PEARL CC22 & ELM-C - RECTANGULAR DUAL DIAPHRAGM MICROPHONES
Pearl has been hand-making unique microphones for 70 years, but very few people know about them. Greg Simmons dives deep…
Text: Greg Simmons / Audio Technology Magazine - Issue 85 - 2011
"I’ll bet that most AT readers have never heard of Pearl microphones, and therefore might assume they’re yet another faux manufacturer hiding cheap Chinese crap behind a glossy Western façade. Or, equally as valid, assume that the well-known percussion manufacturer Pearl has cashed in on the ‘own your own’ microphone scam. Both assumptions are quite wrong. Since 1941 the small team at Pearl Microphone Laboratory in Astorp, Sweden, has been quietly hand-making condenser microphones that are so unique almost nobody knows about them.
I first heard about Pearl microphones in the early ’90s when a musician passed a handful of CDs across my desk. “Reckon you can you make a recording that sounds like these? The engineer uses some strange microphones from Sweden, something to do with rectangular diagrams.” “You mean diaphragms?” “Probably, yeah…” The CDs contained some of the most natural, spacious and dimensional direct-to-stereo recordings I’d ever heard; similar to the sound quality provided by ribbons but without the associated dullness and noise. I’ve been curious about those rectangular diaphragms ever since…
NOT ALL PEARLS ARE ROUND
Before looking at the review models, it’s worth looking into that rectangular diaphragm. The vast majority of condenser microphones use a circular diaphragm that is held under tension, just like a drum skin. The diaphragm’s mass and diameter combine with the tension to produce a single fundamental resonant frequency that exists across all planes of the diaphragm, creating a strong resonant peak in the frequency response that is akin to the note created by a drum skin. The microphone designer has a few options for dealing with the resonant peak. The diaphragm’s diameter, mass and tension can be tweaked to shift the resonant frequency above 20kHz, where it assumedly won’t be audible; this produces a very small diaphragm that has many excellent properties but suffers from higher self-noise. Alternatively, the diaphragm can be damped to tame the resonant peak, but at the expense of sensitivity and high frequency performance – just like putting gaffer tape on a drum skin. Finally, a combination of tweaking the diaphragm’s parameters and applying a nominal amount of damping can be used to turn the resonant peak into something useful; for example, an upper midrange boost to enhance the intelligibility of vocals, or a high frequency boost to compensate for the loss of high frequencies in the air when miking from a distance.
Dozens of excellent condenser microphones have been made using circular diaphragms, but that strong fundamental resonance remains an unavoidable fact of physics that often manifests as a shrillness or harshness when boosting the high frequencies more than a few dB.
Pearl sidesteps this problem by using a rectangular diaphragm, replacing the circular diaphragm’s single strong resonant frequency with two considerably weaker resonances: one for the length, and one for the width. Returning to the drum skin analogy given earlier, nobody makes a rectangular drum skin because it isn’t resonant enough to produce a useful musical note; that’s bad for a drum skin, but good for a microphone diaphragm. By tweaking the diaphragm’s length/width ratio and applying a modicum of damping, the result should be a sufficiently sensitive microphone with a smooth frequency response and natural tonality, free of the effects of a single strong resonant frequency.
An interesting side effect (sic) of the rectangular diaphragm is that it effectively gives the microphone two polar responses: one in the vertical plane and one in the horizontal plane. When placed vertically (i.e. the usual upright placement) the diaphragm is more sensitive to sounds from the sides and less sensitive to sounds from above and below, particularly at higher frequencies. Such selectivity can be a helpful tool for rejecting unwanted sounds. Placing the diaphragm vertically rejects reflections from the ceiling and floor, a useful feature for making direct-to-stereo recordings where strong vertical reflections confuse the stereo image. Placing the diaphragm horizontally minimises spill from instruments to the left and right, a useful feature when close-miking an instrument such as a double bass with other instruments playing in the same space. The diaphragm rejects spill from the sides while providing its full polar response across the length of the double bass.
