are all the factory speakers 4 ohms?.........

[tim s]

my nephews 95 m3 has4 ohm woofers & tweeters, but has 8 ohm mids.
thanks
tim s.

[Hallmark]

Not all auto makers stick to the standard, but it would be highly unusual to mix ohm ratings on a given system. Sounds like aftermarket stuff to me, by someone who probably made it up as they went along. The mids likely are only putting out half the volume they should.