What would you record with an indestructible microphone?
For the most part, microphones are designed to pick up vibrations in the air that have been created by some kind of physically vibrating sound source. But there’s one specialist mic design, called a contact mic, that can cut out the middleman (ie. the air) by directly transducing the sound source’s physical vibrations into a voltage signal.
To be frank, though, contact mics have always seemed pretty niche to me as far as everyday recording tasks are concerned. I remember buying one out of sheer curiosity about 15 years ago, but it was a fiddly, cheap‑looking thing that was noisy as hell and made my violin sound like a cat in a biscuit tin. As such, I’d mentally filed contact mics under ‘break glass in case of drum triggering’ ever since.
A couple of months ago, however, my interest was rekindled by a new product from Chicago‑based company Zeppelin Design Labs: their Cortado MkIII, a contact mic that aims to elevate this transducer concept into a bona fide recording tool. But does a contact mic really deserve a place alongside traditional mics in the studio? Let’s find out...
The business end of the Cortado MkIII looks, for all the world, like one of those little tins of lip‑salve, measuring about 36mm in diameter and 14mm thick. A slim 185cm shielded cable sprouting from the tin’s side connects its internal vibration transducer to a Class‑A preamp, housed in a separate 43 x 43 x 83 mm steel box. The preamp’s active electronics receive phantom power from the box’s single male XLR socket, which also serves as the balanced audio output.
On the underside of the preamp are four miniature DIP slide‑switches, two of which can activate a ‑10dB input pad, while the others determine whether the preamp’s internal high‑pass filter rolls off at either 23Hz or 150Hz. The Cortado’s published frequency response is an impressive 23Hz‑40kHz (at the ‑3dB points), and the provided plots show that the sub‑100Hz region gets a couple of decibels warmer when the pad’s engaged.
The whole package feels neatly put together, and the mostly metal construction seems pretty robust too. Indeed, the manufacturer’s product video shows the transducer being run over by a car without damage, and I can well believe it. Furthermore, the mic’s operating temperature range is listed as ‑40 to +80 degrees celsius, and you can even use the transducer underwater, so it’s clearly no shrinking violet! I do question the use of DIP switches for settings that you’re likely to be changing day to day, though. DIP switches seem better suited for set‑and‑forget parameters, and I’d rather Zeppelin had added another $10 to the asking price and provided more substantial switches that I could operate without taking the toothpick out of the corner of my mouth...
There are lots of ways you can fix the Cortado to a source of vibration. For a temporary solution, the mic ships with a chickpea‑sized blob of sensor putty that can stick the mic to most surfaces. (Despite its technical‑sounding name, my ‘sensor putty’ was supplied on Faber‑Castell backing paper, which suggests that further supplies may not be too hard to come by!) For a more secure solution, Zeppelin suggest those little plastic spring clamps you use for DIY, but while those work well where you’ve got something fairly thin and flat to clip the mic to, I found that mini bar‑clamps provided more scope for experimentation, given their much wider jaw span. For permanent mounting, Zeppelin offer an optional metal screw‑on bracket, but also recommend strong double‑sided sticky tape as a less heavy‑duty alternative.
If you read Sound On Sound regularly, then you’ll likely already know a thing or two about mic technique. But I suspect it won’t help you much here, because a contact mic is actually a very different animal! For a start, the mechanical operation of some musical instruments can create physical vibrations within the instrument’s body that wouldn’t normally impinge heavily upon the listener (or a normal microphone), but which dominate over the instrument’s tone if you’re contact‑miking. So you can pretty much rule out getting any kind of natural balance on woodwind or brass instruments with the Cortado on account of key/valve clunks, for instance. My upright piano’s pedal action also came through more prominently than I’d have expected with traditional mics.
There is one sense, though, in which using the Cortado could be seen as an extension of close‑miking. You see, when you put an SM57 an inch away from your snare drum, you’re mostly going to pick up just that small subset of the instrument’s frequency output that emanates from the coaster‑sized surface area the mic’s actually pointing at. This is why moving the mic just a little bit under those circumstances can make such a big difference to the sound. With the Cortado, though, the transducer’s contact plate picks up vibrations from an even smaller surface area (and more from the centre of that area than from the edges, it seems to me), so the changes in tone you get by moving this mic just an inch can be crazy.
