I routinely DM for 7 to 9 players. My sessions often go from noon to midnight.
With that many people, it can be a long time between turns in combat, and two people next to each other at the table will naturally settle into conversation unless you can keep the pace of combat fast enough.
I have finally taken to requiring my players to work out all their damage circumstances (sneak attack, elemental damage, this, that, the other thing) and be ready to give me damage based upon a 2d4. If they roll a 2, they do minimum damage on that hit, if they roll an 8, they do maximum damage. If they roll a 3, they do 25% of max, if they roll a 7 they do 75% of max. If they roll 4, 5, or 6, they do 50% damage. That's the way it is, they don't have to like it.
For years, I had everyone roll every damage roll, and, given time to add, and having that many players, it took probably more than 2 hours of our session just counting up damage. So, I decided to hell with that, and they all have little tables. Everyone rolls to hit, and then has a simple table to consult for damage. If things are going particularly slowly, I'll drop it to a d4. A 4 means max, a 1 means minimum, and a 2 or 3 is half damage.
With 10 players, they're going to win battles anyway, unless you really are into TPK, so, they can just suck it up.
Dave