Kent's highend audio universe

Devialet AXD

Expert Pro Active X-over Design Technology

Why did we develop AXD®?

At Devialet, we were the first to develop an exclusive technology capable of adapting our amplifier’s performance to the characteristics of the loudspeaker it is connected to, in real time. This technology is called SAM® (Speaker Active Matching) and is based on a mathematical model deducted from measurements made on each loudspeaker so Expert Pro can tailor the sound signal to fit their precise requirements. For the first time, it was possible to achieve perfect temporal alignment between the recorded signal and acoustic pressure from your loudspeakers.

Today, more than 800 speaker models are SAM Ready but we wanted to go further and offer a solution to the most demanding audiophiles capable of taking the best from ultra high-end loudspeakers. That is why we developed a partnership with some of the top speaker manufacturers, to design the shortest analog signal path between an audio source and speaker drivers while limiting analog sections to a minimum. The result of this quest of perfection is AXD®, the perfect match between Expert Pro and some of the world’s best loudspeakers ever built.

What is AXD®?

AXD® (Active X-over Design) combines the endless possibilities of Devialet Expert Pro DSP to the knowledge of the crossover networks of some carefully selected high-end speakers, to create a complete, perfectly optimized setup. AXD® is the only technology capable of getting the best from these extreme audio systems and deliver sound in its purest form.

AXD® is:

●  an active crossover (X-over) design for the speakers, performed in the digital domain,using DSP-based crossover filters already available inside Expert Pro systems. Each speaker active profile is validated and signed by their creators and designers, with no exception.

●  the shortest analog signal path in the history of audio, with even less distortion and noise, defining a new level of transparency and precision.

●  the future of extreme high-end audio systems, giving loudspeaker designers whole new possibilities only available in the digital domain.

How does AXD® work ?

Modern multi-way high-end speakers are difficult to design and to drive, with drivers of different characteristics and massive passive crossover filters which have to be designed with many constraints such as counter electromotive force on drivers (woofers can load other drivers), sensitivity driver leveling, etc.

Here is an example of a classic High-end setup, with passive crossover filters.

Every input signal has to go through a number of analog devices before being transformed into music by the drivers. On average, the length of analog electronic circuitry in a classic setup is 55-110 cm, excluding cables. Along this distance, according to the number of in between components in the signal path, the signal loses integrity, and distortion appears.

In Expert Pro systems, the analog path has been reduced to the minimum, achieving a huge improvement in sound quality associated with signal processing capabilities such as our exclusive SAM® technology:

Passive X-over:

● Analog domain
● Filter network composed of resistors, capacitors and coils
● Loss of efficiency (can only lose energy)
● More distortion from the amplifier
● Tolerance issues (variance between analogue components)
● Thermal distortion issues (analogue components)
● Aging of analog components
● Imperfect L/R matching

Active X-over Design AXD®:

● Digital domain
● DSP-based digital filters
● No tolerance issues (100% reproductible from one DSP to another)
● No thermal distortion (digital computation)
● More overall power (more Expert Pro units)
● Signal path(straight wire between Class A transistors and Speaker Driver’s coil)
● Software upgradable
● Multiple structure
● More phase-accurate oriented
● Shortest Analog signal path in the history of Audio
● No aging issues of analog components
● Nonlinear corrections up on request

Active crossover filtering has been long time regarded as an ideal solution for crossover filters for the following reasons:

● Accuracy

○  Active crossovers are an easy way to vary or fine tune each frequency band to the specific drivers used, the frequency response is then independent of the dynamic changes in a driver’s electrical characteristics.

○  It provides a better isolation of each driver from signals handled by other drivers, thus reducing intermodulation distortion.

● Efficiency

○  The power amplifiers are directly connected to the speaker drivers, thereby maximizing amplifier damping control of the speaker voice coil, reducing consequences of dynamic changes in driver electrical characteristics, all of which are likely to improve the transient response of the system.

○  It reduces power amplifier output requirements. With no energy being lost in passive components, less powerful and more accurate amplifiers can be used, especially for tweeters and mid-range drivers, which potentially increases quality.To achieve active filtering, Devialet developed an easy to use technology. Together with the speaker manufacturers we developed a dedicated R&D tool and invested resources to make sure it is easy to create the most accurate active profile for each speaker.

What are the benefits of AXD® ?

Three key advantages of AXD® to remember:
● AXD® provides ​superior possibilities to the loudspeaker designer, compared to

passive crossover constraints.
● AXD® enables ​higher precision and purity​: no tolerance spread on component

values, no distortion nor noise induced by the passive components of the passive crossover (inductance non-linear distortion, thermal distortion and resistors noise,…). The shortest analog signal path in the history of audio. Less is even more.

● AXD® ​maximises the efficiency and linearity of the amplification system​: 100 % of the power delivered by the amplifier is used by the speaker driver. The amplifier does not have to deliver extra useless power dissipated as heat by the passive crossover. The overall distortion level is further reduced, the dynamics enhanced.

  1. Michael Fanning

    14 November

    1) Do the crossover networks in the speakers have to be modified? In other words, is this a prospective feature?
    2) If the crossover networks do NOT have to be modified, would this technology work with my current Vivid Oval 1.5 speakers?

    Thanks, Michael

    • Pierre Isabelle

      25 January

      The speaker’s passive crossover does not need to be modified. Rather it needs to be bypassed altogether. Frequency splitting is done in the amplification setup. Consequently, the amps must be connected directly to the speaker drivers. See the relevant threads on the Devialet forum, including this one where I describe my two AXD setups:
      I don’t know how easy it will be to bypass your passive crossover. In my case, I am using Naim speakers that were designed in a way to make the passive to active conversion straightforward.
      — Pierre

  2. Martin

    14 November

    Nothing on the Devialet website about this?

    • admin

      14 November

      Dear Martin, as you read on the front page this is my underground audio world. Enjoy. =)

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