Opera Seconda (Second) is the intermediate model of the “Classic Series”. It is a two-way and half floor diffuser in closed case, characterised, thanks to the two woofers assembled in pneumatic suspension in separate chambers, by a great response and power seal in the low frequencies. The diffuser is equipped with four golden connectors of large diameter and predisposed for the bi-amplification.
The furniture of Opera Seconda is realised in finely-shaped MDF with rounded edges, veneered in real wood finely polished. The front panel, the top and the rear panel are covered with synthetic hide that, beyond the aesthetic finish, also work as packing for the loudspeakers.
The size of the front panel, following Opera’s tradition, is large enough to hold the loudspeakers.
The internal volume is divided into two separated chambers, that beyond strengthening the structure, remove the resonant frequencies associated with the height of the piece.
The internal volumes are filled with a good quantity of acrylic sound absorbent material that controls the lowering of the frequency response and pulls down the internal reflections.
Because there is no reflex duct, the diffuser can be drawn near to the rear wall and is therefore optimal used both as front and/or rear system in Home Theatre Systems.
All the models of the Classic Series use the same drive units; the one inch tweeter (the same used in the Callas SP) is a silk dome unit, ferrofluid filled and having an ample rear decompression chamber. The qualities of this SEAS tweeter are well known and appreciated. The woofer, also made by SEAS, was developed specially for this line of loudspeakers. It is a 6.5 inch unit with 18cm chassis, 38mm voice coil, aluminium diaphragm and rubber outer suspension. It has a dynamic mass appreciably higher than the norm, and an impedance of 4 ohm. Two copper rings are fitted above and below the T-shaped pole piece, which both reduce distortion and stabilize the magnetic flux. Finally, the bullet-shaped phase plug in ABS helps to dissipate heat and overcomes compression effects associated with normal dust-caps. It also improves emission at the high-frequency end of the unit`s range. The cast chassis, of aerodynamic design, is fully open even beneath the inner suspension.
The Cross-Over Filter
In designing this new “Classic Series”, particular attention has been paid to the electric impedance. In particular, we wanted to guarantee a load condition compatible with any type of amplifier.
In order to do so, the impedance minimums have been kept within the limits allowed by the DIN regulation that provides that, for the nominal 4 ohm diffusers, the impedance does not go below 3.2 ohm.
The electrical impedance modulus of Opera Seconda is always over 4.25 ohm (4.23 for the real part of the impedance) and the progression is regular with contained phase rotations.
Electrical Impedance of the Opera Seconda model
Electical Impedence : Black = Z module,Green =Phase, Red =Real[Z], Cyan Imag[Z]
We believe that the cost of a loudspeaker system has to be assessed together with the cost of the amplifier more suited to guide it. Opera Prima is a nominal 4 ohm diffuser that can be easily guided by a wide range of amplifiers, either with valves or solid.
The cross-over of Opera Seconda is characterised by the almost-parallel connection of the two woofers and by asymmetrical slopes of 12 and 18 dB for the sections low-pass and high-pass.
The cross-over frequency is at about 2300 Hz and the sensitivity is 89 dB (2.83 V at one metre).
Opera Seconda Filter Scheme
Opera Seconda is a floor standing system. We advise against placing the diffuser in a corner and we suggest to keep a minimum distance of at least 30 cm from the side walls. The best position within the surroundings has to be found experimentally.
In case two pairs of Opera Seconda diffusers are used, these have to be connected in series as illustrated in the figure below.
Positioning of two pairs of diffusers, suggested by Righini