The best speakers I have heard have all been fairly easy to drive. Getting saddled with a hard to drive speaker is next to criminal in my opinion- if you can't play all the volume you want with 200 watts you are in big trouble due to something often called 'gold plated decibels'.
The idea has to do with the fact that it takes double the amplifier power to increase the volume by 3 db which is not a lot by the human ear. The trick is that your amplifier has to produce musical power- and the smaller the amp (tube or solid state) often the better it might sound being the popular wisdom (actually I think our amps fly in the face of that, but they the unusual exception). So you might a musical amplifier that makes 200 watts, but how many are really out there than can make 400 watts or 1200? The fact of the matter is that if you want an amplifier of that sort of power that sounds like music, you can count the number of amps that qualify worldwide on your hands.
In short, its impractical to have a speaker that requires a lot of power regardless of its price. I usually draw the line at about 86 db 1 watt/1 meter - anything below that is not really a contender for the best speaker in the world- the math simply does not allow it.
Now keep in mind the difference between efficiency (which I think is a more honest statement of how easy the speaker is to drive) and sensitivity (which is 2.83 volts at one meter). If the speaker is 4 ohms instead of 8 ohms, subtract 3 db from the sensitivity figure to get the efficiency figure.
So if you have a speaker that is 86db sensitivity and is also 4 ohms, its actual efficiency is 83 db. In my room, which is 17' x21', I need about 200 watts to make a speaker of 89 db play to a satisfying level. If I had a speaker as in the preceding example, I would need 800 watts to do the same job. If we flip this around, right now my speakers have 98 db, which means that I only need about 25 watts to do the same job right now. Its a lot lot easier to find a nice sounding 25-watt amp than one that make 800 watts!!
So far impedance has not been explored but that too plays a huge role in the sound of speakers. Not directly, but it affects the amps playing the speaker, whether tube or solid state or class D. Essentially, all amps make more distortion into lower impedances, and the distortions that they make are higher ordered harmonics and increased IM distortion, both of which are easily audible. In addition, the lower the impedance the more critical the speaker cable becomes! Conversely a 16 ohm speaker is not critical of the cable, and all amps make less distortion driving the higher impedance.
So if the speaker forces the amp to work harder, you will hear increased distortion. In a nutshell, such a speaker cannot possibly be the best except in theory, as in the real world the amps driving it won't sound like music- they will sound like electronics. If you like a nice hifi, this is OK, but if you want real music, this is something to keep in mind.
Two speakers that I like a lot as they are easy to drive and are full range are the Sound Lab Majestic, which has gotten very easy to drive with a change that was made about a year and a half ago. The other speaker is the Classic Audio Loudspeakers model T-1.4, which is 16 ohms and 98 db 1 watt/1 meter and goes to 20Hz no worries. Rather than say 'this is the best speaker' I like to think about what speakers might be the top 5 or top 10 made world wide. These are two examples. Sorry to say, many of the speakers I have seen on this thread don't belong there IMO. Some do though...
The idea has to do with the fact that it takes double the amplifier power to increase the volume by 3 db which is not a lot by the human ear. The trick is that your amplifier has to produce musical power- and the smaller the amp (tube or solid state) often the better it might sound being the popular wisdom (actually I think our amps fly in the face of that, but they the unusual exception). So you might a musical amplifier that makes 200 watts, but how many are really out there than can make 400 watts or 1200? The fact of the matter is that if you want an amplifier of that sort of power that sounds like music, you can count the number of amps that qualify worldwide on your hands.
In short, its impractical to have a speaker that requires a lot of power regardless of its price. I usually draw the line at about 86 db 1 watt/1 meter - anything below that is not really a contender for the best speaker in the world- the math simply does not allow it.
Now keep in mind the difference between efficiency (which I think is a more honest statement of how easy the speaker is to drive) and sensitivity (which is 2.83 volts at one meter). If the speaker is 4 ohms instead of 8 ohms, subtract 3 db from the sensitivity figure to get the efficiency figure.
So if you have a speaker that is 86db sensitivity and is also 4 ohms, its actual efficiency is 83 db. In my room, which is 17' x21', I need about 200 watts to make a speaker of 89 db play to a satisfying level. If I had a speaker as in the preceding example, I would need 800 watts to do the same job. If we flip this around, right now my speakers have 98 db, which means that I only need about 25 watts to do the same job right now. Its a lot lot easier to find a nice sounding 25-watt amp than one that make 800 watts!!
So far impedance has not been explored but that too plays a huge role in the sound of speakers. Not directly, but it affects the amps playing the speaker, whether tube or solid state or class D. Essentially, all amps make more distortion into lower impedances, and the distortions that they make are higher ordered harmonics and increased IM distortion, both of which are easily audible. In addition, the lower the impedance the more critical the speaker cable becomes! Conversely a 16 ohm speaker is not critical of the cable, and all amps make less distortion driving the higher impedance.
So if the speaker forces the amp to work harder, you will hear increased distortion. In a nutshell, such a speaker cannot possibly be the best except in theory, as in the real world the amps driving it won't sound like music- they will sound like electronics. If you like a nice hifi, this is OK, but if you want real music, this is something to keep in mind.
Two speakers that I like a lot as they are easy to drive and are full range are the Sound Lab Majestic, which has gotten very easy to drive with a change that was made about a year and a half ago. The other speaker is the Classic Audio Loudspeakers model T-1.4, which is 16 ohms and 98 db 1 watt/1 meter and goes to 20Hz no worries. Rather than say 'this is the best speaker' I like to think about what speakers might be the top 5 or top 10 made world wide. These are two examples. Sorry to say, many of the speakers I have seen on this thread don't belong there IMO. Some do though...