I agree when it comes to wiring dual drivers in series vs. parallel.
But I can think of other features in speaker building that are considered theoretically better, but we rarely see them done well in practice. Two examples:
- Tweeters mounted coaxially in a woofer. Everyone will point to the KEF LS50 speakers as the example, but there are many other 2-way speakers with separate woofers and tweeters that perform very well.
Having recently owned KEF ls50's for 3 days, I'd like to comment on the first of these. In theory, coaxial drivers should,
improve imaging, but adding the weight of the tweeter to the mid-woofer and being forced to use the mid-woofer cone as a wave guide does no favors. I believe it is a design choice/compromise more than something that should be accepted as a generally better design.
I can state that the coaxial drivers do indeed offer amazing imaging. I could close my eyes and pin-point the location much better than I ever have heard before, and IMHO, I don't think any non-coaxial speaker could do that.
Listening to solo sax, trumpet, or trombone on the ls50's allowed the instrument/player to solidify like I have never experienced (well I'll reserve electrostatics until I compare them side by side)! In the showroom, I could find no fault with them and did notice the improved imaging as being special. Once I got them home where I could level match and switch instantly between speakers, even the "lowly" Philharmonic AA's beat them for detail and fullness! I would pick the ls50's over the AA's, but the lackings of the ls50's were obvious with the AA's in the room. Comparing the ls50 to the RBH 41B-se was the nail in the ls50's coffin (to my ear)! The RBH brings enough detail beyond the AA's to the point that almost every time I switched, the RBH sounded better.
To further clarify, a solo brass instrument (which is directional) took great advantage of the imaging ability of the KEF's; however piano (which has sound radiating in all directions) sounded comparatively "thin" while the RBH (and the AA's) provided fuller spectrum and the detail of the ambiance of having a piano in the room. Part of this effect I suspect comes from the lack of even dispersion from the tweeter being mounted in the back of the mid-woofer cone. The breathiness of Norah Jones - "Don't know why" really exacerbated a "horn" type sound out of the ls50's revealing a weakness of the waveguide, IMHO.
I found the KEF's strengths to be imaging and transients in the upper bass to lower midrange.
The good transients are a bit of an enigma because they seemed poor in upper midrange and higher.
So in conclusion, I think coaxial drivers have their advantages, but not without adding problems.
Why does KEF put the tweeter in the "pit" of the mid cone? Is it a phase coherence thing? Cheap car speakers have the tweeter on a metal brace that spans the mid. That would probably remedy some of the dispersion issue.
I really cannot comment on the active speaker situation, it seems that properly executed ones in home audio are indeed rare. I will, however point out that Floyd Toole covets the (discontinued) active JBL M2's. If Floyd considers them the best, they probably sound pretty good. He has probably heard and compared more speakers with a better trained ear than most anyone on the planet! (the passive M2's don't seem to catch his interest).
