We gathered together a suitably varied bunch of five microphones from the current Shure range and asked engineer Dave Lockwood to test them under stage and recording conditions. Here are the results...

There can be few musicians who have not at some stage in their career used a Shure microphone, for their ubiquitous SM58 and SM57 models have been an 'industry standard' for so many years now. However, Shure's reputation for producing particularly rugged, dependable moving-coil models optimised for stage use has perhaps tended to obscure the development of their range in other areas, as this brief overview of a varied selection of Shure mics, from both ends of the price scale, demonstrates.

PROLOGUE 16L

The Model 16L from Shure's Japanese-made, budget 'Prologue' series, is a general purpose cardioid electret condenser, of simple tubular construction, with a screw-on capsule that is removed to gain access to the battery compartment within the body. A single AA 1.5V battery is required, and with the circuitry having a current drain of less than 1mA, a battery life of over 1000 hours can be expected. The partially recessed battery slide-switch, on the review model at least, produces an immense turn-on 'thump', and with hand-held use envisaged in the spec-sheet, it should perhaps have been placed less invitingly for use as an On/Off switch.

Output is via a regular 3-pin male XLR connnector located in the base of the housing, and is balanced (Pin 2 'hot' - the phasing standard adopted by all Shure mics), as well as low impedance, nominally 600 Ohms.

The 16L exhibits a rather average sensitivity for a mic of this type, equivalent to an open circuit voltage of 0.33mV, quoted as -69.5dB (ref. 0dB = 1V/ubar @ 1kHz). The maximum SPL (sound pressure level) permitted by the specification is 120dB (@ 1kHz), and in use, some limitations were evident in this area. Although no figure is quoted by Shure, some pre-amp output noise is apparent in recording applications, particularly where distant pick-up of quiet sources is attempted. This is a common failing in budget electrets however, and the 16L seemed little worse in this respect than equivalently priced competitors in my experience.

Overall frequency range is claimed as 50Hz to 15kHz; however, the whole response is tilted, and both extremes are well down. 50Hz and even 100Hz are some 6dB below the 1 kHz level, whilst the HF (high frequency) region displays a minor peak around 7kHz before declining sharply above 10kHz.

The boosting of low frequencies that occurs when a mic is used very close to the sound source (known as 'proximity effect') is strongly evident in close-up use with the Prologue 16L, and certainly compensates for the lack of real bottom-end in the distant response, without sounding unnaturally boomy in voice applications. With a demanding wide range acoustic source, such as piano, the 16L in fact sounded not too unduly coloured, although comparison with a reference mic reveals the subjective limitations in terms of 'openness' and 'transparency'. Less demanding sources were all handled capably in general, although close-miked snare drum begins to show early signs of clipping and should thus be avoided.

The off-axis response is a little wayward, emphasising the presence peak effect in the upper midrange, causing crosstalk from distant sources to sound rather harsh and unnatural, and leading also to a difficult to control tendency to 'ring' unpredictably in PA usage. Although 'rock vocals' is among the manufacturer's recommended applications, no popshield is incorporated or supplied. I employed a simple add-on foam screen for test purposes, but popping and blasting effects were still quite severe, as was handling noise which, as often with condenser mics, contained a considerable degree of subjectively more obtrusive high frequency components.

The Shure Prologue 16L is supplied with a lightweight plastic mic stand clip, without an additional thread adapter (5/8 thread only), and without cable. Its extremely competitive price should perhaps betaken into account when assessing its moderate performance, for under the right conditions it is certainly capable of producing worthwhile results, and might make a useful 'all-rounder' in a modest home recording set-up, where the mics may also have to double for stage use.

SM96

The Shure SM96 is an electret condenser cardioid mic, seemingly tailored specifically towards high quality hand-held vocal applications. An integral steel mesh and foam ball-end protects the capsule, whilst the slim, partially tapered body is beautifully weighted to feel balanced and comfortable in the hand. Output via the 3-pin XLR is balanced, and nominally rated at 150 Ohms (200 Ohms actual), although the recommended minimum load impedance is 800 Ohms, with lower loads giving a reduced clipping level - this should not be a problem when used with any modern mixing desk however. A single AA 1.5V battery can operate the system for up to 5000 hours where no external power is available, whilst phantom voltages of 11 to 52V are acceptable, with no degradation of performance being evident at lower voltages.

