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RE: I was using a different chart
Posted by Lew on June 5, 2012 at 19:18:09:
Since I can see none of the numbers on the X or Y axes, and since the curves are not labeled, the graph means little to me, except to say that my measurements are nothing like that, assuming the bottom two curves are of impedance. There is no such huge peak at whatever frequency that is, with no resistor, using either their toroid or the AU transformer. My speakers were built in late spring of 2011. Anyway, if that peak is up to 40 ohms, then the impedance at lower and higher frequencies would appear to be too low to be ideal for our amplifiers. Looks like 5 to 10 ohms mostly. OK for an MA2 but nothing lesser.
Edit: After sleeping on this post overnight, I decided that I over-stated the problem. In fact, an MA1 should also be able to drive the load(s) represented in that graph. (I think the lower two curves show impedance vs frequency, and the upper two curves show amplitude in db vs frequency.) But things get a lot better than suggested by those data, when one removes the parallel resistance in the hi-pass filter, which was my main point.