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Microtech Gefell M 930 and SH 93 X-Y Bar, May 2003
May 14, 2004 12:00 PM, By Ty Ford
In August 2000, I reviewed the Microtech Gefell M 930 large-diaphragm cardioid condenser for Mix. Now, the company offers the SH 93, a stereo mic-mounting accessory that simplifies X-Y pattern setups.
The M 930 sounds a lot like the Neumann TLM 103. The two share a 7dBA self-noise, which makes them among the quieter mics on the market. In low-noise studio environments, this comes in handy when miking quiet voices and instruments.
Celtic harp, for example, usually needs all the help it can get, especially if you subscribe to the theory that you must mike it from a distance to capture the whole instrument. Quiet voices for spoken-word recordings also benefit from the M 930's low self-noise, especially if the tracks are going to be heavily compressed and then digitized to one of the many data-compressed audio file formats. The quieter the mic, the less noticeable the rising self-noise.
The M 930 has a 21mV/Pa sensitivity. This means that you don't have to use as much preamp gain to achieve a good level. In fact, with much louder sounds, you might need to pad the output of the M 930 to keep it from overdriving the preamp. Even though the M 930 has no pad or roll-off, it can withstand 142 dB before reaching a THD of 0.5%.
IN THE CHURCH
During some recent recordings of a madrigal group I work with in a church, I used a kit comprising a frequency- and phase-matched pair of the M 930s with the SH 93 X-Y stereo bar and a pair of MH 93.1 mic clips ($2,350 retail). The stereo mic bar lets you mount both mics on one stand. Laser-etched angle engravings on the bar and the mics allow precise, repeatable setups.
The large church had a vaulted 40-foot ceiling and an altar-to-back distance of several hundred feet. To the naked ear, the church sounds fine; however, the M 930 through GML mic preamps to a Panasonic SV 3900 DAT machine to my Sony MDR7506 headphones told a different story. There was a definite LF “huuunh” presence, probably the result of being a quarter of a mile away from a four-lane suburban thoroughfare.
The M 930 capsule is quite sensitive to very low LF sounds. As a result, I could also hear heavy footfalls in the carpeted congregation area through the mic stand, even though it was resting on a down-filled parka on the wood floor up in the chancery. If you intend to use the M 930 in environments where LF physical vibrations may be a problem, then get the EH93 suspension mounts ($215/each) to reduce the amount of LF transmission through the stand.
Gefell also makes the TD 93 tandem ORTF mic holder, and you can choose the M 940 hypercardioids for either array. I didn't have them to compare, but the specs show that they roll off on the bottom a dB more steeply, starting at 200 Hz. The M 930's 6kHz to 15kHz presence peak is also less accentuated with the M 940.
IN THE STUDIO
In the studio, I transferred the M 930 DAT tracks to Pro Tools, imported a section of the LF noise floor into SparkXL and found it between 164 Hz and 20 Hz. I used a -6dB shelf at 54 Hz to trim the unwanted LF presence. Ironically, if the M 930's self-noise were higher, the LF content in the room would probably not have been as noticeable.
In the more controlled environment of the studio, the extra low end of the M 930 can be put to better use. I set the mic bar about a foot out from my 1972 rosewood D28S Martin and positioned the mics. Calibration markings on both the M 930s and the mic bar made for quick alignment. I fed the two M 930s to an Aphex 1100 2-channel preamp/A/D converter. I didn't use LF roll-off on the Aphex 1100. Then, I positioned the mics so that they would look up and down the body of the Martin and so that each mic picked up the same amount of signal.
On playback, the Martin was big on the bottom, but not woofy as it usually is without roll-off. A bit of compression and minor LF EQ tucked the low end in nicely, allowing the Martin to take up most of the space with a wide, unexaggerated stereo presence. Even though the strings weren't new, the mics provided a hint of sparkle.
Based on my experience with this set, I would also expect them to do a great job on acoustic bass, viola or cello, where the X-Y pattern could capture the different frequencies that radiate from different surfaces of those instruments.
A pair of phase- and frequency-matched M 930s and the SH 93 X-Y bar make stereo recording easy and precise. The Gefell M 930s are definitely up to the task, but opt for the suspension mounts if you'll be stepping out of the studio.
Microtech Gefell, www.gefell-mics.com
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