Sensitivity, quoted as -74dB (0dB = 1V/ubar @ 1kHz), and slightly reduced under battery power to -75dB, is perfectly adequate for all envisaged close-up applications, whilst microphone self-noise seemed subjectively so low as to be undetectable at normal gain settings. The maximum SPL figure it can handle, with the recommended load and phantom power, is a healthy 148dB, although this is degraded somewhat to 128dB by battery power - the performance of the SM96 in this area is comparable to a dynamic mic and would certainly permit close miking of drums and amplified instruments if desired.

The tightly controlled cardioid polar pattern of the SM96 displays excellent front to back signal discrimination and the minimum of off-axis colouration effects. The uniformity of the off-axis frequency response assists in producing an exceptional resistance to feedback in the SM96, showing the most tolerant characteristics under less than ideal conditions.

As is to be expected in a dedicated vocal mic, the specified frequency range of 70Hz to 16kHz in fact reveals little of the microphone's actual performance for the response is extensively tailored in specific areas. Low frequencies are gently rolled off below 200Hz to be 10dB down by the 50Hz point, counteracting any proximity effect, whilst the region between 1kHz and 10kHz is rising smoothly all the way, lending a natural clarity to the sound whilst avoiding the harshness often associated with a midrange presence peak. In use, the sound of the SM96 is characterised by a clean, open quality notably absent from most dynamic stage vocal mics-speech and vocals are always well articulated and clear, without ever sounding thin or lacking in warmth.

Although an additional foam shield is available as an optional accessory, popping and blasting seemed minimal during testing in a PA context, whilst handling noise too seemed reasonably controlled for a condenser mic, perhaps assisted by the electronically generated LF roll-off, and the effectiveness of the transducer shock-mount system.

The SM96 comes complete with the usual Shure accessories: small vinyl carrying bag and indestructable, though single thread, stand adaptor, with no cable being supplied.

This is one of the nicest stage vocal mics I have had the pleasure of using, and in a live recording situation in particular, made an excellent compromise between the requirements of adverse acoustic conditions and the need to obtain the most natural recording signal possible.

SM48

The SM48's model designation suggest: perhaps a down-market SM58, and indeed that is certainly what it resembles, externally at least. Finished in the same charcoal grey, with matt chrome steel mesh ball-end, it could hardly look more conventional, or more familiar.

The balanced output, via standard XLR, is rated 150 Ohms nominal impedance (270 Ohms actual), and recommended for connection to inputs rated 19 to 300 Ohms. Being a moving-coil model, sensitivity is relatively low at -77.5dB (0.13mV) open circuit output level (ref. 0dB = 1V/ubar), however this is never likely to be a problem in a microphone designed specifically for hand-held vocal use, for it will rarely, if ever, be employed far from its sound source. As with any dynamic mic, with no on-board electronics to worry about, it offers the virtue of practically unlimited maximum SPL, giving complete freedom of use in the most hostile of loud, live performance environments.

The nominal 55Hz to 14kHz frequency response displays the anticipated tailoring, with a low frequency decline counteracting proximity boosting around 100Hz, and a rising upper midband featuring a classic presence peak effect around 7kHz, with quite a sharp decline and roll-off in the true HF region. The sound of the SM48 in vocal applications is undeniably crisp, and quite well balanced overall, but with the inevitable hardness and typical colourations that characterise practically all such dynamic vocal mics. Whilst eminently suited to aggressive vocal styles, allowing vocalists to cut through the sound of a loud band, the sound can be exposed as rather fatiguing on the ears and noticeably unnatural under more controlled conditions. Similarly, with other suitable sources such as drums or instrument amplifiers, the response tailoring of the SM48 might prove most useful in PA work, where separation and maximum presence for every signal is usually at a premium, whereas one would seldom choose a microphone in recording applications that imposes so much of its own character on the source.

