Полочная акустика — Opera Loudspeakers Callas

The Callas is the bookshelf model of the Callas series built by Opera Loudspeakers of Italy, whose brand line is The Voice of Italy. The series also includes two floorstanding models, the Callas Diva and the Grand Callas, and the bookshelf Callas is the smallest of the three.

Key specs that matter

The Callas uses a two-way layout with a rear bass-reflex port. A 1 inch Scanspeak tweeter works with a 7 inch woofer. Opera quotes sensitivity of 89 dB measured at 2.83 V and 1 m, and a frequency response of 40 Hz to 25,000 Hz. Nominal impedance is 4 ohm, with a minimum of 3 ohm, which is the figure that matters most for amplifier choice. Maximum power handling is 100 W, and the maker states that suitable amplifiers start from 10 W. Each cabinet measures 42 x 24.5 x 42 cm and weighs 15 kg.

Engineering and use context

Putting the reflex port on the back rather than the front leaves the baffle to the two drivers alone, but it also means the speaker needs a gap to the wall at its back so the rear vent is not blocked. The enclosure is as deep as it is tall, which gives the woofer a generous internal volume for a stand-mount and explains the high mass. That weight and depth make a rigid, wide-topped stand more suitable than a shelf, and the stand should be sized so the tweeter sits near seated ear height. Two finishes are offered, lacquered walnut and lacquered mahogany, both in a high-gloss treatment in keeping with Opera's furniture-style cabinets. The larger members of the series, the Callas Diva and the Grand Callas, add a rear-firing radiation system, which the bookshelf model does without, so its output comes from the front baffle only. The speaker is a passive design, so all equalisation is fixed in the crossover and there are no level controls on the rear. A room of about 20 m2 is a sensible fit for a pair of two-way monitors of this size.

Pairing

The combination of moderate sensitivity and a low minimum amplifier power opens the choice to low-power valve amplifiers besides transistor models. The low impedance minimum is the more important constraint, since the amplifier has to stay stable and deliver current into a load that low. Staying below the rated maximum keeps the drivers within their rating.

Alternatives

The Opera Prima, a more compact stand-mount from this Italian brand, uses a 6.5 inch woofer in a roughly 10 litre reflex box.