Coaxials - Reality vs. Experience?

@prof “:The other thing with the Thiels is the insane imaging prowess.  There is a focus and precision and density to the imaging I have rarely heard before.”

I had the Thiel CS5 monsters, had to work at placement really hard to get imaging and even then it was finicky relative to slight changes in sitting position. Granted that model didn’t have coax drivers. Eventually gave up on them, too much work.

Regarding coaxial drivers, as a general statement to OP with my take, slanted baffle speakers get the time domain right in the vertical plane. coax drivers get them right In both horizontal and vertical. So my question is this : a stereo setup offers a center image as if there was a center channel. So with D’appolito driver setups sandwiching a tweeter between 2 equally spaced midranges, do you get a phantom centered midrange that seems to come from where the tweeter is? Is that faking a coaxial presentation?

@jacksky I think the prime benefit of the D'Appolito configuration is narrow vertical dispersion.  with wide horizontal, so it is very different than a coaxial with equal dispersion in either direction.

Because of the changing time alignments in a D'Appolito, he's gone away from low order filters and now recommends 4th order (combined electrical + acoustical) crossovers for best off-plane axis listening.

This is an interesting thread on coaxial speakers. It was nice to read the comments on the HSU CCB-8’s.

I upgrade my speakers every 15 years or so and this summer I replaced my L/C/R speakers with the HSU CCB-8’s. They sound great, providing exceptional detail with a very full soundstage.

Of course, I also wanted to replace the rear surrounds and originally thought about two more CCB-8’s but that seemed like overkill for surrounds. Instead, I purchased KEF Q-150’s for the rear surrounds. They are also a coaxial speaker and blend very well with the HSU’s. Picked them up at Crutchfield at $254 for the pair, which was a great price (they retail for $599 a pair, but they go on sale frequently now).

Our home theater, with new speakers in the 5.1 setup, has never sounded this good before. Very pleased. And while I’m sure that upgrading to any speakers in this general price range would have made a difference, I like to think that the coaxial speakers are punching above their weight class!

@erik_squires The main design objective/benefit of a D'Appolito array is to mimic a point source. Benefits that inherently follow are higher power handling (plays louder) and lessening of the potential impact of floor and ceiling reflections due to two drivers producing the same frequency range. The design doesn't actually reduce vertical dispersion, just potentially helps alleviate some negative interaction of the floor and ceiling. Before the D'Appolito array the only way to mimic a point source was to use a dual concentric driver (with its attendant pros and cons).

One downside of the D'Appolito array is the tighter vertical listening window created by the three drivers (five drivers in my fully active 3-way design)(seven drivers in the Duntech Sovereign). It just so happens that the symmetrical drivers couple optimally at a certain distance........which you are calling "narrow vertical dispersion" and as a "benefit" It is not a benefit, but a downside. There is no free lunch, each design has its pros and cons. You get the benefits of that narrow window of optimal coupling when in the sweet spot, and the downside of potentially less coherent sound outside of the sweet spot (in reality...not so terrible).

Unfortunately, we can't give full respect to the details in this short response form. 

Please explain "off plane axis listening".

which you are calling "narrow vertical dispersion" and as a "benefit" It is not a benefit, but a downside.

I absolutely disagree.  In a brief reading of articles online you'll see that the horizontal dispersion control of D'Appolitos is in fact a good thing, as it is for tall ESL's.

Generally speaking, the more controlled dispersion of a speaker the less acoustic treatments a room will require. 

Further, you literally can't have a point source if you are deliberately changing the dispersion on one or the other axis.