This month we conclude Ken Dibble's enlightening feature on miking the acoustic guitar by looking at some examples of mic types and positions.

In Part 1 of 'Making the Most of Acoustic Guitars' (H&SR Jan 86) we looked at the physical problems associated with miking the acoustic guitar and discussed the interaction between the microphone characteristics and its position in relation to the instrument. To round off the series, here are a series of photographs illustrating particular miking arrangements accompanied by the authors comments.

Figure 1. The Accusound supple tape transducer does not require a pre-amplifier or power supply and is shown here in the bridge position on an Ovation Folklore guitar. Effective though this type of system is, there is no doubt that it does modify the tonal qualities of the instrument and finer nuances and subtleties may be lost. Consequently such devices are more popular in a live environment but a discerning recording engineer will invariably utilise traditional miking techniques.

Figure 2. Response curve of typical dynamic cardioid mic.

Figure 3A. Not recommended. Notwithstanding the quality of the Shure 545 dynamic cardioid microphone, when used in this position an over bearing, boomy, and heavily coloured sound quality will result due to coupling effects between the proximity effect characteristics of the microphone and the body resonances of the instrument. Also, the microphone will impede the musician.

Figure 3B. Good practice. This is the same microphone, moved slightly away from the sound hole and up towards the base of the neck. Much cleaner sound and musician unhindered.

Figure 4A. Another angle on the same position, this time with an AKG C535EB condenser microphone.

Figure 4B. Same microphone, showing the very useful response selector switch of the AKG C535EB giving a choice of flat response or two different bass roll-off curves at normal mike level or plus 14dB. Apart from the added clarity of the condenser capsule, the bass roll-off facility is particularly useful in filtering out body resonances when it becomes necessary to close mike, and can be sufficient to overcome the proximity effect rise.

Another excellent condenser microphone for acoustic guitar work is the AKG C451EB pre-amp fitted with the CK1 or CK1s capsule. The EB is the version of the C451 which has an inbuilt bass roll-off switch, and the CK1s capsule has a presence lift characteristic whilst the CK1 is flat. The choice between the two is entirely to personal preference - i.e. whether you like an artificially lifted attack (e.g. the Cat Stephens/Paul Simon sound) or if you prefer it natural (e.g. John Williams).

The Shure SM81 condenser, also with bass roll-off switch, is another good choice.

Figure 5. An AKG C451 EB used in the far field with the CK22 omni-directional capsule. The Shure SM82 provides similar characteristics.

Tailpiece

Though the recommendations set out in this series will no doubt get you off to a good start, remember that no two guitars sound quite the same and there's such a wide range of playing styles that it would be optimistic just to work to a given formula every time and still expect optimum results. Some degree of experimentation is essential and this includes trying out different mics and noting the effects of changing their position whilst listening critically to the results.

Using these notes as guidelines, you should be able to produce results that do justice both to the player and to yourself as an engineer.