The gorgeous and very substantial Opera Grand Callas floorstander doesn't exactly come cheap, but given its no-compromise build and finish, it actually costs rather less than you might expect – especially when you consider it has a number of interesting and unusual features.

It's the latest from Opera, a company that's associated with electronics specialist Unison Research; the two firms share premises on an industrial estate just outside Treviso in north-east Italy.

Luxury listening

The Grand Callas (£6,500 in the pictured luxury-gloss finish) might be a brand new model, but it has much in common with the rather unconventional second-generation Callas standmount we reviewed last year.

Apart from the fact that the regular callas uses its solitary cone driver for bass as well as midrange, with further assistance from reflex-port loading, the midrange and top end of the two models are effectively identical, and also very different from the high-end speaker norm.

Instead of just the usual single tweeter, there are no fewer than five tweeters in each speaker – two at the front and three at the rear. It's an arrangement that has a number of implications, especially in the way that high frequencies are distributed in the listening room, though pinning the consequent effects down precisely will be tricky.

Speaker enclosure

The Grand Callas is therefore essentially a floorstanding variation on the standmount Callas theme, with a built-in passive subwoofer.

The very attractive full-height enclosure fills in the space that would otherwise be used for a stand with a sealed sub-enclosure, roughly 40 litres in capacity. This loads three matching 135mm drive units (apparently identical to each other as well as to the midrange driver), featuring 100mm-diameter magnesium-alloy cones around large (38mm), fixed solid-copper 'bullet' phase plugs.

The enclosure sides are crafted in subtle curves, and built from very substantial MDF panels, variously 30mm, 40mm and 50mm thick. Careful internal front-baffle sculpting avoids blocking the rearward radiation from the cone drivers, while further shaping on the outside should assist lateral dispersion.

Elegant design

Presentation is exceptional, in the very best Italian tradition. The curved sides are formed with veneer strips that simulate horizontal staves, while the top is a chamfered solid wood slab.

The shaped front panel is elegantly trimmed in hide. furthermore, the floor-coupling arrangements are first class, with substantial steel 'wings' and hefty spikes, extending the lateral footprint and ensuring superb physical stability. The spikes here are brass with large domed tops, which not only look a bit classy, but are also highly visible – helpful in avoiding stubbed toes!

Two pairs of notably substantial terminal pairs provide a bi-wiring or bi-amping option, but are linked by brass strips when delivered.

Powerful performance

The SEAS-sourced bass and midrange drivers have advanced excel motors, with copper rings above a T-shaped pole piece to minimise distortion. High power handling is assured via 38mm aluminium-former voice coils, with a 14mm peak-to-peak excursion capability, and the solid-copper pole extension aids cooling.

The tweeters, also sourced from SEAS, have 25mm coated soft-fabric domes, again have high linear excursion capability, and use compact neodymium motors so they can be mounted close to the midrange driver and each other.

Distributing the treble signal across five tweeters naturally increases the treble power-handling dramatically, though part of this extra headroom is used up by opting for a relatively low crossover frequency of 1.5khz in actuality the front two tweeters only operate in parallel at the bottom end of their working range; although both come in at a nominal 1.5khz, as the frequency rises the upper tweeter is slowly rolled off, so that the overlap 'lobe' is directed progressively upwards, and output below the three spaced sources is somewhat suppressed.

At the same time, the triple-tweeter array on the rear will tend to behave as a line source and concentrate its output in the horizontal plane, adding to the room-reflected treble output and helping to flatten out the overall far-field power response.

Smooth and balanced

First impressions are always useful, and with the Opera Grand callas these were mostly – though not entirely – favourable.

The fundamental 'differentness' of the stereo imaging initially gave some cause for concern, but happily further acclimatisation after trying the speakers with a wide variety of material tended to accentuate the positive.

One of this speaker's most notable strengths is its fine overall tonal balance and smooth even-handedness. It sounds pleasantly open without any aggressive tendencies, and no part of the frequency band seems exaggerated or out of place.

Rich bass

The in-room measurements do suggest that the top end might sound rather bright, but that's probably because the extra reflected high-frequency output, derived from the rear-mounted triple-tweeter array, shows up in the power response.