AKG's new range of dynamic vocal and instrumental mics incorporates some interesting design concepts, and is designed to stand up to life on the road. But surely there are already more than enough dynamic mics on the market? Paul White explains why the Tri Powers deserve some serious attention.

When it comes to capacitor microphones, there are certain models which are rarely seen outside the studio; no such distinction seems to exist for dynamic models — it's common to see exactly the same mics being used on stage as in the studio. AKG's new Tri-Power range seems aimed at both areas of performance, stage and studio, and is certainly distinctive in appearance, all the mics in the range having a smoothed, triangular cross section, the casings being made from die-cast alloy. The idea for this shape came about after examining the natural shape of a closed hand, which suggests that a triangular handle is the easiest to grip.

There are four hand-held vocal mics in the range, all adaptations of the familiar ball-on-a-stick styling, plus three instrument mics, which are squat and chunky with inbuilt swivel stand adaptors. But new outward styling on its own doesn't make for a great microphone, and AKG have put a lot of thought into what you don't see. In order to produce a high output signal, the microphones are built using a proprietary Neodymium/Iron Boron magnetic system, optimised using computer modelling techniques. Likewise, the diaphragm design came about after studying the motion of various diaphragm structures using holographic analysis. Such tests can be very valuable because, under varying conditions, a typical microphone diaphragm will depart from true piston motion and exhibit modal vibrations which cause non-linearity and hence distortion.

Previous neodymium-based microphones have been criticised for having a slightly 'honky' sound, due to artificial exaggeration of the extreme high and low frequencies, but AKG have opted for their own equalisation curve, which they call 'Vocal Contoured'. This is intended to give a tighter sound with plenty of brightness but without obvious colouration. The vocal capsules also have a fairly tight, hypercardioid pickup pattern but with a decent off-axis response.

To minimise handling noise, the D3900 and D3800 vocal microphones use a Moving Magnet Suspension, while the other models use a system known as IsoDamp, which effectively allows the capsule to absorb shock in all three dimensions.

There are seven microphones in the complete range, four vocal mics and three instrument mics, so rather than attempt to cover them all in detail, I confined my more rigorous tests to the D3600 instrument mic and the D3900 vocal mic. All three instrument microphones have the same outward appearance, while the four vocal mics differ only very subtly from each other in cosmetic terms.

D3900

Like most hand-held vocal mics, the D3900 is a dynamic, cardioid model, in this case with a tight hypercardioid response. It differs from the D3800 only in that it has integra frequency-contouring switches, providing bass roll-off below 100Hz and a degree of top boost which takes the useful response right up to 22kHz. Because the microphone has a high immunity to handling noise, the bass-cut system is less fierce than on most models, which should produce a more natural sound.

The top end response is high for a dynamic microphone, even a Neodymium alloy-based model and is, I suspect, achieved only because the microphone has been designed with a broad presence peak centred at around 5kHz. Without this degree of boost, which amounts to around 6dB at 5kHz, the high frequency roll-off would start somewhat earlier. The response is characterised by a gentle rise starting at around 2kHz, with the response dropping away again above 16kHz or thereabouts.

The design of the microphone has several interesting points, not the least of which is the way in which the grille is attached. By pushing down on the grille and turning anticlockwise, it can be detached from its bayonet-style fitting and the loose foam insert may be removed for cleaning. I understand that the pro touring companies soak their foam shields in Listerine! Also eminently sensible is the fact that the grille assembly is not rigidly mounted to the body, but sprung to some extent, which makes the microphone much better able to withstand shock if dropped basket-first onto a hard surface.

Inside, the capsule utilises AKG's own Moving Magnet Suspension, which attenuates the handling noise to a useful degree — the idea is that when the mic is subjected to shock, the diaphragm and magnet tend to move together, which reduces the level of unwanted electrical output. There's also a humbucking coil arrangement which cancels out electromagnetic interference such as mains hum and dimmer noise.

A standard XLR connector is used to link the mic to the outside world via a standard mic cable, the electrical output being balanced, low impedance. The electrical sensitivity is quoted as being 2.5mV/Pa at 1 kHz, which compares favourably with other good dynamic microphones, though it is still far less sensitive than a typical capacitor microphone.

