A mini Fostex-style folded horn built around a two-dollar speaker driver

Here is a small speaker project I enjoyed reading: a mini folded horn in the Fostex style, built around a 2-inch full-range driver that costs about two dollars. The author, mircemk, published it on Elektor Labs in September 2026 and updated it shortly after.

The starting point is modest. The driver has no datasheet, so there are no Thiele-Small parameters. The author measured the resonance frequency himself, about 170 Hz, using an audio generator, a series resistor of 10 to 47 ohms, and a multimeter, with the driver hanging in free air. It is a simple method that any hobbyist can repeat.

The speaker is a rear-loaded folded horn. Behind the driver, a first semi-open chamber is filled with damping material, and then an exponentially expanding duct follows. Its dimensions depend mostly on the resonance frequency. The calculations are deliberately rough, and the exact dimensions appear only in the drawing attached to the project.

The author is honest about the result. It is not a high-fidelity speaker but an experiment. Listening against a NAD 801, he notes a noticeable boost between 150 and 300 Hz, a sharper sound on voices, and more lower-midrange energy than a small sealed speaker. There is no real subwoofer extension, and the response measurement, done with pink noise and a small microphone, is very approximate.

I find this approach refreshing: little budget, home measurements, and conclusions without exaggeration.

Source: Elektor Magazine