Floorstanding loudspeakers — Opera Loudspeakers Callas Diva

The Callas Diva is the floor-standing three-way speaker of the Callas line from Opera Loudspeakers, the Italian brand that shares its premises near Treviso with the electronics maker Unison Research. The Callas line, reworked in 2014, is Opera's top range and consists of the Callas stand-mount, the Callas Diva and the larger Grand Callas. The current Callas Diva was completely redesigned from its predecessor of the same name and brings much of the Grand Callas engineering into a smaller cabinet meant for rooms of more modest size.

Key specs that matter

The Callas Diva is a reflex-loaded three-way design with a rear radiation system. The front carries one 8-inch long-throw woofer, one 7-inch midrange with an annealed polypropylene cone and a phase plug, and a 1-inch Scan-Speak 9700 tweeter, while two more tweeters on the rear form a natural dipole. All crossover sections use 12dB/octave slopes, with crossover points at about 200Hz and 2kHz. Frequency response is 30Hz to 25kHz, sensitivity is 90dB at 2.83V/1m and nominal impedance is 4 ohms, with a minimum above 3.2 ohms. Power handling is 240W without clipping. Each speaker is 116cm high, 37cm wide and 53.5cm deep and weighs 65kg including its metal base. Finishes are lacquered mahogany or walnut.

Engineering and use context

The defining feature of the Callas line is its back radiation system. The two rear tweeters, arranged as a natural dipole, feed the room's reflected field from behind the speaker, and this energy reaches the listener later than the direct output of the front drivers. Opera designs the rear system so that the reflected energy does not interfere with the direct sound, and it is almost identical to the one in the Grand Callas. The midrange cone is annealed polypropylene, heat-treated to raise its stiffness and damping, and a phase plug replaces the usual dust cap to smooth the top of its band. The long-throw woofer is reflex-loaded for deep bass extension. Second-order slopes throughout give smoother phase transitions between drivers than steeper filters would. Opera specifies at least 10cm between the Callas Diva and the rear wall so the rear tweeters have a surface to reflect from.

Pairing

With 90dB sensitivity the Callas Diva does not demand a large amplifier, and Opera itself pairs its speakers with Unison Research electronics, including valve amplifiers. A gap behind each cabinet is part of the design, since the dipole tweeters depend on it.

Alternatives

Opera Loudspeakers' own Grand Callas is the larger floorstander of the line, with two 8-inch woofers in a 130cm, 75kg cabinet.