Best Loudspeakers for Rich Timbre?

As an amplifier designer I can tell you that many speaker designers have very little grasp on the relationship that has to exist between the amp and speaker.
If the speaker is harder to drive, the amp makes more distortion. In particular if the amp is solid state, the distortion will be mostly higher ordered harmonics to which the ear is keenly sensitive as it uses those harmonics to sense sound pressure.
So to prevent this, the speaker should be higher impedance and no weird phase angles. This pretty well precludes four ohm speakers unless they are really efficient! Why four ohms is a Bad Choice if your goal is high end state-of-the-art reproduction is a topic worthy of its own thread!

IOW distortion plays an enormous role, because our ear/brain system simply converts distortion into some form of tonality. So if you want a rich timbre, your best approach will be to obtain a speaker that is easily driven by a tube amplifier, since tube amps make less of the higher ordered harmonics, and thus are smoother. At the very least, a higher impedance loudspeaker means that a solid state amp will make less distortion, and so will sound smoother and more detailed. When 'smooth' and 'detailed' occur at the same time, that's when you are making progress.

I do not think this means any sacrifice need be made to detail and neutrality on the part of the loudspeaker! An excellent example of this sort of craft are the loudspeakers made by Duke (audiokinesis) which are easier to drive due to moderate efficiencies and higher impedances. I can name quite a few others but in a nutshell, the actual tech isn't nearly as important (so long as the designer knows what he is doing) as is the simple drive-ability of the finished loudspeaker.

Ralph; I hope my DeVore O/93’s are on your list of the speakers that meet your preferred characteristics. But be that as it may, I want to add that I made timbre my number one pursuit when I had my last go-round with equipment upgrades. Based on my experimentation, everything makes a difference including-"crap, not again!" cabling. I hate to bring up past beaten-to-death topics but with my ARC Ref6 and Ref 150SE, the cabling between the preamp and amp was critical. The more I invested in cable, the better timbre sounded. I settled on Cardas Clear Beyond. I know you are firmly of the opinion that a properly designed preamp and amp running true balanced obviates the need for elaborate cable, and if you wish to malign ARC as then being sub-optimally designed, I can take that criticism. The very same thing held true with speaker cable. Every speaker cable I tried sounded markedly different. I know all of this makes the average person want to shrug off an impending headache. It is easier to say that this is all a bunch of nonsense. The truth lies somewhere and whether one chooses to search for it or accept what is easy as "truth" is up to each individual.

My Legacy Signature IIIs are 4 ohm and 94db efficiency but only dip a little lower.  They are very easy to drive.  I bought them when I brought along a Sherwood 7100 18 watt receiver.  Fantastic bass and dynamic as well.  I've driven them with Yamaha CR 620 35 watt receivers as well.  Tom Port of Better Records drives his Legacy Focus with the same Yamaha despite their 4 ohm impedance, 1 ohm lower bass impedance than the Signature IIIs but 96 db efficiency.  

I've noted whenever I see difficult to drive speakers like Magico, Wilson and B&W, that the bigger the better solid state amplification is needed.  I'll stick with high efficiency speakers despite lower impedances (which just means that they are often current hungry).  My favorite speakers generally have lower impedence, higher efficiency and easy to drive with smaller tube and solid state amps.   

The problems with measuring THD (Total Harmonic Distortion) in loudspeakers especially seem to be legion.

https://www.audioholics.com/loudspeaker-design/audibility-of-distortion-at-bass/total-harmonic-disto...

Not the easiest of reads, my head still hurts, but this following extract may be especially relevant to our perception of timbre.



"One more factor that can make it more difficult to detect distortion is personal familiarity and understanding of the intended reproduction. For example, most people know what a middle C note of a piano is supposed to sound like, but how many people know what a fist fight between two robots from another world is supposed to sound like? Furthermore, the timbre of musical instruments are heavily defined by the harmonic resonances of the instrument’s fundamental, and these resonances typically occur at even order harmonics, which is considered musical since an even order harmonic is always the same note in an upper octave.

These even-ordered harmonic resonances of musical instruments can make the detection of even ordered harmonic distortions very difficult, since they are ‘tuned’ to the instrument’s fundamental. On the other hand, this fact makes odd-order harmonic distortion a bit easier to hear since the frequency of that distortion doesn’t cleanly relate to the fundamental, at least in the scale of conventional musical notation. In other words, it’s easier to detect ‘off’ components in a sound we are familiar with.

If we have no reference by which to judge the sound, we have no way to know if what we are hearing is apart of the input signal or a distortion in the output. To tie this into the previous discussion, one test showed that even trained listeners were not able to identify as much as 30% distortion peaks from material which had a dense spectra with a high amount of transients and synthesized sounds."



Hopefully, in the not too distant future the type of data revealed by tests such as CEA-2010 will start to become more readily available to any potential customers of high quality loudspeakers.

One of my more surprising, and joyous pairings of amp and speaker actually turned out to be my MBL 121 monitors - spec'd at 4ohm/82db sensitivity, and my lil' old Eico HF-81 integrated tube amp.  A measly 14W/side.  It just sounded glorious:  rich, big, detailed, and the overall sound and bass just seemed to enlarge.  The speakers never sounded bigger and more authoritative than on that little Eico.  (Which, though out of my depth here, I presumed was likely due to some underdamping of the speaker, enrichening the bass).