Dusty memories from 24 years ago.
From the long lost archives. This is the last pair of monitors that I worked on in The late 1980's. This set was made in 1993. Drivers were by Dynaudio. A 15W75 midwoofer and D28-2 soft dome tweeter. They sounded pretty good. The cabinet had a massive front baffle of 62mm (2 1/2") and a dual enclosure. The interior enclosure used a partial ellipsoid shape and the voids between this and the outer enclosure were sand filled. The ellipsoid inner volume was constructed in such a manner that it allowed a complete collapse of a reflection off of the back wall in half a wavelength. Sound waves bounced off of the rear wall and then reflected to a predetermined focal point and converged into a crisscross of counteracting reflections. It was a pretty successful design in terms of high quality audio reproduction. It's handicap was that it was a very expensive design from a company that had no real footing in the market. Lesson learned through the engineering was priceless. Lessons learned in unsuccessful marketing was equally priceless. Remember that this was pre-internet.
This design was out at the same time as the original Totem Loudspeaker. In fact I had a good conversation with the designer of the Totem speaker at the 1989 Montreal Audio Show. Our discussion centered around the merits of the tweeter they used versus the Dynaudio tweeter. Then I was able to follow up that discussion with the owner of Solen Electronique (Denis Oullete) who was the supplier for both of us. Denis asked my opinion of how it sounded? My reply was "a cheap tweeter that was doctored up". "Exactly" was the reply. Then Denis and I traded ideas on the best crossover for my implementation. I think Denis taught me more about crossovers in that conversation than in any other one place. I stand on the shoulders of giants in this industry. From those generous enough to share their perspective and experience. That has been through the printed page and through one on one contact. Through emails and phone conversations in later years.
The cabinet Fc was tuned to 45 hertz. And the little driver that we used could be rather great sounding in a medium sized room. The beginnings of understanding driver marketing were hitting me. The X-max Dynaudio presented was not specified as a plus or minus. Just total combined. The frequency response graph included a lowpass circuit for the woofer and a highpass circuit for the tweeter graphs. Things you learn along the way. Calculations were done using the loudspeaker cookbook and my good old TI calculator. Measurements via a function generator and a paper chart recorder and my trusty RadioShack SPL meter. You did what you could with what you had. Now we can do a little better!
Mark's Ramblings, show and tell. And other sundries.