Opera Callas Diva 2004/2005


With the new loudspeakers of the Callas Series, Opera`s intention is to recreate within the

home environment,  the emotion and pleasure of listening to music:  to provide a stable and focused musical soundstage in three dimensions with correct timbre, dynamics and detail, and to do this with no sense of listening fatigue.


To achieve this goal, every single technical aspect of the design was subjected to intense  musical listening tests at Opera.



The new loudspeakers of the Callas Series use techniques and components which reflect the state-of-the-art in electro acoustic design, including controlled-diffraction cabinets, drive units and crossovers. Every type of distortion has been analyzed, quantified and reduced. The sonic result is tonally correct, convincing, involving and most of all, enjoyable to listen to. The Callas Series loudspeakers are elegant and beautifully finished, and will discreetly enhance any room.





The Diva model is floor-standing loudspeakers system with two 5” woofer-midrange and a state-of-the-art one inch fabric tweeter for the high range. An extra tweeter, placed on the rear side of the cabinet, fills up the overall power response.

Diva and Divina share the same components project philosophy: to recreate well defined, focused and stable acoustic stage image as the best small two way system can do.


Far from theory results are clearly audible: the new Diva loudspeakers system performs as a small two way-system but with the power, dynamic and low freq. extension that only bigger diameter woofer can perform.


The cabinet


The cabinet is made in a mix of MDF and plywood, with teardrop-section curved sides, veneered and finely lacquered in the best Italian tradition. The front baffle is finished in leather. This, along with the benefit to appearance also reduce edge diffraction.

Internally there are a number of interlocked braces which increase the rigidity across the cabinet.

Thanks to the chosen geometry, together with other detail design features the Diva obtains a substantial increase in low frequency radiation from the reflex port which extends the bass response to the very lowest frequencies.


The reflex duct is placed in the rear side of the cabinet near the floor where low frequency radiation impedance is larger and duct noise, if any, less audible.  A good quantity of lining material is carefully placed inside the cabinet.


The Components


Diva and Divina share the same drivers.

Woofer and front tweeter, are made in Norway by ScanSpeak and modified for Opera Loudspeakers application.


The tweeter has a one inch soft precoated fabric dome loaded by a wide decompression rear chamber , there is no magnetic fluid in the gap. The excursion of the dome is 3 mm. pick-to-pick (!). It sounds clear, linear and free from any coloration.


The woofer has extreme characteristics and it is 80% hand-made.  This same woofer performs excellent in high-end two-ways system (and the Callas model is the prove of that). When  2 or 4 woofers like this are used in the same system, the acoustic quality of the reproduction is dramatically increased.


Woofer and tweeter have both a very low voice coil inductance which reduce to a minimum distortion due to impedance coil and flux variations. The rear tweeter has a one inch fabric diaphragm an a neodymium magnet.



The Cross-Over Filter


With two vertically aligned woofers the polar dispersion on the horizontal plane, say two meter away from the cabinet, is the same as a single unit: wide and regular. But the linear dimension of the whole source increases and, while increasing frequency, the vertical dispersion angle is decreased because of interference.


To avoid this undesired effect and to keep the polar dispersion characteristic of the whole system similar to a small two-way system, the two woofers are wired in semi-parallel.

 The lower woofer is up-limited so that in the low frequency region all woofers act as a single large diameter driver while, in the cross-over frequency range with the tweeter, only one woofer is fully powered. The emission coherence in mathematically proved.


We believe that the cost of a diffuser has to be assessed together with the cost of the amplifier more suited to guide it. Opera Callas Divi is a nominal 4 ohm diffuser that can be easily driven by a wide range of amplifiers, either with valves or solid.



The frequency and power response



The frequency response curve is partially shaped according to loudness curves obtained by Churcher-King and Pollak which are better, for hi-fi listening, than the well known Fletcher e Munson loudness curves. Doing this Opera Loudspeakers can recreate, in home listening, the real instruments size and feeling.


Frequency response, in normal rooms, range from 20 to 20000 Hz. For a better balance of the power response a small neodymium tweeter has been added on the rear side of Diva. The rear tweeter works in a frequency region where the main front tweeter starts focusing energy on his axis. The effect of the rear tweeter depends on the room walls absorbing properties. In some “live” room it may be useless  so you are allowed to switch it off.




Woofer and tweeter need at least 20 hour playing to reach the best performance.




Position in the listeming room


Opera Callas Diva is a floor standing system. We advise against placing the diffuser in a corner and one needs to keep a minimum distance of at least 50 cm from the side walls. The best position within the surroundings has to be found experimentally.

In case two pairs of Opera Callas Diva diffusers are used, these have to be connected in series as illustrated in the figure below.


Positioning of two pairs of Opera Callas Divina, suggested by Righini





Technical Specifications: Opera Callas Diva




Floor Standig – Bass Reflex , rear duct

Finishing: wood and hide


2 woofer 5” with paper cone


1 tweeter with a 1”  silk dome with decompression chamber

1 rear tweeter with 1” silk dome with neodymium magnet

Number of Way

Two ways

Frequency response

32 -20000 Hz 


On Printed Circuit Board


12 dB/octave for the woofers (semi-parallel)


12 dB/octave for the il tweeter


Cross-over frequency around 2000 Hz

Maximum power

 120 watt RMS

Suggested amplifier

From 10-15 Watt RMS to 300 Watt RMS (no clipping)


89 dB/2.83 Volt/1 metre

Nominal impedance

6 ohm (Zmin >4.4 ohm)

Position within surroundings

At least  50 cm from side walls





Net Weight


Packed weight