It depends on your TV model. What model TV do you have? Do you use any streaming devices?

Thanks for the answer.

My TV has eArc port, and my Beam gen 2 works in Dolby Atmos (I watched more movies in Dolby Atmos). My question is not about my TV, but about Dolby Atmos using two ONE SL as surround (back speakers, Beam in the front).

Yes, Atmos will work with Ones in the back as surrounds.

You just won’t get height channels from the rear, that’s all.

Hi, what is need for height channels?

It would need you to use 2 x Era-300 speakers as the HT surrounds, instead of the 2 x One-SL’s.

Ok, I understand, maybe next time. I think the beam gen 2 doesn’t deserve 2 Era 300, maybe they are more indicated on Sonos Arc

The Era’s do seem a bit like “overkill” with a Beam.