THE REVIEW MODELS
Two Pearl microphones were provided for this review: the CC22 and the ELM-C. Both are housed in handsome wooden boxes reminiscent of those supplied by Schoeps, with radiused edges and an engraved plaque on the side showing the model number of the microphone contained within. A foam insert separates and cushions the contents, including the microphone (protected from dust in a soft fabric sleeve) and Pearl’s #1930 shockmount, which uses Rycote’s Lyre suspension system. Each microphone is individually hand-tested with MLSSA, and the signed specification sheet shows its serial number, frequency response, sensitivity and self-noise.
The CC22 is a cardioid condenser microphone using a rectangular dual diaphragm measuring 30mm x 20mm. The supplied specification sheet shows a sensitivity of 18mV/Pa and a self-noise of 12dBA; both respectable figures. The measured frequency response remains within 1dB of flat from below 40Hz up to 3kHz, exhibits rises of up to 2dB between 3kHz and 9kHz, remains within 1dB from 9kHz to 17kHz, then rolls off to -5dB at 25kHz. Very promising.
The ELM-C is a cardioid condenser microphone using a considerably longer rectangular dual diaphragm measuring 70mm x 11mm. The specification sheet for the review unit shows an impressive sensitivity of 28mV/Pa and an equally impressive self-noise of 9dBA. Its measured frequency response begins 2dB down below 40Hz, is essentially ruler-flat from 60Hz to 7kHz, rises to +2dB at 10kHz, deviates within ±2dB up to 20kHz, then rolls off to -7dB at 25kHz. Also very promising, and possibly well suited to distant work.
No information is given regarding the distance from the source that the frequency response measurements were taken from, but the extended low frequency response suggests about 30cm.
Both microphones are satisfyingly heavy for their size, and include solid XLR inserts with gold-plated pins. The Pearl logo and model number are etched into the front with gold lettering, the serial number is etched into the back. A red LED mounted immediately beneath the diaphragm on the back of each microphone illuminates when phantom power is supplied – clearly visible to the engineer but sufficiently inconspicuous to the artist. The build quality is good and solid, the design is sensible and acoustically unobtrusive, and the high gloss black lacquer finish is so lustrous out of the box that merely touching it feels like a sin.
The CC22 and ELM-C offer very agreeable specifications and tick all the right boxes in the look and feel categories, but how do they sound? To find out, I tested both microphones during a number of sessions at the Australian Institute of Music. In most of the tests I level matched the Pearl microphones against established industry standards to provide points of reference that many readers would be familiar with.
THE CC22 IN USE
This is a very natural sounding microphone that is highly suited to close-miking acoustic instruments. Placed perpendicular to the soundboard of a violin at a distance of just over a metre and compared to a Neumann KM184 in the same position, the CC22 sounded subtly sweeter and rounder, less ‘steely’ on edgier high notes without sounding dull, and offered a touch of the instrument’s body and resonance that was sorely missing in the KM184. It tracked the aggressive transients of Bartok-styled pizzicatos with ease, and held its composure through harmonically complex passages that left the KM184 sounding thin and etched. The CC22 produced an excellent sound that did justice to the instrument, clearly superior to the KM184 yet remaining tonally compatible with it.
In contrast to the violin recordings, I tried the CC22 on two different electric guitar recordings. The first was a heavily distorted sound created by a Fender Squire through a Fender 15 amplifier. Placed 30cm in front of the cabinet the CC22 gave a smooth and clear rendition with no apparent glare or harshness, bringing the microphone’s subtle frequency response rises between 3kHz to 9kHz to the fore. One would have to be careful when applying EQ to avoid pushing the sound towards thinness. In comparison, Neumann’s U87 in the same position sounded as if it was going through a band-pass filter, with no low or high frequency extension. It was duller and very nasal, but offered more chugga-chug grunt. The second was a relatively clean-sounding Fender Telecaster through a Roland JC120. Placed a few centimetres in front of the cabinet and slightly off-axis to one speaker, the CC22 sounded smooth and uncoloured, prompting another engineer on the session to remark that it reminded him of Royer’s R121 but with better high frequency extension.
