Advanced Transition Horns by Marcel Batík

Associated diyAudio threads: Theory & Design | Practicalities

OS-SE Waveguide

As a result of extensive experimentation and numerical BEM analysis, a new formula for a smoothly terminated waveguide profile was developed, extending the work of Dr. Earl Geddes [1,2].

The above formula provides a simple closed-form expression for a very general horn profile smoothly terminated into flat baffle, ranging from a straight conical to nearly exponential with a pure Oblate Spheroid (OS) waveguide in between. The formula also sets an opening angle at the throat, matching compression driver exit angle.

Further reading: OS-SE Waveguide.pdf

Example: Interactive formula in Desmos calculator

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

Ath software

Ath is a program for acoustic waveguide design, utilizing the OS-SE formula. By virtue of this formula and usage of BEM analysis, state-of-the-art devices can be designed.

Ath allows for variation of the formula parameters arbitrarily and independently in every radial direction, offering virtually unlimited possibilities of the overall horn shapes.

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.

Now you can 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 a freeware project. Donations can be made via PayPal or Bank Transfer:

IBAN: CZ1401000000194381070237

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

The latest release (18th December 2021): Ath 4.8.0
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.