The Teenage Engineering CM-15 and iPhone: A Studio in One Cable

The CM-15 is Teenage Engineering's first microphone, part of the Field series that also includes the TP-7 recorder and the OP-1 Field. That lineage matters, because the Field series is TE's premium travel line, gear built to be carried and used rather than left on a desk. The CM-15 is that idea applied to a mic.

Underneath the design it is a genuine one-inch large-diaphragm condenser, the kind of capsule you would expect in a studio, with a built-in preamp and a USB-C audio interface inside the same machined aluminum body. It is small, about 90mm long and 132 grams, roughly the size and weight of a chunky phone, and it has a fold-out kickstand so it can sit on a table and angle itself without any stand at all. It is not a cheap USB podcast mic. It is a studio condenser that happens to fit in a jacket pocket, and it is priced like the former, somewhere around 1,100 to 1,200 dollars.

This is Teenage Engineering's own demo of the CM-15, which is the fastest way to get a feel for the mic and how it sounds before we get into the setup.

This is the whole reason the CM-15 pairs so well with a phone. Its USB-C port is a fully class-compliant, driverless audio interface. The preamp and the analog-to-digital converter are inside the mic, so there is nothing to add between it and your phone. On a USB-C iPhone you run one USB-C-to-USB-C cable, and it appears as an input with no drivers and no setup.

That is what makes the rig so small. A normal studio condenser needs an XLR cable, an audio interface and phantom power before a phone can hear it. The CM-15 folds all of that into the mic itself, so the minimum viable setup really is three things: the mic, one cable, and the phone. With the kickstand you do not even need a stand.

Because it is class-compliant, the CM-15 is not tied to any one device. Over its USB-C port it works driverless with an iPhone, an iPad, a Mac and a Windows computer. On a USB-C iPhone or a USB-C iPad it is a single USB-C cable with nothing else in between. On an older Lightning iPhone you add an Apple camera adapter. On a computer it simply appears as an input.

An iPad is just as happy a home for the CM-15 as an iPhone, and takes it over one cable in exactly the same way. Reel is the iPhone recorder in this guide, but the mic itself will pair with any class-compliant host you point it at. Through its analog outputs it also works with traditional gear: a mixer or interface over the mini-XLR, or a camera or recorder over the 3.5mm line output.

It is worth knowing that the CM-15 is really three microphones in one body, because it has three separate outputs, each for a different job. The USB-C port is the digital path, the class-compliant interface you use with a phone or computer, and it also charges the mic. A mini-XLR output gives you a traditional analog, phantom-powered path into a mixer or interface, exactly like any XLR condenser, using the included mini-XLR-to-XLR cable. And a 3.5mm jack provides a line-level output for feeding a camera or a recorder's line input.

For an iPhone and Reel, you want the USB-C output. The others are there for when you fold the CM-15 into a bigger analog or camera setup. One safety note straight from Teenage Engineering's guide, worth repeating because it can cost you a mic: never plug a 3.5mm cable that is carrying active phantom power into the CM-15's 3.5mm jack. That jack is a line output, not a phantom input, and phantom on it can damage the mic.

The capsule is a one-inch large-diaphragm condenser with a fixed supercardioid pattern. That pattern matters more than it sounds, and it is the spec most write-ups get wrong, so to be clear it is supercardioid, not omnidirectional. A supercardioid is a tight, focused pattern that rejects a lot of what is off to the sides and behind the mic, which is exactly what you want when you cannot control the room you are recording in.

Reviewers consistently describe the sound as detailed, open and transparent, clean without being clinical, with a slightly present character. Vocals come across crisp and airy, acoustic guitar keeps its nuance without getting harsh, and bass stays defined. Combined with that room-rejecting pattern, it is genuinely well suited to mobile and field use: vocals and acoustic instruments in an untreated space, interviews, podcasting, foley, and ambience or sound-design capture. It is still a condenser, though, so it hears more than a dynamic mic would, a noisy air-conditioner, a live room, close plosives, and while the tight pattern helps, it does not erase that.

The numbers back up the studio-mic claim. Max SPL is 138dB, self-noise is a low 14dBA, and the converter is a high-end ESS Sabre part. Over USB the CM-15 streams 24-bit at 96kHz. That is real studio resolution from a proper large-diaphragm capsule, not the thin output of a built-in phone mic.

Here is the honest part about the whole chain, because it is easy to overstate and I would rather be accurate. The CM-15 delivers a true 24-bit, 96kHz signal. Reel records class-compliant USB audio at up to 96kHz into a 32-bit float file. So the sample rates line up perfectly at 96kHz, and nothing in the chain downsamples or degrades the mic. On bit depth, be precise: the mic itself is 24-bit, and Reel storing that in 32-bit float gives you clip-proof headroom and lossless level and mixing changes afterward, not extra resolution from the microphone. The accurate, and still impressive, way to say it is this: a genuine 24-bit, 96kHz studio-condenser recording, captured into a 32-bit float engine, in your pocket. That claim survives fact-checking, which the 32-bit-float-mic claim you sometimes see would not, because the CM-15's USB output is 24-bit.

