What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakersare used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Giussani Research GR DELTA 4 R9

The Hi-Fi Speaker GR Delta 4 R9 is a hi-end system perfectly able todeliver at the highest level all the positive values of the "Delta 4 Systems", already proven and widely appreciated in many installations in a timeframe that, ranging from 1977 to current days, is now over 30 years long.
The designer of GR Delta 4 R9 is Eng. Renato Giussani, of whom we should at least remember thedesign of ‘Audiolab Delta 3’speaker system in 1975, ‘Audiolab Delta 4’in 1977,’ ESB Serie New LD’in 1980, ‘ESB Serie 7 DSR’ from 1981, ‘Aedon Audio Serie NPS’ from 1990 to 1994, plus of courseall the GR (Giussani Research) systems from 2003 to present days.

While listening music with a pair of ‘good’ electrostatics, isodynamic, systems with separatemid-high head, omnidirectional or free-standing mini-speakers... the user may easily have thesensation to listen to music in front of the real stage: the physical presence of the speakers isdisappearing in a much more evident way than in any other experience involving speaker systemswith wide front panels (say wider than 8 inches, to set a reference) The reasons of this achievement are partly related to psychoacoustic reasons (also depending fromthe external appearance of the speaker), but for the most part they are related to specific andobjective acoustic properties, derived by some common emission modalities of this systems, even ifthey look quite different from each other. In the following chapter we will review four main aspects of sound emission, that will be put inrelation with the operation modalities of the listed systems, highlighting that, among them, only themini-speakers (even with their well known limits in dynamics and extension at lowest frequencies)can provide the best and most realistic "phantom scene". In order to enjoy this quality to “become invisible”of the best mini-speakers, without having to giveup in terms of extension of low frequencies, max dynamic of the reproduced program and apleasant and realistic "phantom vertical dimension" of the reproduced soundstage (as delivered, forinstance, by electrostratic and isodynamic systems with large vertical extension), an extremelyeffective solution is provided by systems Delta 4 like, characterized by a very small emission areafor mid-high frequencies, coupled with a floor-loaded woofer (not a "subwoofer") able to coherentlycomplete the full musical message.
One of the main features of the GR Delta 4 R9 is that the mid-high unit is mounted on a specificpanel 16,6 cm. wide (about 6”) with bevelled edges. The dimensions of this front panel are chosen to minimize the perception of its physical presence,since from 1.000 Hz. This means that the horizontal dispersion of the sound waves generated by the speakers mountedon this panel can spread to reach the value that it would have without any mounting panel for allfrequencies up to 1.000Hz, while above this value the behavior of horizontal dispersion will besimilar to the one it would have if the soundwaves would be generated by any natural source havingan horizontal dimension similar to the one of the panel itself. Such effect leads to have a dispersionsimilar to the one that we find around a human head… And this explains the very peculiar perceptionthat a listener experiences by walking around a Delta 4 while the speaker is reproducing an humanvoice. This perception is very similar to the one experienced walking around a real person standingin the loudspeaker position.Of course the rear emission should not find obstacles on their path, and this is why the system hasan acoustically transparent rear panel, exactly like the front one. Another acoustic phenomena that makes perceivable the presence of the ‘box’ in electroacousticsystems is the one defined ‘diffraction’, that in this case happens around the edges of the frontpanel.

Emission: monopolar full-range (Never dipolar)
Number of ways: 4
Nominal Crossover Frequencies: monopolar full-range (Never dipolar)
Resonance Frequency: 41,5 Hz
F -3 dB: 34,2 Hz
Sensitivity: 87dB/1W in normal enviromental conditions
Nominal Impedance: 8 ohm
Max amplifier power, per channel: between 50 and 500 watt RMS
Dimensions: 44 L x 38 P x 163 H cm
Recommended listening distance: 2,5 meters or higher ( 8” 6’)
Recommended listening height (at rec. distance): between 105 e 165 cm from floor (41 inch to 65 inch)
Min - Max distance from rear wall (internal corner): Min=10 cm (4 inch) – Max = depending on the room

Speaker Components:
woofer GR-W12/A;
low-mid planar BG Neo10;
mid-high planar BG Neo3 PDR;
tweeter Scan Speak D2010.

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