Contact Miking Stringed Instruments
Contact miking stringed instruments.
Many musicians, guitarists in particular, have been driven away from acoustic instruments because of the problems of amplification, recording and using effects. With the C-ducer contact mic system, studio quality sound can be achieved from almost any stringed instrument without the traditional open-miking problems.
Getting a really good, even sound from acoustic stringed instruments has never been easy with conventional mics. Even when you've achieved it, persuading the musician to remain totally stationary in front of the microphone is not simple, but if he doesn't then the timbre and level of the sound can change dramatically. Thus when the C-ducer came along, several die-hard engineers as well as acoustic players approached it with considerable enthusiasm. Guitarist Gordon Giltrap (who has a C-ducer tape mounted inside his guitar, incidentally) was not untypical in virtually having to abandon the acoustic guitar in favour of electric, until he was 'C-duced', because of the problems of feedback, having to remain stationary in front of the mic and the poor sound quality of the 'bugs' around at the time.
In the studio, the problems are somewhat different, but no fewer.
As with recording the piano, discussed in September HSR, the first problem is eliminating background noise. With the quieter stringed instruments particularly eg. dulcimer, harp and - to some extent - classical guitar, the background noise not only comes from outside the studio, but from other musicians and even from the musician playing the instrument - the sound of breathing, the rustle of clothes, etc. The use of a good contact mic can go a long way to eliminating these.
The C-ducer package consists of a tape microphone and its preamplifier, a handbook and a spare reel of adhesive tape (for attaching the mic to the soundboard of the instrument). The manufacturers will also supply Application Notes (one sheet on drums, one on keyboards and one on strings) and these really are very helpful if you have any problems.
There are two ranges of C-ducer, one - the 'Gigster' range - is mainly for semi-pro live work and the other - the 'CX Series' - is aimed at studios and large groups. The tape mic used is the same in both cases.
The Gigster is battery-powered, can be clipped on the belt and has an unbalanced ¼" jack output (plugging the jack into the output socket actually switches the unit on, by the way, so do remember to remove it when you're not using the system). The preamp is all-metal and seems pretty sturdy.
The CX Series which has just been launched and replaces the old C-Series system features balanced outputs as well as unbalanced and is phantom-powered. If you don't have any phantom (or you only have 24V) the system can be powered by a C-ducer power supply.
The Gigster system is an excellent, budget-priced option (around £60) and well applied gives excellent results. Being aimed more at the live musician, however, the bass has been lifted slightly to reduce 'boominess' and feedback problems. For this reason, as well as the extra facilities, I would go for the CX Series in a recording application.
There is the option of two lengths of C-ducer tape, the 3" for smaller instruments - violin, banjo, mandolin - and 8" for use on guitar, 'cello, string bass. There is also a system for the harp which uses two 3" tapes. The 8" length of C-ducer is best suited to drums and piano (two tapes required), so one C-ducer CX Stereo will mike up two stringed instruments (or a pair) drums, or a piano (in stereo) and I found this versatility very useful.
I tested the C-ducer first on guitar and double bass. The guitar is a nylon-strung Estruch and a fairly typical flamenco size and shape. Following the instructions (just by way of a change) I removed the backing strip and stuck the C-ducer in the suggested position under the strings parallel to the bridge and 'biased' towards the treble side. I plugged it all together without incident and connected it to a mixing desk. I only have phantom power on mic channels so, rather than use the C-ducer power supply, I went in at mic level (there's a preset level control on the base of the unit which alters the output level from mic to line). The guitar sounded extremely good - very acoustic. I was less keen on the second position (Figure 2) shown in the application notes behind the bridge - this was very bass heavy; when I tried it on the 12-string in this position it sounded better than under the strings, it just depends on your instrument and your ears.
I first heard C-ducer on the double bass at a Sky concert. It was impressive and so I was expecting good things in the studio. The double bass used was an old instrument with rather a delicate surface, so at the manufacturer's suggestion we applied a thin 'low tack' film to the bass and then stuck the C-ducer to that. The low-tack film turned out to be the thin vinyl used for covering books; it did the job, though, and the instrument varnish stayed in place. I have heard that the ubiquitous 'clingfilm' can also be used, and has even less tack.
Having got an excellent bass sound with the tape in the recommended position, we played around. It didn't seem to be very critical where you put the tape. We ended up with it vertically alongside the 'f'-hole. We did get some pick-up of sound from the neighbouring piano but placing a rubber under the spike of the double bass cured most of this, however.
By the way, the latest CX Series C-ducer is audibly better than the old C-Series model, the sound has more clarity and the electronics are absolutely quiet (not that the old unit was excessively noisy).
One of the C-ducer users I spoke to was engineer Keith Grant of Olympic Studios, who has used C-ducer on a variety of instruments from sitar through to mandolin and not only when conventional techniques were unsatisfactory, either. In fact the mandolins on the, now infamous, "just one cornetto", ad were done by him using C-ducer.
So, we picked up a variety of instruments to try. Firstly we stuck one 8" tape on each of the two gourds of a sitar. The sound was very interesting and had a somewhat surreal, stereo image. A tape of the sound was played back to the sitarist who liked the sound but was not convinced it was the same as the acoustic sound - but he was even less convinced with the conventionally miked sound!
Using a 3" tape we tackled a variety of folk instruments and with a bit of experimentation got good results from various dulcimers (including hammered), folk harp, concert harp (using the two 3" tape system) and balalaika. The hammered dulcimer had an ethereal quality that was quite stunning.
The banjo was a little more tricky, but eventually, with the C-ducer stuck partly on the rim and partly on the vellum, we achieved an accurate sound without over-emphasis of the flailling (percussive effects on the vellum).
On one, admittedly slightly dusty, instrument, we had a problem with the PVC moulding which joins the tape to the cable not adhering reliably to the instrument. This was solved by sticking a double-sided adhesive sponge pad (from the local stationers) between tape and instrument - do check that the varnish is tough enough, though.
We had a great few days checking out the C-ducers, and it really was very difficult to find fault with the sound on any of the stringed instruments that we tried. One small mod which can make the system easier to use for the musician is to fit an inline connector near the tape (say 6" away). You can then unplug the tape from the lead before you put the instrument away (without having to find space for 8 feet of cable in the guitar case). You can also clip the connector into a plastic cable grip stuck to the guitar which acts as a cable restraint and helps prevent the PVC moulding pulling off the instrument. If you choose to fit the connector, however, beware; the C-ducer has an extra, conductive-plastic earth shield which must be stripped back to the earth braid or intermittent shorting-out of the signal line results.
In the next issue I'll be talking about my findings with the C-ducer on the drum kit, Latin drums and steel drums.