An upgraded mic for an iPad is easy to use (and not expensive). I do it all the time with REW -
https://www.parts-express.com/dayton-audio-imm-6-calibrated-measurement-microphone-for-tablets-iphone-ipad-and-android--390-810
I also have a USB mic ( https://www.parts-express.com/dayton-audio-umm-6-usb-measurement-microphone--390-808) that I'll use with a PC.
I also have a USB mic ( https://www.parts-express.com/dayton-audio-umm-6-usb-measurement-microphone--390-808) that I'll use with a PC.