A uniform polar response ensures both good feedback rejection and separation, with a noticeable absence of problems at both extremes of the frequency range, despite some enforced adverse speaker placements during testing. Handling noise was well suppressed and almost exclusively low frequency in content, whilst popping was minimal due to the efficiency of the foam blast screen incorporated in the ball-end mesh - a vital component in a successful stage vocal mic design.

Furnished accessories include a vinyl carrying bag and swivel stand adaptor, which when the mic is fully inserted is sufficiently tight to mark its outer finish! Still, at least you know it's not going to fall out!

The SM48 is a welcome addition to the Shure range, offering many of the virtues, and indeed vices, of its acclaimed forbear, at modest cost. The exceptionally rugged construction suggests that the mic could withstand considerable physical abuse and still give years of trouble-free operation. Combined with a performance that is both predictable and familiar, this makes the SM48 seem an attractive and cost-effective competitor in a crowded field.

SM94

The Shure SM94 is a cardioid electret condenser mic with a wide, flat frequency response suiting it principally for use in recording, or high quality sound reinforcement applications. Of rugged construction and suitably durable finish, it offers an XLR, balanced output, at a nominal 150 Ohms (200 Ohms actual). The recommended minimum load is again 800 Ohms, although loads down to 150 Ohms are acceptable with slightly degraded headroom. Phantom voltages between 11 and 52V can be employed to power the mic, with an internal AA 1.5V battery acting either as back-up or alternative supply, albeit at slightly reduced spec. Battery current drain is nil during phantom use and normally only just over 1mA, so a fresh battery should give around 5000 hours of use. Output level is quoted as -69dB (0.35mV) ref. 0dB = 1V/ubar, which represents fairly moderate sensitivity for a mic of this type, however, self-noise is extremely low and in use no signal-to-noise problems were in fact encountered, with distant mic placements or sources requiring a large amount of mic-amp gain.

The SM94's nominal response of 40Hz to 16kHz is slightly tilted over virtually the whole range, but no significant low frequency roll-off or presence boost deviations are displayed. The extent and smoothness of the overall response makes for a fairly neutral characteristic, particularly suited to acoustic instruments and other natural sound sources which are normally quick to expose excessive microphone colouration. The SM94 conveys both clarity and detail, without the brittle, false top-end that leads to harshness with certain sources in some models, the sound remaining well balanced with an extended, but controlled, full bottom-end response. Despite indications in the accompanying literature, this model certainly seems most suited primarily to stand-mounted instrumental pick-up, for significant levels of HF and LF handling noise are evident, and popping and blasting results from any attempt at close range speech. Employment of an external foam popshield (an optional accessory) largely alleviated this problem however, and the maximum specified SPL figures of 141dB (phantom powered) and 123dB (battery) would permit the hand-held vocal amplification usage suggested by Shure, although I feel that the PA would have to be of very high quality and the acoustic environment generally favourable for a mic with such a 'wide open' response to give its best in this type of application.

The cardioid polar pattern is remarkably uniform with frequency, causing minimal colouration of distant and off-axis pick-up, which certainly reduces the destructive nature of any sound spill in recording usage, as well as avoiding any feedback-provoking 'hotspots' in the response that would otherwise cause problems in a sound reinforcement context. Excellent front/rear discrimination at all frequencies, and the fine polar characteristics in general, make this microphone an outstanding performer in terms of directivity and controlled separation.

The SM94 is supplied with the usual Shure accoutrements, but without cable, and exudes a ruggedness that inspires confidence in its longevity under the severest conditions. There are some recording mics that one might think twice about using on stage, but this model looks as if it would survive any amount of live performance abuse or mishap, perhaps making it a natural choice for live and location recording situations in particular.

SM91 BOUNDARY

Since the advent of the original, innovative Crown PZM in 1980, 'pressure zone' or 'boundary' mics have become quite commonplace. Based on the principle that sound pressure doubles in the area just above a reflective surface at the point where the incident and reflected waves are in-phase, PZMs (pressure zone microphones) offer striking performance advantages in terms of sensitivity and freedom from colouration.

