Car Audio Speaker Question

[User]

 

[Levo-Lon]

Earth is usually the one with a black line..so you would have a green and a green/black etc

this will help..as thers a few ways..if you have a multi meter? Its a lot easier to find the live feed..
or a test bulb?

http://www.doityourself.com/stry/knowing-the-difference-between-positive-and-negative-speaker-wire

 

[Profpointy]

the signal to the speakers is AC so positive and negative is moot. What does matter is that all the speakers are wired the same way round else the signal, hence sound, from one will tend to cancel out the other one. You can't diagnose with a meter - if the wire is continuous the wire colour both ends may help. Otherwise swap one pair round - if they are "out of phase" then they will sound worse / slighlty muffled on the lower notes.

NB I am specifically speaking of the speaker leads, not any power supply to other boxes which must be right way round and will be 12 volts dc

 

[Levo-Lon]

Sorry ,black line should be positive..its ages since i did stereo and speakers..
the terminals are different..im guessing your wiring from scratch? And fitting terminals

If PP is right then you cant check with a meter? I thought you can ....

 

[Levo-Lon]

I posted this just to have a read,,as it tells you how to get a meter reading for the speakers

http://www.talkaudio.co.uk/ipb/inde...g-a-multimeter-to-solve-headunit-wiring-hell/

 

[Profpointy]

the linky looks sensible at quick glance. You can indeed use a multimeter to check if you've got both ends of the same wire - in ohms or "bleep" mode. . You can't measure which way round an AC signal is though

 

[Levo-Lon]

the linky looks sensible at quick glance. You can indeed use a multimeter to check if you've got both ends of the same wire - in ohms or "bleep" mode. . You can't measure which way round an AC signal is though

ill bow to your knowledge @Profpointy ..im not that clued up on speakers and such.
id have to do it after taking the stereo out ,then going by the loom connections ..

 

[speccy1]

[QUOTE 4020863, member: 9609"]Why not ? I can with home 240v ac[/QUOTE]
I would like to see how? 240V ac, or any ac for that matter, will show as 240V no matter which way round it is, because the voltage cycles (alternates) either side of zero, so a multimeter will see it as the same no matter how it is connected.

It sounds as though your wiring has been a bit bodged (apologies if you did it!!), and however tricky it might be, you need to get at both ends of the wire to test them through. Car stereos from about 30 years ago used to have the negative speaker wires connected to ground, so therefore it would have been easy to do what you are trying to do, but modern stuff has "floating" speaker outputs, so without removing stereo, you`ve had it

 

[speccy1]

the linky looks sensible at quick glance. You can indeed use a multimeter to check if you've got both ends of the same wire - in ohms or "bleep" mode. . You can't measure which way round an AC signal is though

Totally agree

 

[Profpointy]

[QUOTE 4021352, member: 9609"]idiot ...[/QUOTE]

actually you can as neutral will be a similar voltage earth, whilst live will be 240 odd volts adrift.

Positive and negative are of course misleading terms for AC

 

[Dan B]

You can tell live from neutral with a multimeter (or a light bulb) but what you need to test for speaker polarity is phase : the signal alternates between +ve and - ve 440 times a second (for example, supposing your music of choice is a sine wave somewhere about middle C) , but if one speaker is wired backwards to the other(s) its cone will be "out" when they are "in" and vice versa, so will tend to cancel them out. The effect is more pronounced at lower frequencies, I speculate because (1) you need to move more air for the same perceived volume level, (2) speaker cones are physical objects with mass and momentum so tend to "keep up" better with a slower-moving input than a fast one.

 

[mr messy]

Can you not trace the spurious cable back presumably to the factory wiring?
Proper speaker wire is usually marked in some manner to identify pos and neg. Could be a ridge on one side if colours are same

 

[Profpointy]

You can tell live from neutral with a multimeter (or a light bulb) but what you need to test for speaker polarity is phase : the signal alternates between +ve and - ve 440 times a second (for example, supposing your music of choice is a sine wave somewhere about middle C) , but if one speaker is wired backwards to the other(s) its cone will be "out" when they are "in" and vice versa, so will tend to cancel them out. The effect is more pronounced at lower frequencies, I speculate because (1) you need to move more air for the same perceived volume level, (2) speaker cones are physical objects with mass and momentum so tend to "keep up" better with a slower-moving input than a fast one.

umm 440 is concert A I think you'll find - the note the oboeist plays for the rest of the band to tune to

The.cancelling out explanation is partly right, but reason it's more significant for low notes is wavelength. For higher notes.the wavelength is relatively short so cancellation is as dependant on speaker disstance as much as phase
eg 20Hz wavelength 17m so out of phase will cancell out, but 20kHz 17mm so irrelevant. ok you arent going to here 20kHz but you get te idea.

PS i did have to check the numbers, I'm not quite.that.clever