AKG D7

Just when we thought stage, dynamic mics had evolved about as far as they were going to, companies such as Heil, Rode and Telefunken demonstrated that there was still extra mileage to be had without turning to capacitor technology. Most improvements come about by refining diaphragm materials to make them lighter and stiffer or by improving the magnetic system. AKG’s contribution, in the case of their D7 supercardioid vocal mic, includes the use of a new laminated diaphragm material, ‘Laminated Varimotion Diaphragm Technology’, which, it is claimed, allows the D7’s frequency response to be optimised without the need for extra tuning resonators. As I understand it, this technology also allows the diaphragm thickness to be varied across its diameter so the mass can be minimised while still maintaining adequate stiffness. In theory, this should produce a more natural-sounding top end, as lighter diaphragms respond better to high frequencies. The design also includes a new capsule mounting system, which employs both mechanical and pneumatic means to isolate the capsule from vibration.

Supplied in a heavy-duty zip-up fabric tube, the mic is outwardly conventional with a substantial cast body and a spring steel wire-mesh grille that is more resistant to denting than plain steel grilles. Two versions of the mic are available: one with switch (D7S) and one without. All exposed parts other than the silver ring around the basket are finished in a matte blue/grey metallic paint. The inside of the basket is lined with acoustic foam, and the head simply screws off so the foam can be pulled out and dunked in your favourite antiseptic mouthwash for cleaning.

Unscrewing the basket reveals an elaborate capsule mounted in a fairly soft suspension, which allows both lateral and vertical movement. An exposed coil sitting on top of the capsule acts as a humbucker or hum canceller, and there’s also a fixed 80Hz low-cut filter to minimise the proximity effect and to reduce the risk of popping or low-frequency noise pickup. The output from the mic is via the usual balanced XLR connector, but this may be used unbalanced if necessary as long as the cable is kept sensibly short. Overall dimensions are a comfortable 185.2 x 51mm with a weight of 340g, translating to a well-balanced mic that feels solid, but not excessively heavy.

On the spec front, the mic claims a nominal 70Hz to 20kHz response, though if you go by the traditional -3dB points, this is more like 180Hz to 16kHz, which is pretty much what you’d expect for a good dynamic vocal mic. At 20kHz the response is down by something approaching 15dB, according to the graph provided. As with most vocal mics, there’s a presence peak built in to help the sound cut through a busy backing, and here this takes the form of a broad hump between 5kHz and 10kHz, rising only 3dB or so at its maximum height. In theory, this should help with projection without making the sound seem too harsh, which can be the case with a narrow presence peak in the 4kHz region.

The sensitivity of the mic is comparable with other dynamic models at 2.6mV/Pa, and the maximum SPL is 147dB for one percent distortion or a massive 156dB for three percent distortion. That means the mic should be happy with just about anything short of being shot!

It is sometimes assumed that dynamic mics, being passive, make no noise contribution, but all resistive sources produce noise unless kept at a temperature of absolute zero (-273 degrees Centigrade), which is generally regarded as being too cold to give one’s best performance! The D7 has a quoted EIN noise figure of 18dBA, and its 600Ω impedance is designed to run into a mic input with an impedance of around 2kΩ — again typical of a live sound mixer or studio preamp. Given that live vocal mics are used very close to the singer, the self-noise of any well-designed dynamic microphone is simply not going to be an issue, and in reality the mixer input stage is likely to contribute far more noise than the microphone. When placing stage monitors, it should be borne in mind that this is a supercardioid mic, so the ‘dead’ spot is around 45 degrees off from the rear axis, rather than directly behind the mic, as is the case with a regular cardioid model.

Before hooking up the mic to a PA system, I checked it by doing some voice recording in the studio, just to see what its real tonality and susceptibility to popping was like. It was recorded flat with no additional low-cut filters and managed a pretty natural sound with an open, but not aggressive high end and a surprisingly good resistance to popping. The sound warms up if you get right on the mic grille, due to the proximity effect, but not excessively so. Predictably, the high end wasn’t as ‘airy’ as with a capacitor model, but for a dynamic mic it actually performed rather well, so I was keen to try it in a live situation.

A few days later, we took the mic out to a gig, where it was used by Alan, our singer/bass player. We often have problems with getting adequate level without feedback, and when we use a system with subs, popping is sometimes a significant issue with our existing mics. Fortunately, the D7 behaved well in both respects, delivering an adequate level of clear and well-balanced sound with no significant popping problems. If used hand-held, the handling noise is also adequately low, though we had to use it on a stand due to Alan’s inability to play bass with just one hand! For the rest of the evening we simply forgot about the mic and got on with the performance, which is how it should be. If a mic draws attention to itself, it is probably doing something it shouldn’t be doing.

The list price of the D7 is a little above that of its obvious competitors, but as always in the music business, the street price tends to be somewhat less. Personally, I think it is well worth spending a bit extra on a good vocal mic, as with care it will last decades and can make all the difference between a disappointing gig and a well-balanced one. We’ll definitely be buying this one for the band! 0

AKG D7

Dynamic vocal microphone