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Sony C100

Dual-element Capacitor Microphone
Published February 2018
By Sam Inglis

Sony C100

Twenty-five years after the release of the iconic C800G, Sony are back with a brand-new studio microphone — with a unique ultrasonic twist...

There are times when the unattainability of a piece of equipment only adds to its desirability. It’s true of vintage gear that was made in limited quantities, but it’s also the case with at least one current product. Launched in 1992 and presently listing at just over $11,000, Sony’s C800G valve capacitor microphone is one of the most expensive mics in production today — but even if you happen to have $11,000, you won’t necessarily be able to buy one. In order to be legally sold within the European Union, electronic devices must be compliant with current ROHS legislation, and the C800G is not. So, although some European resellers nominally include it in their catalogues, actually getting your mitts on one could prove difficult.

Nevertheless, there’s no denying that the C800G is desirable. Thanks both to its characteristically bright, detailed sound and its unique appearance, Sony’s flagship has become a must-have for any high-end studio catering to rap and R&B vocalists.

The popularity of the C800G is all the more remarkable when you consider not only its exclusivity, but also the fact that its makers haven’t exactly spent the last 25 years singing its praises. Where other companies would have plastered the press with adverts and testimonials, and used the C800’s reputation to spin off more affordable mass-market products, Sony have quietly let the mic do the talking — until now. At last November’s AES Show in New York, the Japanese mega-corporation unveiled not one, but three studio microphones, their first new models in a quarter of a century. And, whereas many mic manufacturers hark back to a supposed golden age of valves and transformers, Sony’s new mics embody a forward-looking philosophy. All three use newly developed capsules, and are billed as “high-resolution” mics, with a frequency response stated as 20Hz to 50kHz (though no tolerance is quoted). The ECM-100U and ECM-100N are small-diaphragm pencil microphones, which will be the subject of their own review, while the C100 is altogether more unusual.

Small Is Beautiful...

One of the many trade-offs involved in the design of capacitor microphones concerns the mutual relationship between diaphragm area, bandwidth and noise. At very high frequencies, the wavelength of sound becomes shorter than the width of a standard diaphragm, meaning that the diaphragm encounters positive and negative phases of the same cycle simultaneously, with no net pressure and hence no net output. Reducing the diaphragm size allows smaller wavelengths to be captured. Smaller diaphragms also have less inertia, enabling them to respond more nimbly to very high-frequency sounds. At the same time, though, they convert proportionally less acoustic energy into electrical energy, so the level of the wanted signal above the noise floor of the electronics is lower. Thus, mics that use a miniature capsule to capture frequencies above 20kHz tend to be noisy, which has perhaps hindered mass-market acceptance. And, of course, engineers don’t want to be forced to use small-diaphragm microphones on everything just because they’re the only way to capture ultrasonic frequencies.

Here you can see the unusual dual-capsule configuration. The lower capsule operates between 20Hz and 25kHz; the upper captures sound between 25 and 50 kHz.Here you can see the unusual dual-capsule configuration. The lower capsule operates between 20Hz and 25kHz; the upper captures sound between 25 and 50 kHz.With the C100, then, Sony have set out to create a mic that has the familiar characteristics of a large-diaphragm capacitor mic within the inherent bandwidth limitations, but which also meets the “high-resolution” goal of having a very extended frequency response. Their designers have achieved this goal by combining two capsules, just as a two-way loudspeaker has a woofer and a tweeter. The difference here is that the crossover is at 25kHz!

The 20Hz-25kHz range is covered by a newly developed large-diaphragm capsule. This is an externally polarised true-capacitor design, apparently edge-terminated; at least, no centre termination point is visible. The diaphragm material isn’t stated, but looks to be the usual gold-sputtered film of some sort, and both front and rear capsules can be energised, allowing the mic to be switched between cardioid, omni and figure-8 polar patterns. Two further switches on the rear of the mic engage a 10dB pad and a high-pass filter. Frequencies above the crossover point, meanwhile, are captured by a single, forward-facing small-diaphragm capsule. This is the same capsule used in the ECM-100 mics, and is a back-electret design. Its contribution is the same regardless of what pattern is selected.

There is clear merit in the thinking behind Sony’s design. Whether or not frequencies above 20kHz are really detectable by human hearing is hotly debated, but even the most ardent believers surely have to concede that crossover artifacts are less likely to be audible at 25kHz than they would be at, say, 3kHz. Likewise, since the small-diaphragm element is only contributing from 25kHz and above, any noise that it adds will also be restricted to this part of the spectrum, where it’s unlikely to be heard as noise; and although the directionality of the high-frequency capsule doesn’t follow that of the main capsule when the patterns are switched, this too is unlikely to be an issue for anyone but bats. Ultrasonic vibration is quickly absorbed in air, so any energy reaching the mic in this frequency range will mostly be coming directly from the nearest source in any case. In theory, a C100 recording made at base sample rates will feature only the large-diaphragm element, so it’s up to the user whether to record at high sample rates and bring the smaller capsule into play too.

