The news that Shure were to issue two new microphones in the guise of upgraded versions of those venerable old classics the SM58 and SM57 came as something of a surprise, for despite their ageing design a recent UK studio survey found that 76% of those polled were still using SM57s, with 61% owning an SM58 or two. Of those who were willing to express a preference, without attaching it to a specific application, a clear majority cited the SM57 as their first choice dynamic mic, with the runner-up being the SM58, of course, and the rest nowhere. Just how does an unassuming dynamic cardioid, apparently developed primarily for live performance use, achieve such a large slice of the action in the recording field? Does it deserve it? And if so, why do we need these new Beta models?

CLASSIC STYLING

The Beta 58 is styled exactly in the manner of its classic forerunner (to have done anything else would surely have been a grave error), with only the lighter colour scheme and modest Beta badge to give away the fact that you are looking at the new model (although a flashy chrome finish ball-end is now an option for those of more dubious taste). The Beta 57, however, has acquired a distinctive new steel grille, with a square end and slotted sides, that leaves it closely resembling the short-lived (but much-loved, at least by me!) Unidyne IV. This grille is reputedly machined from extra strong, dent-resistant steel, which should effectively remove perhaps the one area of physical weakness in the original design. Namely, the fact that if you dropped it enough times you could eventually break the top off!

The original SM58 is renowned for being a design with which you could hammer in nails, without either denting it or affecting its performance, so there was probably quite rightly felt to be little scope for external improvement there. Inside, however, is a different story. An entirely new capsule design, incorporating neodymium alloy magnet (neyodymium-iron-boron), and a directional tuning network, claims enhanced performance in all significant areas. With frequency response extended, polar response tightened, sensitivity increased, as well as handling and induced noise lessened, it will be evident that this is no mere cosmetic upgrade. Neodymium can produce a more intense magnetic field than most other magnetic materials and the improved efficiency of the voice coil that this offers creates all sorts of benefits for the designer. Higher output gives increased sensitivity, or he can use less wire in the coil to make a lighter diaphragm assembly resulting in better high frequency performance, whilst the possibility of employing a physically shorter capsule allows greater freedom in the area of acoustic ducting and porting (which endows the mic with its directional characteristics).

DIRECTIONAL PROPERTIES

The Beta 57 and 58 are both described as supercardioid - a sort of hybrid between a true cardioid and hypercardioid. The true cardioid offers maximum rejection at 180 degrees off-axis, ie. from directly behind. This does, however, leave a considerable degree of side area pickup. The hypercardioid trades off vastly reduced side area sensitivity and high directivity for the creation of a rear 'lobe' or pickup zone. The supercardioid design employed here perhaps represents the best compromise between these two, accepting a small rear lobe in combination with low side area pickup, which creates a polar pattern with two areas of maximum rejection at 60 degrees to the rear.

In practice, a rear lobe is never as feedback-inducing as you might expect, for the capsule is always shadowed by the body of the mic and often the hand of the performer as well, leaving the rear response usually devoid of higher frequency content. As the original SM57 and SM58 were regular cardioids, Shure actually make a point in the supplied literature of recommending a specific monitor placement for the Beta models, with wedges being better placed at 120 degrees rather than the usual optimum spot of 180 degrees. But in testing, I must admit, I could induce no feedback anomalies anywhere at all in the rear arc.

FREQUENCY RESPONSE

The way in which a microphone's frequency response varies with the angle of pickup is one of the most important factors in determining its usage. A directional model will always exhibit some degree of narrowing at high frequencies, but where this extends into the midrange, or the transition is not particularly smooth, then such 'off-axis colouration' can become a significant cause of feedback or spill, or create difficulties with tonal changes if the source is unable to maintain a constant aspect in relation to the mic. Both Beta Series models exhibit an outstanding polar diagram for a directional moving-coil design. The Beta 58 claims a pickup pattern that is still in good shape at 10kHz, and practical testing certainly bears this out. The Beta 57 shows a fraction more narrowing at the limits of its response, but the transition is smooth and barely perceptible in actuality.

