"Opera claims on its website that 'every single aspect of the [Callas] design was subjected to intense musical listening tests at Opera.'", writes John Marks in Stereophile.  "I can believe it—the Callas sounds like that kind of a speaker. So if you regret having missed the ASA Pro Monitor, here's that rare thing in life: a second chance. And the price hasn't even gone up."  Read the full review of the Opera Callas loudspeaker at Stereophile.