Yes, Yet another important omission! It’s called ‘measurement mode’… I’m quite surprised you didn’t use this in the first place? If you had, we would now be able to enjoy full bandwidth input via the headset mic input… Take a look at these response charts since iOS 6: http://blog.faberacoustical.com/2012/ios/iphone/finally-ios-6-kills-the-filter-on-headset-and-mic-inputs/
Regards…