Can these two low-cost back-electret mics really deliver studio-quality performance? PAUL WHITE finds out.

Audio Technica are definitely in the big league when it comes to microphones and I think it's fair to say they're one of the few Japanese companies to have achieved the same 'solid' image as the top European and American mic manufacturers. This success can, in the main, be credited to the AT4033 studio mic, and more recently to the AT4050 multi-pattern studio mic, but what may be less well known is that Audio Technica also build relatively low-cost back-electret mics such as the two under review here.

The ATM33a is a cardioid back-electret mic that can be operated either from a single AA battery or conventional phantom power, and the ATM10a is in many ways similar, but has an omni pickup pattern. Both mics are part of the Artiste Series, and as the name suggests, they are rugged enough for live performance, but their extended frequency response suggests that they might also be useful in studio applications where dynamic mics often have insufficient high-end sensitivity.

These mics utilise very thin, gold-vaporised diaphragms, much as in conventional capacitor mics, and while they are not as sensitive as most true capacitor models, they are rather more so than typical dynamic models, generating 6.3mV ref 1V at 1Pa when used with phantom power and 5.6mV when run from battery.

Physically, the mics are slim yet very solid, rather like Maglite torches, and they come with a stand clip and soft carrying case. There are no on/off or pad switches, and the only significant cosmetic difference between the two is that the cardioid model has side grilles on the capsule to allow the porting to work, which results in it being slightly longer. The capsule itself is held in a reasonably effective shockmount which helps minimise handling noise in a live environment, and the lower section of the body unscrews to reveal the battery compartment. Connection is via a conventionally wired XLR.

The frequency response of these mics is nominally flat with a slight presence lift above 5kHz, and an upper limit of 20kHz for the cardioid model and 18kHz for the omni. As dictated by the physics of microphone design, the cardioid model exhibits a proximity effect, which causes a rise in the bass response if the mic is used very close to the sound source. Omni models do not have this characteristic. The lower frequency limit is between 20 and 30Hz, a range in which popping is likely, and although foam pop shields are provided, they are only really adequate for stage work, so I would recommend that separate pop shields are used in the studio.

These mics are adequately sensitive for most close-miking jobs and have a good enough HF response to do justice to acoustic guitars, cymbals and so on. Tonally, the sound is subjectively uncoloured, and although the top-end detail is no doubt enhanced by the deliberate presence peak, this doesn't extend far enough down the spectrum to introduce any harshness.

For comparison I dug out my faithful AKG C1000S (which has given me many years of stirling service), and did a straight A/B test. Surprisingly, the ATs were more sensitive by several dBs, but it is possible that my old C1000S is feeling its age now. Tonally, the ATM33a is very solid and warm when used fairly close up, but has slightly more 'cut' than the C1000S, presumably because of its presence characteristics. I was actually very happy with its balance of warmth and detail.

By comparison, the ATM10a sounded decidedly less warm -- but I then realised that the difference was almost entirely due to the lack of proximity effect. Used at a distance of a couple of feet, the two AT mics sounded reasonably similar, but as I moved closer to the sound source, the cardioid gradually took on more warmth, while the omni sounded far more consistent.

Given the low cost and overall sound quality of these mics, they can be highly recommended for both studio and live performance applications, as well as for live recording. The signal-to-noise spec of 70dB is very respectable, and the build-quality of the mics is excellent -- they are both elegant and tough. Having the choice of battery or phantom power use may be a deciding factor for those working with cassette multitrack systems that don't provide phantom powering, and those of you with non-standard phantom powering systems will be pleased to note that these mics will work happily right down to 9V. The battery life of a premium alkaline battery is in excess of 1200 hours, but as no switch is provided, the battery is effectively on all the time, giving a practical life of around seven weeks unless it is removed between sessions.

Is there a catch? If anything, the ATM33a and ATM10a fall slightly short in the dynamic range department; the figure is 113dB, or 99dB when powered from batteries, so these are not the ideal mics for close miking drums or for sticking down loud brass instruments. In all other applications they should be able to cope admirably, and a pair of either would make good drum overheads (although I'd be inclined to use phantom power in this case, just to make sure I had enough dynamic range in hand). Given that these mics cost about the same as a typical dynamic stage mic, they have to be considered excellent value. They might not sound as refined as a top-end studio mic, but you might be surprised at just how close they get.

OMNI OR CARDIOID?

Most users will probably find the cardioid model most versatile as it will help maintain separation in a small studio, as well as add warmth to close-miked vocals. However, omnis are useful as drum overheads, or in applications where the sound source is relatively wide, as may be the case when recording a choir or ensemble with a spaced stereo pair. The main benefit of an omni mic is that off-axis sounds are generally captured more accurately than they are with a cardioid model.

pros & cons

AUDIO TECHNICA ATM33A £150
& ATM10A £120

pros
• Low cost.
• Excellent standard of construction.
• Well-balanced sound.
• Battery or phantom power operation.

cons
• Dynamic range may be too low for close drum work,
especially when battery operated.

summary
These are very cost-effective, general-purpose mics
that have a nice vocal tonality as well as the necessary
HF response to do justice to acoustic instruments.

£ ATM33a £149.95; ATM10a £119.95. Prices include VAT.

A Audio Technica, Technica House, Royal London Industrial Estate, Old Lane, Leeds, LS11 8AG.

T 0113 277 1441.

F 0113 270 4836.

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