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Soyuz SU-013

Small-diaphragm Capacitor Microphone
Published November 2017
By Hugh Robjohns

Soyuz SU-013

This stylish Russian-made microphone certainly looks the business — but can it compete with the classics?

When I reviewed the Russian-made Soyuz SU-017 ‘bottle’ microphone back in May 2015, the company’s product portfolio only had two entries: that lovely large-diaphragm valve mic, and a small-diaphragm valve ‘pencil’ mic, the SU-011. However, it seems the catalogue has doubled in size since then, with Soyuz adding solid-state versions of both models. The FET-powered equivalent of the SU-017 is called the SU-019, while the transistorised version of the SU-011 is called the SU-013 — and it is this latter mic that is the subject of this review.

As you might expect, the new SU-013 is virtually identical in size to its valve counterpart, and both models share the same set of replaceable capsules. These are currently available with cardioid, hypercardioid and omnidirectional polar patterns. So the core difference between the SU-011 and SU-013 really is just the replacement of the former’s valve for the revised impedance-converter circuitry in the latter, built around an FET stage coupled to a custom-wound output transformer.

From Russia With Love

Soyuz mics are entirely hand-built, and to emphasise and personalise that point, the mics are supplied with a little envelope containing small cards bearing the portraits and names of those responsible for manufacturing the mics. In this case, Daniil machined the parts, Olga assembled them, and Vladimir tested them — with further proof of that quality control in the form of individual frequency-response plots for each capsule, tested on the supplied mic body!

There are three SU-013 packages available. The basic kit (labelled the SU-013) comprises a single mic with cardioid capsule, a -10dB pad module, and a simple stand clip. For stereo applications there is the SU-013M package, which comes with two of everything, as matched pairs. However, the unit sent for this review was the ‘full Monty’ SU-013MAC set, which contains a matched pair of SU-013 bodies fitted with cardioid capsules, plus a pair of interchangeable hypercardioid capsules and a pair of omnidirectional capsules, as well as two -10dB pad modules and two 5/8-inch clip stand mounts (with 3/8-inch thread adaptors).

All of these different packages come in high-quality, foam-lined wooden boxes, but the size of the box obviously varies to suit the content. Initially, I really struggled to get the box lid open, as there is no visible latch and I was convinced for some time that there must have been some invisible tape sealing the joint. Eventually, I discovered that the lid is held shut only by magnets embedded into the front of the lid and case. It’s an elegant solution, but the effort required to open the lid is unexpectedly high. On the upside, the lid won’t fall open if the box is held — or even shaken when held — upside down.

In line with Soyuz’s standard house colour scheme, the review set’s mic bodies, pads and clips were all painted in a glossy cream colour, while the capsules themselves featured a highly polished and lacquered brass finish. The overall effect is quite ‘blingy’ and flamboyant, but that will undoubtedly appeal to many potential owners. For those that prefer something a little more inconspicuous and restrained, the microphone bodies and capsules are also available in a matte-black finish. The Soyuz company logo is in the form of a green, Neumann-esque diamond lozenge pinned on the side of the mic bodies.

With any standard capsule attached to the mic body, the total length measures 122mm, and the diameter is a chunky 25mm. Much of that girth seems to come from the body tube’s substantial side walls, which are nearly 5mm thick at the base around the XLR connector. The -10dB pad module is exactly the same diameter and height as the standard capsules, but it has a solid outer shell without the side slots featured on the capsules. Installing the pad module between the mic body and capsule adds another 22mm to the length. The combination of the hefty machined-brass body and internal transformer makes the mic pretty heavy at 192 grams, and that rises to 262g with the metal stand clip, and 312g with the -10dB pad module in place as well. Each and every capsule and mic body is uniquely identifiable, with individual serial numbers hand-written onto the plastic insulating disc around the capsule’s connecting pin and the mic body’s spring-loaded receiving socket.

