Why older halls for symphony orchestras sound better than new ones?

According to Witold Rybczynski, it is partly a matter of size and shape.  Older halls were more likely in a shoe-box shape, such as Musikvereinsaal (1870),the Concertgebouw (1888), and Symphony Hall (1900).  The orchestra is at the narrow end of the hall, and “Sound is reflected to the listener from the two parallel walls (which are about sixty to eighty feet apart) as well as from the ceiling.  Because the concertgoer is relatively close to the musicians, the atmosphere is intimate, visually as well as acoustically.”

The need for greater seating capacity, because of revenue, swells the halls to as large as 3,000 seats and renders these properties more difficult to achieve.  Most of all, it is now difficult “to reflect bass notes from the side walls.”

Different halls also have different “reverberation” times, and thus the more that a hall is used for different kinds of music, the more the design of that hall reflects a compromise.  In theory there should be different halls for playing Gorecki and Bach, so an all-purpose hall will sound ideal only rarely.

That is all from his new book Mysteries of the Mall and Other Essays, pp.188-192.