What component is responsible for dynamics ?

Agree w/"Onhwy". For better dynamic capability in loudspeakers, driver Sd does matter. Such drivers tend to be of higher sensitivity and have (paradoxically)relatively shorter Xmax. At equal loudness they generally sound more open. For home audio many are be found in 2 way designs with a compression driver on top (just one example is http://lsv-achenbach.de/kits/tricolore.htm).

Johnk,

I know you've designed with the SEAS Exotic W8 woofer. Have you tried the SEAS Exotic T35 midrange/tweeter? What did you think of its sound? FWIW, I'll be using it above a Jantzen JA-8008 driver (OEM by SEAS) as a midrange with a PHL 5011 (updated version of the 5010 driver used by Nelson Pass as woofer in his original "Rushmore" loudspeaker) on bottom. Only a moderately high efficiency loudspeaker, but a true 92-93dB that'll move lots of air.

Thanks, Johnk. Nearing age 60 I don't hear much at all above 10-11 kHz, so I'm hoping I'll not miss anything without a supplemental tweeter/supertweeter! I'll keep in mind that the T35 is easy to damage.