whoa David speaks
take note members Dave is not the only expert here,
great Joerg you have given some direction to future modifications. Yes I will take the time to rewire the two 3ohm audiobahn amd 6.5 inches to a series circuit from a parallel one allowing the bridged amp to see a 6ohm load versus a 1.5 ohm load so that in the future I can add another 6x9 inch box containing another two 6.5inch midbass drivers wired in series and then I will wire the two boxes in parallel to give a 3 to 4 ohm load at the amp, maybe.
Yet still Joerg the issue of which circuit, series or parallel, absolutely produces the highest spl from the speakers per a specific input voltage has not been answered.
Dave can you take it from here?