Interactive crossovers use a shim diameter larger than the shim stack clamp. The larger crossover diameter transfers force from the face shims directly into the high speed stack forcing the high speed stack to deflect before the crossover closes. Interaction with the high speed stack softens the crossover closure event (more).

Valving Logic on Thumper Talk demonstrated the performance of an interactive crossover. The damping force data shows no evidence of the crossover closing.

However, Shim ReStackor calculations of the shim stack deflection and stack flow area make it easy to spot the crossover closure velocity at 20 in/sec,

Soft closures of interactive crossover with a soft high speed stack often do not produce any specific “event” in the damping force curve. The data at 20 in/sec where the crossover closes shows that.

Interactive crossover configuration produces a "soft" crossover closure event