The original waveguide experiments started with a 5"
2-way system on a standard enclosure, which was refined over a period of time until it became obvious that any further efforts would require a significant reduction in the diffraction effects caused by the rectangular enclosure shape, and the standing wave energy inside of the enclosure also caused by the rectangular shape. The actual driver/filter combination from a pair of those early 502s was removed and placed in the original 502R enclosure, which was a refinement of the rectangular
enclosure that had radiused edges to reduce diffraction. This did have the expected effect, and prompted further experimentation. The next step was to build a trapezoidal enclosure to test both the waveguide effects and a non-rectangular interior. This 4" 2-way experiment ended up being sold as a prototype to Seifert-May along with the original Slot-loaded subwoofer, and became the Seifert-May Trapezoid. The next experiment added the top wing and resulted in the bottom-right speaker in
the picture above right, the 502 Trapezoid. This was very successful in reducing the diffraction effects and increasing control over the wave as it left the speaker, plus it reduced the standing waves inside of the enclosure quite a bit. Further experiments were conducted with this waveguide shape, resulting in several products shown above. The three-way system above left, the Electro-Magnetic Induction Trapezoid, was shown along with a Slot-loaded subwoofer at the 1984 CES show, illustrating
the results of the work to date (a fair amount of which was funded by the modification of Infinity Reference systems, hence the availability of the EMIM and EMIT drivers). Further work in 1985 resulted in the speakers shown below, the 803S and the original Trapagon.