Ribbon mics are commonly used when:
• A smoother, rounder, warmer representation of high frequencies is desired, or a sound that is very bright and shrill needs “mellowing.”
• A “vintage” character is desired.
• The extreme side rejection of a bidirectional pattern would be useful, minimizing spill from sources to the sides, above or below the mic.
• Huge proximity effect is beneficial. Or when you want a warm, full sound from a foot or two away.
• You want the ability to quickly rotate the mic 180°, and exploit the potentially dif-ferent backside character of the mic.
• High SPLs, moving air currents, and physical shocks will not be a threat to the mic!
3.7 TUBE (VALVE) MICROPHONES
Guitarists have long favored the subtle harmonic distortions, sonic character, and warmth of tube or valve electronics in their amplifiers. Tube, or valve microphones, use sonically color-ful tube amplification circuits instead of more modern, reliable, and stable solid-state head-amplification stages. This tube head-amplification colors the sound of the condenser capsule with sonic fullness, musical warmth, and smooth silky high frequencies.
Original, classic, vintage tube mics, built using very high quality materials and tubes were expensive. Faithful modern recreations of these classic designs are very expensive! There are also many cheaper tube mics on the market. To keep the price down, some very cheap mics use poor quality modern tubes and components – so assuming a tube mic is always better than a regular condenser mic is not correct. A classic tube mic will cost $5,000 to $10,000. There’s
just no way a $200 copy/clone/rip-off is going to have the same qualities, or automatically be the right choice, just because it’s a tube mic!
Additionally, due to the high degree of coloration a tube mic produces, it is not necessarily the best choice for all sound sources or production styles. If a sound source is already very thick and warm sounding, the additional coloration added by a tube mic may be too much.
But if a sound source is a little thin, and needs some warmth, body, or “phatness,” a tube mic could provide useful “sonic makeup.”
As a tube ages, its characteristics can change – negatively affecting its performance and sound. Tubes do need replacing. Tubes are fragile, and physical abuse will damage them – so care must be taken when setting up and tearing down. Tube circuits also tend to be noisier than solid-state electronics, so tube mics are noisier – making them less suitable for recording very quiet sound sources.
For rock music, the coloration, warmth, “phatness”, and “bigness” characteristics of analog tape have long been favored over digital recording systems by many engineers. With the demise of analog tape, and prevalence of digital recording systems, some stylistically desir-able sonic colorations are missing from the recording chain. In recent years there has been renewed interest in tube technology, and modern tube mics, tube pre-amps, and tube and tape saturation plug-ins have been developed to add analog coloration to digital recording systems.
3.8 OTHER MICROPHONE TECHNOLOGIES
LOUDSPEAKER CONE MICROPHONES
For decades, recording engineers have experimented with reverse wiring loudspeaker cones into mic inputs, and exploiting the very colored sound that such a large and heavy loudspeaker cone “diaphragm” produces. Nowadays, commercial products are available to do the same, as shown in Figure 3.11.
Fi g u r e 3 .11 A commercial loudspeaker cone mic on a kick drum.
recorded kick drum sound is a non-natural, engineered sound anyway!
BOUNDARY MICROPHONES
A boundary microphone (trademarked “PZM” by Crown) features a very small condenser mic capsule mounted above, and facing down towards a sound reflective boundary plate, as shown in Figure 3.12. Sound takes two paths to the mic capsule:
1. Directly into it.
2. Reflecting off the boundary plate up into it.
A regular mic picking up both direct and reflected sound, the reflected sound arriving at the capsule momentarily after the direct sound due to the extra distance it travels, would usually exhibit audible comb filtering – the sound would be “phasey.” Because of the extremely small distance between a boundary mic’s capsule and the boundary plate – usually less than 0.050” – the sound waves remain in phase throughout the audio frequency spectrum. Boundary mics are not commonly used in music recording, but they are common in theater, conferences, and broadcasting.
Boundary mics should be mounted flat, on large, hard surfaces. The larger the surface area of boundary the mic is mounted on, the better its low frequency response. A surface of at least several feet square is necessary for good bass response. Most boundary mics have a hemispherical pick-up pattern – like the “front half” of an omnidirectional pick-up pattern.
Directional boundary mics (cardioid, or hyper cardioid) also exist, which reject sound coming from behind the mic to varying degrees. Hemispherical boundary mics tend not to color off-axis sounds in the way that other types of mic do. This means that sound sources placed around the entire front hemisphere of microphone will be picked evenly, and that off-axis reflected sound (such as reverb) will be picked up more neutrally and accurately than they would be by other types of mic.
Fi g u r e 3 .12 A cross section of a boundary mic capsule.
Boundary M ic Capsule/
D iaphragm D irect Sound
Reflected
Sound-Boundary Sound
Source