Out Of The Box

The review C100 arrived in a smart and robust Pelican-style case made of hard plastic, which is a lot more roadworthy than your average wooden box. Included are a foam windshield, a stand adaptor and a cradle-type plastic shockmount. The shockmount supplied with the review mic was apparently not the finished article, so I won’t comment on it except to say that I hope the finished article is less fiddly.

Sony C100Measuring only 40mm in diameter and 175mm end to end, the C100 is one of the smaller large-diaphragm mics I’ve encountered. Finished in matte black, its construction appears very neat and, with no visual gimmicks or affectations, looks reassuringly professional. Its design also outwardly recalls that of the C800G, though without the latter’s enormous heatsink, it isn’t quite as imposing. Sony say that the C100 uses the same “advanced noise elimination” as the C800, a claim which seems to refer to a construction technique that isolates the capsules from vibration transmitted through the body of the mic. What’s less clear from Sony’s marketing materials is whether the C100 is also intended to sound similar to the C800, or to be its own thing; and whether they see it as primarily a vocal mic, or as a studio all-rounder.

If you asked me rather than Sony, I’d lean towards the former option in both cases. Over the course of the review period I put the C100 up alongside various Neumann large-diaphragm microphones including a TLM102, U87 and U47 FET, and also auditioned it side-by-side with a ‘brass ring’ AKG C414EB. These comparisons demonstrated that the C100 has a prominent high-frequency emphasis from perhaps 6kHz upwards, balanced by a tight but deep low end and a slightly lean low-mid response, at least at the usual working distances for vocals and other close sources. It was brighter than all the above-mentioned mics, and although the AKG was perhaps second in terms of high-frequency response, the two did not sound much alike. The C414’s timbre is soft and airy, with a hint of sizzle and added excitement that perhaps comes more from the mic’s capsule and transformer than from the source. The C100, though brighter still, does not impose a ‘processed’ character at all: its high-frequency lift is subjectively much more transparent, and serves to enhance the impression of openness and clarity. Other mics often sounded cloudy or veiled in comparison.

The microphone has switches for polar-pattern selection, a 10dB pad and a low-cut filter.The microphone has switches for polar-pattern selection, a 10dB pad and a low-cut filter.I’ve only had the chance to use a C800 once, and remember liking the unprocessed sound a lot on my own voice. The C100 made the same impression, and whereas I’d usually feel the need to cut somewhere in the 200Hz region and boost at the top end, recordings made with this mic worked just as they came. It also made a really good close mic for acoustic guitar, cleanly resolving complex harmonics and presenting the instrument with a focused, slightly adamantine clarity. Although the mid-range is not as prominent as it is on some mics, it is subjectively smooth; the C100 doesn’t get harsh when things get loud, and if you need to boost somewhere between 500Hz and 5kHz or above in order to make the source cut through in a mix, you can do so without bringing to light unpleasant resonances or edginess. I rarely use large-diaphragm capacitor mics in patterns other than cardioid, but the C100’s omni and figure-8 pickup behaved as you’d expect, with no obvious change in tonality, and without any obvious negative consequences caused by the presence of the extra capsule.

If there’s a downside to the C100’s ‘mix ready’ sound it’s that, compared with more neutral mics, it might prove less universal as a studio all-rounder. Some sources are plenty bright enough without any help, and you’d need to tread carefully with anything of that sort, perhaps positioning the mic a touch off-axis. Although it puts across sibilants very cleanly, without noticeable distortion, they can become distracting on some vocals, and as an overhead mic on a drum kit, the C100 delivers a sound that’s crisp rather than full-bodied, with plenty of transient definition and cymbal ‘ping’.

New Heights

Taking Sony’s claims about the C100’s “high-resolution” capabilities seriously, I recorded most of my test projects at 96kHz. A spectrum analyser revealed that it definitely has greater extension in the ultrasonic range than conventional large-diaphragm capacitor mics. Whereas my C414 had rolled off completely by 30kHz, the C100 was still going at 40kHz and above, and what it had captured was obviously audio generated by the source, rather than random noise. As to whether this energy makes a difference to the music, I remain genuinely unsure. By repeatedly inserting and bypassing a linear-phase low-pass filter set to turn over at 25kHz, I convinced myself that I could hear a difference in the way transients were represented, at least on some material; but it was a subtle difference and for me, wouldn’t always justify the extra system and disk overhead involved in recording at high sample rates.

