yes, the BMW speaker has 4 wires to each speaker. I got the idea for the replacement from a guy on an R18 FB group, and he said he has decades experience with car audio installs. He's the one that said you have to get 2-ohm, dual voice coil subs to replace the BMW's. The ONE that I've done so far does sound great, but bear in mind you are adding 7 lbs of weight to the lid of each case and 15 lbs overall to the weight of the bike by doing both. Makes opening the case lid a little bit of a "take it easy" exercise. If you throw them open with any force, it might overtax the hingesI thought I read that the Amazon posted speaker specifications stated that the impedance as 6 Ohm (which I thought was odd); did you look into the Skar Marine line of speakers.
Does the BMW speaker have four wires going to each speaker; if so, perhaps it's coming from a frequency cross-over? High freq. & the low freq. sub audio range.