I'm using two upfiring speakers (not a soundbar, separate speakers) for a 5.1.2 Atmos configuration, and I have to say that it's not very effective. You get a hint of overhead sound, but can't come close to a true overhead speaker array. And since I can place my speakers in a more optimal location compared to a soundbar, I really question the value. Yeah, it's nice to see Atmos or DTS:X light up on my AVR display. But I wouldn't worry about missing much. I only did it because I had some spare speakers lying around, and one of my AVRs supports Atmos. If I had to spend money specifically to have it, I doubt I'd bother if I wasn't using dedicated ceiling speakers.
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