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This is a heartfelt tribute to the late Siegfried Linkwitz, a true pioneer in the audio world. His groundbreaking work, which continues to resonate even after passing in 2018, is a testament to his enduring legacy. The Linkwitz LX521 is a truly remarkable loudspeaker.

I was honoured to meet Siegfried Linkwitz in person at one of the many Consumer Electronics Shows (CES) I have attended in Las Vegas. I was already familiar with his name due to my interest in speaker building. Furthermore, I frequently used variants of the Linkwitz-Riley splitter filters he designed in collaboration with Russ Riley. These filters were renowned for their impressive amplitude and phase response and ability to effectively integrate multiple drivers in complex loudspeaker systems.

Nuno Lopes and his open-baffle Thor loudspeaker.

However, Linkwitz is best known for his innovative approach to open-baffle speakers with acoustic correction using active crossovers. Open-baffle speakers have gained a significant following worldwide, including in Portugal. In the photo above, you can see the Thor speakers created by Nuno Lopes from NLaudiospeakers. These speakers were notably inspired by the work of Linkwitz, particularly evident in the open tweeter design.

In 2011, I also heard the Linkwitz Orion model at the Axpona Show in New York and the Jamo (open baffle) speakers.

But it was not until I attended MotorWorld in Munich in 2024 that I was truly blown away by a pair of Linkwitz open-baffle speakers with active filters for the multiple drivers. Each driver was powered by their own Hypex NCore amplifier module.

Everyone should be able to listen at least once to a pair of Linkwitz speakers to realise the true meaning of stereo imaging, lateral separation, and sense of presence. These speakers are particularly impressive in providing phase correction and sound without box colouration, even at low frequencies, resulting in a unique sound that combines the energy of dynamic speakers with the clarity of electrostatic speakers.

Let me provide some technical information about open-baffle speakers for those unfamiliar with speaker construction before I share my experiences with the Linkwitz speakers. It's important to note that the Linkwitz LX521 does not have a distributor in Portugal, and their prices range from 13 to 21 thousand euros, depending on the version with an aluminium, wood, or acrylic panel. The price already includes the active crossover and the 8 to 10 digital amplification modules, with the source being the only additional component required.

Despite the lack of a national importer, the good news is that all the components are available online, and the speakers can be built DIY. If someone finds it challenging to assemble the speakers after obtaining all the parts, they can be sent back to www.linkwitz.store for assembly at a cost.

The Linkwitz LX521 room at the MotorWorld, Munich, May 2024.

Open Baffle Concept

The drivers are mounted on a flat baffle, allowing the rear sound waves to propagate freely. This helps minimise the reflections and standing waves that typically colour the sound in traditional box speakers. The result is a more natural and spacious soundstage.

1. Dipole Radiation Pattern: Linkwitz speakers operate as dipoles, radiating sound equally from the front and back. This dipole radiation pattern helps to create a more immersive and realistic listening experience, as it more closely mimics how sound is produced and heard in natural environments.
2. Active Crossovers: Linkwitz designs often use active crossovers, dividing the audio signal into separate frequency bands before amplifying. This allows for more precise control over the crossover points and better integration of the drivers.
3. Equalisation: To compensate for the lack of an enclosure and the resulting dipole roll-off at lower frequencies, Linkwitz employed sophisticated equalisation techniques. This helped to extend the bass response and maintain a flat frequency response across the entire audio spectrum.

Compensation for Phase Cancellation

One of the challenges with open baffle designs is phase cancellation, where sound waves from the rear of the speaker can interfere with those from the front, especially at lower frequencies. Linkwitz addressed this in several ways:

1. Baffle Size and Shape: The size and shape of the baffle are carefully designed to minimise phase cancellation. By optimising the baffle dimensions, Linkwitz reduced the frequency at which phase cancellation occurs.
2. Driver Placement: The placement of drivers on the baffle is also critical. Linkwitz's designs often feature carefully calculated driver positions to ensure the best possible integration and minimise destructive interference.
3. Electronic Equalisation: Active equalisation boosts the lower frequencies most affected by phase cancellation. This electronic compensation helps maintain a balanced frequency response despite the open baffle design.
4. Cardioid or Dipole Patterns: Cardioid or dipole radiation patterns help direct sound energy more effectively and reduce rear wave interference.

After learning about open-baffle techniques, readers can better understand Frank Brenner's English presentation in the video above. Under his leadership at Sound & Design, Brenner manufactures the Linkwitz LX521 and other models, ensuring that the innovative principles and designs developed by Siegfried Linkwitz remain available to audiophiles and audio enthusiasts. Renner's work involves maintaining the high standards Linkwitz set, focusing on delivering exceptional sound quality and accurate audio reproduction.

Based on what I heard, I can attest to it. Listen to the Linkwitz LX521 playing Mancini's Pink Panther to get an aural 'glimpse' of what I am talking about. Of course, the holographic effect is lost in the recording, so you'll have to trust me on that one.