Higher sensitivity - more dynamic sound?

I know Doug Button, one of the brilliant engineers of the late 80s and 90s who led us to a series of higher output JBL drivers called "vented gap" which enabled dissipating higher heat which enabled higher SPL (and more reliable live sound systems with fewer boxes producing the same output). These were no home hifi drivers, but Live Sound drivers.

This whole efficiency argument is twisted by marketing. If you ask a designer like Billy Woodman at ATC (who is on Dougs level), he will tell you if you want additional low end from a driver, you can optimize it for more bass but the efficiency will decline. So a lower efficiency driver may have a better performance from a bandwidth perspective and may indeed be desirable. This is what folks like ATC and B+W and Magico do to get superior bandwidth. Its a choice, not a mistake; this choice does not improve or decrease dynamics- the size amp you mate it with does. 

Its the combination of efficiency and power handling of the driver that determine dynamic range.

So your 102dB 1w/1m speaker may not have such good dynamics with a 20W amp if 1W= 102dB SPL then .2W=105, 4W =108, 8W =111, 16W=114dB SPL and we are out of [low distortion] power.  That’s 12dB of dynamic range!  That's not even equal to the dynamics of vinyl.

So now compare a speaker with 86dB 1w/1m:  2W = 89dB, 4W = 92dB, 8W=95dB, 16W = 98dB, 32W =101dB, 64W=104dB, 128W= 107dB, 256W = 110dB SPL!  So the 86dB 1/1m speaker on a 250W/ch amp has 24dB of dynamic range! That's a huge increase when you take into account the log level nature of dB SPL, ideas such as 10dB SPL is considered twice as loud.  12dB dynamics is never better than 24dB dynamics, under any measurement or circumstance.  

Don’t drink the high efficiency kool aid kids!

Brad

Duke, nice post on thermal/mechanical driver compression. It’s an esoteric topic, but almost every transducer designer has to come to terms with what steps to take in their driver design to cope with heat, bandwidth, efficiency and intended performance. I know the ATC driver designs are remarkable, such as short coil/long gap, in lowering distortion while maintaining a wide dynamic range.  Some of the live sound driver designs these days are insanely good.    

Phusis

I think your post makes my point.  Efficiency alone is not the sole issue or a spec to chase.  Amp power, purpose and many other factors matter a lot.  In live sound, 127dB SPL is important.  In home audio, its damaging to our hearing. 
The 20W limit was only responding the post of the 25W amp mated to an efficient loudspeaker had better dynamics (earlier in this and other threads).   Good amps with high power are very available.

Valid points all Duke- my point about dynamic range was "system dynamics" not one system vs another.  The 86dB efficiency speaker on a 250W amp has more total dynamics to cover incoming source material of a wider dynamic content than the 102dB/20w amp system. 

Brad