OK, I'll admit it, I have no clue what it means (the above graph), even as I read this thread last night, I could get a little out the comments after you posted similiar graphs/results, but for the average smoe like me, it might as well be written in chinese or something. Can anyone provide a translation?
See the legend at the bottom of the graph. The light gray response curve is that of my "Standard," the second Minimus of this pair that I haven't done anything to/with, measured at the same time and under the same conditions. I include that as a reference for comparison of whatever change is under evaluation.
The red curve is the response of the test unit using the revised crossover circuit you propose. It flattens the response somewhat and reduces the exaggerated high-frequency response a bit. From a response perspective, then, it's an improvement, albeit not a particularly substantial one, and I suspect you'd have to A/B them directly for it to be audible. Looking back at the results with the eBay kit, I'd say this is a "better" mod, but the proof would only come with comparative listening.
The red curve is the acoustic sum of the green and blue, which are the woofer and tweeter on their respective filters, individually. The fact that the red curve is lower than the blue, the tweeter alone, indicates that what we hear, on axis, at least, is in part the result of interference between the drivers, which will likely be different from different listening angles. It'd take a far more complex measurement strategy to show all what is happening there, but generally, a stable design seeks to avoid relying on driver interference as an operative element in the overall performance; it's better if both drivers are not playing in the same frequency range, hence the term "crossover."
It's clear, however, that there is less of that with a filter now on the woofer as well as the tweeter, and the influence of the most probably nasty resonant peak in the woofer response at 7.5 kHz is now reduced, resulting in the apparent improved smoothness of the summed response in that region. How much that results in a "better" sounding speaker is, again, a subjective matter. There is still substantial overlap in the ranges of frequencies the two drivers are producing, which may be substantively reduced using one of the more sophisticated filters shown in several of the other mods studied here.
The violet curve is a gratuitous "what would happen IF" experiment; I inverted the tweeter polarity, and that shows the result. I can virtually guarantee that it's not an improvement, read "sucks."
Bottom line: Try your proposal, and see what you think. It's a simple expedient to potentially improving the Minimus 7 response a bit, but if you really want to "fix" them, it's not going to get there. When you do that, report your findings here, please, to expand the Minimus 7 knowledge base for the benefit of the forum.... :yes:
