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Warm Audio WA-84

Small-diaphragm Capacitor Microphone
By Sam Inglis

Like the original, the WA-84 features a recessed switch to engage the -10dB pad.Like the original, the WA-84 features a recessed switch to engage the -10dB pad.

Many engineers believe that Neumann's classic KM84 has never been bettered. Have Warm Audio produced an affordable alternative?

Warm Audio have a simple but very effective business model based around recreating vintage studio hardware on a budget. Their range encompasses affordable copies of classic compressors, EQs, mic preamps and now microphones, of which the latest is an homage to one of the great studio workhorses.

Introduced in 1966, the Neumann KM84 made history by being the first ever phantom-powered microphone. It soon established itself as a popular choice not only in recording studios but also in broadcasting, thanks to its excellent sound and unobtrusive physical presence, and remained in Neumann's catalogue until 1992.

Like rival systems from Schoeps and AKG, Neumann's KM series was modular. The KM body contained the impedance converter, balanced line–driver circuitry and output transformer, with a switchable -10dB pad, and could accommodate one of three capsule assemblies. These were the KK83 omni head, the KK84 cardioid and the KK85 'speech cardioid', which had a fixed bass cut. The 85 and especially the 83 are good mics in their own right, but the classic pairing is the KM body with the KK84 cardioid head.

The KM84, as this combination is known, is an undisputed classic, and Neumann have always struggled to convince the world that its successor represents an improvement. Nearly 30 years after it was discontinued, you'll still pay considerably more for a second-hand KM84 in good condition than you will for a brand-new KM184. Hence Warm Audio's belief that there's a market for a low-cost recreation of it.

Getting Warmer

The WA‑84 follows the original design in having the capsule housed in a detachable head which can be unscrewed and removed from the body containing the electronics. At launch, there is only a cardioid capsule available, which is said to be a close replica of that found in the original KK84; other patterns are apparently in the works. The electronics are billed as "fully discrete" and a Cinemag USA output transformer is used, although it's not stated whether this is an exact copy of the Haufe BV107 used in the original.

The stereo set comes in a plastic carrying case, along with foam windshields, plastic mic clips and elastic cradle-style shockmounts.The stereo set comes in a plastic carrying case, along with foam windshields, plastic mic clips and elastic cradle-style shockmounts.

For review, we were sent the WA‑84 stereo set, which comprises a matched pair of mics with clips and shockmounts, in a fitted case. It's fair to say that the low price of the WA‑84 is somewhat reflected in its presentation. Compared with the real thing, Warm Audio's satin nickel finish looks a little tacky, and the printed black legending on top of it is prone to wearing off (like the KM84, the mic is also available with a black finish). The clips and shockmounts are unremarkable generic affairs, and the plastic case is thoroughly cheap and nasty. Against this, it should be borne in mind that at today's prices you'd pay more for a single KM84 without any accessories than you will for the full WA‑84 stereo set.

When I first saw a KM84, I was amazed at how small it was. The WA‑84 is unlikely to provoke the same reaction, being considerably longer and a shade wider into the bargain. The difference in diameter ensures a Neumann capsule head can't be attached to a Warm body, nor vice versa. The slide switch that engages the -10dB pad is even more difficult to operate than on the original, which at least means you won't change it by accident.

Scaling The Heights

Warm Audio's quoted specifications are mostly within 1dB or so of those given by Neumann for the KM84. Only an on-axis frequency response plot is given for the WA‑84, and this closely follows the published response of the KM84 up to about 7kHz. Thereafter there's a small wiggle, followed by a broad 3dB peak at 15kHz which is absent from Neumann's own plot. One should not read too much into this, as frequency response charts are usually a poor guide to the subjective sound of a microphone, but it's interesting — because if you ask engineers what's so special about the KM84, one answer usually has to do with its flat or 'unhyped' high-frequency response. By contrast, the KM184 is often perceived as harsh or over-bright, and this is definitely my perception of the AKG C451/CK1 combination that was the KM84's chief rival back in the day.

