aTrak

Biradial horns for AMT drivers

aTrak is the biradial horn line of Lautsprechermanufaktur Heyder, specifically tuned for Air Motion Transformer (AMT) drivers.
It combines a controlled flare geometry with the directionally controlled radiation characteristics of AMTs — delivering detailed, open, yet efficient dispersion in the mid and high frequency range.

Pricing & lead times

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aTrak horns are developed for system projects where even, controlled dispersion in the relevant frequency range is required — without excessive beaming, and especially where AMT drivers are meant to operate at their full potential.

Biradial horns combine two curved axes, resulting in a tuned dispersion behavior across two planes. This makes them ideal when a wide yet controlled horizontal dispersion is desired, without compromising the inherent characteristics of AMT drivers.

Typical applications include:

Mid/high frequency systems using AMTs
High-resolution audio projects
Studio monitors with precise detail reproduction
Applications requiring open, natural sound with controlled dispersion

Fast transient response due to low moving mass
High detail resolution within the horn’s dispersion range
Efficient interaction between driver and horn
Uniform dispersion across the intended frequency range

Acoustics & Geometry

The biradial contour is designed to support and extend the radiation characteristics of Air Motion Transformer (AMT) drivers without altering their fundamental behavior.

This geometry optimizes the transition between driver and horn flare, resulting in uniform sound distribution across the intended frequency range, while maintaining effective control of directivity.

Unlike constant-directivity (CD) contours, the focus here is not on maintaining an exactly constant dispersion angle across the entire frequency band, but rather on a practical horn-geometric support of AMT radiation.

Material & Manufacturing

aTrak horns are manufactured from beech or birch multiplex as well as solid wood, and are CNC-precision machined.
Material selection and wall thicknesses are optimized for mechanical stability, low self-resonance, and homogeneous acoustic properties.

Manufacturing features:

Robust wall thicknesses
CNC-machined precision components
Reproducible dimensional accuracy
Resonance-optimized geometry
Manufactured in Germany

Integration & Interface

aTrak horns are specifically tuned for Air Motion Transformer (AMT) drivers.
The horn geometry guides the radiation in a way that supports the driver-specific emission characteristics of AMTs without interfering with their natural operating behavior.

Configuration & options:

Optimized for AMT drivers
Mounting options: flush-mounted or external installation
Adapter solutions to minimize airflow separation

Final design parameters (cutoff frequency, size, crossover frequency) should be defined in relation to the selected AMT driver and the overall system design.

Woods & Finishes

Structural Wood

sTrak horns are based on dimensionally stable beech or birch multiplex.
This material provides uniform density, high dimensional accuracy, and excellent mechanical damping — essential for a mechanically calm horn body without unwanted structural resonances.

For rotationally symmetric horns, multiplex is structurally superior, as it absorbs internal stresses in a controlled manner and remains dimensionally stable even under changing climatic conditions.

Solid wood is available for project-specific applications at any time.
For this purpose, we have built a dedicated sourcing network over many years to ensure the highest material quality.