The phrase "an empty theater" is correct and usable in written English.
You can use it to describe a theater that has no audience or people present.
Example: "As I walked into the building, I was struck by the sight of an empty theater, the silence echoing in the vast space."
Alternatives: "a vacant theater" or "a deserted theater."
That first year they found an empty theater in a friend's R.V. park in Lake George.
Each Monday, between interviews, he sat in an empty theater at the athletic offices, watching clips of Wooden that gave him chills.
"There are more important things in the world than a 75-seat space on Reade Street, but we had an empty theater.
Yet sitting with Mr. Chu in an empty theater adjacent to the boisterous "Never Say Never" screening, Mr. Bieber seemed more like a typically restless adolescent who is very much on the edge of 17.
There's also an attractive little nontext painting of instruments on a stage in an empty theater, by Sam Nhlengethwa, and three stimulating free-associational "word towers" by the South African artist Moshekwa Langa, a most welcome visitor (Cotter).
I am still, in other words, a bit of a grown-up spoiler when the exit yields not the ice-cream parlor but more dust, more heat, a cluster of bungalows, vacated stores, an empty theater.
Instead, I found myself sitting alone in an almost empty theater early on a Friday morning laughing out loud.
You have to sit directly across from me in an otherwise empty theater where they're showing a horror movie.
In fact, I started sneezing uncontrollably, so much so that I could tell that it was bothering the two angry young men sitting a few rows behind me in an otherwise empty theater.
A 22-year-old Orson Welles, presiding over the affair, marched the actors uptown to perform in an otherwise empty theater offered at the last minute.
A dozen or so high school students — in jeans and hoodies, sweaters and dresses, boots and sneakers — have divided into clusters of two to four, most on and around the stage, in an otherwise empty theater at the Masters School in Dobbs Ferry.
