There are acoustic differences between 4Ohm and 2Ohm voice coil subwoofers, because it affects the coil size and position. This affects the Free air resonsance frequency, that affects everything else you need to design a good speaker box. Unless you don't design your box based upon Fs, Qes, Qtc, and overall desired Q factor,
In which case you are just dumping a speaker into a box becuase you "think" it will sound good. instead of knowing exactly what your box will be tuned to, what type of frequency response curve you will end up with..
That's completely wrong !!
just look at the dual voice coil 4 ohm and 2 ohm Xenon here under Fs and Qes and you will see what i mean :
ftp://208.187.38.55/Phoenix_Gold/Man...ofermanual.pdf