Focal Utopia Beryllium Line user manual Γ front structure

8	The "γ" front structure™
	User manual Utopia Be line

The structure of the front baffle needs to reconcile inertia and damping properties in order to guarantee the dynamic range and the absence of coloration in the bass.

A loudspeaker is a transducer. Its role involves causing molecules of air to vibrate under the influence of a voice coil coupled with a membrane. A variation in electrical current mirroring the musical message stimulates the voice coil, which (submerged in the magnetic field) moves “in rhythm” with the musical signal. The electrical energy is converted into acoustic energy. This is the principle. In reality however, in order for this conversion to be as faithful as possible to the original audio signal, it is vital that the membrane moves in relation to a perfectly fixed reference. When the membrane moves, the chassis must not budge, and its acceleration must be zero. It should

comprise a totally inert mechanical reference.

Inertia: it’s a mass thing!

The chassis of the loudspeaker is solidly attached to the front baffle of the speaker system, the baffle. The mass ratio between the mobile assembly (voice coil plus membrane) and the frame (the chassis plus the front panel) must be as high as possible. This is an application of the fundamental principle of dynamic range: F = m ϒ.

The “ϒ” (gamma) acceleration taken by the chassis subjected to the moving cone force “F” must ideally be zero. Consequently, the mass “m” must be as high as possible: it must target infinity. Thus, regardless of the material chosen to produce the front panel in terms of rigidity, it would be a mistake to forget the mass. One could easily imagine that a highly dampened front panel would be the solution to avoid spurious vibrations set up by the “kickback effect” but this would be at the expense of dynamic output. Only a high mass can guarantee the transients. Damping can never substitute for mass.

Coupling between loudspeakers

The highest energy is in the lower register. The woofers induce vibrations in the front baffle which will interact with the medium and high end drivers and will thus cause intermodulation distortion, mainly in the high-end where the scale of displacement of the driver membrane is particularly low. The faithful reproduction of small details will be masked.

The adopted ultimate solution consists in giving each driver its own individual enclosure, set in a complex curve that is expensive to engineer but is guaranteed to give a total mechanical decoupling of the drivers.

The Structural solution

The front baffle solution in the Utopia Beryllium introduces a very high inertia to allow the bass driver to reproduce the transitory information of the low register with all its impact.

The baffle is a massive structure of 50mm thick MDF which gives the front face a very high mass. For an indication of the scale of that mass, the Grande Utopia -Beryllium weighs 210 kg whereas the original 95 version weighed 186 kg. The new version is free from any distorting vibration and the report/ratio of mass - the moving element compared to the frame + box – of the new Utopia is more than ten times superior to the traditional solutions using curved enclosures.

The “piston” function of woofers

The rear clearance profile provided in the 50mm thickness offers another decisive advantage. Carefully calculated, it offers a genuine wave-guide for the back emission of the woofers. As such, the membrane operates like a true “piston”, and is not hindered by waves reflected from inside the housing which impact against it creating distortions through torsion and/or rolling effects. When operating ideally, reproduction from the woofers is not affected by distortions arising from mechanical constraints.

Enhanced listening quality

Every effort is made to remove the source of spurious vibrations and to provide an outstanding dynamic output from the bass. The sound image is enhanced and the tone offers greater differentiation due to the absence of the coloration from the cabinet. The midrange and treble regis- ters are consequently better defined and more transparent as the micro-information is transmitted without any “masking effect”.

In response to the force stimulating A the cone, the front panel applies a reactive force R of equal amplitude

Front panel with gamma structure, produced in solid medium density fiberboard with a thickness of 50mm provides a mechanical reference.

The ultimate solution consists in using individual cabinet for each drive-units to avoid any intermodulation beetween the drivers.

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1

1 The motor systems of the drive units are mechanically coupled to the internal braces.

2 The optimized profile offers perfect guidance for the cone, which functions as a true piston. This is not affected by turbulence from the back wave.