@daveyf wrote:
How important is the efficiency of a speaker to you?
In effect: a lot. Comparing speakers of different efficiencies isn't an apples to apples scenario. With either "camp" there are implications with regard to the nature of directivity (and -uniformity), driver and enclosure size, driver type/segment and other, which in turn has sonic consequences. My eventually veering towards the high efficiency segment of (large) speakers wasn't due to some blind rationale of attaining high efficiency (and SPL) in itself, but rather what those speakers offer in vital parameters of sound reproduction that separates them from the low efficiency segment of speakers here, also with regard to the interaction with acoustics.
With passively configured, low efficiency speakers it was very much about finding that particular speaker which had the desired characteristics in a given listening space. Not an easy task. With DSP-based and larger, high eff. speakers that are outboard actively configured it's more about getting the basic physics and design execution in place as a framework to go by, call them macro parameters, and then slowly work your way in from that outset to get to where it all gels.
The worst outset dynamically are small, passively configured, low efficiency, low impedance and load-heavy speakers, although it's the bigger multiway iterations that'll more readily get the amp(s) to their knees. Even served a ton of watts such speakers never escape the fact they're the sonic equivalent of a liquid-saturated sponge that never truly lifts off and comes to life.
Getting rid of a complex passive crossover is a good start, and then higher efficiency will be a further improvement - certainly dynamically. Amp-wise I'm not really the SET-guy (although they can sound great through very high eff. horn speakers), but I like class A/B studio designs which in my case are high powered (~600W/8 ohm per stereo amp, three of them) and of the same brand and series. They're essentially similar top to bottom, incl. the subs, and it pays off sonically. To those squinting at the high power rating here, remember it comes down to how it sounds..
What many seem to forget is that bi-amping actively will have each amp delivered its limited frequency span to feed its respective driver segment (as opposed to passively where they receive the full signal). So, the amp unloading power into the subs won't affect the other amps at all, the HF-amp is relieved of LF, etc. - with all that implies.
No power draining, complex passive crossovers; high efficiency, large and sufficiently tall speakers (i.e.: 97 (plus corner load) to 111dB sensitivity); plenty of power from independently configured amps, not too heavily damped acoustics - to me this is all about efficiency, less energy store-up and achieving proper headroom. Not as parameters standing on their own, but an essential outset to build on.