Listening to the CS2.4 and comparing to my own speakers I notice a couple of things. The CS2.4 like most Thiel speakers use concentric tweeter midrange driver. And because of that, the soundstage is very stable. I can move my head but the sound remains constant most of the time.
There are not a lot of quality off the shelf concentric drivers available commercially and those that are available are not of high quality. So my speakers use separate dome tweeter and midrange driver. Since I build my own speakers, I could afford very high end capacitor.
When I listen to Jewel song 2 Find U on her album 0304 on my speakers, there is this treble glow that sort of being sprinkled over the soundstage that is kind of addictive. It's like the golden glow over the atmosphere you see during a sunset at the beach. I use the track above as an example but on my speakers this treble glow is there in every track. I mention that because I use very expensive cap in my tweeter cross over, but when I put in a low cost cap the glow was greatly diminished.
When listening to the same track above on the CS2.4, I notice that treble glow was not really there. So I was wondering if the CS2.4 might not have used a good cap? Or it could be the concentric tweeter midrange driver is a compromise to achieve time-phase coherent?
Also, some time-phase coherent designs use a phase delay network on the tweeter, and the phase delay network uses up 2 capacitors per network so if you want to use high end capacitors it will cost a lot of money especially for a commercial design. I don't know how the CS2.4 xover is designed so I am not sure.
As for the CS2.4SE version, from what I heard, the xover was modified to use more expensive capacitors, and some people have said that the SE version sounds sweeter than the regular version so maybe it's the capacitor that is responsible for the treble glow. My speakers tweeter is ScanSpeak AirCir soft dome tweeter where as the CS2.4 uses aluminum so that could explain the difference as well as soft dome is known to have a sweeter sound vs. aluminum.
Anyway, back to the concentric tweeter midrange driver. Theoretically I always knew that concentric driver has the advantage as far as soundstage presentation stability and coherent and having a bigger sweet spot. Now that I can personally listen to the CS2.4 in my own home, I am more than convinced that it's the way to go if you want a good soundstage presentation. Earlier Thiel speakers used separate tweeter and midrange driver. But later designs, all Thiel designs have all used concentric drivers so I guess he came to the same conclusion.
The problem of concentric is the motor design. Basically you need to have a motor that have to drive both the tweeter and the midrange, hence you have to compromise. Not only that, when the midrange driver vibrates, it modulates the tweeter as well so it's another thing you have to take care off. If you have to separate tweeter and midrange driver, you can optimize separately to your heart's content.
I have seen a few concentric drivers available commercially but their frequency response do leave a lot to be desired. In that sense I admire what Thiel have done. They have gone their own way and I wish more speakers manufacturers could take a bit more risks.
