Grand Callas - VMAX Services

Grand Callas - VMAX Services
Grand Callas
With this new model in the Callas Series, Opera`s intention is to create at home the emotion and
pleasure of listening to music: to provide a musical, focused, three-dimenional soundstage with the
correct timbre, dynamics and detail - and to do this with no sense of listening fatigue.
To achieve this goal new technical solutions have been applied and every single aspect of the
design was subjected to intense musical listening tests at Opera.
The new Callas 2008 model use techniques and components which reflect the state-of-the-art in
electro acoustic design, including not only cabinets, drive units and crossovers but also new
devices as the front doublet and the new Triplet rear radiating device. The sonic result is tonally
correct, convincing, involving and most of all, enjoyable to listen to. The new Callas 2008 is elegant
looking and beautifully finished and will discreetly enhance any room.
The System
The new Grang Callas is the natural evolution of the Callas Model (2007) with three more woofers
added to enhance low frequencies responce. The bass section is loaded in a completly sealed
enclousure to give the best possible bass quality. The new Grand Callas is a real three ways,
floorstanding system which includes two complementary sub systems:
-the (main) front radiation system with three 5”woofer, one 5” midrange and a couple of stateof-the-art one inch fabric tweeter for the high range (the doublet).
-the rear radiation system with three tweeters forming the device called Triplet located on the
rear of the cabinet.
The rear system act as the CLD implemented for the Tebaldi and Caruso models. The rear
radiation from the Triplet feeds the reflected sound field without interfering with the direct sound
and thus preserving the loudspeaker transient response (as the CLD). The rear radiation balances
the power response of the system at higher frequency (where the front tweeter became directional)
and increases the “Brilliance” which is a quality related to the perception of sound details. Details
in the music are related to the acoustic properties of the environment where the original event was
recorded. More detail enhances the sense of space in the reproduction which is not a just simple
boost in the mid-high frequency range.
The main front system uses two tweeters (the doublet) placed above and below the midrange.
Fron the electrical point of view they are connected in a quasi-series configuration. The doubling
the radiating surface (respect a single tweeter) allows a lower cross-over frequency, reduces non
linearity and, more important, moves the main beam of sound radiation upwards as the frequency
increase. This solution gives a more realistic height to the sound stage as proved by the Callas
model. The Triplet and the Doublet are devices developed by Opera Loudspeakers to improve the
three-dimensional aspects of the reproduction.
Far from theory, the results are clearly audible: the new Grand Callas produces a sound stage
which expands the depth with an excellent transient response and with the power, dynamic and
low frequency extension tipical of the sealed box. Three 5” woofers acts as a single powerful 10”
woofer with a linear dispacement equal to 22 millimeters .
The front “dublet”: loudspeakers assembly, cross-over frequency response.
The Triplet is described in details in a separate technical note.
Directivity pattern on the vertical plane
The cabinet
A great care has been taken in cabinet design and realization to obtain a compact, heavy, stiff but
still elegant one. Many prototypes has been tested to find out the best solution.
The cabinet is made with MDF and solid wood. The cross section of the cabinet is similar to Diva
and Divina models.
The front baffle is obtained from a thick MSF board (40 millimeters) which is shaped on both side:
on the outer side to reduce the diffraction effects and on the inner side to eliminate “whirlwind” and
air flow noise that affect the woofer diaphragm motion at low frequencies. The shape of the inner
side of the front baffle is very important and is a feature of all our model from many years. To
reduce edge diffraction the front baffle has rounded edges.
The glue used to assemble the cabinet is extremely rigid and hard as glass. The result is much
more stiff then solid wood, MDF or regular plywood of the same thickness. This make the structure
more stiff and increase the quality of lower frequency range. The back of the cabinet is a block of
MDF 50 millimeter thick. The top and bottom side are 40 millimeters thick. So the thickness of the
cabinet range from 30 to 50 millimeters instead of the usual 20-25. The lateral sides are veneered
and the top side is solid wood, all them are finely lacquered in the best Italian tradition.
The front baffle is finished in leather that is elegant and fine to see but also works as an air washer
for the loudspeakers.
Because of the closed box disign there are no problems related with duct noise. The cabinet
volume is completely filled with lining material. On the rear side there are four big, solid, gold
plated, brass connectors that accept a wide range of cable termination.
The Components
The Grand Callas model uses the same woofer and tweeter developed for the Callas model, made
by Seas (Norway) and customized for Opera applications.
