The Whamodynes - a short history of five years of design development

In early 1995 or thereabouts our bud Ron Welborne did a noble thing, announcing his sponsorship of a contest for ultra efficient speaker designs to go with triode SE amps.
Unfortunately six months later there was only one entry, and the contest was cancelled.
Here is the story of that lonely entry, and its offspring.

Doc decided that an interesting approach for high efficiency might be an array of many medium sensitivity drivers. At that time there were very few designs along those lines. Doc's discovery of MCM Electronics, a supplier of a huge variety of inexpensive quality drivers, fed the fire to pursue this angle, as their catalog listed lots and lots of potential drivers.

After buying and trying about a dozen different types, the most intriguing driver ended up being an odd little 8 ohm aluminum cone 5" driver, PN 55-1290, designed as a knock off of a Hartke stage monitor driver. The driver had a very high Q of .94, a resonant frequency of 115 Hz, a stated sensitivity of 91 dB and a small Vas of .18 cu.ft. The bandwidth was stated as 95 Hz to 15 kHz. The plan was laid to use four 8 ohm drivers mounted in a vertical linear array and wired in series/parallel to achieve 96 dB sensitivity and retain the 8 ohm impedance.

Both Ways - the original Whamodyne
The first attempt to use these drivers was full range in a very large box. The vented box was about 6 cu. ft., and was constructed of 1-5/8" carbon filled foamcore insulation board with a foil covering for stiffness. The resulting box was about  6 ft. tall, but you could pick it up and throw it! Early on the lack of deep bass became apparent (although there was in fact greatly reduced output clear down to around 35 Hz!), and the cabinet inside was restructured to incorporate a sealed cabinet for the four full range drivers and a crossoverless bandpass woofer enclosure, which utilized another very inexpensive driver from MCM Electronics, PN 55-945, rated 8 ohms, an optimistic 96 dB, Q of .46, Fs of 34 Hz, and Vas of 3.3 cu.ft. The bandpass box volume was about 1 cu ft. in the back chamber and about 1.3 cu. ft. in the vented front chamber. Doc's early enthusiasm for the potential of the design can be found in this .pdf file from the April 1995 issue of VALVE. Imaging of this low mass "quasi open baffle" was reminiscent of QUADs, but unfortunately the low mass cabinet panels tended to be quite diaphragmatic in the bass region. The sideways mounted woofer was louder through the side than from the vent on the front of the cabinet!

Superwhamodyne -
the prototype

The results from the first experiment led to a more complex design, intended to add frequency extension at both ends, and a more conventional cabinet construction from 3/4" MDF. The bandpass woofer was moved to its own cabinet, and midranges were housed in a sealed cabinet, augmented with a titanium dome tweeter, PN 53-325.
Here the prototype cabinets are seen being tested with an AudioNote Ongaku and Krell CD player.