Why are high efficiency speakers preferred for low volume listening?

I frequently say that if you have to turn your system up  to sound good, then your system sucks.  

I'm not going to say all systems with high power ss amps and 87dB speakers suck.  That would offend lots of people with very expensive systems.  But isn't it a nice coincidence that the dealer has to sell you a very expensive amp to drive your very expensive 87dB speakers.

So instead I'll say that I think the easiest way to get an awesome system is a well designed SET tube amp and some nice 98dB speakers.  No I don't care for horns.  

But once you have a great sounding system, it will sound great at 70dB and you can listen for hours on end without fatigue.  I know this sounds like a fairy tale to many.

Jerry

PS Sitting here listening this morning since 0330 and I just checked the volume with my cell phone (not calibrated) and it's showing an average of 63dB.

@immatthewj Wrote:

But I am assuming it is how easy the speaker actually is to drive (and this would be due to its nominal impedance?) versus the number/sensitivity the speaker is rated at?

Yes, nominal impedance and minimum impedance. In my opinion all three specifications are important, efficiency, impedance and sensitivity. My speakers are 96 dB SPL @ 1 watt @ 2 meters @ 8Ohms, efficiency is 2.7% and minimum impedance is 6Ohms. And the speakers excel at low level listening at 60-65 dB, and at that level the speakers are operating with milliwatts. 😎

Mike

Not sure that one detail matters too much but dynamics are super important and people underestimate how much power it takes to go instantly from 60db to 70db with a drum hit. The speaker/amp combo needs to be able to triple its power in a fraction of a second. At high volume many speakers compress those peaks. You need very large speakers or controlled dispersion (horns etc) to get there. i am firmly in the horn camp these days. The negatives of horns are reduced sound stage depth (it is more or all in front of the speakers) and in some rooms lack of sound stage width too. The benefit is better transients which to me sound more real.

At the risk of over-simplifying (and I'm not saying this is the only factor):

A significant contributor to high efficiency is a high motor-strength-to-moving-mass ratio, and it just so happens that a high motor-strength-to-moving-mass ratio is also a contributor to good articulation at low SPLs, making it easier to hear the details without needing to crank the volume up. 

High efficiency in and of itself is not a requirement for good articulation at low SPLs, as electrostats (with their incredibly lightweight diaphragms) tend to excel at delivering the details at low levels despite their typically modest efficiency. 

Duke

@audiokinesis I like your answer.