The tractrix curve is over three centuries old, but applying it inside an existing loudspeaker cabinet is still a modern engineering problem.
Originally studied by Christiaan Huygens in 1692 and later analyzed by Gottfried Wilhelm Leibniz and Johann Bernoulli, the tractrix became one of the most influential mathematical curves in horn loudspeaker design. In the late 1920s, P. G. A. H. Voigt applied the tractrix to loudspeaker horns, demonstrating principles that continue to influence horn design today.
During the 1980s, Dr. Bruce Edgar helped popularize tractrix horns for the home audio community by developing practical rectangular implementations that could be manufactured using the techniques available at the time.
Today, modern CAD software, acoustic simulation, precision measurement systems, and additive manufacturing allow horn designers to explore geometries that were previously impractical or impossible to manufacture.
FastLane Audio builds upon that history.
Every horn is a collection of engineering tradeoffs.
There is no universally "best" horn.
There is only the horn that makes the best set of engineering decisions for its intended application.
Our goal is to optimize those decisions through measurement, simulation, and listening—not by following a single design philosophy at the expense of all others.
Every dimension is a compromise between acoustic performance and practical installation.
A theoretically ideal horn is not always practical when the mouth size, depth, driver location, and original cabinet opening are already fixed.
FastLane Audio's approach is to preserve the useful acoustic behavior of tractrix-style expansion while optimizing the geometry for real-world installation.
Rather than following a single curve blindly, each design balances throat transition, flare rate, mouth size, depth, directivity, printability, and cabinet fit to achieve the best overall result.
The objective is not theoretical perfection.
The objective is to make the best engineering decisions within the available space.
The original tractrix horn is a surface of revolution—a round horn.
As horn designers adapted tractrix geometry to rectangular loudspeakers, practical implementations evolved to meet the manufacturing capabilities of their time.
FastLane Audio continues that process by exploring modern symmetric rectangular tractrix geometries made possible through CAD design, acoustic modeling, and precision 3D printing.
Our objective is not to reinvent tractrix.
Our objective is to continue refining its implementation within the constraints of existing loudspeaker systems while remaining faithful to the acoustic principles that have made tractrix horns respected for generations.
SymTrac™ began with a simple engineering question:
Can a rectangular tractrix horn maintain a more continuous geometric expansion beginning immediately at the driver exit?
The SymTrac™ geometry explores an approach where all four walls begin expanding immediately from the throat, maintaining continuous expansion in both axes from the very beginning of the horn.
This approach was developed to reduce unnecessary geometric compromises while remaining compatible with existing loudspeaker cabinets and modern manufacturing methods.
Every new concept is evaluated through measurement, simulation, and extensive listening before becoming part of a finished design.
FastLane Audio products are designed primarily for high-efficiency, two-channel music systems.
The design goals are straightforward:
No single horn geometry is perfect for every application.
The goal is not to create the perfect horn.
The goal is to create the horn that best satisfies the engineering priorities of its intended application.
The SymTrac™ geometry is the result of a collaborative effort.
The original concept for exploring a symmetric rectangular tractrix expansion originated with FastLane Audio as part of our continuing effort to optimize horn geometry for existing loudspeaker cabinets and modern manufacturing methods.
Turning that concept into a practical design required the mathematical expertise of Al Klappenberger of ALK Engineering, who developed the computational program used to generate the SymTrac™ geometry.
FastLane Audio then applied those mathematical results to practical loudspeaker design through CAD development, 3D printing, measurement, and extensive listening evaluations.
We are grateful for Al's contribution and his willingness to help explore new approaches to horn design.
Every generation of horn designers has worked within the limitations of the manufacturing methods available to them.
Modern tools do not eliminate the need for sound engineering—they simply allow us to explore new ideas that were once impractical to manufacture.
FastLane Audio continues that tradition by combining established acoustic principles with modern engineering tools, always guided by the same objective:
Performance driven by measurement, simulation, and listening.
Engineered—not guessed.
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