With a room of that size, my personal choice would be to go with a Sonos Arc, 2 x Era 300 Surrounds and a Sonos Sub (gen3). A Beam (gen2) might be enough too, but the Arc sounds better, has wider soundstage and upward firing drivers to complement the Era 300s etc. I would also put at least a 55”, or larger, Dolby Atmos surround sound capable TV with the HT setup too. Why settle for less?

My recommendation would be ARC and the large SUB. If you are a bass freak, two SUB’s are great fun.

Your room is almost identical to mine in size (WxD). The only piece missing from your description is ceiling height and whether or not the room is closed or open to another area. Those missing dimensions can make a difference as to what Sonos gear might be the best options.

The above said…here’s my layout (closed room):

12 feet width x 20 feet length x 8 feet high

Smooth walls and ceiling (non-acoustic)

LG 65 inch TV positioned at one end of the length

Sonos Arc, full size Subs x 2, Era 300’s as surrounds

In my room a Beam2 would work although with reduced Dolby Atmos effects. A sub-mini would also work albeit with less low-end. Budget may dictate your choices as well. If full immersion in Dolby Atmos is not a must you might substitute Era 100’s as surrounds. 

If you provide the missing dimensions of your room members can offer better recommendations. Providing a floor plan that shows doors, cabinets, windows, openings and proposed furniture placement would be excellent.

Thanks so much for all the answers already. We will have a projection screen that comes down from the ceiling. 135” in diameter. The room is partially open on one side. So not perfect… Also 8ft high ceiling. 

Thanks for the additional information. Using a projection screen puts an entirely different spin on using a Sonos Arc or Beam 2.

Simply put a Sonos sound bar needs to be placed up front. How you would accomplish that is a challenge with a projection screen unless you have a stationary cabinet in place at all times. That assumes the screen comes down to a fixed point and when raised the space appears normal.

The next hurdle is running an HDMI cable from the projector to the Sonos soundbar. The run length is possible but how to do so attractively is the question.

Sound output for projectors such as Dolby Digital 5.1 and Dolby Atmos is a concern depending upon your projector.

Assuming you want to get Dolby Atmos sound you may want to consider an option like the HDFury Arcana as shown in the link below. After clicking the link scroll down and click on “Getting Started” for a diagram.

https://hdfury.com/product/4k-arcana-18gbps/

In truth Projection setups are better suited for traditional sound equipment with separate speakers. A Sonos alternative is to use Sonos In-Wall Architectural speakers by Sonance which can be wired to a Sonos Amp. The speakers would flank the screen left and right side. The Amp can be placed close to the projector for the HDMI connection and the speaker wires can be hidden during construction. 

Feel free to post with more questions.

Thanks! I had the same setup prior to our current renovation where we have a separate room and I ran the HDMI in the wall, under the floor, etc. It worked very well. 

Also, we did not see any vibration on the screen. But in the old setup, I just had a beam and two play:1 in the back, no sub. 

My main question was if a beam is sufficient for the room size or if I need the Arc instead. And if the room size requires the large sub or if the small one is also fine. 

Here is the layout of the room

Thanks for the diagram. I’d suggest the Arc this time around just due to the room size. However, unless you follow the setup in the link the sound will be limited to DD 5.1; that would also make using Era 300’s unnecessary. You could continue using your Play 1’s as surrounds; unless your projector has ARC/eARC capabilities. The same would be true for the Beam2.

Note: If you want more clarity for the rears you could upgrade to Era 100’s. Then use the Play1’s elsewhere.

Question: How will the Arc be mounted? Behind the screen on wall or in front on a cabinet? The ladder is the preferred option. 

Latter. Autocorrect for the win!

Yeah! I also reworded the post for more clarity

18+ feet from the viewer?!

Using opera glasses perhaps? 

Don’t make the assumption that the seating is up against the rear wall….nor are my surrounds

The screen comes down the wall and the arc will be mounted on the wall - but not behind the screen - so the latter :) 

The room will be painted dark grey - so I need to buy new speakers since I do not want to have white play 1s in the back. 

I think I will go with Arc, Sub, and two 100 in the back… 

Thanks so much for all the ideas and help here! Once we are done I will share a picture. But will be a while - they just finished framing the walls…. haha

@Idontlikeusernames 

Glad your plan is coming together. I highly recommend using the Sonos wall mount and not a generic. Click the link for information on the mount.

https://www.sonos.com/en-us/shop/wall-mount-for-arc

BTW…for someone who doesn’t like “user names” yours isn’t exactly unremarkable

Looking forward to pictures of your finished room.

Consider some SoundSkins to adjust the color of your Play 1s.

https://www.amazon.com/Soundskins-Sonos-Textile-Cover-Charcoal/dp/B07F692RDQ/ref=sr_1_17_sspa

https://www.amazon.com/Soundskins-Sonos-Textile-Cover-Stone/dp/B07F6FMWHT/ref=sr_1_11

Haha, I typed 10 different things that were all taken until I gave it a last chance with that one and it worked :)