Consequences? The most obvious one is the audio that is supposed to be coming from in front of you (where the screen is) will be coming from behind you. This is not ideal and not how the audio track is designed to be heard.

Thanks, Rashi! 
My question being: how much would it impact the overall experience? Is it an absolute no-no or can I live with it?

And, are there ways to mellow the altered experience? Would tilting it up/down by a certain angle help?

In my opinion, it's not even an option.  

Are there ways to connect the arc to the projector without cables?

I couldn’t live with it. I’d rather run cables to the front of the room. But it may not bother you. You just have to try it out for yourself.

Ultimately, only you can answer the question about “best” sound (for you). That said, we don’t recommend placing TV sound behind the viewer.

Do you want surround sound? If not, I don’t think that ARC is the product for you.

If you want surround and can establish a direct wired connection (using network cable) between the projector and the screen area, there are some possible solutions that were not available until recently. A quick and inexpensive way to get sound up front would be to attach Bluetooth transmitter to the projector and use a Bluetooth speaker in the front. In my opinion this would not be premium sound, but this would be better than TV audio from behind.

You can experiment with sound from behind if you have a temporary way of somehow attaching a speaker in the rear.

What is the source of your video?

Have you considered other options than cutting your ceiling?

I’d look at a surface mount cable run, some are nearly invisible once painted to match your surface. You might run it along the wall/ceiling joint that would make it even less visible.

@ Buzz: Thank you for the reply.

I will be using a Firestick with the projector for video.

Do you want surround sound?

Putting the speaker behind you will also mess up the stereo image.

@buzz : hoping for surround sound

The left and right will be swapped unless you either turn the Arc upside down (with up-firing speakers pointing at the floor) or face it backwards away from you (which is crazy). 

It is a LOT of trouble and there will likely be some operational quirks, but it is possible to establish an HDMI wireless connection to ARC. I’d prefer a wired or fiber optic connection. While it’s tricky to find and manage the right fiber connection, it is possible to hide the fiber in a crack, corner, or simply use drywall tape and paint over it. I recommend hiring a pro who wants to take on this sort of adventure.

Note that wireless HDMI is vulnerable to the room’s “body count”. If humans absorb enough of the wireless HDMI energy, the connection will go down.

Hi @Arun Vijay 

Welcome to the Sonos Community!

With a soundbar, we’d recommend the use of a short-throw projector - this would be located at the front of the room along with the Arc, eliminating the need for long cables.

Alternatively, use an Amp instead of an Arc - the Amp can be located next to the projector at the back, and the speaker wires should be easier to route across the room than HDMI.

I hope this helps.

Thank you all for your responses!