Tom Thiel and All,
My thinking is that everything matters, and everything is in the circuit. Every nut and bolt and fastener are part of the "Speaker System" While not directly hooked to the crossover the proximity of steel fasteners bend and alter the magnetic field which is part of the drive assembly. When these steel fasteners are removed and replaced with nonferrous the difference is immediately audible and more musical with a more open and resolved soundstage. While some of the improvement in performance is not measurable it certainly is audible. If you perceive improvements numerically and 1 upgrade makes a 5 % gain and you find four or other areas which you can be offered similar improvement, then you made for a net improvement of 25%. This 25% net gain in resolution will greatly offset the net loss of selling and replacing your current speakers or components. Of course you must have a product of initial high quality to begin with such as the Thiel speakers..
Speaking of capacitors, and the same would be true of the resistors, all can be improved whether in series or in parallel with the drivers. Those in series with the drivers will be most important, those in parallel will add noise which is returned to the amplifier and will be added to the overall system. Energy always seeks ground and therefore all the component parts are important. Parts quality in notch filters are often discounted as not critical. My point is there are to those want to increase the overall resolution of their component /system by reducing interfering energy returning into their amplifier and then becoming part of the next signal.
TomD
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