D3600

Though all three instrumental microphones appear physically similar, the D3600 is the odd one out, in that it has not one but two capsules, mounted in an IsoDamp isolation system. One capsule is forward facing and handles only the high frequencies, while the other is mounted behind it, facing into the body, to pick up the bass end. The outcome is a microphone that exhibits very little proximity response and has a wide, relatively flat frequency response ranging from 20Hz to 22kHz. The other two models have similar high frequency extension but are designed to roll off steadily below 200Hz, presumably to compensate for the fact that these models exhibit the same degree of proximity effect as most other conventional dynamic cardioids.

In shape, the mic rather resembles a grenade, except that it has an integral stand adaptor which folds flush into the body for packing. This is coupled to the rest of the body via an elastomer suspension to provide another layer of protection between the microphone capsule and the shocks of the outside world. I was pleased to note that the adaptor had a smooth but stiff movement which was easy to set yet stayed where I put it.

Unlike the vocal models, the presence peak on this microphone is far more subtle, amounting to around 4dB in the 3-5kHz region. The capsule has a cardioid rather than hypercardioid response and provides a response that is almost ruler flat from 40Hz up to 1kHz, where the presence rise starts to take off. Because of the extended bass response, a bass rolloff switch is provided, which starts a very gentle roll-off just below 1kHz. Sound Pressure Levels of up to 156dB can be accommodated with only 3% THD, making the D3600 eminently suitable for use with drums, including bass drums, as well as brass instruments and loud guitar stacks. Its sensitivity is only slightly less than for the D3900 at 2mV/Pa at 1 kHz.

In use, the D3900 proved itself to be a serious vocal microphone which could equally find use in the studio for vocals and secondary tasks such as electric guitar recording. It has a warm, confident character but with sufficient openness of sound at the top end to provide good vocal articulation. Though not designed as a clinically accurate microphone, I feel the over-used term, 'musical' could be applied here with some justification. Handling noise turned out to be low, though I'd still go for stand mounting in the studio, and even though you might expect the triangular body to be a problem when it comes to mic clips, I found it sat quite securely in a standard clip designed for a circular mic body. A suitable clip is provided with each of the vocal mics and all the mics are supplied in rugged, plastic carrying cases with foam inserts. Though unorthodox, the handle shape is quite comfortable to hold, though I've never had any real complaints about round mic handles, and the tapering of the body helps keep the hands away from the circular port slits, which form an essential part of the acoustic system in tailoring the directional response of the capsule.

I found the D3600 quite a surprising microphone in that it had a far more open, extended sound than I've come to expect from dynamic models — undoubtedly due in part to the dual capsule approach. Normally I'd never use a dynamic for recording acoustic guitars, because of their lack of HF detail, but this fared very well and also proved sensitive enough so long as the instrument was played with enthusiasm. It produced a very even, well-balanced sound and also proved itself a very worthy vocal microphone. Indeed, in the studio I preferred it to any of the dedicated vocal mics as it seemed to give a more open and subjectively more accurate sound.

Summary

You really have to handle this range of microphones for yourself to realise just how beautifully engineered and stylish they really are. The easily removable grilles and washable foam shields are excellent, while the overall aesthetic really appeals to me. In price, the range extends from mid-priced vocal mics right up to what you'd expect to pay for a very serious dynamic microphone, and in the case of something like the D3600, a very serious microphone is what you get.

For stage use, the improved capsule suspension, sprung grille baskets and generally good sound are all strong selling points, but to write these models off for studio use simply because they have so many good live features would, I feel, be a big mistake. While vocals are often handled by capacitor microphones in pro studios, there are singers whose voices work better with dynamic models, and for the smaller studio, dynamic microphones are significantly cheaper than any of the big-name studio capacitor models. For brass and drums, there are a great engineers who would opt for dynamic mics regardless of cost, purely because of their hard-hitting sound, and I feel the D3600 in particular could excel in a variety of studio applications.

Brief tests on the whole range confirm that even the less costly mics have the same family air of quality about them while, for my money, the D3600 is the best of the lot. If I had to go out and gig for a living, then come home and record vocals, electric guitar, bass, brass and drums — all with the same mic — the D3600 is the one I'd want to hang on to.

Further Information
AKG Tri Power mics: D3400, £158.99: D3500, £178.99: D3600, £268.99; D3700, £138.99; D3700S, £148.99; D3800, £228.99; D3900, £279.04. All prices include VAT.

AKG Acoustics, (Contact Details).