One of the other things for which the original is renowned is excellent off-axis pickup. If you point a KM84 at one instrument, you can be confident that spill from other instruments in the same room will be captured cleanly and without nasty coloration. And for some of us, the 84's relatively graceful behaviour when overloaded is also relevant: place it right up on a snare drum and even with the -10dB pad switched in, you'll likely be pushing it past its 130dB maximum SPL rating, but the result is a fat snare sound that still has plenty of transient snap.

The WA–84s sounded very close to the KM84s both on- and off–axis, and in many cases, I doubt I'd have been able to tell the difference in a blind test.

When I'm 84

Warm Audio WA-84I had the review WA–84s on loan for several weeks and was able to try them out on snare drum, drum overheads, acoustic guitar and electric guitar, among other sources, usually with my own KM84s set up as close as possible to provide a direct comparison. I also made several recordings with the mics pointing away from the source in order to compare the off-axis response of the two.

Subjectively, I thought the WA–84s sounded very close to the KM84s both on– and off-axis, and in many cases, I doubt I'd have been able to tell the difference in a blind test. Where I did hear a difference it was a subtle one. On close-miked snare drum the WA–84 seemed a touch fuller in the low mids, perhaps suggesting that the Cinemag transformer saturates in a slightly different way from the original; and in a couple of other cases it came across as being a touch darker at the top end than the KM84. Certainly, the WA–84 is anything but over-bright or harsh at the top end, despite that 15kHz peak.

I don't have access to a proper test chamber, but out of interest, I also tried feeding pink and white noise into both mics through a good-quality monitor speaker in a well-treated control room. Such a comparison can't give you a reliable absolute measurement of frequency response, since it's not calibrated, but as long as both mics are placed in exactly the same position and the test signals are identical, it should provide a worthwhile comparison — at least, I repeated the exercise a couple of times and got fairly consistent results. These suggested that the differences between Warm Audio's and Neumann's published frequency responses are accurate. Measured on-axis with one of my KM84s as a point of comparison, the WA–84 showed a peak at 15kHz and a narrower dip around 10kHz, neither greater than a couple of dB. Measured off-axis, impressively, the two mics were more closely matched.

The WA-84's frequency response.The WA-84's frequency response.

Assuming that the KM84's frequency response really is as flat as it's said to be, this suggests that Warm Audio haven't quite matched that linearity above 10kHz, but the discrepancies are small enough to be disregarded in most cases. To my middle-aged ears, a difference of 2 or 3 dB at 15kHz is inaudible, and while the slight dip at 10kHz perhaps makes itself heard on some sources, it really is very subtle and belongs in the realms of 'slightly different' rather than 'better or worse'. If you're in the habit of using KM84s as a main pair on very exposed sources such as a solo piano or string quartet, the WA–84s' slightly less flat high-frequency response might conceivably be to its detriment, but for the majority of applications I think it either won't be noticeable or won't matter. We should not forget that Neumann's stated frequency response for the KM84 was only ever guaranteed within ±2dB, and that many of those still doing service in studios around the world have had hard lives and probably aren't in spec in any case.

Overall, then, I think Warm Audio have done a good job of replicating the sonic character of the KM84, and to my mind, the WA–84 gets a fair bit closer to the mark than the same company's WA–87 does to the U87. The KM84 was discontinued for a reason — by comparison with modern designs, it's relatively noisy, lacks sensitivity and can't cope with extreme SPLs — but it's an enduring classic that still gets used on sessions every day. Warm Audio's tribute inherits the limitations of the original, but what's much more important is that it goes a long way towards capturing the special qualities that make it so highly regarded. I'm sure it will be very popular.

Know Your KMs

Neumann have applied the designation 'klein mikrofon' — literally, small microphone — to quite a few different models over the years, and there's some potential for confusion in the history of the KM84 and its relatives.

