CSO management put a brave face on the 1966 renovation of Orchestra Hall, but as I recall the reaction of the majority of the public was one of shock and a feeling of great loss. I don't know what management thought themselves, but it wasn't many years before work was done to try to repair some of the sonic damage. Further efforts followed, most significantly around 1997. It's a little better. At least fortissimi really get loud again rather than seeming to be cut off by a limiter, there's again a semblance of tone in the strings, and one can hear the basses again. All of that was ruined in 1966, along with any semblance of "air" around the sound. Regarding the installation of air conditioning in old buildings, in addition to what Steve Smolian wrote there was also the issue of the low-level noise that older systems caused. By 1966 that had been resolved well enough to permit its installation. Don TaitI stand corrected, and apologise for my hasty comment. I guess it was less a tale of greed than a tale of mismanagement, if that: doubtless other aspects of the hall improved with the renovation, and attendance probably increased.
Brenda is correct. It's true that air conditioning was added to Orchestra Hall during the 1966 renovation, but the project was undertaken for far bigger reasons. The majority were calamities, above all the idea that the sound of the hall could be improved, whereas it was wrecked. But another was the practical one of giving the CSO members a reasonably comfortable backstage space for themselves, which they'd never had. I remember standing on Michigan Avenue during the summer of 1966 and looking through the glass on Orchestra Hall's doors. I could see traffic on Wabash Avenue, a block behind the building. Everything in Orchestra Hall, including its stage and back wall, was gone. All was rebuilt and reconfigured during the renovation.
Don Tait