I know that it runs contrary to the usual philosophy.
So I would be dating myself here, but as an avid young audio enthusiast of the 70's I was entirely ready to jump on the multichannel bandwagon. Without exception all of the demo rooms had 4 identical speakers describing a shallow rectangle, and depending on the intent of the producer, one may listen from a mid hall perspective with the ambient reverb coming from behind as we would with most movie watching. And this would be the obvious way to do classical recordings (though it wasn't always--predictably with mixed reviews. While many might dream of having a conductor ear's view of matters, does one really want to be the tuba player right in front of some serious percussion? With rock it wasn't as clear--maybe one does want to be on stage hearing the audience in front, surrounded by guitars, keyboards and drum kit. Long story short: there was mostly piss-poor attempts with a few jewels thrown into the mix.
Those jewels were good enough to keep the dream alive and with the "rapid" technological development of multichannel audio for home theaters, we are in a position to witness some very cool experimentation--just about 50 years later. I haven't had chance to hear the Apple mch remixes, but have finally been coerced into biting from the apple (to use an absolutely extraordinary technology out of Princeton U. known as BAACH, must have Mac platform. Interesting story: Renowned plasma physicist/rocket scientist genius with dozens of patents and huge interest in audio tackles problem of spatial recreation with gob smacking results, using in some cases normal stereo recordings
https://www.youtube.com22/watch?v=r161zrgV1HQ )
So the need to have 4 fully full range speakers anchoring corners is not a new idea. I used to be obsessive about a/v and esp when it was coming out I paid a lot of interest to both home theater and audio press. One of the guys I followed way back was Brent Butterworth who reviewing some B&W tower speakers talked about having 4 set up and had what I refer to as the "I touched the sky and talked with God" experience where it goes well beyond the usual BS and you hear the reviewer say "make no doubt about it, this is the really, really good shit that you must try." At least I think it was Butterworth, I paid attention to a few and its been a few decades ago. So there's that. I also believe if you wanted to do a lot of gaming (I suspect VR and a good head set is the e-ticket), it makes sense. Finally, we talk a lot on these pages about the difficulty of reproducing bass accurately and that the consensus and numbers tell us the best results come from multiple sources. Here I'm talking maybe high 30's and above--stuff within the reach of a competent tower, and not so much the special effect stuff that depends on SW's--and having 4 sources to start with gives one a pretty good shot of getting some clarity, assuming that your AVR could do it--it's likely beyond the capabilities of much of the stuff and best left to Dirac Live multi-woofer eq. Also I would still bring in a dedicated SW or two that have complete freedom of placement to get it extremely well sorted. So by no means whatsoever, mandatory, but if you got the floor space and the 500 extra to spend, why not towers on the rear?
And of course when it gets right down to it, I am talking mostly about special use cases, and for the usual envelopment needed for a convincing experience the usual recommendations apply. It's great that ELAC makes it affordable to do so.
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