Best Loudspeakers for Rich Timbre?

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). 

prof, I think you're right about the underdamping of the speaker. I recall getting a wonderfully unrestricted breathing bass from a pair of Rega bookshelves when driven by a cheap 7 watt amp.

The sheer unfettered free sound coming from those small boxes was highly compulsive listening. Rega don't give much away regarding construction but as the speakers don't feel particularly heavy I guess some form of thin wall cabinetry
(in best British style) must be involved.

I also remember that you had to turn up the volume to get them singing in this fashion. The timbre of the free flowing bass was as good as I've heard. If only the midrange had been as expressively free. 

Still, whilst not being ideal as main speakers, mainly in terms of scale, openness and bandwidth, they remain far too good for me to ever pass on.

@atmasphere 
I generally try to ignore your posts because many times you indirectly seem to be hawking your own amps. But I have interject here in protest of your negative statement about 4 ohm speakers. I owned on of your amps in the past and very aware of their limitations. Namely, your amps don’t do well with speakers that are 4 ohms or less.  But it doesn’t mean other great amps have this limitation.  In fact, some of the greatest speakers made are 4 ohm or less and are inefficient  (Apogee and Magnepan are few examples).  Paired to proper amp, these speakers can sound unbelievably real.  Sorry, Atmasphere amps paired with Classic horn speakers always sounded colored and unreal to me despite your claims.

@dracule1I think you might be glossing over my comments here.
All amps, tube, solid state and class D, make more distortion driving lower impedances. Its a simple physical fact- you can see it in the specs.
Its also a fact that the human ear converts distortion into tonality, and a further fact that the distortion generated by all amps into lower impedances tends to be higher ordered harmonics and increased IMD. Both are extremely audible to the human ear and contribute to harshness and brightness.
I agree that the Apogee and Magnapans are excellent speakers (and if you have enough power, work quite well with tubes). But what you may not be considering is that if these speakers were higher impedance, they would sound smoother and more detailed- in fact, more real, regardless of the amplifier employed.

If you have a 4 ohm speaker, and a solid state amp, you may have a 3 db argument for 4 ohms if sound pressure is your goal.

But if **sound quality** is your goal than your amplifier investment dollar is best served by a loudspeaker of higher impedance.

Now one problem with a speaker that is simultaneously low impedance and also low efficiency is that you need a lot of power to make it work. There really aren't many amps out there that make a lot of power while also sounding like music. It puts them at a disadvantage. Its really a Bad Idea to make any amp work hard for its living- the result is less musical.

Regarding your comments about the Classic Audio Loudspeakers (which are 16 ohms), as you already know the impedance is not what makes them sound a certain way. Some people look at them and see a horn, and don't take the speaker seriously no matter how it sounds.

In my case, I recorded an LP (Canto General) and because I recorded it, I was actually at the recording sessions :) 

I know what that LP is supposed to sound like- I was there. It makes an excellent reference for me.

The Classic Audio Loudspeakers do more of what is needed to sound like that than any other speaker I've heard, but by no means have I heard all speakers. While many speakers can make the soundstage, often the bass is missing or colored, or the highs don't sound like O'Shaughnessy Hall and so on. My choice to use the Classic Audio Loudspeaker is purely based on them providing the most neutral presentation of that reference. I have high regard for Sound Labs, and would have bought a set if I could have figured out how to make them work in my room (I've also considered Magnaplanars as many of our customers own them, but couldn't make them work in my room either).

Please pardon me for walking my talk. I'm not going to tell you something that I don't believe myself. If you feel that I should not be participating on this thread, please say so.