Hands On - Quality Microphones (part 3)
Microphones generally dont have much in the way of controls. I imagine that one day they will have LCD readouts and up/down nudge buttons like the rest of the equipment we have to deal with. They will probably also have dedicated software running on a Mac or Atari to optimise the mics performance for your particular task. Anyway, for now we only have to deal with three switches on the U87, which I would say is about the right number. On the front (you can always identify the front of a mic by the makers badge - Lenny Kravitz obviously couldnt on his Are you gonna go my way? video!) is the pattern switch selecting omni, cardioid or figure-of-eight. Around the back are switches to set a 10dB attenuation and a low frequency roll-off. But why should you need these facilities on the mic when you can more easily adjust gain and EQ from the console? The answer to this question is that a capacitor mic consists of two parts - the capsule which picks up the sound, and the amplifier which makes the signal strong enough to travel down more than a hundred metres of cable if necessary. The capabilities on the amplifier are limited by the maximum of 48V available from the power supply, so with an exceptionally strong sound source, such as a close miked drum, you would risk clipping the amplifier causing distortion. Also, its quite possible to get high levels of low frequencies finding their way into the mic and these are again best disposed of at source. The attenuator is only single stage with a fixed 10dB cut. You would probably still need to make sure that Pavarotti stands well back from the mic.
As well as vocals, the U87 is also widely used for orchestral miking, not so much as an overall stereo pair, but as individual section mics. Having spent a lot of money on you U87, you might not want to put it within ten metres of a drummer, but in fact the U87 has often been used for close miking the kit. Its a bit bulky for the job perhaps, but if you have a drummer who is willing to shift his kit around a bit the U87 will give a nice solid drum sound.
It must be frustrating for microphone designers when they are full of ideas for brand new microphone designs, but all the customers want is improved versions of the mics they know and love. Like the Neumann U87, the AKG C414 has been in the catalogue for a long long time and is a very popular microphone. Once again, this is a multipattern mic with a double diaphragm. One characteristic of multipattern mics is that you dont point them lengthways at the sound source, they are positioned sideways on so that the sound strikes the diaphragm squarely. This doesnt cause any problem to sound engineers since even if you have never met one of these mics before you can hear that the sound is wrong and reposition it accordingly. I have however met musicians who thought that the mic position was wrong and helpfully adjusted it themselves! Like the U87, the C414 has the makers name and logo at the front so you know which way round the mic goes.
The AKG C414 currently comes in two versions, the C414B-ULS (can you imagine any sound engineer saying, Pass me the AKG C414B hyphen ULS please, to his assistant?) and the C414B-TL. The ULS version is the standard model and like most other professional mics has an output transformer to drive an interference-cancelling balanced line. Although transformers are useful devices, they need to be large to work perfectly at high levels of low frequency. The maximum sound pressure level (SPL) spec for the ULS is 140dB SPL at 1kHz and 134dB SPL at other frequencies between 30Hz and 20kHz. With the TL model, which has a transformerless output stage, the maximum level is 140dB SPL at all frequencies between 30Hz and 20kHz, which is obviously a significant improvement. 140dB SPL is, by the way, very loud.
The AKG C414B-ULS and TL have the same combination of switches as the Neumann U87, but here they are a bit smaller and fiddlier. The 414 has four polar patterns, cardioid, hypercardioid, omnidirectional and figure-of-eight. The attenuation switch offers -10dB and -20dB (raising the maximum level to 160dB SPL!), and the filter gives roll off frequencies of 75Hz and 150Hz.