LEEDH Acoustics E2 speakers

I've been again pointed to these unique French speakers. The LEEDH C and LEEDH E speakers are the result of several innovative technologies and patents. LEEDH seems to implements two breakthrough technologies, currently awaiting international patents. Below is some further description from the company.

These two technologies apply to the enclosure, composed of the speaker.

They are independent of each other and can be used separately with a traditional enclosure to enhance the performance.

LEEDH C brings together two completely innovative technologies in one speaker: the HPAB (Acoustical Beauty Sound System), which is described in detail in the section entitled LEEDH C. These technologies are both designed to replace the mechanisms of traditional speaker system, which constitute the main source of distortion.

The extensive description of these two technologies is detailed in this section.

The ironless motor :

The function of the motor of a dynamic driver is to convert the electrical signal (coming from the amplifier) in a mechanical force signal, which by moving a diaphragm in the air, generates a sound pressure signal.

The principle of the dynamic motor is always the same. The coil of an electrical conductor is crossed by the current coming from the amplifier. The coil is crossed radially by a constant magnetic field. The combination of this current and this magnetic field generates an axial force on the coil.

The cause and effect relationships between these physical quantities being proportional, if the coil undergoes a constant magnetic field, during its movement and if the diaphragm moves well in proportion to the force of the coil, the electrical signal will be faithfully converted in an acoustic signal (Laplace law).

These two operating conditions are necessary and sufficient for the fidelity of a speaker.
In the driver motor, two methods traditionally used, leads the coil not to suffer a force proportional to the current flowing through it.

First, the air gap (motor space in which the coil moves and in which the magnetic field is concentrated) is shorter than the coil, and then the force is maximum when it is to its equilibrium position, and then significantly reduces outside.

On the other hand, the process of concentration of the magnetic field of the magnet to the gap, is obtained by a set of soft iron pieces (pole pieces).

This material (ferromagnetic) is the seat of complex electromagnetic phenomena (Eddy currents, saturation, hysteresis, flux modulation, self-inductance variation) which causes a fluctuation of the magnetic field in the gap when the coil moves and/or the coil current varies.

To reduce these inherent defects in the architecture, of the traditional driver, « historical » solutions consisted to increase its size, to move more air through the diaphragm surface than by its movement, with the consequences that one can find on the size of the speakers... and increase its sensitivity, to minimize the current in the coil, but to the price of diaphragms being too big and too light to be sufficiently rigid.

Among other compromises, attempts to make coils shorter than multiple gaps, have run into instabilities (flux modulation) still associated with the soft iron pole pieces.

The radical solution has been to create a motor without pole pieces, called « ironless » motor, based on the assembly of rings and sectors of rare earth magnets (neodymium-iron-boron).

The optimization, performed using a magnetic simulation software, has resulted in the confinement of the magnetic field in an air gap bounded by two magnetic structures (internal and external to the coil).
The coil being shorter than the gap, it becomes possible to obtain a constant force throughout the useful movement of the diaphragm.

This new motor technology allows to obtain a perfect transformer of the electrical signal in a strength signal. Its high cost (heavy use of rare earth magnets) reserve it to applications where ultimate fidelity is desired.

The « ironless » motor has been an international patent in 2005.

The ferrofluid seal suspension :

In the traditional speaker, twice guiding of the cone diaphragm is performed using a suspension comprising surround and spider (for the speaker dome, a simple guide with surround).

When deforming, the surround and the spider allow the diaphragm to move axially relative to the basket.

Their geometry (concentric half-tori) allows this deformation by development of half-tori.

The force applied by the coil on the diaphragm deforms the surround and the spider. Thus, to be sure that the suspension does not introduce defect in the operation of the speaker, the movement of the diaphragm should be proportional to the force of the coil.

With a traditional suspension, this condition is never satisfied because, in principle, the deformation of the surround and the spider being limited to the development of its full half-cores, the diaphragm can not move beyond this limit.

To reduce distortion defects, on the small movements of the diaphragm, a compromise was reached by optimizing the geometry of the half-tori.

In addition, the flexibility of the surround and the spider causes parasitic vibrations (torsional resonance modes) that colors the sound in the form of artificial reverberation.
Finally, the return force applied by the suspension of the diaphragm causes the resonance frequency of the driver, which limits its ability to reproduce low frequencies.

It’s possible to offset some of this effect by increasing the volume of the enclosure.

Thus, this suspension process is inherently unsatisfactory. As for the « ironless » motor, the radical solution has been to rethink the overall suspension/diaphragm system, to ensure its functionality perfectly and naturally.

The cone or dome diaphragm was replaced by a piston (tube sealed at one end by a dome).

To move, this piston slides in a ring sliping on magnetic oil (ferrofluid).

This material benefits from a long experience in the speaker domain, as it is commonly used to ensure the handling power of dome tweeters, since the late 70's.

The ferrofluid is held in place, in the form of a liquid seal, in the intermediate space between the piston and the ring, by a magnetic device associated with the ring.

The height of the ring being smaller than the piston, the movement has no other limits than the length of the piston.

The movement takes place without friction, without constraint, as if the membrane was « floating » on a fluid bed.

This suspension does not exert return force on the diaphragm, the speaker has no resonance frequency, which provides low-frequency in a reduced enclosure volume.

The movement of the diaphragm is then naturally proportional to the force of the coil, as it is the air volume of the enclosure which has a restoring force on the diaphragm, hence the removal of all distortions associated with conventional suspension.

In addition, movement of the diaphragm being no longer limited, we can, to get the same sound level (same air flow), increase the movement of the diaphragm and reduce its surface, leading to further decrease the volume enclosure required for the reproduction of low frequencies.

Finally, the ferrofluid seal does not resonate, but on the contrary, amortized any parasitic modes of the diaphragm, while promoting the heat dispersion from the coil, for improved power handling of the speaker.

This new suspension technology makes it possible to reduce drastically the defects of distortions of the traditional driver, but also to reduce the volume of the speakers, while eliminating the traditional colors associated with resonance modes of the surround and the spider.

The « ferrofluid seal suspension » was the subject of two international patents in 2005 and 2007.

Features :

Dimensions (ground)) : 39cm x 108cm x 41 cm
Weight : 15 kg
Impedance : 4 ohms
Minimum impedance : 3,5 ohms à 300 Hz
Power Handling : 500 watts
Regularity bandwidth : +/-1,5 dB de 100 Hz à 20 kHz
Low frequency response (Bessel 2nd order): - 3 dB à 50 Hz /- 6 dB à 25 Hz /- 8 dB à 20 Hz
Phase Response : +/- 15° de 500 Hz à 20 kHz
Directivity from 500 Hz to 20 kHz : - 3 dB at 30° / - 6 dB to 45°
Sensitivity : 83 dB / 1 m / 2,83 v

Price :

Retail price generally observed (France) : 
LEEDH E2 : 16.000 €/pair