The practical result of such a uniform polar response is a very low tendency to provoke feedback and the best possible separation. Reference to the polar diagrams in the spec for the original SM58 shows how it loses its shape a little, in the classic manner, with high frequencies narrowing and low frequencies spreading, yet this mic is renowned for its strong performance in this area, and there is no way it can be rubbished by comparison. The fact is, the new model is outstanding.

Quoted on-axis frequency response of both Beta models is 50Hz to 16kHz, showing a slight high frequency extension over the original models, but as usual the figures tell you very little about the actual performance of the mic. Ruler flat response and neutrality are not quite such an asset in a hand-held vocal mic, and it is the deviations in response that gave the SM58 its renowned 'powerful' vocal sound. A double presence peak - the first one quite smooth and centred between 5 and 6kHz, the second rather sharper and fixed at 10kHz just before the response falls away steeply - gives great clarity and definition to voices, and this feature is faithfully reproduced in the new model. The Beta 58 is very smooth through the midrange and appears to have lost the very slight dip at around 500Hz exhibited by both the old SM58 and 57. As with its previous version, the presence peak of the Beta 57 is centred slightly further down the frequency spectrum, begins its rise earlier, and although greater in amplitude has less of a marked signature than its companion model. It is more of a plateau than a peak, really, and gives the Beta 57 its characteristic combination of smoothness and punch.

The low frequency response of models primarily intended for close miking applications is always tailored to counteract the enormous bass boosting of proximity effect, which can be as much as +10dB at 100Hz. This may not be entirely 'natural', but much of the warmth that we associate with a good vocal sound comes from proximity effect; the task facing the designer is to retain the right amount of bass boost without allowing it to become overpowering. The Beta 58 rolls off gently from around 200Hz to be more than 6dB down by 50Hz. As before, the Beta 57 is slightly more extended in the bass, starting to roll off at nearer 100Hz, although it still betters -6dB at 50Hz. In fact the old 57, although overall less extended at low frequencies than the new model, had a slight bass rise in the region of 200Hz which balances its rising upper response.

It is good to see that the 'improvements' made to the new Beta models in the area of frequency response have lost none of the essential features of the originals, but rather enhanced the characteristics that have made them so outstandingly successful.

NOISE ABATEMENT

The Beta Series claim improvements in all areas of resistance to unwanted noise. Popping and blasting from explosive breath sounds is effectively minimised by a dual-element foam filter within the steel mesh ball-end, but the 57 too now has superior pop rejection built into its new extra rugged top. Hand-held, stand-borne, and impact noise is supposedly counteracted by an "advanced electro-pneumatic shock mount design", which passes without further explanation in the literature supplied to me, so I can't say if that is promotional hyperbole or a technological breakthrough. Nevertheless, impact noise performance (never a weakness in the original SM Series) is outstandingly good, with handling noise virtually devoid of the subjectively more irritating high frequency component.

The usual hum-cancelling extra coil is featured, working on the same principle as a humbucking guitar pickup, whereby any induced noise is picked up anti-phase by one coil and then cancelled by combining it with the other at the output. This one certainly does its job and direct comparison in testing between the old model and the new reveals quite a difference. Once again, it is not that the older models are poor in this respect, but that the new Beta models are outstanding, with typical electro-magnetic hum pickup quoted as 13dB equivalent SPL per millioersted - ie. the hum output will be about the same as that produced by an acoustic source of 13dB SPL, such as quiet speech at five metres. A 1 millioersted (mOe) field might typically be found in a well designed studio, but of course many environments are a lot more hostile than that, particularly in live performance where high powered lighting is in use.

