They are not (tweeter mid)in series they are in parallel in a Hi Fi 676 option.
I have repaced mine I know this to be true.
Base system has door speakers in parallel with the floors.
There is a component that splits the frequency between them.
The static resistance measurement on a Hi Fi door mid is 2 ohms.
And it measures as 2 ohms at the amp connector.
http://www.e90post.com/forums/attach...4&d=1278871872
The above document was generated by MusicarNW regarded as one
of the best BMW stereo shops on the West Coast.
I have no seen one install that puts tweeters in series with mids
or anything else.