Screw Fix

And that brings us neatly to the method of capsule attachment. The capsules, pad module and mic body connect together in the usual way for a modular mic of this type, with relatively fine screw threads cut into the metal housings. These take about four complete revolutions to become fully seated. As with all threaded capsules of this type, the safest and easiest way of avoiding disastrous cross-threading damage is to offer the capsule (or pad module) onto the body and, with gentle pressure holding them together, initially rotate the capsule anti-clockwise until a click is heard or felt. At this point the threads on the two elements will be positioned correctly to engage accurately without cross-threading. The capsule can then be rotated clockwise relative to the body to screw it safely and securely into place.

Clearly, the key feature of the fully loaded SU-013MAC package is the provision of three different capsules for each mic. However, I have to say that on opening the box and examining the contents I was initially rather perplexed, as all six capsules look absolutely identical! Normally, omni capsules don’t have side slits at all (because there is no requirement for sound access to the rear of a pressure-operated capsule), and the rear-entry slots on (pressure-gradient) cardioid and hypercardioid capsules often differ in number, size or position, which generally make it easy to identify the different capsules at a glance.

Frustratingly, that’s not the case at all with these SU-013 capsules: the three different models are, visually, absolutely identical. They all have three bars across the top of the mesh grille; they all have three sets of three side slots around the circumference of the body; and they are all exactly the same size. In fact, the only differentiation is through a very small (4mm diameter) and delicate polar-pattern symbol etched lightly into the side of the top ring of the capsule. Even in good light, when you know what to look for, these symbols are really quite difficult to locate on the polished brass design — and they are virtually impossible to find in low-light conditions. Perhaps it’s easier with the matte-black versions, but I would suggest this is an aspect of the design that really would benefit from a rethink. Simply writing the letters ‘O’, ‘C’ or ‘HC’ on the capsules’ bases alongside the serial numbers would be a very simple but perfectly effective solution, for example.

Tech Specs

The microphone’s published technical parameters state a nominal sensitivity of 20mV/Pa with a maximum SPL capability of 143dB (although Soyuz don’t state the defining amount of distortion at this level), and self-noise is given as 16dB SPL A-weighted — all of which are pretty good figures for a microphone of this type. However, given that the capsule diaphragm is a little larger than that of most ‘pencil’ mics, being closer to 22mm in diameter than 19mm, I was surprised the self-noise figure wasn’t lower. (The Neumann KM184 has a published self-noise of 13dB A-weighted, for example.) Standard 48V phantom power is required, of course, but the specifications don’t indicate the specific current requirement, and the output impedance is a nominal 150Ω.

Looking at the six included QC frequency plots, it was not immediately obvious which pairs of charts are derived from which capsules/polar patterns since, bizarrely, only the mic body serial numbers are recorded on the print-outs, not the capsule serial numbers. However, each plot includes three frequency responses, measured on-axis and at both 90 and 180 degrees, so it’s actually quite straightforward to work out the polar pattern being displayed on each chart by comparing the responses at 90 and 180 degrees.

The sensitivities of the alternate capsules vary slightly relative to the standard cardioid (which is given as 20.4mV/Pa for both mic bodies). In the review set, the omni capsules were slightly less sensitive, at 18.3 and 18.6 mV/Pa, while the hypercardioid capsules were a little hotter at 22.5 and 22.7 mV/Pa. However, these production tolerances lie comfortably within a ±1dB range overall, and each pair of capsules is easily within 0.15dB of each other. In fact, the matching between pairs of similar capsules is impressively tight across the full spectrum, as evidenced by overlaying pairs of plot print-outs and holding them up to the light. This revealed only very minor and occasional discrepancies and deviations.

