Friday, Dec 29, 2017 at 15:14
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Hi Michael, OK, a short course in Ohms Law, or at least, speaker connection.
Radios, like many things, are rated to support specific loads and if exceeded may cause problems. Typically, car radios are designed to have 4 Ohm speakers (there are exceptions). 4 Ohms is the 'impedance' (similar to electrical resistance) of the speaker winding. The lower the impedance number, the more load it will consume so if you connect two 4 Ohm speakers in parallel it will become a 2 Ohm load trying to draw twice the original power and that may be too much for the radio output stage.
You could use two 8 Ohm speakers in parallel which becomes a 4 Ohm load which would be safe but will now only deliver one half of the former power (loudness) from each of the speakers. Similarly, you could wire two 4 Ohm speakers in series but again will now get half the former power from each speaker.
Of course, you can probably simply turn the volume up to compensate for the impedance change, but in your case where I understand that you are only adding a speaker to one channel, doing the above arrangement would produce a L/R channel imbalance. Trying to use the balance control to compensate would unbalance your front speakers.
Soooo, here is what you may wish to try................
Let's assume you want the additional speaker on the Right channel. Take the existing Left 4 Ohm speaker and wire it in series with the existing Right 4 Ohm speaker, creating an 8 Ohm load. Use a new 8 Ohm speaker for the Left channel. You now have an 8 Ohm load on each channel but you will have to turn the volume up to compensate and that upsets your front/rear balance although you may be able to adjust the radio Setup to rebalance front/rear.
The other (and better) way is to add two new 4 Ohm speakers placing them in series with the existing Right and Left 4 Ohm speakers. Each channel is now 8 Ohms so there will still be the front/rear balance issue.
The front/rear balance thing may not bother you too much if a lower volume at the rear is acceptable.
Now a note about connection. Speakers are 'polarity' conscious. Not quite in the same sense as batteries but they do need to be connected correctly or you will have 'phase imbalance'. This will cause poor output and strange acoustic effects for the listener.
Speaker cones 'push out' and 'retract' alternately to create sound and it is important that they do so in unison. Each speaker's terminals are marked with a positive and negative sign.
If connecting speakers in parallel join the positives on each speaker together and the same for negatives.
If connecting speakers in series, remove the original wire from the negative of the first speaker, join the negative terminal of the first speaker to the positive of the second speaker, then wire the negative of the second speaker to the wire you removed from the first speaker. If you need, sing out and I'll put up a diagram.
Now, after all that, there is the really correct way to do it but it requires installing a small secondary amplifier for the additional speakers and I figure you don't want to go there!
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