I'm wondering how to interpret artifacts on the following spectrogram which shows the recording of a linear frequency sweep.

The recording is done with a cheap microphone and cheap sound card, and playback was done using an off-the-shelf system, which could have its own issues.

There are obviously harmonics which can be seen at the beginning of the chirp, but I can't remember where these can come from, then also those "X" patterns that are catching my attention.