Furthermore, the exact way the transducer is coupled with the vibrating surface can make a huge difference to the resultant output level and tone. This makes using the sensor putty (as I suspect most users will) a little bit of a lottery. For instance, when I repeatedly remounted the mic in an identical location (as close as I could judge it) alongside the bridge of my acoustic guitar, I kept getting audible timbral variations — the amount of low end in particular seemed to be quite fickle in this respect. (The Cortado’s user manual recommended using a uniform layer of putty across most of the contact surface, but for my part I found that a kind of ‘bullseye’ pattern seemed to give a slightly more predictable tone.) Using clamps instead of putty made things a lot more repeatable, especially when using the bar clamps, since these were able to press the transducer down more firmly.
The upshot of all this is that finding a suitable sound with the Cortado usually takes a good deal more trial and error than when you’re using normal mics. And even when you find a mic position you like the sound of, if you’re working with the sensor putty then there’s no guarantee you’ll be able to recreate that sound again on a future session — or indeed if the player accidentally knocks the transducer between takes! To be fair to Zeppelin, though, I wouldn’t say these are criticisms of the Cortado per se, because such difficulties are inherent with any contact mic, as I see it. And there’s a silver lining too, in that you can also deliberately tamper with the transducer coupling for creative tonal ends, perhaps by sandwiching a layer of some different material between the source of vibration and the mic.
Another practical consideration is what to do with the tether cable from the preamp, because it will happily carry vibrations to the transducer too, and I did on occasion get undesirable buzzes coming through on the signal simply because the cable had come into contact with some vibrating component of the instrument. In addition, if the cable is pulled taut, it may interfere with the transducer’s own vibrational characteristics, effectively applying a kind of mechanical filter, as well as potentially altering the transducer’s surface coupling. So having a couple of spare clips and a rag to damp the cable and hold it out of harm’s way isn’t a bad precaution.
As you’d expect, the Cortado’s basic sound on instruments like acoustic guitar and bass has the same kind of super‑dry compactness you’d associate with a regular pickup DI signal. But to my ears the mic also captures a lot more of the unique resonant character of the instrument by comparison, so its timbre always feels somehow richer and more full of personality, if inevitably less predictable in terms of frequency response. Furthermore, moving the Cortado’s contact position and coupling method delivers a vast menu of evocative tone colours. This isn’t a mic I’d choose for uncomplicated transparency, but if you want a sound you’ll really care about, something with bucketloads of earthy musicality, then the Cortado delivers that in spades! It just feels like everything that comes out of it belongs on some kind of fantasy Tom Waits record co‑produced by Mitchell Froom, Tchad Blake, and Joe Henry for the Nonesuch label. (If none of those names mean anything to you, then this might not be the kind of product you’re looking for...)
Furthermore, the strongly coloured tonalities this mic typically produces can frequently be made a lot more general‑purpose by combining signals from multiple Cortados, in much the same way as you might construct a more representative close‑miked snare sound by multimiking the drum from different angles. In fact, this improvement felt so striking when contact miking, that I reckon you’ll get significantly better value for money from a pair of Cortados than from a single one — even setting aside the issue of stereo capture (which I really shouldn’t, given some of the genuinely wonderful bone‑dry panoramas a pair of these mics have conjured up for me during the review period).
All this good stuff is, however, only one facet of the Cortado. For a start, its ability to extract sound from all sorts of unlikely physical objects will doubtless appeal to anyone working in sound design. For instance, I recently managed to contact‑mike a bit of toast while it was being spread with butter! But this same attitude also feeds back into the music‑recording world once you start harnessing the idea of sympathetic vibration. A pair of Cortados on a window, floor, or radiator will catch a drum room sound that’s unlike anything normal mics would, because of the physical filtering and resonant properties of the different materials involved. Again, it most definitely won’t sound transparent, but who cares when it sounds extremely cool?
