MartinLogan SL3 loudspeaker Trying to Control a Lightning Storm part 3

Phillips: We were just talking about your prototype, which used flat panels. How did you determine that you needed curved panels?

Sanders: That's the classic drawing-on-a-napkin-in-a-Chinese-restaurant design story. Ron and I were eating dinner, chit-chatting about speaker design. As we talked, I sketched a waveform moving away from a point-source. It became clear to both of us that the information on-axis was farther away in time than the information coming from the sides—I drew these little points and we literally connected the dots. I looked at the napkin and said, "Ron, could it really be this simple? Could we just curve the diaphragm?"

I couldn't sleep that night, so I got up and tried to build a curved panel, with no success. I couldn't stretch the polyester in two dimensions and get it to curve. I finally found a way to curve the diaphragm in free air, and then use curved back and front stators to control it.

Phillips: How do you do that?

Sanders: We don't really discuss that. Just say that, under tension, the panel is rigid enough to maintain the curved shape, despite the fact that the material resembles Saran Wrap in its free form. Any competent engineer could devise a system of controlling the material enough to keep it from caving in to the rear stator, but the challenge is to do it repeatedly and predictably. Forming the panel into an arc allows us to control the way its acoustic energy interacts with a room.

Phillips: So that's the major breakthrough?

Sanders: One of them. We also developed a new insulating technique for the stators, and utilized the vapor-deposit method of making the panels conductive. Vapor deposition actually shoots the copper oxide and palladium into the diaphragm material. These were the major factors that made our speakers reliable and long-lived. We actually made—and sold—speakers before settling on the vapor-deposition process, and it cost us a lot of money in our first few years, replacing all the diaphragms we'd already sold with better ones. But it was worth it—I don't think Martin-Logan would be in business today if we hadn't stood behind our products from the very beginning.

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