Very accurate small diaphragm omni condensers that give even B&Ks a run for the money

Review by Kevin Becka

First reaction: a $399 fixed omni condenser?! Those are usually high-end instrument mics. Second reaction: a beautifully crafted cherrywood case containing what, matched dueling phaser pistols? These funny-looking mics are 9" long and less than 1" in diameter at the XLR end. About half way up toward the capsule it tapers down until it's thinner than a pencil. The capsule is only about 1/4" across.

And one would have to be more than a little skeptical about Earthworks' claims about their OM1. How good can any mic in this price range be? Surprisingly good, as you'll read.

This is a mic designed for accuracy above all, a goal that involves one trade-off: a higher noise spec. Does that end the review right here? No, it just means that the OM1 isn't a good choice for applications where noise would be a problem, such as exposed sources with a wide dynamic range. But they're an excellent choice for many other things.

Interestingly, Earthworks actually admits the problem right up front. They explain that smaller diaphragms inherently generate more self-noise than larger ones, but also provide a high degree of sonic accuracy. The idea is that a little noise is a good trade-off for a true, uncolored sound.

Earthworks also lists the fixed omni pattern as a liability, but an inevitable price for accuracy. And they're right: omnis are much more accurate than directional mics. Off-axis, cardioids become boomy and can have strange peaks at certain frequencies. I always use omnis whenever I can get away with them because they color the sound the least.

Small diaphragms have lower mass and thus are able to take more SPL (sound pressure level) and provide better high frequency response. They also help with the problem of lobing, where the off-axis frequency response is not flat. The problem with low mass is that it gives you low output, so you must boost the gain electronically. Needless to say, the cleaner your amplification, the cleaner your signal will be.

Small diaphragms are nothing new. They have been used for years in work involving ultrasonic, point source, and high SPL measurement. But because of their limitations, they are rare in pro audio.

Before we get to to the tests, there is one potential problem to mention: the OM1 doesn't work with mic preamps that have direct-coupled transformers. This eliminates mic preamps from Neve, Trident and quite a few other high-end manufacturers. According to Eric Blackmer at Earthworks, the simple solution is to provide phantom power from a source other than the mic pre; they're aware of this, and future products in their microphone line will not have this problem.

The test

I tested the OM1s through an Otari Concept console in a very nice room that is well designed and quiet. All tests were done flat and through no VCAs. The first test was on a grand piano, freshly tuned, with the lid open to the widest position. Both mics were about 2 feet off the sound board. One was positioned looking down at the hammers, about an octave above middle C; the other was at the skinny end, over the sweet spot for the low end is on this particular piano. Up against the OMls were two very expensive B&K 4006 low-noise omnis-very tough company.

I had the pianist play a very dynamic classical piece. First impression from everyone: the OM1s sounded great! They didn't sound like $400 dollar microphones. The separation between the mics was surprising. The stereo picture was much wider than with the B&Ks. I did my usual checks for phase, and all was okay. It's baffling how two sets of omni mics placed in almost identical positions can produce such a different stereo picture. In fact, the stereo width with OM1s was almost too much-it sounded like two guys playing the same piano in different rooms. I had to bring the panning to a 3 o'clock/9 o'clock position to match the B&Ks.

I also noticed that the levels of the two sets of mic preamps were set almost identically and I was getting the same VU reading so I didn't have to make up any gain on the OM1s. At the level I was listening, about 85dB, the inherent noise wasn't a problem.

We ran the mic through some severe SPL tests. I close-miked a snare and had the drummer play as loud as he could. There was no apparent clipping. It sounded very smooth on the transient peaks and, once again quite accurate. That's where the small diaphragm struts its stuff, although I wouldn't recommend an omni for close miking drums in a kit because leakage would be a problem. Omnis can work really as overhead mics, however.

For some noise tests, I left a B&K and an OM1 in the studio alone with the air conditioning turned off. This is where the differences become more apparent. I cranked the mic preamps and listened to both mics at equal level. The B&K was whisper quiet and only gave up room noise. The OM1 was quite hissy in the upper range. But again, this was a highly exaggerated level. At a normal operating level, on an instrument where you're getting plenty of input level to the mic, the noise is not readily apparent.

Next, I recorded an alto sax using the B&K/OM1 setup. On first listen, the OM1 hung in pretty well. The B&K was a little warmer (I hate that term but it does describe the difference) with a slightly bigger bottom end. I had the sax player play some long notes at various frequencies and A/Bd the two mics. Mid frequencies were barely discernible between the two. Lows were bigger and better on the B&K with a more natural representation of the "breathy" component. Upper mids and highs had exaggerated overtones on the OM1, making the B&K sound more natural. [ Earthworks says that above about 10-12kHz, the on-axis response rises gently to 22kHz, typically 2dB, while the off-axis falls, usually down about 4dB at 22kHz. So recording the sax 90° off-axis would get rid of the exaggerated overtones.- NB ]

Okay, the B&Ks are better-and they should be. But when you weigh the price difference between the two, the OM1 hangs tough.

Analysis

I'd recommend the OM1 highly for any personal or project studio owner. It's unbeatable at $399.

Earthworks gets a solid A+ for execution, price, and presentation. It's rare to find a manufacturer whose intention is to make the best product possible. Price is no object, so their products are expensive and often become collector's items. It's even rarer to find that attitude in a company that through innovation and intestinal fortitude makes a high-end product at a modest price.

I wouldn't use OM1s for exposed sources with a wide dynamic range such as vocals, classical music, or choral applications-depending on the selection of mics available, of course. But I would use them for any instrument, especially horns, percussions, acoustic piano (where the material and the instrument provides sufficient level), drum overheads, guitar amps (you get interesting results using them with an SM57 or 421 and mixing them properly), and any other instrument or application where the level is between moderate and nuclear.

Congratulations to Earthworks for a great microphone. Keep your eye on this company for interesting developments in the years to come.

Price: $399. When purchased as a pair, the mics are matched at the factory and come in the cherrywood case at no extra charge.

More from: Earthworks, PO Box 517, Wilton, NH 03086. 603/654-MICS (6427), fax6107.

Kevin Becka is an independent Recording Engineer. He can be reached at kbecka@aztec.asu.edu. Kevin would like to thank Paul Brewer for his help in the evaluation tests.