Advanced Transition Horns by Marcel Batík

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Ath - Acoustic waveguide design tool

Ath is a program for acoustic waveguide design. By extending the work of Dr. Earl Geddes [1,2], a new generalized waveguide formula was developed, including a smooth acoustic termination. By virtue of this formula and usage of BEM analysis, state-of-the-art waveguides for high quality sound reproduction can be designed.

Associated diyAudio threads: Theory & Design | Practicalities

[2] The Intellectual People Podcast (YouTube): Waveguides, Acoustics and Speaker Design with Dr. Earl Geddes

OS-SE Waveguide Formula

As a result of extensive experimentation and numerical BEM analysis a new formula for a smoothly terminated waveguide profile was developed, which is now implemented in Ath.
  • The original OS (Oblate Spheroid) contour formula:

  • New "OS-SE" contour:

The above formula provides a simple closed-form expression for a very general horn profile that smoothly terminates into a flat baffle, ranging from a straight conical to nearly exponential with a pure OS waveguide in between.

Ath allows for variation of the formula parameters arbitrarily and independently in every radial direction, offering virtually unlimited possibilities of the overall horn shapes. The formula also sets an opening angle at the throat, matching a compression driver exit if needed.

In addition a secondary flare roll-back algorithm was developed to terminate the profile into free air seamlessly, making free standing waveguides a viable option. The algorithm itself is proprietary but can be utilized in the Ath tool. This shows to be the key part of the pristine performace of the free standing wavegides, as in the CE series.

Further reading: OS-SE Waveguide.pdf

Example: Interactive formula in Desmos calculator

Ath download

Create your own waveguide model and test it with BEM analysis using R&D Team's ABEC (*). Ath will generate all the necessary files automatically.
(*) Since ABEC changed to AKABAK in the meantime and there seem to be some compatibility issues, you may still want to use the old version of ABEC 3 until the issue is resolved.

Ath is available as freeware for personal non-commercial use:

The latest release (7th October 2021): Ath 4.7.2
Previous release (including the demos): Ath 4.7.0


If interested in the project, please contact the author via e-mail or the diyAudio thread.


Ath is a freeware project. Donations can be made via PayPal or Bank Transfer:

IBAN: CZ1401000000194381070237