Crown CM700

Paul White reviews an uncharacteristically compact mic and discovers that size isn't everything.

The perfect mic would translate any sound without adding to or detracting from it in any way, yet the modern engineer is faced with a multitude of different models designed for different applications or to give different tonal 'enhancements'. This is due, at least in part, to the technical impossibility of making a microphone that performs optimally for all parameters that are of concern to the end user; a mic designed to withstand huge sound levels, for example, might tend to be noisy on low‑level signals, and a mic designed for a pristine on‑axis response might fall short when faced with off‑axis sounds.

Then there's fashion: do you actually want a mic that sounds accurate, or do you want one that flatters — rose‑tinted spectacles for the ears? And what about pickup pattern? Omnis invariably produce the most natural sound, but they may pick up sounds we'd rather not hear. Cardioids, on the other hand, provide better rejection of off‑axis sounds, but often at the expense of tonal neutrality. Multi‑pattern mics are available, but they cost rather more than fixed‑pattern models, and choosing one makes little sense if it's going to be left set to 'cardioid' day in, day out.

Crowning Glory

With the CM700, Crown haven't been rash enough to try to build a mic that promises all things to all people. Instead, they seem to have tried to deliver most things to most people, all at an affordable price. Most live performers use cardioid mics because of the need to reject spill, and in the studio, cardioids are popular for the same reason. That narrows it down a bit — let's build a cardioid. In order to get high‑frequency accuracy, you need a capacitor capsule because of the low moving mass of the diaphragm when compared to a moving‑coil mic, but you can get the same performance from a well‑designed back‑electret capsule, often at a lower cost, and with the added bonus that you can use lower phantom power voltages when the full 48 volts is unavailable. So it's no surprise that the CM700 is a back‑electret and can run from any phantom power voltage in the 12‑48V range. However, Crown have resisted the temptation to provide battery power as an alternative, because this rather compromises the amount of available headroom.

In order to maintain a reasonably accurate off‑axis response (the level should drop, but the frequency response should stay as nearly the same as possible), Crown have used a fairly small‑diameter diaphragm. Indeed, the whole microphone is surprisingly small — so small that when you plug an XLR into the end of it, the mic almost doubles in size. In fact, the black powder‑coated finish and the general proportions of the mic make it look like a small Maglite torch.

Recessed into the side of the mic is a switch for providing a bass roll‑off characteristic, and there are also two alternative filter positions: a steep slope and a more gentle roll‑off. Without the filter switched in, the mic has a useful response from 30Hz to 20kHz, enabling it to capture the entire audible spectrum.

People like the idea of honest microphones, but in listening tests, they still tend to pick the ones that sound the most pleasing rather than the ones that sound the most accurate. What's more, in live situations, mics tend to need a little help in the 3‑5kHz presence region to aid projection. Pragmatically, Crown have introduced a gentle presence rise, which is just enough to add that all‑important 'air' to the top, and to improve diction in difficult environments. To put this in perspective, some mics provide between 5 and 10dB of boost at around 3kHz; the CM700 has only around 2.5dB of lift above 4kHz.

For live vocals where capacitor mics are used, popping is always a problem, but you can't really go on stage with a pair of tights stretched over a coat‑hanger. To try to get around this, Crown have included a push‑on foam windshield which has the unusual feature of a secondary foam disc suspended a few millimetres above the main section of the foam by means of a plastic moulding. I would expect this to compromise the off‑axis response slightly, so it's probably best to use it only when working with close vocals.

Turning to specifications for a moment, the mic has an equivalent self noise of 21dB SPL (A‑Weighted), which is not untypical for this type of microphone. Working with a sound level of 94dB, this would provide a signal‑to‑noise ratio of 73dB SPL. The maximum SPL (Sound Pressure Level) is 151dB for 3% distortion (using 48V phantom power). This is incredibly loud; no wonder, then, that the manufacturers also recommend the CM700 for drums and percussion, as well as vocals, pipe organ and classical music.

On the sensitivity front, the quoted figure is 2.5mV/Pa, which is adequate for most purposes, though actually quite low when compared to some other capacitor mics. This brings me back to my point that mic design is a compromise: Crown have obviously designed with close to middle‑distance miking, where high sound levels are a distinct possibility, in mind. As supplied, the mic comes in a tough, zip‑up carry case with a stand adaptor clip and the aforementioned windshield.

Soundcheck

Most mics I review surprise me in at least one way. The first thing that surprised me about the CM700 is that it doesn't sound small at all. I compared it side by side with some other high‑quality back‑electret stick mics and found that, although the CM700 was noticeably less sensitive than most of its competitors, it delivered a smooth, full sound with an open, natural top end, while some of the other contenders sounded slightly thin or scratchy by comparison. This was particularly evident on the acoustic guitar tests.

Low sensitivity can sometimes be a problem, but tested with a small Mackie mixer and an acoustic guitar around 12 inches away from the mic as the subject, the CM700 provided adequate level with no obvious background noise. To some extent, I think the CM700 may sound full‑bodied in comparison to other mics of the same type because many other manufacturers introduce a deliberate, and quite severe, low‑frequency roll‑off to counteract the bass rise caused by the proximity effect (of cardioid mics), when the mic is used very close up. By fitting two different roll‑off filter settings, and perhaps by keeping the sensitivity down to prevent breath noises from overloading the electronics, Crown have been able to extend the useful low‑end response rather further.

The pop shield arrangement makes an obvious difference on vocals, and is quite effective when used in conjunction with one of the bass roll‑off settings. However, for studio use, an external pop shield is still recommended.

Summary

This is a surprisingly nice‑sounding and versatile little microphone that will deliver first‑class results in most high‑SPL or close‑up miking situations. On the other hand, its low sensitivity really makes it unsuitable for jobs like distance miking of choirs or classical ensembles. Close‑miking of classical instruments is no problem, and pipe organs at a distance should be well represented, but for cockroaches mating at 50 yards, you need to choose a mic with a different set of compromises.

As to subjective sound, the CM700 gives the impression of honesty, delivering a smooth, articulate sound with just the right sense of openness at the high end. Vocals sound clear without being thin, and if I hadn't seen the mic first, I wouldn't have been able to guess at its size from listening to the results it produces. Crown are a very reputable microphone company and this little mic will do nothing to damage their reputation. In short, if you don't need to impress clients with a 'grenade on a stick' mic, the CM700 will meet the majority of recording needs.