Despite offering a comprehensive range of microphones, including some very high specification models, Audio Technica have never quite made it into the 'big name' league in the UK. One reason for this may perhaps have been the lack of a 'flagship' condensor model, aimed primarily at studio vocal recording. This is always a high profile application, with very few models seemingly able to sustain a serious challenge to the fashionable established names. Habit, prejudice, or the simple comfort of predictability born of experience, tend to steer the engineer or producer away from experiment in this area — vocal performances are rather ephemeral, so there is always the fear of getting a great take via an 'adventurous choice' that you wish you hadn't made.

PRECISION MANUFACTURE

Audio Technica's latest challenge to the old favourites is their AT4033 fixed-charge cardioid condensor, a dedicated vocal and speech recording model, utilising an extremely lightweight diaphragm to offer a combination of high sensitivity and excellent transient response, in conjunction with high SPL handling capability. 'Fixed-charge' is just another way of indicating 'permanently polarised' or 'electret' operation. Mics using this principle used to have an inherently limited performance, but the development of the charged back-plate enabled a much lighter, and therefore more responsive, diaphragm to be used, allowing them to compete with 'true' condensors. Some of the finest mics available now employ this principle.

The 4033 achieves an extremely low moving mass by employing a diaphragm with a thickness of just 2 microns. The long-term stability of the physical properties of the material is ensured by a temperature and humidity-based pre-aging process prior to installation in the capsule assembly. To create the necessary conductive surface, a layer of gold effectively just a few molecules thick is then vapour deposited, ensuring uniform coverage whilst adding the minimum mass to the final structure. Whilst this sort of precision is not at all unusual in the manufacture of modern high-quality studio microphones, it does normally command a premium price — the AT4033 offers its qualities at a significantly more economical rate.

In common with the majority of 'studio' models used for vocals, the AT4033 has a fairly substantial housing, finished in an attractive non-reflective black chrome. The cardioid polar pattern is achieved by a single diaphragm, pressure gradient configuration, and a high-pass filter (80Hz 6dB/oct) can be switched in to counteract the consequent bass rise due to the proximity effect. A switched 10dB pre-attenuation pad is also, incorporated, to protect against pre-amp overload in very high SPL applications. The AT4033 is particularly well specified in this area, with an impressive maximum SPL handling figure of 143dB (@1 kHz, 1 %THD).

The AT4033 appears to utilise a slightly smaller capsule diameter than some of its rivals in this field — a larger diaphragm will have an inherently greater sensitivity, but must also have higher mass, whereas a smaller diaphragm may, in theory, offer extended frequency response and low distortion. Unusually, there is an integral pop-shield of open cell foam between the diaphragm and the front grille, although I still found regular levels of further protection necessary on a vocal. The 'live' side of the mic, designed to operate with its long axis in the vertical plane (sometimes referred to as 'side-fire') is indicated by a discrete Audio Technica logo on the housing. Mounting is via a conventional stand clamp, or a more sophisticated tensioned-rubber, shock-mount cradle (AT8441), although the floating capsule suspension system seems to have endowed the AT4033 with inherently good isolation from mechanical noise and vibration.

The electronics employ a direct-coupled, transformerless (electronically balanced) design, aiding signal integrity, and offering a low self-noise figure of 18dB SPL. Output (250 Ohm impedance, recommended load >1kOhm) is by means of a standard XLR3(M) at the base of the housing, and 48V external (phantom) powering is required (+/-12V).

IN USE

The AT4033 was quite a revelation in use, displaying an unexpected warmth and transparency. Absolute frequency extension and behaviour at the roll-off points are not really so critical in a mic intended primarily for vocal applications (although the AT4033 has a highly respectable 30Hz-20kHz nominal range). What does matter is smoothness through the vocal range, which the AT4033 certainly has, lending a characteristic delicacy and detail to its pick-up, without ever sounding unnaturally bright. I hesitate to use the word impressive, for in a direct comparison, it is the 'voiced' model with the flattering presence peak that often sounds initially more appealing, but the more neutral response ultimately offers greater openness, which can, on occasions, be more appropriate.

Being a cardioid, the precise amount of artificial depth can be tuned by distance. I found an average working distance of about six to nine inches to be the optimum, although this will vary with singers and styles. Level was never a problem during testing; the mic seemed to maintain its effortless, clean sound regardless of SPL. Electronically, the unusually high output level (1.8mV for 74dB SPL, -35dB, ref 1V) of this model should help to maximise the performance of any mic amp it might partner. Although high sensitivity is perhaps not a primary consideration in a mic which will normally be used close to the source, a high quality condensor model like the AT4033 could in fact have many uses beyond just vocal applications.

The off-axis response exhibits no damaging anomalies whatsoever. The same impressively smooth output, merely at reduced sensitivity, is found at angles of incidence just out of the normal frontal working area, in the horizontal plane. The importance of the physical properties of microphone housings in generating diffraction and interference effects is now appreciated as never before — the AT4033 has been designed to minimise these effects, with a simple, symmetrical open-weave mesh surround. The theoretical ideal in this respect is an infinitely small, open capsule, which will therefore cause the minimum disturbance of the sound field it is picking up. In the real world, a large diaphragm cardioid, with suitable physical protection, is going to have to be something of a compromise, but it is good to see practical evidence of a greater awareness of this aspect of microphone design.

VERDICT

Audio Technica's new fixed-charge condensor mic is a high quality performer in every way, offering tonal neutrality, controlled directivity, high sensitivity, and good SPL handling, in a single economically priced package. It represents an attractive alternative to a 'big name' model for the private studio, where the absence of the risk of client prejudice encourages more adventurous selection. Commercial studios will get them when producers start wanting them; producers will only start wanting them when they have heard one in use. I am not quite sure how you break out of that cycle — a rave review perhaps? The AT4033 is an excellent model, and I unhesitatingly recommended that you include it in any future microphone evaluation.

Further information

Audio Technica AT4033 £435 inc VAT.

Audio Technica, (Contact Details).