Try blowing into the xm4's microphone on passthrough mode, and you'll discover it can work as a loudspeaker (it will amplify the noise). This discovery made me

Try blowing into the xm4's microphone on passthrough mode, and you'll discover it can work as a loudspeaker (it will amplify the noise). This discovery made me a little worried that there's no volume limit that can be transmitted to your ears. Then again, someone blowing directly into your ear is probably worse :D