However, Crown's original design, and many of its subsequent imitators, offered a hemispherical pick-up pattern in the plane above the integral boundary plate, making them perform effectively as omnidirectional mics, and rather reducing their effectiveness in some applications, where separation and directional discrimination were important. Physical isolating barriers can be used to achieve directionality, but sufficiently large ones are usually impractical, and small ones are ineffective at lower frequencies.

Shure's SM91, however, has a polar response described as 'half cardioid' displaying a cardioid pick-up pattern in the hemisphere above its mounting surface, giving much greater control and increasing the range of applications, without losing the benefits of the original principle.

The SM91's low-profile, matt-black boundary plate and capsule assembly is enclosed by a perforated steel grille and fine-mesh wind/dirt screen, making for a very robust, but elegant and unobtrusive unit. A generous length of small diameter cable, fitted with three-conductor miniature Switchcraft connectors, joins the mic to its pre-amp/power supply unit. Power can be supplied either by means of two PP3 type 9V batteries, housed in the pre-amp casing complete with an LED to indicate battery condition, or by phantom voltages of between 11 and 52V. Pre-amp output is by normal balanced XLR, rated at 150 Ohms (90 Ohms actual), with a minimum recommended load impedance of 800 Ohms.

As with all PZMs, the response at low frequencies is modified by the size of the mounting surface, with frequencies whose wavelength exceeds the size of the boundary being rolled off at about 3dB per octave. On a theoretically infinite surface, the specified frequency response is 20Hz to 20kHz (within approximately 3dB limits), making wall, floor or ceiling mounting ideal for wide range music pick-up. Table or lectern mounting is recommended as adequate for speech, but in fact during testing, with a wide variety of sources, I rarely felt any desire to experiment with an extended boundary, often finding the SM91's naturally 'tight' bottom-end a distinct asset. The pre-amp unit offers a switchable electronic low frequency roll-off facility, converting the 6dB/octave slope below 30Hz of the nominally 'flat' response, into a 12dB/octave roll-off beyond 80Hz - perhaps useful to reduce the transmission of physical shock effects when the microphone is mounted on a resonant floor or stage, or directly onto a percussive instrument, although again I encountered no requirement to use this in any of the test applications.

The flat and wide, uncoloured response of this type of microphone can produce exceptionally natural sounding recordings of practically anything, regardless of the distance or angle of incidence of the sound source, and with the remarkable ability to apparently discriminate against random background noise. Famous PZM uses include, taping the mic to the underside of the lid on a grand piano (with the lid up or down!), placement inside bass drums, taping to the ceiling above a drum kit for superbly natural cymbals, or just laying them around a studio floor using their ability to pick-up remarkably usable ambience, perhaps to artificially inject a live quality into a rather dead studio recording using some controlled spill.

In most of these applications, as well as the most simple single mic recording, the directivity of the SM91 proved a considerable asset relative to all previous designs I have used.

The maximum SPL figure of 144dB SPL (quoted at 1 kHz, for a 30 degree incidence to infinite surface) effectively imposes no limits on usage, and is allied to extremely low pre-amp output noise, and high sensitivity (measured under similar conditions), expressed as an open circuit voltage of -69dB (0.35mV) ref. 0dB = 1V/ubar.

The SM91 is attractively presented in a rigid plastic case that contains the capsule/boundary plate unit, pre-amp, and interconnecting cable. The whole system is ruggedly constructed and exudes quality, and would certainly make a most valuable addition to even the most complete microphone collection in view of its unique attributes. Having been a committed fan of PZMs since they first appeared, I feel that this model is a significant step forward within the field, and is further evidence of Shure's continuing design innovation and engineering quality.

Prices of the reviewed mics are as follows (including VAT): Prologue 16L £53.63; SM48 £108.01; SM94 £224.74; SM96 £224.74; SM91 Boundary £371.24.

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