Okay, maybe calling it “Broadcast Quality” is pushing it a little, but maybe not. The ability to disable iOS processing and Automatic Gain Control for the iPhone's built in microphone really gets tremendous results. It's like the true potential of that little mic has been shackled all this time. We know our users are made up of EarHeads, Audiophiles, GearDudes and DIY Media Monsters. You guys mean business, but that is why we felt compelled to get this feature into your hands as soon as possible.
But don't just take our word for it…
It turns out Apple's secret sauce for getting good audio has much more in common with conventional audio processing then we previously thought. It starts with the basics. To make sure the audio from the iOS microphone doesn't distort they set the gain for the microphone preamp very low. This ensures that if the volume of the audio you are capturing gets loud, then there is plenty of headroom to accommodate the signal spike. If the gain was set too high it would result in distortion, so Apple plays it safe.
Then there is another problem; Pops and Plosives. If a user speaks directly into a microphone then words that start with “P” like “Popcorn” and “Platypus” or words starting with a “B” like “Baby” can wreak havoc because the audio waves created by your voice can overload that little mic diaphragm. That's why in studios people use Pop Filters or Wind Screens to handle the rush of that type of audio. The little iPhone Mic has no space for that so Apple applies what is called a High Pass Filter. It is an audio filter that only lets the audio frequencies over a certain frequency threshold get by. Basically, the bass and lower mid range frequencies don't make the cut and the resulting audio is much less full and can sound very tinny. No popping problems however.
Finally, the resulting audio after the conservative preamp and HPF is a little wimpy and requires a boost. This is where Apple makes use of a dynamics processor to increase the overall volume of the mic signal to a healthy level. A dynamics processor is usually made up of a compressor/limiter to increase the average volume of the audio and even out any sudden peaks or valleys that may arise from the natural volatility of capturing speech. There is a catch to this, because the audio being fed into the dynamics processor is very low and close to the natural noise floor of the room. So when the vocal recording is boosted so is the noise from the room. It's Noisy!
Bottom line, Apple's iOS processing and Automatic Gain Control is a lowest common denominator “Safe Mode” that ensures the least amount of trouble for users but also sounds pretty lame.
You can do better. And this is not only for iPhone users, iPad users will also benefit from disabling AGC. There are some limitations however. iPhone users who disable AGC will see a little “Gear” that appears on the Fader Selector Button above the Master Fader on the Studio interface. Tapping on this gear will let the iPhone user fine tune the gain setting. We set the fader at around 7/10 but you should experiment to see what works best for you. If you hear distortion, turn it down.
iPad users have a fixed gain setting, so they must compensate for the difference in volume by increasing the Mic Fader till they get a nice loud voice recording. As with all audio settings our guides are helpful but trust your ears. The fixed gain of the iPads puts it at a slight disadvantage to the the iPhone but as you can hear below the results can still be way superior to the stock iOS settings.
Users of headphone jack connected external Mics should also experiment with disabling AGC. The same processing and filtering is applied to all audio sources connected via the headphone jack. So if you use a mic like IK Multimedia's iRig MIC CAST or their iRig PRE xlr mic dongle you should experiment with disabling AGC.
You may also want to check out our iOS Microphone Roundup to learn more about great headphone jack connected gear that will benefit from disabling iOS Processing and Automatic Gain Control.
bossjock studio version 1.5 should be available now. Look for the AGC control behind the Gear button in the Settings menu. Give it a try and let us know what you think.