Most conventional cone speakers have a rising impedance as frequency goes up.
I’m sorry that’s not really true. You are describing the impedance of a coil.
It is true that larger cone drivers have this, and that this effect needs to be dealt with but it is not true for a speaker as a whole. A quick survey of impedance curves at Stereophile would show this.
Here’s a random sample:
https://www.stereophile.com/content/stenheim-alumine-three-loudspeaker-measurements
It is also true that the most challenging areas for a conventional speaker tends to be in the bass, but the impedance curve of a raw woofer is not at all a good indicator of the impedance curve of the speaker as a whole.