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Radio Speakers

Thread starter #1
Hi Guys

I’m trying to sort the speaker wires out on my Isuzu Trooper, I’ve disconnected the wires on the rear speakers without making a note of where they fitted, the speakers have a large and small spade on them but the wires themselves have all large spades on them.

I’ll do my best to explain what I can see.

First off referring to the rear speakers, the speakers themselves are marked plus and minus.
The passenger side rear has two wires, one is all yellow the other is yellow/blue.
The driver’s side rear has two wires, one is all orange the other is orange/black.

The front speakers have a pair of wires connecting onto each of the two speaker connectors respectively ie there are four wires to each front speaker and unlike the rears there are no markings to indicate which is plus or minus.
I know how to find out which is plus and minus using a 9v battery on the speaker itself, but how can I find out which of the wires are plus and minus.

I’d like to get the speakers wired up correctly so they are not fighting each other and I’d prefer to do it without having to pull the radio out.


On the rear passenger side, I’ve tried to find out which is the minus wire by using a multimeter connected to the bodywork of the car and touching each wire in turn, !!Result!! the continuity buzzer did not sound.
I know I’ve more than likely done the test totally wrong.
Can someone out there tell me how I can check which is the negative wires both on the front and rear speaker wires.
The speakers are working fine, it’s just that I’d like to get them wired correctly.

I hope some electonics wiz out there can make some sense of the above and thanks to anyone who can help me.

Clive
 

MikeMl

Well-Known Member
Most Helpful Member
#2
There should be two wires per speaker (+ and -). None of the wires should show continuity to vehicle frame. Use a 1.5V D cell to find pairs of wires that make the speakers click. After you have found all the pairs, try each pair on the D-cell with both polarities. If the speaker cone moves closer to you when you connect the pair, you have found the correct polarity. Mark the wire that is connected to the battery center post + and the other wire in the pair -.
 
Thread starter #3
Hi Mike

Thanks for your reply, right so at least I now know there should be no continuity to the vehicle frame from any of the wires.
What I'd already done before posting my question on the forum was to disconnect the front speakers from the car wiring and I used a 9 volt battery, the the type where + and - are on the top to istablish which was + and - on the speaker by obsevering which way the cone moved, in or out, so Iv'e got that sorted.
But can you tell me again, how do I find out which wires on the car wiring is + and -

Cheers

Clive
 

MikeMl

Well-Known Member
Most Helpful Member
#4
...
But can you tell me again, how do I find out which wires on the car wiring is + and -
Same way you did on the front speakers... See which way the cone moves. (I am assuming that the wires are connected to the rear speakers).

The center post on a 1.5V D-cell is positive, and the can is negative.
 

audioguru

Well-Known Member
Most Helpful Member
#5
To test the radio wires, extend one wire from the left front speaker to near the right from speaker. Carefully that you do not short any wires together connect a speaker from that extended left wire to one then the other wire of the right speaker with the radio playing not very loudly. The connection that makes no sound has wires that are the same polarity. Do the same for the rear wires. Then do the same for a wire from front left to wires at the rear left. Then you will know the polarity of all the wires from the radio.
 

camerart

Active Member
#6
There should be two wires per speaker (+ and -). None of the wires should show continuity to vehicle frame. Use a 1.5V D cell to find pairs of wires that make the speakers click. After you have found all the pairs, try each pair on the D-cell with both polarities. If the speaker cone moves closer to you when you connect the pair, you have found the correct polarity. Mark the wire that is connected to the battery center post + and the other wire in the pair -.
Hi M,
I didn't know that! Thanks.
As a matter of interest (Sorry to jump in the thread) is this how noise cancelling is done?
C
 

MikeMl

Well-Known Member
Most Helpful Member
#7
...
As a matter of interest (Sorry to jump in the thread) is this how noise cancelling is done?
C
What kind of noise? Common-mode Alternator ripple current flowing in the car body? Then yes...

Biggest reason why automotive speakers are "floating" is so they can be driven differentially by equal-amplitude, 180 degree out-of-phase signals from two"bridged" audio amps. This produces four times the audio power per speaker compared to it being driven single-ended. The maximum un-distorted voltage that a single-ended amplifier channel powered with 14Vdc can produce is about 12Vpp, which is 12/2√2 = 4.24Vrms. With a 4Ω speaker, that is 4.24^2V/4Ω = 4.5W. If that same speaker is driven with two identical out-of phase voltages, then the power is quadrupled to 18W per speaker.
 
#8
to determine speaker phase, just connect them then play some music and put your head in the middle of the two speakers, if there is lack of bass, then reverse the polarity on one... you will easily hear the difference
 

camerart

Active Member
#9
What kind of noise? Common-mode Alternator ripple current flowing in the car body? Then yes...

Biggest reason why automotive speakers are "floating" is so they can be driven differentially by equal-amplitude, 180 degree out-of-phase signals from two"bridged" audio amps. This produces four times the audio power per speaker compared to it being driven single-ended. The maximum un-distorted voltage that a single-ended amplifier channel powered with 14Vdc can produce is about 12Vpp, which is 12/2√2 = 4.24Vrms. With a 4Ω speaker, that is 4.24^2V/4Ω = 4.5W. If that same speaker is driven with two identical out-of phase voltages, then the power is quadrupled to 18W per speaker.
Hi M,
I was thinking more about general noise being negated.
C
 

audioguru

Well-Known Member
Most Helpful Member
#10
to determine speaker phase, just connect them then play some music and put your head in the middle of the two speakers, if there is lack of bass, then reverse the polarity on one... you will easily hear the difference
Remember years ago when there were stereo stores? The salesmen always connected the speakers wrongly out of phase then cranked up the bass control so that the bass cancellation was not too bad. When I walked past the out-of-phase sounds made my ears feel odd so I always corrected the wiring and turned the bass control down to normal.
 

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