The CM-15 has a small three-position gain switch on the body, offering minus 18, zero, or plus 18 dB. You set that coarse level for the source first: leave it at zero for normal voice and instruments, drop to minus 18 for loud sources, push to plus 18 for something quiet, then fine-tune the level in Reel. Because Reel records in 32-bit float, you have plenty of headroom, so if in doubt err toward not overdriving the mic's own analog stage.

On power, the CM-15 has a genuinely useful trick: its own internal rechargeable battery, good for around ten hours, which it uses automatically. That means it does not have to lean on the phone for power, which is a real advantage over bus-powered USB mics that can be flaky when a phone alone cannot feed them enough. It charges over USB-C when you need to. On a long field session, keep an eye on that ten-hour battery.

On a USB-C iPhone, an iPhone 15 or later, it could not be simpler: run a USB-C-to-USB-C cable from the mic to the phone, open Reel, select the CM-15 as the input, and record. On a Lightning iPhone you need an Apple camera adapter in between, and while the mic's own battery makes it a low-draw device, the powered version of the adapter is the safe choice.

Stand it on its fold-out kickstand and angle it, or thread it onto a mic stand with the included adapters. One thing to plan for: there is no windscreen in the box, which is a real omission for a field mic, so add a foam windscreen for outdoor recording and for taming plosives on close vocals. Monitor through Reel and the phone, since the mic is the interface.

It is one microphone, so it records in mono. A stereo recording means two CM-15s, which doubles an already high price. It is a condenser, so it wants a reasonably quiet space to be at its best, and the fixed supercardioid pattern, while helpful, is not switchable to omni or figure-eight if a job calls for those.

Then there is the price. It is expensive for a single mono mic, and worth saying so plainly. Some reviewers have noted variability in the feel of the gain switch across units too. None of this undermines the core pitch, but you should go in knowing exactly what it is: a superb, very portable, single mono studio condenser at a premium price, not a do-everything mic locker.

The CM-15 is designed to live inside Teenage Engineering's Field kit, alongside the TP-7 field recorder and the OP-1 Field. If you own the TP-7, the CM-15 pairs with it exactly as you would hope, and it is a lovely, all-TE setup.

But you do not need the TP-7 to get everything out of the CM-15. Reel does the same recording job on the phone you already carry, and it does it for a tiny fraction of the price, a few dollars against a TP-7's four figures. For a lot of people that is the whole appeal: the mic and an app, without the cost of the dedicated recorder.

If you do own a TP-7, Reel is the perfect backup. For the days you would rather not bring the TP-7 out, or when it is charging, or when you simply have your phone and the mic in a pocket, Reel is the always-with-you option that captures the CM-15 just as cleanly.

There is also one real technical difference worth knowing, and it happens to fall in Reel's favour. The TP-7 records at 24-bit, a hard-ceilinged format and a superb one, but once a level is near the top there is nowhere left to go. Reel records into 32-bit float, which has effectively no ceiling, so you can push a take up, pull it down or process it as much as you like without ever clipping the recording, and re-level it afterward with no penalty. With the CM-15's coarse three-step gain switch, that headroom is genuinely handy, because you do not have to land the level perfectly. The one thing float cannot undo is the CM-15's own input clipping if you overdrive its analog stage, so the gain switch still matters, but everything past that point has room to breathe.

It is also, in my admittedly biased opinion, about as native as an app can feel for this mic. Reel is genuinely plug and play with the CM-15, tested and detected the moment you connect it, with no setup at all, and its tactile, hardware-inspired feel sits naturally next to a Field-series mic. It was built for exactly this kind of plug-in-and-record capture.

Full disclosure, I make Reel, so weigh this accordingly. The CM-15 and Reel share the same idea from opposite ends. The CM-15 puts a studio condenser and its interface into one pocket-sized body. Reel puts a four-track recorder, with a tactile jog wheel, overdubbing and 32-bit float, into the phone that is already in your pocket. Put them together with a single USB-C cable and you have a real recording studio that fits in two hands.

The mic gives you the sound, and Reel gives you somewhere to put it and something to do with it. Capture a vocal, then overdub a harmony and a guitar on the other tracks, all from that one mic, and mix it, without a laptop or an interface anywhere. A mic, a cable and a phone. For anyone in the Field-series world, or anyone who just wants the most portable serious recording rig they can carry, it is a genuinely hard combination to beat.

Reel is the recorder I make and use to capture the CM-15, so here is a quick overview of how it works.