Does anyone play two pairs of speakers at the same time?

Check out the following video by speaker design wiz, Danny Richie. He explains why 2 tweeters on the same baffle is a bad idea, but a lot of what he says can be translated to multiple speakers of different designs also. Unless special circumstances are taken into consideration, like line arrays, for example.

Hee Hee, why do you think Danny used TWO tweeters as an example?
If you know the history, you know the reason, though NEVER spoken out loud... really do a little research, on GR research, when they came into existence, and what motivated, Danny into the Speakers designer he is.
HE just didn't like VMPS's owner Brian. Didn't like his approach to speaker building, not measuring things, ect... Funny Brian inspired a lot of people, weather through INSPIRATION, or, DESPERATION.  Servo Bass, Danny's got some cool products, for sure...

Danny lives with a mic in his hand, simple. He's VERY good at his trade.
Yet, that marketing though serving him VERY well, shows others who DID NOT follow the leader, and  took home prize after prize at CES.

So what gives?... I HAD a pair of  LS6s.. got sold, WHY??? They  had a ways to go to catch some of the VMPS crazy measuring speakers, simple...
Cool speaker, just something was missing, like the whole top end...
Where is the TWEET... lol
I'd give my last two teeth for a pair of the LS9 though....Right NOW...

Different folks, mate.. 

Has anyone seen the Tekton "The perfect Set"? It has a few tweeters in each cabinet!

The "speaker for each" instrument was the point of the Dead's famous "Wall of Sound" system back in the 70s. So it has been done. 

i have 4 speakers from the '4 chanell' days so i use all 4 in my 2 chanell system!!!

Why stop at four, one of my systems has 15 speakers and four subs. I even have a special name for that system. Home theater room. Sounds wonderful. Lol