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RE: Possible impedance sweep alternative

I'm sure they already knew the Thiele-Small parameters of the 1.6 and other technical information. They did, after all, design the 1.6! But I'm sure there was also experimentation, measurement, and the dreaded blind test to insure that any changes made a significant improvement. Certainly, a significant R&D effort.

Our own job is much simpler, since they've already done the hard stuff, including determining the ribbon width that works best. All we really have to do is figure out how to wire the foil and select the crossover values, maybe compensate for Fs and Q changes due to the mass reduction. The T-S values of the MMG would be nice since they'd allow us to calculate behavior in advance, but they aren't strictly necessary, so I wouldn't go to too much trouble. What we do need at a bare minimum are the physical dimensions and number of traces of the MMG ribbons and the width or resistance of a length of the tweeter foil. From that, we can calculate the DCR of the woofer and tweeter (and supertweeter?) sections. Wendell wrote to say that "it may be necessary to use a series/parallel combination to exploit a solid state amplifier's maximum current." The objective would be 4 ohms, but as I said, it doesn't have to be precise with a series crossover, the issue here is getting the most juice out of the amp. It may be enough to do the woofer in two sections of tweeter ribbon and parallel them, but we can't know until we have the foil spec.

So at a bare minimum:

- Length of MMG traces, number of loops, and magnet-magnet spacing for both new and old MMG's. Mine are unsocked so I can get the info for the new ones.

- Width of the foil, or resistant measurement of a known length, e.g., of the 1.7 tweeter.

Optionally:

- T-S parameters of the existing MMG(s)

- Some more information about the 1.7, e.g., crossover points, foil section and magnet spacing dimensions, DCR of the three sections, anything we may have missed when we were looking at the photos and schematic. The idea being to skip as much experimentation as possible through reverse engineering, e.g., if the 1.7 tweeter is a certain width and the crossover point is 1 kHz it's a fair bet that if our tweeter is the same width we can use the same crossover point without unduly compromising dispersion, distortion, or power handling.

I think between the two of us we have the MMG covered, but we'll need that ribbon spec.


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  • RE: Possible impedance sweep alternative - josh358 06/26/1116:58:19 06/26/11 (0)

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