The first series of KM microphones used the AC701 miniature valve as an impedance converter, and employed distinctive metal-skinned capsules with a characteristically bright sound. These were the omni KM53, cardioid KM54 and multi-pattern KM56, all now highly prized by vintage mic aficionados. The more conventional gold-sputtered Mylar diaphragm later used in the KM84 made its debut in the KM63, KM64 and KM66, also based around the AC701, while the final valve model in the series was the U64, which paired the KK64 cardioid capsule with a Nuvistor valve, and is generally less well regarded.

As the '60s wore on it became obvious that Neumann needed to develop solid-state microphones. First off the blocks was the rather obscure KTM, swiftly superseded by the KM73, 74 and 75. These omni, cardioid and 'speech cardioid' models all used the same transformerless preamp body and were powered by 12V 'Tonader' power, as supplied by many portable tape recorders of the day; so too was the multi-pattern KM76.

Then, in 1966, Neumann staff were invited to Oslo to consult on reftting the studios of the state broadcaster, the NRK. The NRK studios already had a distributed 48V DC supply in place for lighting purposes, and their engineers wanted to employ this for powering microphones too. The result was the now-ubiquitous 'phantom power' standard, and the first production microphone to take advantage of it, the Neumann KM84.

From a design point of view the KM83, 84 and 85 remained pretty consistent throughout their long life, but some production variations are worth knowing about. Although the internal electronics are identical and they can be freely used with any of the three capsule assemblies, early bodies had a model number such as 'KM83' or 'KM84i' engraved on them, while later versions just bore the designation 'KM' or 'KMi'. The lower-case 'i' indicates that an XLR output connector was fitted as standard; the KM-series bodies were also available with a locking three-pin DIN or 'small Tuchel' connector. Adaptors for these are fairly easy to obtain. It's also worth mentioning that although the KM84 preamp was designed to present a nominal 200Ω output impedance, some of those sold in the US market were adapted for a 50Ω output and will deliver lower output levels into modern preamps. This modification is said to be fairly easily reversible.

Since the KM84's demise in 1992, there have been several other ranges of 'klein mikrofon' in the Neumann catalogue. The omni KM183 and cardioid KM184 directly replace the 83 and 84 respectively, the main differences being their transformerless output stages and the addition of a noticeable bump in the high-frequency response. (It is sometimes stated that the 184 uses the same capsule as the 84, but this is not quite true: the diaphragm 'platelet' is identical but its housing is not.) Confusingly, though, the KM185 is not a 'speech cardioid' like the KM65, 75 and 85; rather, it has a full-range capsule with a hypercardioid response.

Another difference between the two ranges is that the KM18x mics do not form a modular system. For that additional flexibility, you'd want to investigate Neumann's current KM-A (analogue) and KM-D (digital) series, or their predecessors in the KM100 series. These series include a much larger range of capsules and accessories than were available in the original KM8x range, with transformerless preamps and a more 'modern' sound similar to that of the KM184.

Finally, there have been various other KM models over the years, including the multi-pattern KM86, which was to the KM84 what the KM56 and 66 were to the KM54 and 64. The nickel-skinned capsules used in the KM56 survived into the solid-state era in the multi-pattern KM88, and the KM range has also included shotgun, stage vocal and lavalier mics.

Pros

  • A pretty decent attempt to capture the character of the Neumann KM84, at a compelling price.
  • Shockmount, clip and case included.

Cons

  • The fact that this is an affordable mic is apparent in the quality of the finish, accessories and especially the case.
  • Although the general sound is KM84-like, the frequency response is not quite as flat above 10kHz.

Summary

A bold and largely successful attempt to recreate a classic vintage mic on a budget.

information

£399, stereo pair £749. Prices include VAT.

Nova Distribution +44 (0)20 3589 2530

sales@nova-distribution.co.uk

www.nova-distribution.co.uk

warmaudio.com

$399, stereo pair $749.

Warm Audio +1 512 348 6585

info@warmaudio.com

warmaudio.com

Published September 2019