How important is the efficiency of a speaker to you?

If a speaker requires an amp/ arc welder up front to drive it, then IMO, there is a problem with the speaker design. YMMV.

Exactly! Such speakers border on criminal as there simply aren't amps that sound like music that can drive them nor would they be all that musical due to thermal compression.

I look at it this way- if you can't drive it well with 100 Watts (in most rooms), its a problem. That is because the ear hears sound pressure on a logarithmic scale. So to get twice as loud (perceptually) that you can get with 100 Watt, you need 10x more- and 1000 Watt amps that sound like music don't seem to exist although class D is getting close with amps that can make 600 Watts or so.

The problem (again) is getting enough Gain Bandwidth Product in the design such that it can support the gain of the amp along with the feedback it has (together, known as 'loop gain'). If not, and this applies to almost all amplifiers ever made prior to about 2000 or so, you get distortion rising with frequency with its attendant unpleasantness- this is a good portion of the reason feedback has gotten a bad rap in high end audio. 

Its not feedback's fault so much as poor execution of feedback.

Plus a 1000 Watt amp would not be able to make up for the thermal compression that would be present- as I mentioned before, as you try to turn it up to get around the problem, it just gets worse. 

This has been discussed ad nauseum here on Audiogon. Low impedances can lower sensitivity which can make amps work harder to produce power and increase amp distortions. The degree to which the amp distorts due to this depends on the stoutness of the amp. The greater the loudspeakers sensitivity the more likely it will be a more open gateway to what distortions are still presented by upstream components, including but not limited from the amp. What is often less discussed is that varying impedances can strain amps too, and is more likely to present difficult phase angles to the amp as well. It is far easier to present and maintain a steady impedance by lowering the impedance of loudspeaker than visa versa. Electro-mechanical components are much more difficult to make perform well than purely electrical components. The variance between loudspeakers is typically much greater than between decently designed amps. This might suggest that more leaway be given to loudpspeakers than amps. As has previously (and wisely) suggested here; speakers designers have to choose what paramters and associated compromises combine to best meet ultimate design goals. Some if not most of the best measuring loudpseakers have lower impedances, and ergo lower sensitivity. There are a bountiful number of well designed amps that can handle such loads with minimal consequence.

Dear @daveyf  : First than all I'm a MUSIC lover and each single week at least I ttend to enjoy Live MUSIC and this " attitude " I have it for the last 25+ years.

I hate to listen the system Hardware and my room/system is builded through several years around nothing less than MUSIC but to enjoy MUSIC in my home we all need some kind of source/hardware.

I used tube electronics over 10+ years till I learned.

My ADS L2030 " old " speakers has 95db efficiency, no there is no single design problem with:

Vintage Holy Grail ADS L2030 High Fidelity Stereo Speakers and ADS C2000 Control Photo #1889387 - Aussie Audio Mart

The other gentleman ixs totally wrong, maybe he need to talk with J.Curl about that design or learn in other way about that specific design. I really don't care on his post that only shows high ignorance in tha specific regards amps.

R.

@rauliruegas Which other gentleman are you referring to? I don’t think anyone on this thread is totally wrong…except maybe you, lol😁.

just kidding..😎

@daveyf  : Yes, maybe me.

@unsound   " speakers designers have to choose what paramters and associated compromises combine to best meet ultimate design goals. Some if not most of the best measuring loudpseakers have lower impedances, and ergo lower sensitivity. There are a bountiful number of well designed amps that can handle such loads with minimal consequence. "

In total agreement with you.

R.