Shure's product catalog is truly extensive, which makes sense given the success of its products and the fact that it has been in business for more than 85 years. The launch of new products is usually accompanied by improvements to existing models, which can sometimes mean a change in the model name and/or product line. That was the case with the KSM27, which became the first one-inch-diaphragm condenser in the legendary SM line, renamed the SM27.

Something similar has happened to the KSM109, which has seen its champagne color changed to the usual dark gray/black of the SM range, to be reborn under the name SM137.

It has kept its status as a small-diaphragm condenser —in fact, the specifications seem identical to those of its predecessor— and in terms of price, it sits between the PG81, SM94 and SM81.

Mind you, the name shouldn't be confused with the KSM137, another small-diaphragm condenser mic, but in a different product line.

Confused by so many models? Don't worry; while we tell you how we got on with the SM137, we'll try to clear up any doubts.

SM137
The mic's dimensions and weight haven't changed from its predecessor, except for the aforementioned change of outfit, which in any case is dictated by the range: the characteristic champagne finish of the KSM line had to give way to the dark gray/black that defines the SM line.

It also keeps the recessed switch for the attenuation pad (–15dB), which raises the mic's maximum SPL to a by-no-means-negligible 159dB (for 1% THD, with a 2500 ohm load), which means the mic will easily handle the loudest drums or amps you're likely to come across.

The diaphragm is made of Mylar and is of the 'ultra-thin' type, just 2.5 micrometers thick. This element is polarized thanks to its 24-karat gold coating, and as a whole, the manufacturer says it offers 'fast transient response'.

The same description applies to the preamp, a transformerless Class A design providing >50dB common-mode rejection which, combined with the other elements, gives the mic a self-noise of 19dBA.

The frequency response covers 20Hz to 20kHz, with a couple of boosts around 3.5kHz and 9kHz and a slight constant roll-off from 400Hz down, surely designed to give the mic clarity.

The polar pattern is cardioid, and judging by the diagrams supplied by the manufacturer, the SM137 offers very consistent directionality, something we were able to confirm during testing.

The four side openings that give the mic its directionality are protected by a triple grille, which also covers the front and acts as a built-in pop filter.

The mic comes in a cardboard box containing Shure's classic cloth pouch, the equally classic A25D clip and a windscreen, along with the manual and other documents.

The specifications state that the mic is an 'electret condenser' type and requires 48v phantom power to operate.

In action
For the test bench we put four mics to work side by side. One of them was, naturally, the Shure SM137, and another position was taken by one of its little brothers, the PG81.

The other two mics were two well-known models —from different manufacturers—, one in the same price range as the SM137 and the other in a noticeably higher range.

All four were placed on separate mic stands lined up with each other, and then a parade of instruments passed in front of them, from small percussion such as egg shakers, shakers and tambourine to several acoustic guitar models, plus some vocals.

In every case, the instrument was kept far enough from the mics for the sound to have room to develop before reaching them, ensuring that any differences in sound were due solely to each mic's response.

The mics were connected to the four inputs of a Universal Audio 4-710d preamp, and all channels were set the same way: '100% solid state' position, high-pass filter and compressor off, and equal input and output gain settings.

Compared with the PG81, the SM137 was consistently superior. It captured more 'air' around the instrument and showed better definition (which makes sense given the frequency response of each). In the low end, the SM137 was also more solid than the PG81.

Compared with the model in the same price range, the results were also somewhat to be expected. For some applications and instruments we would have preferred to use one model, and for others, the other. If anything, the SM137 was a bit brighter than the other manufacturer's mic, but never unpleasantly so.

And as for the noticeably more expensive mic, the good news for Shure is that in some cases the mic held its own against it without any problems. Naturally, in many cases this wasn't so (we're talking about a price difference of more than 10 times), but in some it was, and that in itself is a point in the SM137's favor.

Conclusions
A Shure is a Shure. The SM137 upholds the manufacturer's name in terms of sound quality, construction and sturdiness.

It's a rugged, good-sounding mic whose features and price are very well positioned relative to the manufacturer's other models.

Its sound is a noticeable improvement over the PG line model, and that's no accident, since it's part of the SM product line, perhaps Shure's best known.

Compared with the manufacturer's other models in a higher price range, the SM137 is a more affordable alternative to mics such as the SM81 or KSM137, although compared with the latter, the sound may suffer slightly (but the price is almost half).

And as for its evolution, if you liked the KSM109, you'll like the new SM137 too, since it's essentially the same mic.

In short, a new offering from one of the best-known mic manufacturers, with very well-targeted and well-conceived performance, features and price.

Shure's ranges
With so many model names and product lines, it's easy to get lost. In short, Shure's main product lines are called PG, SM, BETA and KSM.

The PG range is the most affordable, designed to offer Shure's sound and quality to those on the tightest budgets.

The SM line is probably the best known, for its quality, sound and sturdiness. It includes renowned mics such as the SM57, SM58, SM7B and SM81.

The mics in the BETA range are defined as 'application-specific mics built to capture every detail in challenging acoustic situations'. They usually offer frequency responses and/or polar patterns specifically designed to improve performance in certain circumstances.

As for the KSM line, it's Shure's high end: 'premium' mics built with top-quality components.

We're clarifying this because the SM137, the subject of this test bench, resembles —either in name or in physical appearance— other Shure mics such as the PG81, SM94, SM81 and KSM137, and there may be confusion.

However, each one offers its own characteristics —technical and economic— that make it suited to a particular market segment.

For example, the PG81 and SM94 can run on either batteries or phantom power, so besides musical applications, they're also commonly used for video-related work.

The SM137 sits between them in price, although in terms of specifications it's somewhat 'superior' to the SM94 (which, for its part, offers battery operation and has better figures than the PG81).

The SM81 and KSM137 are in a higher price range, so the SM137 can be seen as a more affordable alternative to them.

How does that saying go: divide and conquer?

Specifications
Type: Condenser
Frequency response: 20 to 20k Hz
Polar pattern: Cardioid
Output impedance: 150 ohms (actual)
Sensitivity (@1kHz, open circuit): –41dBV/Pa (1 Pascal=94 dB SPL)
Max. sound pressure level (SPL) (1 kHz at 1% total harmonic distortion): 1000 ohm load:
139 dB (154 dB with pad engaged)
2500 ohm load:
144 dB (159 dB with pad engaged)
Signal-to-noise ratio (ref. 94 dB SPL at 1 kHz): 75dB
Dynamic range (1kHz): 1000 ohm load: 122 dB
2500 ohm load: 128 dB
Common-mode rejection (10 Hz to 100 kHz): >50dB
Clipping level (20Hz-20 kHz at 1% THD): 1000 ohm load: 3 dBV
2500 ohm load: 9 dBV

Mic preamp THD measured with an applied input signal equivalent to the cartridge output at the specified SPL.
Self-noise (typical equivalent SPL, A-weighted): 19 dB
Polarity: Positive pressure on the mic diaphragm produces a positive voltage on pin 2 relative to pin 3
Net weight: 195 g
Pad: 15 dB
Frequency response: flat across the spectrum; 6 dB per octave below 115 Hz; -18 dB per octave below 80 Hz
Connector: Male XLR connector
Power: 48 VDC phantom power, 5.2 mA