11. FAQ

It depends. A small diaphragm condenser is more likely to capture the natural sound of your guitar, a large diaphragm condenser will give a more voluminous and „bigger“ sound. Not every large diaphragm condenser works well on any acoustic guitar. LD condensers are mostly geared toward vocal recording. Small diaphragm condensers are usually more linear and work well on many sources.

A low self-noise figure is more important than high sensitivity. High sensitivity only improves actual noise performance when you use a noisy mic preamp. Sensitivity on condenser mics is almost always high enough to be a non-issue. High sensitivity is desirable for dynamic mics, though.

Most probably you just used it the wrong way (don’t worry, that happens all the time). LD condensers are side addressed, but that doesn’t mean that both sides are equal! Most mics have a cardioid pattern, which means they are sensitive to sound from the front and reject sound coming from the rear. The front side of the mic is usually where the manufacturer logo is. If you reverse it and the backside faces the singer, what the mic pics up is mostly room reflections, hence the dull and distant sound. Just turn the mic around so the front faces the singer, and everything’s fine again :-)

That’s probably due to high humidity. Place the mic below a desk lamp for a few hours; the warmth of the light bulb will evaporate the humidity and the noises will disappear.

Please, never ever blow into a mic! Condenser mics are very sensitive to both air blasts and humidity and can be damaged permanently. Studio microphones are not as rugged as stage microphones.

Many dynamic moving coil microphones do in fact have a large diaphragm. However, people hardy ever talk about diaphragm size when it comes to dynamic microphones, probably because the actual diaphragm is often hard to see. Usually there’s a lot of protective foam and other stuff in front of the actual diaphragm. Plus, many moving coil microphones use diaphragms that are somewhere between large and small diaphragm size.
If you’re looking for a dynamic mic as a sound alternative to a LD condenser, take a look at announcer microphones for broadcast use. Mics like the EV RE20, RE27 or Shure SM7 are often used for typical large diaphragm applications such as rock or rap vocals. Some ribbon microphones, too, give a “large diaphragm sound”.

Both sides of the pressure-gradient transducer's diaphragm are exposed to the sound field.

Mics produce noise. The signal-to-noise ratio is the relation between the voltage that a mic produces without being exposed to sound and the voltage the mic transmits at a 1-Pacal sound pressure and a frequency of 1 kHz. The signal-to-noise ratio indicates by how many dB the mic's own noise is lower than the voltage it transmits at a 1-Pascal sound pressure

Whenever the distance between the mic and the source of sound is about 1m or less, the low-frequency portion of the spectrum is increased in the mic out. When a sound source approaches, the sound pressure increases inversely proportionally to the distance. The proximity effect occurs with any pressure-gradient mic. Many mics feature a switchable filter to compensate for the proximity effect. Conversely, artists may also make use of the proximity effect to lend their voices greater volume, for example.

This means that differential signalling is achieved through an audio transformer and not a balanced amplifier (transistor technology). In order to transmit a mic signal without any loss, it has to exit the mic symmetrically. And this can be achieved either trough a transformer or a balanced amplifier.

There's a disadvantage to transformers: budget models usually render bass sound worse, and they produce more noise. Most condenser mics nowadays therefore feature an output without transformer, since these can be built easier and more cost-effectively.

Both these terms are meant to indicate a mic's sensitivity, i.e. the relation between the sound pressure at the diaphragm and the mic's resulting output voltage. The larger the transmission factor is, the lower the mic's amplification needs to be set at the mixing desk. The output voltage of dynamic mics is lower, as a rule, than that of condenser mics. Of course, any mic's sensitivity depends on the frequency. Usually, the nominal value is indicated in mV/Pascal at 1000 Hz.

In phantom feeds, the direct current supplied to the mic is run through 2 6.8-kOhm resistors to the two mic cable cores. The circuit is closed by shielding. The audio signal is not affected by the phantom feed, by the way, because the DC voltage is separated both in the mic and in the mixing desk input stage by condensers. Most studio mixing desks supply such voltage directly at their XLR ins. As a rule, the mixing desk's power supply unit serves as the source of DC voltage. Alternatively, there are various devices available on the market that can be simple plugged into the supply. For phantom power, 48 V DC has become the standard, although the permitted values range from 12 V to 52 V. Most condenser mics work reliably within this range. Many mics can also be supplied with a built-in battery. Batteries, unfortunately, do not have an unlimited run-time and tend to pack it in precisely when you are in the middle of recording. Generally, most mics perform at the specs indicated at the high voltage of 48 V.