Hi Atmasphere . . . I'll mock up the speakers this afternoon and see what happens. It has since occured to me that I will need to in both cases null out the effect of voice coil inductance(s) on the measurements. I think that by calculating the EMF as a power ratio rather than a voltage ratio, it will remove the inductive kick from the voice coil from the equation.
Also, I don't think I have a suitable piece of foam that would couple the D130s together without introducing a lot of extra mass . . . so I think I'll just tape the edges and have them couple with air pressure. I'll make the measurements at the free air resonance frequency, which should be at the lowest point of modulation of the air pressure between the two cones.
For the 375s, I'm going to start by measuring the difference in power input, and change in input waveform, between having a lens on the driver, and having the throat plugged. That should easily separate the effects of the air loading from the diaphragm mechanical damping.
The fact that I'm using power calculations rather than voltage calculations is interesting per our previous conversation. I'll have to chew on that . . . actually, I might start a new thread for the results.
There are three reasons why I've kept the little Knight KG-240. First, it's really useful for a secondary system - it's very small and compact, doesn't put out too much heat, reliable, and sounds fairly decent. Second, I have really come to appreciate the engineering behind it - it's definately a flawed piece, but it was sold for $30 in kit form, and it uses every cent of that in a well-balanced manner to perform as well as it can. Third (and most importantly), it was my father's . . . he bought it at a time when he could afford very little, and soldered it together himself on the kitchen table. He used it for over ten years as the only stereo in the house . . . and it's been used on and off for another three decades. I'd say he got his $30 worth.
