Technology Tuesday: Fostex AR-4i. iPhone 4 Audio Excellence

Before we get to Parker Harrington’s latest Technology Tuesday article, we wanted to take a second to mention that Parker has been named Hidden Track’s Technology Editor in recognition of his amazing work with the column and to help with future projects we have up our sleeves.

While taking pictures with a smart phone used to render relatively mediocre results, the quantum leaps that have come in the last couple of years are remarkable. Lens quality, image size, processing and overall quality are now comparable to many entry and mid-range point-and-shoot cameras. Similarly, video has now become of such quality to render separate video cameras obsolete for most people. See ‘ya later Flip Cam! However, despite gorgeous video quality, one of the things holding smart phone video back from truly stunning results is the audio quality. What can you expect though from a tiny, mono mic that is designed for phone calls and voice?

Thankfully, for iPhone 4 users, Fostex has a solution. With the AR-4i and your iPhone, your audio quality will be of the same great level as that of  the video on your recordings. This week, we’ll look at this affordable & easy to use audio interface for iPhone and give you the opportunity to win one!

[Fostex AR-4i Audio Interface for iPhone 4]

Why would I want this?: You want this if you have an iPhone 4 or iPhone 4s and want to be able to record concerts, seminars, home movies, blog posts or anything else and want high quality audio along with your video. This is perfect for U-Stream and other live streaming applications, YouTube uploads and any other application where you want high fidelity audio that the internal, mono microphone simply can’t offer.

What exactly is it?: The AR-4i is a sleeve similar to a Mophie Juice Pack with a dock connector on the bottom. It is powered by two AAA batteries and has three stereo inputs affording you the choice of recording in portrait or landscape (more on that later). There is also a headphone jack for recording monitoring or playback as well as LED indicator lights for line level. Supplied are two condenser cardioid microphones with foam wind shields. There are two threaded tripod mounts for attaching to a tripod, monopod or other camera mount in either orientation. There’s also a hand grip that can be comfortably held or slipped into a microphone clip on a stand. It retails for approximately $120.

How is it used? There is a free application in the App Store that quickly sets up your device and affords settings such as Stereo or Mono, limiter and advanced settings such as panning for the different audio channels. However, basic settings such as Stereo in the Preset mode will afford most users with the results they desire. Then, once the iPhone is inserted into the connector, and you start recording, your AR-4i will be the source of audio rather than the internal microphone. A thumb wheel adjusts the input level and you are visually guided to the appropriate setting with the LED indicator lights.

[AR-4i with hand grip & left and right side showing inputs, volume control & LED indicator]

So how does it sound? To test the AR-4i, I made a few clips of my brother Fred on both 12-string guitar and a drum kit. Listening through a laptop speaker will likely not afford you the ability to hear the lush and exceptional results. However, listening through my home stereo system and my Bose Companion desktop speakers, the results were fantastic.

Here’s Fred with a quick clip from his recently composed “Cranberry Bog Blues” with the built-in internal microphone:

Now, listen to this recorded with the AR-4i:

If you are listening with decent head-phones or speakers, you’ll notice so much more in the sound from the second clip. Crisp, clean, full sound with much better bass and each string’s notes are much more distinct. While it is difficult to produce stereo results from a single guitar player, keep in mind that this unit will allow for true stereo recording. Unlike the built-in mic, which is mono, the AR-4i gives full stereo separation and separate two-channel recordings.

Here’s another example with drums. Notice in the first clip, with the internal microphone, that all the drums sound relatively the same without much tonal differences and relatively tinny.

Now here is a clip recorded with the AR-4i:

The cymbals come to life, fuller sounding bass and some stereo separation. Don’t let the line levels fool you. I had the levels set a touch low on AR-4i recording. Despite that, the sounds are still fantastic.

Microphones & build quality: Although the microphones are a vast improvement and will afford you much better audio results than the built-in mic, they are still entry level microphones that will not be used for studio-quality album recording. Keep in mind though, that one of features of this device is that it can accept any microphone with 1/8″ plug. Unlike other microphone solutions, like the iRig, the AR-4i is the only device currently the allows for true stereo recording. The main beauty of this device, is not necessarily the microphones themselves, although they are very good. It’s the fact that you can record stereo, with any compatible microphones, without the use of any other hardware like a portable mixing board. The iPhone 4 is not compatible with iPod devices that allow line level input and the mic specs are the same as the now ancient iPhone 3G.

The supplied microphones that come with the AR-4i offer:

  • Frequency Response: 20Hz / 20kHz +-4dB (Mic-Phones / 15mW / 32ohm loaded)
  • Signal to Noise Ratio: more than 73dB (Mic-Phones / Input gain maximum)

The build quality seems quite high with sturdy construction. The dials operate smoothly and the iPhone fits perfectly into the dock without any wiggling or adjustments needed.

iPhone 3G or 5? This device only works for iPhone 4 and 4s right now. Earlier models will not fit into the dock because of their different dimensions. Fostex says they will quickly release a model when and if the design specifications change on future iPhone models.

