Many have asked after my references to 'The Mighty DynaPleats' on the
Bass/DIY List. Shown at the left is one of my two dipole baffles
containing 12 DynaPleat drivers stacked in a vertical line-source array.
The large black rectangle next to the driver array (far left)contains the
mounting assembly for a work-in-progress, a 72" true ribbon driver using
classic pole-piece construction. That project was put into hiatus when the
RD75 became available at discount in May 1997.
The DynaPleat driver is an 'area' driver utilizing 11 separate voice coils on a hard-molded plastic piston approximately 4.5 inches square. The suspension is a dual symmetrical folded-pleat of parchment-like material. They seem to make excellent dipole woofers; but, are unfortunately no longer available in this area. Twelve drivers in an array can move a very large amount of air!
Next to 'The Mighty DynaPleat' baffle is the bare board version of the baffle for the RD75 driver. As you can see, the DynaPleat is a much more robust piece of 'room sculpture'. For about a month I used the RD75 driver in a two-way configuration with the DynaPleat 'woofers', crossed over at approximately 300 Hz. This was an extremely satisfying marrage of drivers as 1st order crossovers were achievable with both drivers using simple passive components. My ultimate intention is to return to this configuration - as soon as possible after completing the woofer phase of the RD75 Dipole Baffle Study.
The final loudspeaker shown in the photograph is a Hsu Model 10W subwoofer. This is a 6th order Butterworth design using equalization to achieve sub-20Hz performance. This model has been highly reviewed in many magazines, including 'Speaker Builder'. As you can see, it is positively tiny - miniscule - compared to the DynaPleat.
The final size comparison is of the '9&SQ' and '3&SQ' square-edge trapezoid baffles. These two baffle shapes, they are 'thick' baffles, were judged to have the most linear frequency response of the eleven basic shapes tested. Prior to development of the 'One-Sided' baffles, the '3&SQ' shape was chosen as the best of the baffles for two reasons: an incredibly linear section of frequency response through the mid-range to upper mid-range; and, its being judged as having greater aesthetic merit in size and shape. Although the '9&SQ' baffle had seemingly equivalent frequency response linearity to the '3&SQ' baffle (with a possible marginal superiority in one area), it was judged as being too large and ungainly in shape for most rooms.
Acoustic Line Source Research - Table of Contents.
