Vifa D27 ... every ScanSpeak was better at that time. What Seas do they use now? How much was the D27 - €50,- or less? It's "successor" tweeter at peerless is now €40,- (but don't know how they compare) and it looks like they use them with the old faceplate?
https://atc.audio/professional/loudspeakers/scm50a-pro/
These are not bad tweeters but compared to what we use now - entry level. And even then far from top notch, I always wondered why they didn't care more cause the rest of the chassis is really world class, even after all these years.
The mid driver has a waveguide… dispersion between the mid-dome and tweeter is well matched in all of the three ways… how would you like them to improve this with a waveguide.
Seriously?
The 3" is about 4dB down already at 30° at the crossover frequency. A 1" doesn't beam at all at that frequency.
There are very little measurements of these speakers around ... why?
So no, dispersion is absolutely not matched. You would at least need a waveguide for the tweeter and to call the rounded edges of the ATC a waveguide ... is marketing.
Rounded edges on my 50ASLs, just like the 100As before them.
How much is this, 10mm radius? That's not working with such a wide baffle. I used 25mm for my first design with a 12" lf driver and bought a 34mm router cause it was not good enough, you still see edge effects.
Don't get me wrong - these are great sounding speakers and give an amount of SPL which you only achieve with a 3" midrange dome and is stunning for big rooms and as main monitors! PMC and ATC got me in the midrange dome wagon and what for e.g. the big PMCs did in a huge room at AES recording competition presentations is incredible.
But to tell that ATC is INNOVATIVE with building the same speaker for 40 years ... simply no.
And they could do better in 2025, add a top notch tweeter with a small waveguide to match or shift the crossover frequency lower (that's what I do in my designs) to achieve a wide radiation speaker.
And ALL speakers from PMC and ATC I heard without the midrange dome ... aren't worth their money (but I don't know all of them, maybe bad luck in selection).