Other nice things about the AR-4i: 

  • Microphones can be pointed in any direction and are not fixed. This would allow you to point one mic towards yourself and one away if you were doing an interview. Or, in a large live music setting, position each mic towards separate speaker stacks.
  • The unit runs off of AAA batteries and affords approximately ten hours of recording time: more than enough for many recording sessions and saving the internal phone battery for other things.
  • Having both the tripod threads and the hand grip are great to have different options for shooting. The aluminum hand grip has great texture & weight for a  nice combination of comfort and no-slip operation.

Bottom Line & Where to Buy: Fantastic device offering great sound quality for a reasonable price. Can be purchased at many audio stores as well as online retailers such as B&H Photo & Video (a personal favorite with their great customer service; $119) or Amazon. ($149)  Compact, versatile and well designed, the AR-4i is a perfect companion for school plays, live concerts, club shows, in the field reporting, live streaming and any other time when high quality audio is desired.

WANT ONE? To help celebrate Hidden Track’s Five Year Anniversary, we have an AR-4i for one of our readers. To enter, simply leave a comment here letting us know what you’d use it for. We’ll pick a random entry at the end of the week and announce the winner in next week’s column. For a second entry, simply tweet a link to this article with #AR4i and @hidden_track somewhere in your tweet. Good luck and thanks for reading!

One More Thing: A pet peeve, but why in the world would you ever opt to record with your iPhone in portrait mode like this device gives you the option of doing? If you enjoy watching your videos with an extremely narrow width & black borders on each side, feel free to hold your phone upright. Otherwise, and especially if you plan on uploading them somewhere: For God’s sake, flip your device into Landscape orientation! Otherwise, you’ll get results like this, which the uploader ironically was using to show iPhone video quality:


[While the AR-4i can record in portrait mode: think twice about using it for better video results]


Hidden Track Technology Tuesday
email: [email protected]
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24 Responses

  1. I will use this device to strip the lo fi tape warps from my recordings and finally be able to unveil them in pristine form for all to hear. I will also bootleg shows with less than 5 people in attendance.

  2. Wow, interesting device. Never seen anything like that. I have actually used external microphones while making videos but it was a complete pain in the ass and negated the portability of the phone. Would be great for the kids holiday concert or even sports events. though of course, I imagine I’d use it most at small club shows or sidewalk buskers singing a tune. Hell, I may have the next viral YouTube video with this thing. sign me up! And shit, if I don’t win, I may just buy one anyway. thanks for the review.

  3. I love this thing! I would use it to record the trio of skunks that sing A Capella outside my window every night. 😀

  4. Looks really good – would love to take this with me to record my son’s concerts at his school assemblies.

  5. Suh-weeet! Looks very cool!
    Would keep it in my glove compartment: on hand anytime a recording situation presented itself. Going to check this out for sure

  6. great…was wondering if something like this existed. I’d tape both my band and the choir I am in…(and some live shows if I can get by security ; )

    hope that iPhone video disabling patent that Jobs (RIP) got for live events never comes to pass.

    hear anything else about that?

  7. I will use this device to record videos of Mike dropping absolute New Years Eve Bass bombs at Madison Square Garden when I win tickets to the lottery, therefore having the best kick off to the last year of earth 2012!!!

  8. I will use this for multiple things;
    1. recording my 12 year old’s bass progress so I can show him that his practice is paying off!
    2. recording interviews with past faculty and students of the University Continuing Education programs that I work for.
    3. recording my own compositions on guitar
    4. recording some of the indie bands in my area in one-take, warts and all, sessions…. (see )
    5. recording family histories as told by my parents, aunts and uncles… for a family history project I am working on….


  9. This mic setup looks awesome. I’m really sick of trying to record amazing musical moments and being let down due to distortion or other noise. I would use this for all kinds of small shows.

  10. That’s pretty sweet, but I’m not my wife would like me to tell everyone what we’d use it for 😉

    brown chicken brown cow.

  11. Awesome device. Used to use a cassette deck then a dat deck to record local show. Have some nice tiny hat mics. Would love to start using em again in a super stealthy manner.

    I would use the ar-4i to record local show as well as recording my guitar playing progress.

  12. I’m a professional cellist who would use this to record rehearsals for either immediate feedback or for listening while I’m driving home using my car’s aux jack. I’d also make rehearsal / concert videos.

  13. PS, re why would one use the iPhone in portrait mode: definitely not for video recording, but if you have an audio-only app like FiRe from Audiofile Engineering, you would want to see their recording window in portrait mode to see if the folks you are recording (or your own playing) are causing the levels to be too high on the app itself.

  14. Joshua: Excellent point…of course. There are a ton of audio only programs for dictation, interview, sound & music. And many likely only work in portrait mode so it is a good thing the AR-4i can do both.

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