WE HAVE been spoiled. The first six of this season's offerings by the Washington Opera have led us to expect it all: great music, great singing, splendid acting and production. What we get in the production of Beethoven's "Fidelio" that opened in the Kennedy Center's Opera House last Saturday is Beethoven's magnificent score (not that this is anything to sneeze at), some fine singing and not much else.

First of all, there are some serious acoustical problems with this set (from the San Francisco production) in this particular hall. The prison walls slope at an angle that reflects the sound up instead of out. Therefore, the only soloists heard clearly are those standing downstage center singing straight to the audience, a position that puts the singer in limbo dramatically. The vibrancy of the prisoners' chorus is eaten up by these acoustics, as are solo lines every time a singer turns to the side.

Except for William Wildermann's fine and convincing portrayal of the jailer, Rocco, the acting in this production is unimaginative. Laila Andersson-Palme sings the role of the gallant Leonore with a considerable intensity that is the most effective when she is singing the most quietly, but her stage presence does nothing to add to her vocal artistry. James McCracken, splendid vocally as Leonore's husband Florestan, is dramatically wooden in the role. Roger Roloff looks nasty enough as the evil Don Pizarro but fizzles as a menacing would-be killer, and Marcus Haddock as Jaquino, Herbert Eckhoff as Don Fernando and Faith Esham as Marzelline are much more interesting to listen to than to watch.

Directors Michael Hampe and Laurie Feldman have blocked the prisoners into awkward-looking clumps as they savor the spring air. This may have some intended dramatic message that does not make itself evident.

Gerard Schwarz has the same strengths and weaknesses as an opera conductor that he displays as conductor of the Mostly Mozart Festival Orchestra: He does a beautiful job of sustaining long legato lines and of getting the weight of these lines just where he wants it. But give him something that moves quickly, and he pushes it to the edge of frenzy. Schwarz is a trumpeter, an excellent one, and he conducts singers in these fast passages as if they were trumpeters with no words to shape. He can push all he wants, but it will always sound messy, not exciting.

WASHINGTON OPERA -- "Fidelio" at the Kennedy Center Opera House, Friday, Monday and March 3, with a matinee March 6.