Are you sure the compression driver isn't damaged? I'll bet something has happened to it, possibly debris behind the phase plug or in the gap. You may have just gotten a bad driver with a damaged diaphragm or something.I ask because I've never heard or measured smoother response than from the four π loudspeaker. The crossover transition is very good, with clean summing and no ripple whatsoever. The amplitude and phase response is as good as it gets, the polars are good, the reverberent field is uniform and distortion is very, very low. This design shouldn't be giving you any problems, so I suspect something has broken.
![](http://www.pispeakers.com/Measurements/fourPi_response.gif)
As for comparison between the DX25 and DE250, they're both very flat in amplitude response. The DX25 goes out beyond 20kHz but the DE250 only gets to 18kHz. Not sure you could hear the difference there.
The biggest differences are directivity and dynamic range. The directivity of the DE250 is set by the horn, and amplitude response is pretty uniform through the bandwidth within the coverage angle of the horn. The DX25 is best used on-axis, as the off-axis response droops. The DE250 is capable of much greater dynamic range than the DX25. The DX25 is nice to be sure, but the compression horn is just loafing at volume levels where the DX25 is straining. So at low to moderate volume levels, the effortlessness of the compression horn is audible and soothing, at least to me.
I don't know, Bill. I like the speakers with DX25's very much. They're fine at moderate volume levels, especially in small rooms. But they don't compare to the larger speakers with compression horns on really any level, except maybe top end extension.
I think something is wrong. If you'd like, send me your drivers, horns and crossovers and I'll measure them for you. I can't imagine wanting to downgrade, and think it might be best to fix what's broke. If the size of the speakers is a problem, that's one thing. But if you're not unhappy with their size, let's just make sure they're working right 'cause I don't think you could make a better speaker with a soft dome tweeter.