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

If you are not running 2 amps off of your pre,(providing the pre has multiple outputs) isn't the amp seeing potentially damaging low impedance?   

i am running all actives... i am still doing some eval on this setup... while i am losing a bit of crystal best-in-class midrange detail from running only the AirPulse Model 1 , the heft and soundstage of this arrangement cannot be denied. the JBL 305 is no slouch and as it onle goes to about 16Khz I am only feeling the love from these 200 dolla boxes... a livelier all-around sound.. i love dem horns

Running 2 pairs of dissimilar speakers at the same time is such a bad idea, in a stereo system. Especially in the high frequencies.

Not sure if the OP is talking about stacking them, or playing them on 4 different walls, but either way, not good.

People, comb filtering is a thing. The frequency response would be completely unpredictable, there is no way to know if some frequencies are going to increase or decrease due to frequencies from one speaker’s dips or rises in frequency response meeting the other speaker’s dips and rises.

Then there are difference in lobing caused by different drivers and different crossovers. I am sure that imaging and soundstage would be close to nonexistent.

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.

https://www.youtube.com/watch?v=MGSfaKWcetQ

I would guess that any result that would sound ’good’ would be the result of certain frequencies, like maybe the presence region (4-6 K), being increased or decreased, depending on if the listener like bright or rolled off sound, or increase in bass response, etc.

Back in the early to mid 70's, some dealers would stack two pair  of EPI 100"s with excellent results. Often besting the stacked Advent pairing. Although the smaller EPI woofers didn't have the bass extension of the Advents.

Why is it people like a blended whiskey ? Or a V8 in a Chevy Monza or a Maverick? Life is complex, the grail elusive....

now a Klipsch and Maggie marriage must sound like a tortured Labradoodle on speed...