Output level for the Beta 58 is quoted as -71.5dB, using the open circuit voltage convention where 0dB = 1 volt per microbar, which converts to 0.27mV for the standard 74dB SPL reference level (74dB SPL = 0.1 Pascal, a standard reference level, roughly equivalent to speech at about 30cm). The Beta 57 is very similar indeed, producing figures within half a dB, or 0.01 mV. Comparison with the originals shows an improvement of some 4dB, or 0.1 mV, representing a significantly higher output level. Nominal impedance for both models is rated as 150 Ohms (290 Ohms actual), for connection to microphone inputs rated at 75 to 300 Ohms. Phasing follows the USA 'standard' of Pin 2 positive with respect to Pin 3.

POSSIBLE APPLICATIONS

Applications for these microphones are really too numerous and too widespread to be worth detailing; at some time or other an SM58 or SM57 must have been used on just about every source imaginable, but I can think of no application in which the performance of the Beta Series will disappoint in comparison with their forerunners.

On vocals, the new 58 is simply more of the same, but better. A little more open, a little bit cleaner, perhaps a little more natural, yet still essentially the same combination of depth and cut, with perhaps a touch more refinement (as if some SM87 had rubbed off on it). I can't think of a situation where I would not have been prepared to use a standard SM58 where I would now use a Beta, but I would certainly use a Beta 58 in preference to a standard SM58 wherever possible. My preferred usages for 57s have always been close-miked toms and instrument amps, and here, once again, the Beta models checked out well. If anything, the improvement made to the 57 is more likely to widen its usage than that of the 58, I feel.

No maximum recommended SPL (sound pressure level) is specified, but although I tested the mics with some pretty demanding sources, I didn't hear the slightest signs of complaint. I would rarely use a moving-coil mic in preference to a condensor when recording brass or wind instruments, but if pressed I think that both the Betas could turn in a respectable performance. Their usage with such sources is primarily intended for live work, though, where their high selectivity and smoothly tailored response is just what is required.

RELIABILITY

The words "rugged" and "reliable" are guaranteed to appear in all microphone manufacturers' literature. However, this is an area in which few would challenge Shure's reputation. I was not tempted to recreate Shure's famous drop test (six feet onto a hardwood floor, repeatedly); knowing that the manufacturer has randomly batch-tested in this way is quite good enough for me. Such confidence is born of practical experience however, for having spent a number of years employed in location and live recording, I have seen many microphone accidents but have very rarely retrieved a 'trashed' Shure.

Unfortunately, the Beta Series mics are supplied in nothing better than a cardboard box, albeit foam-lined. Perhaps Shure deem this to be adequate for studio life, or domestic usage, and that any professional user would automatically transport mics in a heavy-duty road case. Cardboard containers are not adequate for routine storage of any kind in my opinion, simply because they inevitably fall apart after a while, whilst I know of no studios that flightcase their mic collection. It is not that I fear for the Betas' ability to withstand abuse, but simply that a mic without a permanent home tends to fall prey to the ingress of dust, dirt, and the sort of general grime that degrades performance, rather than terminating it altogether. I do not believe that my Shures would have lived such long and happy lives had they not been housed in spare AKG boxes, and I am certain the manufacturer could afford to do better in this area, at minimal cost.

Supplied accessories include stand adaptor (virtually unbreakable non-brittle plastic, a model of its kind, but 5/8" thread - sadly, no 3/8" adaptor is included) plus a vinyl 'protective bag' (no substitute for a box, I feel).

CONCLUSION

It is good to see that the original SM58 and 57 are not to be discontinued, but remain in the range at reduced cost. After all, their performance is not diminished by the availability of something better and they remain classics of their kind, available now at a budget price.

Shure's Beta 58 and Beta 57 are certain to continue the heritage through the coming decade, and, whilst advertising claims to have "changed the future of sound" might be going a bit far, they certainly can lay claim to having successfully managed to significantly upgrade products that were already accepted as qualifying for the ultimate accolade of 'industry standard.

FURTHER INFORMATION

Beta 58; Beta 57 £198.60 each (inc VAT)

H.W. International Ltd, (Contact Details)