dB effeciency vs speaker configuration

I won't claim to be an expert, but I would say that if you can find the display of impedance and phase across the audio spectrum of any given speaker, you should be able to determine whether or not an amp will be able power it. Though, you need to be able to understand what it is displaying.
Just my 2 cents until brighter minds chime in...
I will defer to Almarg, and Atmasphere, who are probably the best qualified to answer here on Audiogon.

Well technically its sensitivity but the difference is hard to explain so efficiency will do. Which one sounds better is impossible to say. Pretty obviously there are great examples, as well as examples that suck, of every design. For every guy who swears by electrostatics there's one in love with horns, for every port lover there's a sealed supporter. 

In terms of amps though its still hard to say its at least a little more clear. Speakers with low sensitivity are gonna be a lot harder to find an amp to make them sound good. Tube or SS. 

Problem being, its hard enough to make even just one watt sound good. Then if you want louder, which you do, well then both power and volume (dB) are log scale. What that means is to play just 3dB louder, which does not sound like much, requires twice the power. 10 dB requires ten times the power. 

So a speaker with only 86 dB sensitivity, that on paper looks not hugely different than 92dB or even 96dB, in reality is gonna need four to ten times the power. 

In practice you go with what sounds good. Regardless of how its made. But no matter how much you might fall in love with one you will be well advised to stare it down real good if its sensitivity is below 90. People do, it can be done, but the 87 you mentioned will need nearly ten times the power of your 95 example. And good luck with that. Because you will need it.

 If you want to use tubes, generally speaking, higher efficiency and higher impedance are desirable. 

Every 3 dB of improved efficiency cuts the power required by half.

Most tube amps can drive 4 Ohms, but they are sensitive to variations in the impedance. Examining the impedance curve can help find things to watch out for.


See the black line in the very first chart for a typical example of how a spaeker's complicated impedance can interact with a high output impedance amplifier (typically tubes):


https://www.stereophile.com/content/balanced-audio-technology-vk-56se-power-amplifier-measurements

Best,
E

I tend to like low powered amps, tube or solid state class A.... with higher efficiency speakers.    I've had some great sounding lower efficiency speakers, 83 to 86 dB/w  but they all ran out of steam quickly and needed a lot of power to shine.    My current setup is a pair of Klipsch Heresy III with a pair of 40 w Quicksilver monos and they sound as close to live music as I've ever had at home.

" sound as close to live music as I’ve ever had at home ".......this, is what it is all about !..........I have heard so many multi 6 figure systems, that do not do this, using live, unamplified music, as my reference........

What impedance and what sensitivity sounds the best?
From an amplifier point of view, the less distortion the amp has to make to do its job the better. To this end, higher impedance followed by higher efficiency will result in smoother more detailed sound, all other things being equal.

The reason this is so is that quite simply all amps have less distortion driving higher impedances. Amps also tend to make less distortion when not having to make a lot of power within their power envelop.

There are some excellent 4 ohm speakers out there! But the simple fact is that if they were 8 ohms or even 16 while otherwise being the same design, they would sound smoother and more detailed with greater impact simply because the amplifier would be making less distortion. Put another way, just because an amplifier can drive a difficult load is not the same as saying its also sounding its best while doing so!

 Best answer is not answer to you question , One speakers with 85db can sound better them speaker 95 db,   Another brand with 95 db will overperform speaker 85db  , same thing with impedance and box enclosure design.    

Not to hijack the thread, but what determines speaker efficiency? Is it the materials used, or is it something else?

what determines speaker efficiency? Is it the materials used, or is it something else?

At a fixed frequency, how it is loaded (i.e. horn or not), magnet size, strength and structure, moving mass and radiating surface, as well as suspension.


You'll notice the speakers with ridiculously high efficiency (i.e. 100 dB+) are almost always horn loaded, and/or or very large bass drivers.

Focal has recently (last 10 years) reintroduced the electro magnet. That is, instead of using a permanent magnet, their subs use a second coil to generate a startlingly strong magnetic field against which the voice coil pushes. This gives the subs amazing amplifier efficiency measured from the amp side alone.

Of course, the total driver efficiency is now different, since the speaker itself has a power supply, but it’s a great example of how the strength of the magnetic field affects efficiency.