THE ELM-C IN USE
This is a very natural sounding microphone that excels at distant work; it is really in its element at distances of 30cm and beyond. It also works well up close but, due to the length of the diaphragm, its relative angle to the sound source becomes quite critical.
The first test was on classical guitar, with the ELM-C placed about 60cm from the point where the neck joins the body and focused where the strings were plucked. Tweaking the microphone placement and angle achieved a detailed, warm and even sound that, like the CC22 on violin, was never harsh or thin and was clearly preferable to a KM184 placed in the same position (for what such a comparison is worth).
For the second test the ELM-C was placed just outside the crook of a small grand piano and aimed towards the centre of the strings. The resultant sound offered full and round low notes and smooth but precisely detailed high notes, even on the harshest short-stringed high notes. A very good result for a tweak-free initial placement – instant piano sound! It was, however, in danger of sounding bloated; I suspect that moving any closer would’ve yielded too much low frequency energy due to the proximity effect. Interestingly, a Neumann U87 placed in the same position sounded unacceptably roomy and distant, and considerably lacking low frequency energy relative to the ELM-C. Placing the CC22 in the same position produced an acceptable sound with the same high frequency character of the ELM-C but with less low frequency energy, and without the U87’s excessive roominess.
As a final test, I pitted the CC22 and ELM-C against each other and a U87 on a close-miked male vocalist performing a soul song a capella. Both Pearl microphones made the U87 sound gritty, veiled and dated. The CC22 delivered a very appealing result but the ELM-C stole the show with a sound that was remarkably ‘present’ and full-bodied with nowhere near the amount of proximity effect I had anticipated after the earlier grand piano test.
PEARLS BEFORE STRINE
Throughout this review I have tried to resist comparisons with ribbon microphones based purely on their visual similarities. It’s an easy trap to fall into; at first sight most engineers and musicians assumed the review units were ribbons. Although they are very different technologies, they do share at least one common trait: a very natural sound due to a lack of any strong resonances in the midrange and high frequency spectrum. Importantly, however, the Pearl microphones do not suffer the perceived dullness and high noise floor associated with ribbons. In that respect, the rectangular diaphragm nicely straddles the gap between ribbons and circular diaphragm condensers without making any concessions to either technology. For this reason alone, every microphone collection should have at least one rectangular diaphragm condenser microphone.
The CC22 and ELM-C are both excellent cardioid microphones for situations that require a natural and uncoloured sound without sacrificing detail and high frequency extension, and without risking a high noise floor. The CC22 is applicable for all close-miking duties that would normally be undertaken by a condenser microphone, and delivers a sound that subjectively lies somewhere between a Royer R121 and Neumann’s KM184. The ELM-C is a very interesting microphone that shares many of the CC22’s characteristics but is best used at distances greater than 30cm or so, producing a full-bodied and present sound where other directional microphones would start sounding thin and detached.
Astute readers may have noticed a recurring observation throughout the tests described above: whenever one of the review microphones was compared with a traditional condenser, the latter always had more room sound. I attribute this to the rectangular diaphragm’s tendency to reject sounds arriving from above and below, as discussed earlier. Without the additional vertical reflections, the rectangular diaphragm always sounded closer and less cluttered than a circular diaphragm at the same distance. With that in mind, I’m very keen to try a matched pair of rectangular diaphragms on a string section, choir, chamber music ensemble or one of my field recordings in a Himalayan monastery. The rectangular diaphragm’s uncoloured tonality combined with its rejection of interfering vertical reflections is bound to yield a direct-to-stereo recording that is natural, spacious and dimensional – just like those CDs that triggered my initial interest in rectangular diaphragms all those years ago.
I look forward to adding a twin set of Pearls to my collection in the near future."