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Audio Technica AT4040 SM

Cardioid Condenser Microphone By Hugh Robjohns
Published September 2002

At a price point of around £300, there are already very good contenders for your money on the quality condenser mic market. Does the 4040 SM have what it takes to become a front-runner?

Audio Technica's 40-series professional large-diaphragm condenser microphones have established a fine reputation over many years — more than 10 years in the case of the classic AT4033. Indeed, the current AT4033a still represents a benchmark for many, being a sturdy, no-nonsense, back-electret transducer capable of producing excellent results with a wide variety of sources.

Audio Technica AT4040 SM condenser microphone.Photo: Mark EwingOther established 40-series stablemates include the switchable-pattern AT4050 and the valve-based AT4060, as well as the AT4047. This last uses a true externally-biased capacitor capsule with a transformer-coupled output, instead of the electret capsule and transformerless circuitry of the 4033. I'm making a point of presenting this lineage because the latest addition to the group, the AT4040 SM (launched at the Munich AES Convention earlier this year) sits halfway between the 4047 and 4033 models in terms of both technology and price.

The Package

The AT4040 SM is a fixed cardioid-pattern mic using an externally-biased, large-diaphragm capacitor capsule (just like the AT4047) but with transformerless circuitry (more like the AT4033a). The one-inch capsule employs a carefully tensioned, gold-sputtered diaphragm to provide "a smooth, natural sonic characteristic" and the surface-mount preamplifier electronics have been designed to provide low noise and a wide dynamic range, with a high SPL capability. Indeed, the specifications boast a 145dB maximum SPL (for one percent distortion) and a dynamic range of 133dB. The noise floor is slightly lower than the AT4033a's, and is certainly good enough for anything you are likely to want to use this mic for, although it remains a few decibels above the quietest mics available. A standard 48V phantom power supply is required for the mic, which produces a nominal output of 25mV at 1pa — pretty typical for the class of mic.

The 4040 SM ships in a vinyl-wrapped, foam-lined case, packed in a larger cardboard box that also contains the AT8449 elastic shockmount, supplied as standard. The review mics (I had the luxury of a pair) came without any manuals or technical notes at all, and I had to surf over to the Audio Technica web site for the published specs.

Design & Construction

The physical design of the AT4040 SM is shared with the other 40-series models, although it is the lightest of the bunch, at just 360g (thanks, mainly, to its output transformer). The nickel-plated brass body is painted black and features a large, dual-layer, wire-mesh grille in front and behind the capsule, accounting for about 60 percent of the microphone body's total height. The unusually large enclosed volume and symmetrical nature of the housing is claimed to minimise unwanted internal reflections.

The front of the mic is denoted by an AT logo, while at the base of the body, around at the back and almost flush with the surface, are a pair of white plastic slide switches. The left switch activates a first-order, high-pass filter turning over at 80Hz, while the one on the right introduces a 10dB pre-attenuator. The output XLR connector is contained within a 'stalk' protruding from the base of the microphone, and the microphone's serial number is concealed inside this XLR socket. I am amazed at how few manufacturers are bothering to put serial numbers on their products these days, and am glad to see Audio Technica maintaining this important security feature, even if only in the form of a sticky label on the base of the XLR connector.

The bare mic seemed relatively sensitive to handling noise, so I was pleased that a decent shockmount is bundled with it at no extra cost. Fitting the mic to the mount is a little fiddly, as an elastic band (for want of a more technical term) has to be encouraged to fit around the diameter of the mic body at its base — an action hampered by the lower part of the shockmount. However, once it was installed the mic felt secure and was reasonably well isolated from mechanical stand vibrations. The shockmount stand adaptor has a 5/8-inch thread, but a plastic insert is provided to accommodate the European standard 3/8-inch thread.

As I hinted earlier, the AT web site provides a reasonable amount of technical information about the AT4040, part of which is a generic frequency-response plot and a fairly pointless polar response chart. The published frequency response suggests that the mic is extremely flat between about 20Hz and 4kHz. Above 4kHz there are a couple of significant peaks in the response, centred roughly at 6.5 and 11kHz, reaching about 5dB at their maxima. It is interesting to note that similar peaks are also present in the AT4033a and SE models — although slightly less pronounced — and are hinted at on the plot for the AT4047. The obvious conclusion is that these are probably a characteristic of the capsule and/or housing design.

The high end seems to roll off quite quickly above about 16kHz — not that my ears do much above that frequency — but Audio Technica claim the overall response extends between 20Hz and 20kHz (without giving any limits). The published polar response shows a very tidy, classic cardioid response, but at only a single frequency, of 1kHz.

Road Test

Listening to the AT4040, it sounds clean and quiet, giving the impression of crisp detail combined with a fairly warm bottom end. These are familiar AT traits. The polar response is much as would be expected for a large-diaphragm mic, in that it tends towards a hypercardioid pattern with increasing frequency, growing a distinct rear lobe. At low frequencies, the polar pattern seems to open out considerably, tending towards the omnidirectional, and moving around the sides of the mic causes the sound to become fuller and less bright, as the low end remains more or less equally sensitive while the mid and high end fall in sensitivity. This characteristic is predictable and can be used to advantage when close-miking sound sources, by making small changes of angle to alter the sound quality.

I found the AT4040 worked well when used to close-mic a grand piano, providing good weight and excellent transient detail. It was also effective on six-string acoustic guitars and general percussion duties — again, because of the decent transient response, I suspect. On voices I found it sometimes worked better than a more expensive Neumann TLM103, but this depended on the character of the voice. The AT seemed to emphasise mechanical noises more than the Neumann on occasion.

However, overall the AT4040 SM is an excellent, well-specified and well-equipped microphone, offered at an attractive price. At a similar point in the retail market the AT4040 will probably find itself being compared against models such as the AKG C3000, the Beyerdynamic MCE90 and the Rode NT1, only the last of which is a true externally-biased condenser in the same vein as the AT. The AT4040 will certainly take sales from this competition and deserves serious consideration from anyone planning to invest in a new microphone at this price level.


  • Externally-biased condenser capsule.
  • Good transient response.
  • Warm, yet detailed sound.
  • Supplied with shockmount.


  • High-frequency response irregularities.


Audio Technica's latest addition to the professional 40-series replaces the 4033's electret capsule with a true externally-biased condenser element, yet retains the transformerless electronics of its sibling. With low noise, a wide dynamic range and a healthy output, this large-diaphragm microphone sounds detailed, fast and smooth, and compares very favourably with its competition.


£299.95 including VAT.

Audio Technica +44 (0)113 277 1441.