In one word: punchy! Very good
Hp that really meets across speaker substitution, eg in boxes or any other martin B115 models flats, I saw very often in PM353 returns home atelier33 replacing the original PR38S100 audax.
Beware of buying opportunity because there are two different versions of the HP version of the old 554 with coil holder that supports 200W nomex and the current version 554 / K with coil capton that supports 600W.
The chassis of the two versions are identical, we can very well replace the mobile version of a current kit nomex version Kapton.