The tweeter has a one inch soft precoated Sonotex dome loaded by a double decompression rear
chamber, there is a low density magnetic fluid in the gap and a small but powerful neodimium
magnet. The linear excursion of the dome is 0.9 mm. pick-to-pick (compared with 0.5 mm of a
good regular tweeters). The overall external size is only 53 millimetres and this allows the tweeter
to be positioned very close to the midrange and to keep the right distance between the triplet’s
sources. This tweeter sounds clear, linear and free from coloration. The woofer has extreme
-magnesium cone
-rubber sorround
-solid copper phase plug for superior heat dispersion.
-“Excel motor” with copper rings above and below the T-shaped pole piece
-wide linear excursion of the moving coil (14 mm pk-pk)
-very stiff cast alloy basket with large windows also below the inner spider
-38 mm aluminium voice coil former
-very low voice coil inductance (which reduce distortion due to impedance coil and flux
All this means low distortion (less than 0.3% in the midrange band), negligible compression and
superior performance.
This woofer has an excellent frequency response up to 3000 Hz free from any breakdown. This is
also due to the rubber rim with special corrugation which better control the higher frequency
resonances of metal cones. This woofer offers the midband reproduction of the best specialized
midrange but with a very long linear excursion that reduce the intermodulation distortion to a
neglible level even at hign pressure level. This is why we use the same driver for the low and midrange sections.
The Cross-Over Filter
The cross-over has two different sections: front tweeters & rear tweeters and woofer & mid-range.
This original topology is designed to reduce the number of passive components in the cross-over
filter. The cross-over frequencies are 200 and 1700 Hz.
The coils in the low pass section, in series with the signal, have a low permeability core while all
other coils in the filter section have no core. Capacitors are low tollerance, high voltage, high
quality MKT type.
New Grand Callas 2008 cross-over
The upper front tweeter is up-limited so that, below 2 kHz, all tweeters produce the same SPL
while, as the frequency increase, only the lower tweeter is fully powered. Due to the quasi-series
connection the emission coherence in mathematically preserved.
The minimum value of the real part of electrical impedance of the Grand Callas is higher than 3
ohm. This makes Opera Grand Callas a real nominal 4 ohm system that can be driven by a wide
range of amplifiers, either with valves or solid state. Sensibility is 89 dB SPL 1 metre/2,83 Volt
which is considerable for a closed box system.
Position in the listeming room
Opera Grand Callas is a floor standing design and, because of the closed box design, is very easy
to be placed in the listening room. We recommend to lightly angle the loudspeakers toword the
listening point. To enhance the image focousing (enlarge the stereo-effect area) position the
loudspeakers as shown below so that the third vertex of the ideal triangle falls in front of the
listener: The optimum mid-bass frequency responce is easily found moving the cabinet from lateral
and rear walls.
Speakers and listener relative positioni to enhance image focousing
We advise against placing the loudspeaker in a corner. Keep a minimum distance of at least 50 cm
from the side walls and choose the distance from the rear wall for the better bass reproduction.
The best position within the surroundings has to be found experimentally.
When two pairs of Opera Grand Callas diffusers are used, they have to be connected in series as
illustrated in the figure below.
Positioning and connection of two pairs of Opera Grand Callas (suggested by Righini). This positioning is
suggested in large rooms and with many listeners.
Technical Specifications: Opera Grand Callas
Foortanding, Closed Box, three ways
Finishing: wood and hide
Front Sistem Loudspeakers 3 woofer 5” and 1 midrange with magnesium cone, Excel Magnet,
solid copper phase plug.
Doublet: 2 tweeters with a 1” Sonotex dome, neodymium, ferrofluid,
decompression chamber
Rear System
Triplet: 3 tweeters (the same as front system) with grid
Number of Way
Three ways with doublet + rear triplet
Frequency response
32 -25000 Hz
On Printed Circuit Board
6 dB/octave for the woofers
12 dB/octave for the midrange
18 dB/octave for doublet and Triplet
Cross-over frequency around 360 and 1500 Hz
Maximum power
240 Watt RMS
(Long Term)
Maximum power
750 Watt RMS (no clipping)
(Short Term)
Suggested amplifier
Starting From 10 Watt RMS
89 dB/2.83 Volt/1 metre
Nominal impedance
4 ohm (Zmin >3 ohm)
Position within surroundings At least 50 cm from walls
106 x 27x 40 (HxLxP)
Net weight
50 Kg each
Mahogany / cherry / glossy
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