Thermal Compression is a speaker voice coil heating. The voice coil impedance increasing with heat, so sensitivity goes done, crossover frequency floats. Ferrite magnets field decreasing with heat too that leads to change of Qms and Qts of speakers and bass response.
https://www.linkedin.com/pulse/power-compression-vs-thermal-distortion-loudspeaker-alexander-wilson/...
https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/Harman_Int%27l/AES-Other_Publications/LS_...
Old high sensitive speakers don’t have thermal compression because need a couple of watt to drive it.
There are example of good old speakers: JBL L200, Tannoy Monitor Red and Silver Series, Altec 604, 604B, 604C, 604E, Altec VOT, RCA LC-1A.
https://www.linkedin.com/pulse/power-compression-vs-thermal-distortion-loudspeaker-alexander-wilson/...
https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/Harman_Int%27l/AES-Other_Publications/LS_...
Old high sensitive speakers don’t have thermal compression because need a couple of watt to drive it.
There are example of good old speakers: JBL L200, Tannoy Monitor Red and Silver Series, Altec 604, 604B, 604C, 604E, Altec VOT, RCA LC-1A.