What impedance are the OE speakers? What about the replacements? And what impedance does the head unit require?
The impedance of the head unit should be the same or
lower than the speakers.
(or put another way)
The impedance of the speakers should be the same or
higher than the head unit.
When I was a lad, most units were 8 ohms; less common were 4 ohms. Now 2 ohm speakers seem to be out and about, so it is wise to check.
The impedance adds up for speakers wired in series. So two 4 ohm speakers wired in series have an impedance of 8 ohms. 4 ohm + 4 ohms = 8 ohms.
However, 2 speakers wired in parallel means
the calculations are a little more complex since the impedance falls - so the impedance of two 4-ohm speakers wired in parallel is calculated as -
1/total = 1/4 ohms + 1/4 ohms = 2 ohms total impedance.
If the impedances are wrong, it is going to sound crap, even if the speakers are correctly in phase.