Fortunately, though, the neat thing about the C100’s design is that this ultrasonic capture can be treated as entirely optional. It doesn’t compromise the mic’s abilities within the normal range in any way I could detect, and it’s these abilities that will be its major selling points for most people. This is not a ‘rock & roll’ microphone. If your ideal vocal mic is something like a vintage Neumann U47, with a thick mid-range bolstered by saturation from transformers and valves, look elsewhere. If, on the other hand, you’ve always dreamed of owning a C800G but don’t have $11,000 to spend, this might just be the perfect mic for you. For anyone seeking a bright, modern vocal sound that majors on clarity and presence, the C100 has to be a strong contender.  

Alternatives

As a large-diaphragm capacitor mic with a second diaphragm specifically designed for “high-resolution” recording, the C100 has little competition; the Sanken CU-44X MkII employs two capsules, but for rather different reasons, as explained elsewhere. If your concern is more about finding a full-range, modern-sounding mic to capture the human voice with as much clarity and detail as possible, however, the field is broader. Audio-Technica’s stunning AT5047 and AT5040 should definitely be auditioned, but they are much more expensive than the C100 is expected to be; more affordable alternatives include the Neumann TLM107 and Lewitt Audio’s LCT540 and 640.

Specs

At the time of writing, the published specifications for the C100 were a little scanty, with no frequency response plot available. In comparison with most modern large-diaphragm mics, its self-noise figures look rather poor at 18dBA in cardioid mode, rising to 21dBA in figure-8 and 23dBA in omni. The A-weighting curve used in self-noise measurements does not completely roll off above 20kHz, so I did wonder whether these figures were being dragged down by ultrasonic noise from the small-diaphragm capsule. However, the fact that the noise figure changes to such an extent with polar pattern would suggest that the large-diaphragm capsule is the main contributor.

Subjectively, though, I did not find that noise was a problem in normal use, and given its target market, I’m sure that most C100s will spend their lives close-miking things in situations where it isn’t an issue.

In other respects, the C100’s specifications are relatively standard for a large-diaphragm capacitor microphone. The output is transformerless and electronically balanced, with impedance quoted as 90Ω, varying by ±15 percent through the frequency spectrum, and sensitivity is listed as -36dB (reference 0dB = 1mV/Pa). The C100 requires standard +48V phantom power to operate; the specs don’t say how much current it draws, or how much voltage variation it can tolerate. The mic is said to be able to cope with sound pressure levels of up to 131dB in cardioid mode, 135dB in figure-8 and 137dB in omni, though it is not stated what level of distortion is reached at those figures, or whether they relate to use with or without the pad.

A Brief History Of Dual-capsule Microphones

The idea of using two separate transducers within the same microphone has a long history. Sony’s use of it to extend the frequency response of a large-diaphragm capacitor mic is, as far as I know, novel, but it has previously been employed to solve many other problems.

Before the development of cardioid capacitor and moving-coil capsules, a unidirectional frequency response (of sorts) was sometimes achieved by combining an omni moving-coil element and a figure-8 ribbon element within the same mic, as in the well-known Western Electric/Altec ‘birdcage’ microphone. Then, in the late 1960s, AKG developed the D200, D202, D222 and D224, all of which used two separate moving-coil capsules within a single housing, with a crossover at around 600Hz. The primary aim of this design was to create a directional mic with minimal proximity effect, and the D224 in particular was a very fine microphone; but eventually it proved too expensive to produce and the idea fell out of favour.

A different application of the dual-capsule principle is found in Audio-Technica’s AE2500 bass drum mic, which mounts moving-coil and back-electret capsules side-by-side. In this case, both are full-range elements, and the point is to allow the user to mix and match the different sonic qualities of the two designs. And, of course, single-point stereo and surround microphones necessarily use multiple full-range elements.

However, the closest parallels to the C100 I know of are found within the catalogue of another Japanese manufacturer. The Sanken CU-41, CU-51 and CU-44X MkII all employ two circular capacitor elements one above the other in an arrangement very similar to that of the C100. The last of these, in particular, is billed as a “high-resolution” microphone, and has a published frequency response extending beyond 30kHz. Here again, though, a different problem is actually being targeted. The use of two capsules in the Sanken designs is less about extending the bandwidth than about maintaining consistent polar patterns across the frequency spectrum. Unlike the C100, the Sanken mics also use titanium-skinned diaphragms, and the crossover point is said to be set at 1kHz, compared with 25kHz in the C100. In an odd parallel with the C800G, the CU-41 is not on sale in the EU, but the CU-51 and CU-44X are both available and highly regarded by those in the know.

Published February 2018