Is it possible to define what would be regarded as a good opera house and how might it be differentiated against a 'standard' theatre ? Are there any acoustic properties which would set the two apart ?
Thanks in anticipation.

I was at the Oslo Opera House (which was one of newest opera house in the world) when I was in Norway last year and apparently there were many features which were designed to acheive optimum acoustics e.g. there's an oval "reflector" on the ceiling (that's the only thing I remember, I'm afraid. Maybe you could google...)

A bit of guess work, but I would imagine an opera house would want a longer reverb time than a theatre (better for music, speech needs relatively short reverb time for clarity).

The opera house would require a well designed orchestra pit and I understand they tend to have massive back stage areas for all that scene changing (even bigger that a theatre apparently).

. . . half a gallon of unleaded and a match?

Surely that is only for those that stage Wagner?

Was that you mooching around the back of La Scala?

I thought Wagner went on a bit - until I went to see Ken Dodd!

Thank you. Perhaps the answer lies in the balance of warmness of the music but clarity for singing. The dome at the Oslo opera may be designed to produce long reverbation times for sounds coming from the orchestra pit as opposed to the seated part of the theatre, to which the voice is being projected, having a shorter time. The fact that amplification is not used in opera may also be a consideration.

Advice on the physical size of pit and back stage also much appreciated.

A good singer or two! He says flippantly.