That waveform looks pretty good imo. When I did it, I the signal was very weak so the signal to noise ratio was bad. There were low frequency impulses from me

That waveform looks pretty good imo. When I did it, I the signal was very weak so the signal to noise ratio was bad. There were low frequency impulses from me moving the headphones around and regular hums from other sources. My best guess for the large attack showing up there is not effects from the microphone, DAC, amp, or anything but the actual speaker. Good audio measurements are hard to come by thanks to all the snake oil, but square wave measurements are common when there is data. The physical models of transducers aren’t trivial, but in a single broad stroke the answer is “physics” and “spring-mass-damper”. https://www.innerfidelity.com/images/AKGK701.pdf https://www.innerfidelity.com/images/AKGK701.pdf The decay is expected, as the pressure around the microphone can only temporarily increase before the pressure wave disperses into the room. As an extreme example, if you turned an entire wall into a speaker and played a square wave, you would be able to make a much more square shaped waveform. There’s no replacement for displacement baby (see: subwoofers). If you want a more square waveform, try using a headphone pushed right up to the mic and going to a higher frequency (like 1 kHz). Edit: If you want to skip the trip down the rabbit hole: I think the end-all for audio quality are sealed in-ear monitors (IEMs). Low group delay from short distance from transducer to eardrum, and sealed enclosure for good bass response (see: square shaped low frequency square waves).