There should be no change in the midrange drivers' amplitude: the two switches affect only the tweeter output. See my schematic in the KLH Library: "MRDB's KLH Five Crossover Schematic". It was not clear to me from the description of your setup if you used an amplifier between the function generator and the crossover/drivers. If not, then the source impedance of the generator (probably 50 ohms) would have been loaded by the crossover and that load would vary depending on switch position, causing generator output level to vary and this could explain the midrange level variation. You mention something about keeping levels constant so I am not sure if this is your problem, but it is worth a look. Bob