And you don’t have to extend this concept too far to realise that the Cortado lets you effectively make a quirky‑sounding ‘traditional’ mic out of practically anything. Zeppelin have videos showcasing Cortado‑based vocal mics they’ve made out of a tin can and a plastic dish, and I had a blast recording vocals with a lampshade, a glazed cabinet door, a stainless‑steel cat dish, a plastic chopping board, an offcut of vinyl flooring, and an upright piano with the pedal held down! Now, admittedly, background hiss can become an issue in these applications if you’re trying to record quiet sounds through recalcitrant materials, but to be honest that noise usually felt totally in keeping with the often retro‑tinged sonic outcomes, so I don’t imagine it’ll much bother anyone who fancies diving head‑first into this kind of stuff. And I should add that when miking any instrument directly, noise was never an issue for me — the Cortado is fundamentally a high‑output, low‑noise design, and I actually think it’s quite impressive how good a job it does of making low‑level sympathetic vibrations accessible and usable for music‑recording purposes.
The Cortado is an absolute gem... it offers a wellspring of exotic, characterful, and unrepeatable sounds that go well beyond what traditional mics can offer.
I certainly wouldn’t recommend the Cortado MkIII as the first mic you buy, and I also imagine it’s unlikely to appeal to engineers who predominately aspire to the faithful capture of acoustic reality. But if you already have a few microphones that cover most run‑of‑the‑mill studio tasks, and want to massively expand the tonal palette at your disposal, then the Cortado is an absolute gem. For a little more than the price of a Shure SM58 (and considerably less than the price of the frequently maligned AKG C1000), it offers a wellspring of exotic, characterful, and unrepeatable sounds that go well beyond what traditional mics can offer. To my mind, it’s already worth the price of admission just for what it can deliver when contact‑miking instruments directly, but on top of that there’s the whole world of sympathetic resonance and DIY mic design to explore, not to mention the simple utilities of spill‑free capture and trigger‑signal generation.
Clearly, some of the Cortado’s capabilities are common to contact mics in general, and you’ll find no shortage of much cheaper (and indeed physically more slimline) alternatives online. But I can’t say any of those tempt me very much, when compared against the Cortado’s solid build, balanced output, and commendable technical specs. That said, if you really can’t conscience paying this much for a contact mic, then you might want to check out Zeppelin’s own self‑build kit of their previous‑generation Cortado MkII, which retails for about a quarter of the price of the off‑the‑shelf MkIII. Knowing the extent of my own soldering proficiency, however, the price‑differential in my case probably wouldn’t cover the inevitable medical bills, let alone the additional costs of on‑going trauma therapy...
Overall, then, I think the Cortado MkIII is a fantastic little product, and well‑priced for what it offers. In case it’s not clear from what I’ve written so far, I’ve not had as much fun with a new mic in years — and it should probably come as no surprise that I’ve already bought a couple of these beauties for myself!
There’s only so much you can do to characterise a mic’s sound in print, so I’ve set up a special web page to showcase Cortado recordings of various different instruments and improvised resonators. I’ve also done a selection of audio examples showing some of the effects of positioning and transducer‑coupling changes, as discussed in the review. Oh, and you can even catch my incomparable stereo toast Foley...
- Overflowing with cool indie/retro sounds, both for traditional instrument recording and creative sound design.
- Can turn pretty much any object into a microphone.
- Solidly built with balanced output and decent tech specs.
- Spill‑free recording of acoustic instruments for ensemble‑recording scenarios or sample triggering.
- Mic positioning involves more trial and error than with traditional mics, and specific sounds are less repeatable between sessions.
- As with traditional close‑miking, general‑purpose sounds can be hard to achieve without multimiking.
The Cortado MkIII offers a whole world of cool‑sounding retro/indie timbres to the creative recording engineer. It can take a little work to get the best out of it (and it works best when multimiking), but it’s bags of fun and excellent value for money.