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Turning Old iPhones Into Wireless Mics

Eric Escobar

Got a few old smartphones sitting around? Go DIY and repurpose some of that aging technology!

If you’re like me, then you have a piles on old tech in your home. The twin forces of guilt about contributing to e-waste, and the laziness of figuring out if there’s any way to resell these items, means that you have valuable storage space filled with junk.

I have three iPhones… two 4s and one 3G. They’re all perfectly functioning units that are just too old to be useful as actual phones. And while they don’t work well as multifunctional smartphones anymore, they are capable of doing some amazing things.

One thing that they are very good at is recording high-quality, high bitrate audio. With the right microphone attachment, an old iPhone becomes a wireless portable audio source with built-in power and storage. There are many different mic attachments available for the iPhone, from lavalier-style to omnidirectional stereo mics. 

I’m going to talk about pairing inexpensive (under 20 bucks, like the used Movo PM10 in the Amazon image below) lavalier-style mics with old iPhones as body mics for on camera talent — A setup that’s great for capturing on-set audio for very little money.

iphone with lav

Wireless, Not Just Transmitting

The biggest paradigm shift you have to get onboard with is real-time monitoring. For the audio purist, that’s a total deal-breaker and it’s understandable. For the low-budget filmmaker, it’s a manageable risk when time is more abundant than money. The cheapest buy-in for owning remote, wireless lavaliere mics with transmitters and a receiver start around seven hundred dollars.

Transmitting, receiving, and recording audio also opens you up to interference, something more likely with the cheaper gear. Spending twenty bucks and putting a physical recording device on your talent could end up costing you way less than even renting a full on transmitter, receiver, recorder setup. The trade-off is that you’re not going to know what you got until after the camera stops rolling. 

The Recording Software

I like to use the free TASCAM PCM Recorder. It records 44.1khz audio at 16 bits right off the built-in mic or any external mic plugged into the headphone jack. It is a “two button” operation, meaning you have to click the red record button first, then the green play button to get it to “roll” just like an old DAT recorder I once owned. That may be anachronistic, which is fine. There are literally a dozen other free to cheap apps that will let you record audio on your phone at 44.1khz in 16 bit. Find the one that matches your style.

Screenshot of Tascam PCM Recorder

One thing you might want to consider is finding an audio recorder that does automatic uploads to Dropbox or some other cloud storage service. While you are most likely using a phone that doesn’t have service any longer (if it does, make sure to put it into airplane mode before you shoot!), it probably still has WiFi.

If you’re recording in a place that has a hot spot, then jump on. At the end of the day, there’s real peace of mind knowing that your audio files are already backed up to the cloud. When you get home, your audio will be ready to work with on your cloud-synched editing system.

The other big consideration (and the way this all will work seamlessly for reasons I’ll explain later) is on-camera audio. Simply put, you want it, you need. You’re most likely never going to use the audio signal recorded by the tiny built-in mic, or even a shotgun mic attached to the top, but you need it as a guide track for post.

How to Do It

RODE LAV MIC

Do not rely on your on-camera talent to handle the job of stopping and starting recording. They need to be focused on the artistic and technical aspects of being on camera, like hitting marks and delivering a performance. You do not want to burden them with the techie AV aspects of filmmaking.

What I do right after blocking the shot is check in with each one of them. At the end of that check in, I look at the iPhone, start the recording, and make sure that levels are moving and numbers are counting on the UI. Then I hide the iPhone and get back to work. Your batteries will last a day, and the audio files are relatively small, so there’s no reason to be precious about stopping and starting. 

The single biggest concern is that you’re recording when your on-camera talent is actually talking and the camera is rolling. Getting a bunch of recorded audio in between takes is not really much of concern after all. This is one of those times where you actually get to fix it in post. 

The Secret Is in the Post

If you’ve ever tried to manually synch up audio with picture, you know how maddening it can be. A single frame of difference is detectable by most of your audience and not something that will be forgiven. 

PluralEyes Screenshot

This is why I love PluralEyes from RedGiant Software. It is your personal, digital, off-line editor. Throw in a bunch of audio and video/audio sources from an event and it will synch everything up perfectly. No need to slate, no need for timecode… as long as each piece of media has audio attached to it, PluralEyes will match it up. And it works in your NLE, so it’s lining up video and audio clips in your timeline. This one application will literally save you dozens of hours over the course of a year.

I think the workflow represents the future of media creation — smart software that determines the relationship between the individual clips and organizes assets for you logically. At some point in the near future, software will “understand” who is present and what is happening in the clip and make suggestions for organization and editorial… but I digress.

If you don’t want to invest in another piece of software, then make sure you buy a slate. It can be cheap, just make sure it’s durable and remember to use it before each take, whether or not you’ve stopped and started recording on your remote iPhone mics. I think a real slate is so much better than the no-budget “hand clap slate” because it shows the synch moment in post so much more accurately. The visible spike in the waveform matches up with the moment the slate closes — simple, single frame. There are “slate” apps for the iPhone and iPad. I’ve used some of them, but none of them are any better than the tried-and-true analog slate.

No One Forgives Bad Sound

Bad sound is rarely forgiven by an audience. Bad picture can be chalked up to “artiness,” but badly recorded sound is the mark of an amateur production. A body mic on every actor combined with a good boom pole capturing the scene will get you cleaner audio right at the moment of production. Mumbled dialogue is clearer, signal to noise is lower, and you have multiple mics capturing the moment. 

The Future

Recording audio without remote wireless monitoring is heart-stoppingly hard at first, but you get used to it. And most likely, someone will develop an app for the iPhone that allows recording and monitoring over AirPlay — and then this will cease to be an issue.  

Have you ever wirelessly recorded with an iPhone? Share your experience in the comments below.

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