By combined system do you mean the MB2 with the delay in the bass crossover in the chamber?

If so then you would get out two cycles, one from the mid dome and then one from the bass driver. The amplitudes would be half of whatever they would be if there was no delay and both drivers sounded simultaneously. I don't think you can record just one sign wave if two are being produced, no matter where the mic is.

Obviously you could if you use a gate or if there was beaming with the woofer and you placed it off-axis or something but I don't think you wanted a silly answer!

What are you getting at? Bear in mind that TL's work by delaying the woofers rear output by a quarter cycle or so at the tuned freqency.