The Marthas

These speakers were started back in 2006 as an attempt to build a fully programmable omnidirectional speaker that could be a 3-way, 4-way or 5-way speaker with any crossover type and crossover frequency. There was a version on display at Dennis Murphy’s house for DIYDC2009 using older technology. However, that earlier technology proved inadequate, and I felt it was best to wait until better solutions were available. The Marthas went into storage for about 12 years and then recently received a technology refresh. A few more years elapsed to develop new software, and they are finally working once again. Like most software-intensive DIY projects, they still aren’t “done”, but they work well enough to draw some conclusions about the approach.

This article is in two parts, with some additional technical details in another article. Part 1 describes the technology refresh–the amps, DSP and an overview of the software. Part 2 describes the initial listening impressions and the rather shocking results from the “dipole mode”. For more details on the DSP and Arduino software, take a look at the Active Line Array Project. Most of the code for the Marthas was developed for the line array project, and that article includes many details and links to the code.