klieb@tekigm2.MEN.TEK.COM (Kurt Liebezeit) (08/25/89)
(sorry about the wide cross-posting, please direct follow-up articles to rec.audio; also, use mail address at bottom for best results) I have a few questions about microphones and live recording, and I hope that someone on the net may have some advice. If you don't feel like writing the answers down, reply with a phone number and I'll be more than happy to call you at my expense. I would like to be able to record acoustic (non-amplified) musical events such as folksingers, string bands, and bluegrass to name a few. Here in Portland OR, for instance, there is a Saturday Market with a wide variety of guitar, hammered dulcimer, marimba, steel drum, piano (outdoors!), and vocal performers. In most cases I expect to be five to ten feet away from the performers, and sometimes I will be holding the microphone(s) in my hand. The Marantz portable stereo cassette deck I will be using has standard quarter inch microphone input jacks, with an input impedance of 10 kohms. Apparently there are two broad classes of microphones: low-impedance "balanced" microphones, and high-impedance "unbalanced" ones. The balanced microphones have a three-wire cable, apparently differential outputs and a ground; I've usually seen impedances of 250 to 600 ohms with these mics. I was told by a salesman that I could use a low impedance mic if I bought a cable with the 3 pin balanced connection on one end, and a quarter inch jack on the other. <Question #1: Does a large impedance mismatch between mic and recorder input primarily cause a loss of sensitivity, meaning I would have to increase the recording level control to a higher level than I would with a mic that matched the impedance? Will this, in turn, increase the hiss or noise present in the recording?> I was also told by the salesman that I could purchase an in-line transformer to convert the impedance at the input to the deck to match the mic. <Question #2: Are there any tradeoffs in using an in-line transformer? Altered frequency response? Do you lose the the low noise susceptibility benefits of the balanced mic?> Most high impedance mics have plastic bodies, while the more professional balanced output mics usually have thicker metal bodies. I'm told that some of the high impedance mics are prone to handling noise, where vibration from holding the mic in your hand is audible in a recording. <Question #3: Is body material the primary factor in whether a mic is likely to produce handling noise? Or is it possible that the better mics somehow shock mount the microphone element internally?> In general, the high impedance mics I have found have averaged less than $40 per channel, and the low-impedance, balanced mics have been $100 or more. The spec sheets lead me to believe that the extra money buys me wider, flatter frequency response better off-axis frequency consistency lower noise <Question #4: In general, is there any correlation between price and fragility? That is, the high-priced mics have very good specs, but does this imply that they usually are more sensitive to mechanical shock?> There are all kinds of mics available . . . instrument mics, vocal mics, choir mics, pulpit mics, and of course general purpose mics. I'm told that vocal mics have a special bass roll-off to make voices sound less boomy. <Question #5: Would a mic advertised as a choral mic be better suited than a "general purpose mic" for the distance (5' to 10') I intend to be recording from? Can general purpose mics such as the AT 813 be used at these distances with success?> I'd like to remain somewhat unobtrusive when recording, and the appearance of the low-impedance mics might put some folk performers off: they look TOO professional with their huge metal windscreens, etc. I think that the manufacturers dress up mics for rock applications where the performers want to look glitzy onstage. Partly for appearance, and partly for cost reasons, I lean toward purchasing a high impedance microphone(s) such as the Audio-Technica AT-9200. <Question #6: Are there any high-impedance mics worth considering? If I keep the cable length under, say, 10 feet will EMI susceptibility be a problem?> Finally, does anyone have any comments about the suitability of any of the following mics for my application (hand-held, 5'-10' distance, durable mic, 10k input impedance): Marantz EC-3 (hi-impedance, $42) Marantz EC-5 (hi-impedance, $58) Marantz EC-33S (hi-impedance, $38) Audio Technica AT 9200 (hi-impedance, $32) Audio Technica AT 9400 (hi-impedance, $50) Audio Technica AT 813 ($130) Shure SM57 ($86) Shure SM58 ($110) Shure 849LC (choir mic, $105) Nakamichi 300 (still looking for a source to purchase these from, too) Thanks in advance for your patience in answering a recording neophyte's questions . . . I look forward to answers from someone who isn't interested in trying to sell me something . . . Kurt Liebezeit (views expressed are those of the author only) klieb@tekigm2.MEN.TEK.COM ...!tektronix!tekigm2.MEN.TEK.COM!klieb