The point of this audition for me is to better define (or invalidate if I could not repeat) the aspect of the ls50 that did not sit so well with me. As such I primarily focused on that aspect of the sound.
I started out listening to the ls50's against the Canton Vento 820.2's. This seemed like a logical comparison since both have a list price of $1500. However, the Vento has a 6" woofer which goes pretty deep and from my perspective, aside from making sure it is not muddy or over-blown, bass is not too relevant as I would generally use a sub with either (the Vento might get away without a sub in a smaller room). In any case, I found the large difference in the bass between these two masked many of the more subtle differences.
I gave it some thought and pulled out my EmpTek 41se/B speakers. These little darlings are still among the best speakers I have ever heard. Their limitations are bass (4" Be mid-woofer) and SPL (as you would expect from a 6-3/4" W x 11-1/2" H x 10-1/4" D box). I listened at a distance of 4 ft. at moderate levels which would not challenge the EmpTek's SPL limits while satisfying my objective of listing to the ls50 under near-field conditions.
Norah Jones - Don't Know Why
Norah has an airiness in her voice. As a perverse analogy, it is kind of like the way Gollum says "precious" along with the pure sound of her voice. Unlike Gollum, it lends a seductive quality and is part of the intimacy of a female singer in a night club. This "whisper" is diminished on the ls50. I could describe the ls50 as sounding like she is singing without a microphone in a small venue. Or, perhaps a music hall where the mic was hanging in the air 10' away.
After I wrote these notes, I looked at John Atkinson's measurements and comments as presented in my post above, and believe that fits my subjective experience fairly well.
Ed Palermo's Big Band - RNDZL
This is a modern Big Band playing a re-arranged version of Frank Zappa'a RNDZL. It starts with an aggressive drum lead in and I was impressed with how realistically the ls50's brought the impacts of the drum hits into my room (especially given its size!). I think this is one of the strengths of the ls50's over other speakers in its price range!
At around 0:30 the drummer starts tapping the ride cymbal while accompanying an alto sax solo. The 41se/b presented this as tap followed by the ring of the cymbal. On the KEF the tap is not as prominent and the subsequent ring is almost inaudible.
Strangely, when the drummer does this later accompanying a trombone solo, the KEF does better with it. I don't know if the drummer was being more assertive with the more powerful trombone or if there is something about the harmonics of an Alto Sax vs Trombone that would mask the ride cymbal more with the sax? The sound is still more prominent on the 41se/b, but I would not have an opinion on which was "right" (to my ear).
I also did not like the loss of the upper harmonics of the glockenspiel in this song.
Pink Floyd - Time
The main difference here is how the bells presented near the start. The EmpTek sounded as if they were closer to being in the room, while the KEF placed them "down the hall".
The KEF did a fine job with both the male and female vocals on this song. Switching between the speakers, the relevant difference was the comparative bass lacking of the EmpTek's, and I fully enjoyed finishing out the song listening to the KEF's.
Yes - Heart of the Sunrise
Bill Bruford's drumming is front and center through this song and the drums sounded somewhat veiled on the KEFs as compared to the EmpTeks. I think, again, this is due to the suppression of the cymbals' HF content.
That said, the KEF's otherwise completely trashed the EmpTeks on this song. They fleshed it out wonderfully and made the EmpTeks sound absolutely "thin" in comparison, and I'm talking more than just deeper bass! This is a good place to point out that if you think I am saying the EmpTek is a better speaker, you would be wrong; my objective is to focus on and explain what I found lacking in the ls50!
Interestingly, the airiness in Jon Anderson's voice was diminished, but it just didn't matter that much with his voice. I don't "feel the loss" of it the way I did with Norah. IOW, when I A-B speakers, I mainly respond to my sense of loss, or the thrill of an improvement. If I don't feel it, it is not so much of consequence in my subjective comparison.
Steely Dan - I got the News
Initially, the KEF sounded great on the tight percussive content of Steely Dan, but later into the song, the drums sounded veiled. Upon revisit, I realized when the high-hat is being played, it sounded like the drum kit was tucked in a recess behind the band (not a very significant difference), but at 1:52 where the ride cymbal is played, once again, the KEF's presentation puts a thin veil over the drum set, which for me is a loss.
Chet Atkins (with George Benson) - Sunrise
Again the difference showed in the drum set. The blur of dozens of individual brush strikes on the snare drum is more realistic with the added high frequency energy of the EmpTeks.
The triangle presents as "somewhere back in the back" on the KEF.
I like to close my eyes and envision the musicians/instruments and in this case, the seemed about 15' away on stage with the EmpTek and in an orchestra pit with the KEF.
I think this song would be the one I would choose if I wanted to demonstrate the shortcoming of the KEF's HF presentation! In a way having it happening in female vocals is more damning, but the brushes and triangle would take on a substantially different nature when I switched between the speakers.
Emilie-Claire Barlow – C’est Si Bon
At this point, I think I am beating a dead horse. I will just say I experienced the same as with Norah Jones - the intimacy from the air in Emillie-Claire Barlow's voice is suppressed on the KEFs.
Lyle Lovett - She's No Lady
Lyle Lovett has one of the fullest richest voices I have ever heard, but I really had not recognized that he actually also has some of that air in his voice! However, just like with Jon Anderson (probably more so), it doesn't matter. For me, it is a difference, but neither good nor bad.
Conclusion
Among the music I listened to, with the exception of the air in female voices, ride cymbal, glockenspiel, brushes, and triangle, the KEF presented sounds with a breath-taking clarity that is a solid benchmark in its price class.
I like a lot about the ls50's and fully understand why they are so well liked.
I know I like a forward rather than laid-back speaker, so that is definitely part of the equation.
Furthermore, if I could not instantly switch between speakers in the middle of a note, I'm not sure how much I would notice these differences.
I believe Steely Dan, Yes, and Pink Floyd would all present perfectly well on the KEF without the instant comparison.
It is the "night club" female vocals (Norah Jones and Emillie Claire Barlow) and the Chet Atkins tune where I believe I would still sense a difference given a 2 minute delay between listening to one speaker or the other.
Listening to the big band, now that I know to listen for the ride cymbal, I would notice, but otherwise, I doubt I would pick it out as an issue without the instant comparison. I don't think I would notice the glockenspiel differences were it not for the instant comparison. It sounded great on the KEF!
What I am hedging at is, I think that for many types of music, the KEFs give up nothing.