Car Stereos: JensenAWM970, continuity tester, rockford fosgate punch

Question
QUESTION: Brian,
All is connected and installed but I am experiencing a problem. The Jensen unit has A, B C speaker selection. I labeled all of the wiring from my old factory unit (4 speaker) to connect the speakers and adapted the Jensen unit the same (six speaker capability). I do not have anything connected to the C speaker wiring of course. When selecting only A speakers to play, I get a low destorted sound coming from the B speakers.  I also have to select A to get B to work. When both A and B are selected all is great and no destortion. The speakers are Rockford Fosgate punch P163C.and you know the head unit.  What might be happening?

ANSWER: Hi Robyn,

Unfortunately, I don't have an easy answer for this one.

I took a look at the owner's manual for the AWM970.  I didn't realize from your earlier questions that this is a head unit specifically made for RV's, but with the exception of the 6 speaker outputs, the wiring setup appears identical to a typical in-dash head unit.  It doesn't appear to have any unusual wiring scheme such as a common-ground system.

About the only thing you can do to troubleshoot this issue is double-check the speaker connections, and make sure you have all the speaker wires connected to the correct speaker outputs.  For example, if one of your speakers has a (+) wire connected to the A output and a (-) wire connected to a B output, that might cause the problems  you're experiencing.  If your speaker wires at the head unit location aren't labeled or might be mislabeled, you can test the speaker wires with a continuity tester (or the continuity function on a multimeter).  The positive and negative wires from a speaker should test with continuity to each other.  

If you're quite certain that each speaker is connected to the correct pair of speaker outputs, then about the only possible cause is an internal defect in the head unit.  You might try using the "C" outputs instead of the "B" outputs for one speaker pair, just to see if that clears things up.  If that doesn't work, however, I'm afraid you'll need to have your head unit repaired or replaced (or just get used to using the A and B speakers together at all times).

Good luck!

Brian

P.S.  Depending on the age of your travel trailer, it's possible that the speakers are currently wired in a "common ground" configuration.  I've run into this a few times in automotive and marine audio installations.  It basically means that the negative wires from the speakers are combined together at some point in the wiring.

With a modern head unit, each speaker connected needs to have its own, isolated (+) and (-) wire.  If the wires from two speakers are combined, it can cause problems with the head unit amplifier.  From the sound of it, I doubt this is the case in your system; but it might be something to check.

---------- FOLLOW-UP ----------

QUESTION: Brian, when I read your response again it was clear that the old unit does have a common ground. Left speaker A & B share the same ground wire same on the Right. At the risk of sounding like a complete idiot, what is the best solution to correct this?

Answer
Robyn,

The best solution might not be the easiest:  run new speaker wiring to each speaker.  My experience with RV's, however, makes me think that running new wires may be no easy task.  

There must be a point in the existing wiring where two wires come together and join into a single wire.  If you're very lucky, that point might be very close to the head unit location.  If you can get to that point, separate the wires, and run a new wire from there so that each speaker has its own negative lead, then that's all that's required.  If it's not right there at the head unit location, however, then fishing new speaker wires through the walls might end up being the easiest option.

Brian

P.S.  If it does seem necessary to run new wiring, you can get away with just running one new wire to each speaker of one pair.  Once you disconnect the negative wire at one of the speaker pairs, it won't be "shared" with the other any more; then all you need to do is fish a new negative wire to each speaker that was disconnected.  The old negative wire will still work for the other speaker pair, just as long as each wire is only connected to one speaker.