On the use of two tweeters?

as in the U$S 20.000 Bosendorfer VC-7 ?


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    Bosendorfer VC7 ES.S-.jpg
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2013-05-10 4:11 pm
There is a line of Sony products that is also doing something like...Advent? I forgot, some old and dead brand. They use a mid-tweeter flanked by a pair of real tweeters. IT's arranged something like a 2.5 way, only instead of the bass being duplicated, it's the tweeter.

The setup must work if they bothered to copy such an old design. A couple of months ago I helped someone here deconstruct the crossover for a pair, you may look it up.
There are interference patterns, and then there are interference patterns. Depends on the specific implementation. A couple mounted very close together -yes, you'll measure some differences, but whether you'd hear it is another matter as the precedence effect kicks in. Plenty of decent sounding speakers have been made with twin (or more) tweeters, so I wouldn't rule it out automatically.
The MTTM has an illustrious history, however it is done, because a ribbon can behave essentially like two regular tweters:



The idea is to get the PA-like projection and +6dB efficiency of twin drivers and keep the dispersion cylindrical.



Combing just sounds like off-axis dispersion falloff IMO. That can be improved with a 90 degree flat power BW3 alignment, which is the original D'Appolito idea where lobing is cancelled out by the symettry.

BW3 is more demanding on the drivers, and time alignment becomes another factor. Some drivers play nicely together, some don't. The modelling is best done time-aligned for a +3dB FR bump and aligned phase, and then muck up the time alignment for 90 degrees which is only 2.5 cm at around 3kHz and the bump goes away.

I was listening to something like these with an electronic LR4 filter recently, quite directional but good:


All deep stuff! Maybe even some sort of Entangled State at the root of it. :)