Wrong, the Sonos Arc has two upfiring speakers.

Atmos for the Beam is simulated in the absence of upfiring speakers.

Both products can play Dolby Atmos soundtracks.

 

How many speakers does the Sonos Arc have? The picture shows Sonos Arc has two sides and two up firing speakers. So there is only one front center speaker. Is it correct? 

The Arc has 11 speakers as seen in the above pic, with 5 facing forward.

• Amplifiers - All eleven Class-D digital amplifiers have been perfectly tuned to the soundbar's unique acoustic architecture.

• Tweeters - Three precisely angled silk-dome tweeters create crisp high frequencies and crystal clear dialogue.

• Midwoofers - Eight elliptical woofers ensure faithful playback of mid-range and vocal frequencies plus impressive bass.

 

How many speakers does the Sonos Arc have? The picture shows Sonos Arc has two sides and two up firing speakers. So there is only one front center speaker. Is it correct? 

Do you really not see the five speakers coming out of the front of the unit?  Really?

How to define the Sonos Arc and Beam channels? Is it 11.0 and 5.1? Can you explain it? Thank you.

It's neither.  By itself, the Arc is 3.2.  Right front, center front, left front, right height, left height.  With sub and surrounds, the system is 5.2.1.  Beam is 3.0 with simulated height channels.

Thanks for clarification. Does Beam 3.0 with simulated height channels mean 3 front speakers with only one real channel?  

Can you explain what you mean with “one real channel"? The Beam is three channels (hence the 3.0): FL-Center-FR. It computes the height channels to make it sound to your ears there are height channels. 

You seem to be equating number of speakers with number of channels in some way.  Don’t.  

I tried comparing the channels between the Arc and Beam. It seems Arc has three channels as the Beam does but more speakers. Is it correct or Arc has more channels than Beam? Thank you for your answer.

A speaker does not equal a channel.  I repeat A SPEAKER DOES NOT EQUAL A CHANNEL!  A single channel could have a dozen speakers.  Now that that is clear, both soundbars play 5 channels.  The Arc does front right, center, left, and height right, left. The Beam does front right, center, left, and simulated height right, left.