In terms of overall tonality, the omni capsule measures very flat on-axis, from 30Hz up to about 3.5kHz. Above that there is a slight presence boost of about 3dB, reaching a peak at around 12kHz, before falling back to the nominal sensitivity by 20kHz and rolling off more steeply above this frequency. Below 3kHz, the 90- and 180-degree off-axis responses follow the on-axis response very closely, suggesting an accurate omni polar response up to that point, before narrowing above about 5kHz. This narrowing is quite normal and is due in part to the self-shadowing effect of the mic body, but also to the fact that the mic is clearly balanced for ‘free-field’ or ‘direct-field’ applications. In other words, it will give a natural sound balance when placed close to sound sources, but will sound a little dull if used as a ‘space mic’ in the diffuse-field region of a room.

The plots for the hypercardioid capsules reveal a slightly lean balance, with the response falling gently below 1kHz to about -6dB at 50Hz. These capsules are also a little darker at the high end, too, being about 3dB down at 10kHz. So, overall, the on-axis tonality of this hypercardoid capsule is a little mid-forward. Looking at the off-axis plots, the 90-degree response tracks the on-axis response fairly well up to 2kHz, before rising towards the high end.

Comparing the on-axis responses of the cardioid capsule plots, these follow quite a similar lean balance at the low end, but are noticeably brighter at the high end with — as you would expect — greater output at 90 degrees and much less at 180 degrees compared to the hypercardioid plots.

A six-page handbook is supplied with the mic, although it seems rather simplistic and contains a few very obvious errors, such as references to removing the SU-019 microphone from its shockmount and packing it away after the session. I’m also a little bemused at how the specifications describe the capsule as having a 25mm-diameter membrane; as the mic’s overall diameter is only 25mm that doesn’t seem very likely... still, at least this mic comes with a handbook, which is more than some I’ve seen lately!

In Use

I rigged the SU-013s alongside my own Neumann KM180-series mics, comparing the omni capsule against the KM183, the cardioid against the KM184, and the hypercardioid against the KM185. Of course, the Neumann mics are transformerless designs, and the KM183 omni is balanced for a flat response in the diffuse field, meaning it has a significant presence boost when used in the direct field. However, after taking these differences into account, I was impressed with the performance of the Soyuz offerings.

The omni capsule produced a very smooth and natural but detailed and articulate sound, with an extended bottom end. It also took HF boost equalisation very well when used in the diffuse field as a ‘space mic’.

Moving on to the two directional capsules, these both had slightly smoother presence peaks than the Neumann equivalents (and are a little closer in voicing to the discontinued KM84 model in that respect). Of course, that alternative tonality could be interpreted subjectively either as lacking in detail or sounding smoother and more natural, depending on your preferences and expectations! Either way, though, both capsules performed excellently, with good directionality and minimal off-axis coloration, particularly in the case of the cardioid capsule.

The tendency towards a lean low end, as indicated on the QC plots, is obviously tempered by the proximity effect, which results in a bass boost when the mic is placed relatively close to the sound source. In practice, I found the bottom end balance of the SU-013 capsules to be quite similar to that of the Neumann mics, and just as controllable with distance.

In conclusion, then, I found the SU-013 to be an excellent microphone, performing well both on a technical level and in delivering an impressively high sound quality regardless of which capsule type was employed. The acid test is whether I would be happy to use the Soyuz mics alongside (or instead of) the Neumanns in my own collection — and the answer is an unqualified yes. Clearly, the Soyuz mics have a slightly different tonality, but mic selection is all about choosing their innate tonalities and other properties to suit the sources and placements.

It would be nice if the company could find a way of making the capsules easier to identify, and I’d also like to see them tighten up the detail and references in their published specifications to compare more favourably with the high-end competition. Nevertheless, the SU-013 is a great-sounding mic which is well built and should last a lifetime thanks to its robust construction, while the ‘full Monty’ SU-013MAC stereo set offers superb versatility for a very attractive price.

Alternatives

The Neumann KM184 stereo set is priced at a similar level to the SU-013MAC set, but obviously lacks the capsule options. The popular Oktava MK012 stereo set costs around half as much, but includes a similar collection of capsules and pad modules, while the Rode NT55 matched pair set includes cardioid and omni capsules and sits, price-wise, roughly midway between the Oktava and Soyuz.

Published November 2017