Microphone Parts SDC-84

With vintage Neumann KM84s becoming ever more unaffordable, does this kit‑based tribute fill the gap?

Microphone Parts is one of those names that leaves you in no doubt as to what the company make! Based in California, they specialise in components for upgrading affordable capacitor mics, but also offer complete self‑assembly kits and fully assembled microphones. Most of their own designs are based to some extent on classic models from the likes of Neumann and AKG, and none more so than the SDC‑84. A small‑diaphragm capacitor mic loosely modelled after the Neumann KM84, it’s available as a kit, but you can also opt to buy it pre‑built individually or as a stereo pair, and it was the last of these options that was sent for review.

What’s In A Number?

Neumann discontinued the KM84 in favour of the KM184 sometime in the ’90s, and although its replacement has better specifications, many people still prefer the sound of the older mic, with its transformer‑balanced output stage. Unlike the 184, the KM84 was a modular microphone; you could pair a KM body with the 83, 84 or 85 capsule assemblies, which were respectively omnidirectional, cardioid and ‘speech cardioid’ with an inherent bass roll‑off. Microphone Parts’ offering can also be ordered with three different capsule types, but in this case the options available are omni, cardioid and hypercardioid. They say they have gone to considerable lengths to replicate the capsule used in the KM84, while a ‘new old stock’ JFET occupies the key role in the impedance conversion circuitry. There is an output transformer, too, but interestingly, it’s not modelled after the BV107 that was used in the KM84 and other Neumann pencil mics; rather, it employs the turns ratio and lamination material of the BV8 transformer from the Neumann U47.

It’s not intended as a slavish recreation of the KM84, then, but the SDC‑84 shares some cosmetic similarities with its inspiration. The matte silver coating is a pretty good match to Neumann’s, and it even sports a cheeky diamond‑shaped badge — which is actually slightly annoying, since it invariably traps the elastic when you slide the mic in and out of its supplied shockmount. The SDC‑84 is roughly the same diameter as the KM84, but about 50 percent longer, and the pattern of vents in the side of the body and capsule is more reminiscent of Schoeps than Neumann. The capsule contacts the impedance converter using a metal rod rather than the KM84’s pin, and unsurprisingly, is not interchangeable with an actual Neumann capsule unit.

The KM84 had a 10dB pad, engaged using a rather fiddly slide switch that often misbehaves, in my experience. The SDC‑84 has no switches, but the kit includes an optional feedback capacitor that pads down the output from the capsule so that it doesn’t overload the rest of the circuitry when high sound pressure levels are encountered. They recommend including this capacitor in your build if you’re likely to use the SDC‑84s as drum overheads, or on other loud sources, but to leave it out if you want them mostly to mic for acoustic guitars and the like. Without the capacitor, the SDC‑84 will typically be 15dB or so more sensitive than the KM84. The review mics had the pad fitted, and were comparable to my own KM84s in sensitivity. Some people, myself included, like to use KM84s to close‑mic snare drums; Microphone Parts don’t recommend the stock SDC‑84 for this, and instead offer a separate kit called the High SPL Edition.

The review pair was supplied with the cardioid capsules, but can be ordered with any configuration you choose. Mics, shockmounts and spare elastics are housed in a lightweight flightcase. Build quality was beyond reproach, and unlike many mics in this price bracket, there’s nothing at all cheap‑feeling about the metalwork or finish.

The obvious question to ask of a mic like the SDC‑84 is ‘Does it sound like a KM84?’ But if someone asked that question, I’d be tempted to respond ‘Which KM84?’.

The Real Thing

The obvious question to ask of a mic like the SDC‑84 is “Does it sound like a KM84?” But if someone asked that question, I’d be tempted to respond “Which KM84?”. Like many vintage mics, the Neumann classics can be somewhat variable, especially if they’ve seen a lot of use, and my two sound noticeably different from one another. On the grounds that one of them has lived a pampered life and is cosmetically in mint condition, I tend to use that one for comparisons, but who knows how representative it is of KM84s generally.

If we rephrase the question as “Does the SDC‑84 sound like this particular KM84?”, then the answer is a pretty enthusiastic “Yes”. One of the things that most people like about the KM84 is its relatively flat frequency response; there’s a hint of sparkle in the 6kHz region, but it’s balanced by a dose of midrange thickness from the transformer, and there’s none of the tizzy or fatiguing high end that other pencil mics can deliver. Another thing that makes it a bona fide classic is its smooth, well‑behaved off‑axis response. On both counts, the SDC‑84 aped my test KM84 very closely indeed. On many sources, in fact, I don’t think I would be able to tell them apart in a blind test. Both mics bring the same sense of solidity and authority to the recorded sound; it’s neutral, in that it doesn’t exaggerate any particular region of the frequency spectrum, but it’s far from dull. The only instrument where could hear a clear difference was on my resonator guitar, where the Neumann mic seemed to bring out the complexity and richness of the midrange more effectively.

Compared with other vintage models such as the U47 and C12, there are surprisingly few modern mics inspired by the KM84. Although it’s not intended as a direct clone, the SDC‑84 gets as close to the sound as anything else I’ve tried, and even if you’re not handy with a soldering iron, you can get a matched stereo pair for much less than the cost of a single original. The kit version is more affordable still, and if you’re confident in your ability to populate a fairly small PCB, will give you a seriously good pencil mic for very little outlay.