamic Range; Dynamic Range; It's a Wrap!
'I'll often put up with a little extra noise in order to use a mic that's brimming with character.'
Noise and Dynamic Range
AKG C 12 |
All mics create their own inherent noise, often referred to as self-noise. All other things being equal, the smaller a mic's diaphragm is, the more self-noise it will produce. But the quality of the mic's output electronics is usually a bigger factor.
A microphone's spec sheet should give you an idea of how quiet it is. If you want dead-quiet recordings, a mic's self-noise and sensitivity performance should factor into your choice. These two specs go hand-in-hand in determining how much background hiss a mic will contribute to a recording.
Keep in mind that specs are not always derived through using the same test methods, so they can be misleading. Still, you should look for a self-noise no higher than 22dBA if possible. The quietest solid-state mics offer 17dBA self-noise or better. With an astonishing rating of 7dBA, the Neumann TLM 103 ($995 list) is one of the quietest mics available today. Many tube mics measure 20dBA or worse, but there are exceptions: The Neumann M 147 ($1,995 list) and Brauner Valvet ($2,700) tube mics yield impressive self-noise specs of 12 and 13dBA, respectively.
A mic with low self-noise can still produce noisy recordings if its output level, or sensitivity, is weak. Using a weak mic on a quiet performance forces you to crank up your mic preamp to the top of its range, thus adding noise. Ideally, you want a mic that offers low self-noise and high output. Look for sensitivity of 10 mv/PA (10 millivolts per Pascal, a measure of how many millivolts a mic will output per a given sound pressure level) or higher. The Neumann U 87 A large-diaphragm condenser has a robust sensitivity of 28 mv/PA in cardioid mode. Combine this strong output with its self-noise level of 12 dBA, and you've got one quiet mic!
Dynamic Range
I'll often put up with a little extra noise in order to use a mic that's brimming with character. For instance, the AKG C 12 VR large-diaphragm tube condenser mic ($4,821) just oozes warmth and lush, fat overtones. But it's fairly noisy in that it's quite susceptible to RFI (radio frequency interference). I just make sure not to use it on quiet, exposed sources such as whispered vocals and recorder. As long as the source is not too quiet or too loud, the C 12 VR rocks!
Which brings us to yet another consideration: dynamic range.
Audio-Technica AT4060 |
The older tube mics, and their newer vintage emulations, offer fairly poor dynamic range. These mics typically start to distort noticeably when presented with levels in the 110 to 125dB SPL range, a level that a saxophone or even a screaming rock vocal (not to mention kick drum) can easily produce. The newer tube mics are much improved, offering performance equal to that of a good solid-state mic. For example, the Audio-Technica AT4060 tube mic ($1,695 list) can take a blistering 149dB SPL before complaining. The B&K 4004 small-diaphragm condenser -- a solid-state mic that lists for $2,040 -- can handle a nerve-shattering 168dB SPL peak level.
Many of the more expensive condenser mics offer an attenuation switch, or pad, that helps prevent microphone overload. The pad typically lowers the output of the mic's internal preamp by 10 or 20dB. Some manufacturers, like AKG, prefer to "pre-attenuate" the output electronics, dropping the level before the internal preamp. This design tends to nip overload distortion in the bud, although it also reduces the mic's signal-to-noise ratio when the pre-attenuator is switched in. Both designs have their place
It's a Wrap!
A well-stocked mic locker should have a variety of mics to choose from. If you're on a tight budget, try to buy at least one small-diaphragm, solid-state condenser, and either a solid-state or tube large-diaphragm condenser. Study your mic's strengths and weaknesses before and during your sessions. With careful listening and evaluation, you will soon know the best mic to use in any situation.
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