How to test which speaker wire is positive or negative?

Discussion in 'Electrical & Interior - Security, ICE, Wiring Loom' started by Space Cadet, Jul 27, 2017.

  1. I’m fitting some new speakers front & rear at t’weekend and rather than faffing with connectors from the car’s existing speaker cables to the new speaker’s terminals I will just crimp or solder on some new spades (plus its one less connection in the circuit).

    Question is please - how do I test which is positive and negative, I’ve Googled it and one result came up as “Multimeter to the rescue! Simply turn your radio on to low volume and pull the speaker out, and you are ready to test for voltage. Turn your volt meter to 20V DC and put the negative probe on a chassis ground and put the positive probe on one of the speaker terminals. The one that has a voltage is going to be positive. Most vehicles have a black or white stripe on the positive wire, but there’s always the chance that they are incorrectly marked.”

    I think they mean put the positive probe on the speaker wire terminals.

    Is this a correct way of testing?

    I know you can hook a speaker up and see if it is in phase, but what if all speakers are out of phase, I was just hoping to find a multimeter type way of testing them like testing which wire is live in the house.

    Last edited: Jul 27, 2017
  2. If they're all out of phase, then they're in phase! :grin:
  3. Smart arse - they could all be pulling, rather than pushing, at the same time, in which case they would all be in the same phase but out of phase.

    Now can anyone provide any constructive help please?
  4. Find a picture of the dacia adapter, that should tell you which side is + and -.
  5. Thanks, I know there are various ways around it, but surely there is a definitive way of testing with, for example, a multimeter....

    What would happen if the Dacia connector was incorrect, or the Renault loom was incorrect?? - Testing which wire is live (if its possibly to do so??) would negate all that.
  6. And in a moving car, that matters why?
  7. An oscilloscope would show you.

    You might be able to do it with a multimeter, though never tried. Just check the potential between the chassis and one wire while playing music. It's not a DC voltage though so I'm not sure how well it'll show up but if it comes out wiht a +ve voltage then you know which it is and if it's -ve well there you go.
  8. Thanks, sounds feasible doesn't it, will let you know if it works!
  9. Gavin.

    Gavin. RSM Admin

    I've normally done it by ear in the past, I find it cause the sound to be lacking/flat when out of phase. Not that my ears are tuned perfectly, always just been a guess.
  10. I'm sure they will be wired up perfectly by Renault to start with and it will be obvious from the wire or the speaker terminal which is positive, I was just hoping it may be easy to test for certain with a multimeter.
  11. when you put your hand in front of the speaker at a high volume you should feel some air blowing away from the speaker
    if you plug them wrong your speakers will not blow air but suck it instead which you cannot really feel but the sound will sound flat anyway.
  12. Thanks for everyone's mostly constructive help, but my question was is it possible to test using a multimeter.

    It seems like possibly it is and I'll give it a go at the weekend.
  13. Can you not just put a low voltage battery across the terminals and see which way the speaker cone moves?
  14. God this is hard. Its the speaker wire I want to test and not the speaker! - I want to know if its easily possible to test with a multimeter. Simple question - simple answer (hopefully).
  15. Step 4 tells you how to test the wire?
  16. Thanks Mikey, I cant view the link at work, will take a look tonight.
  17. It's not hard.

    It doesn't matter as long as they are all the same and you can do this by listening. Good chance are they are wrong somewhere in the loom anyway, and if this offends you, maybe Renault's aren't for you.

    Jimbob 2705 likes this.
  18. For those that are interested – it worked!

    I set the Multimeter to DC20 and with the stereo playing if I connected the positive and negative probes to the car’s speaker cables one way the Multimeter read as a “+” (and a value) and if I swapped them around it read as a “–“ (and a value). So I was able to confirm which car wire is positive and which is negative!

    There is no logic to the colouring of the car’s wires as they don’t match front and rear and the positives are not for example all solid-colours or striped. None are marked positive or negative and neither are the speakers themselves, so apart from listening or watching the speakers once connected the Multimeter test is a great way of knowing for certain.
  19. But you missed that vital bit of information on which way the electrons flow, or in more simple terms, the multimeter probe colour conundrum.
  20. I knew it was too good to be true!

    So what may be wrong (in Layman’s terms please) with my findings above and what should I do instead??

  21. Nothing. As long as you know the basic physics of electron flow. Sort of basic stuff really, but as 99.99% wouldn't even know what a multimeter is, it's worth mentioning the difference between a red and black probe.
  22. Phew, thanks.

    (Funnily enough when drafting it I actually deleted “Red” and “Black” from my post as I assumed all would know the colour-coding for positive and negative.)
  23. I reckon most people would know that, but if you asked when you stick a red probe on an output and the black on the other and it reads neg, what does that mean? People are more likely to know the size of Jordan's tits.
  24. Right, I’m getting there but the plot is thickening….

    I have tested all the speaker cables to the front tweeters, front mains, rear tweeters and rear mains. All positive wires are thankfully the same cream colour, but the front negatives are green and the rear negatives white. So all hopefully seems well on that front.

    I have tested with an AA-battery the polarity of the 4 old main speakers that came of the front doors and rear sides and all have the same polarity, however it appears the front two were wired out-of-phase and the rear two in-phase, i.e. the positive wire was connected to the positive speaker terminal.

    If anything though the rear speakers sounded dull and the fronts “ok”……

    The car didn’t come with any tweeters at all and I have bought the Pioneer ‘custom fit’ set (which actually doesn’t fit without new speaker wire plugs and speaker spacers, but that’s a separate rant!) The front tweeters (if the terminals are connected in the same orientation as the mains) suggests that the car’s tweeter speaker cable plugs are the wrong way around – as it appears were the mains.

    Although I didn’t have any tweeters in the rear, and am not going to fit any, the speaker cable plugs look to have been wired correctly.

    Is there anything that I am missing here? – is there any logical reason why the front tweeters & mains would be wired the same way around but out-of-phase, whereas the rear tweeters & mains are wired the same way around and in-phase.

    As mentioned though the original fronts actually sounded ok and the rears dull.

    I have triple-checked I’m using the Multimeter correctly, its set to DC20 and the probes are definitely the right way around, so I’m 99% sure I’ve checked all the cable polarities correctly and hopefully this is backed up by all the speaker wire positives being the same cream colour.

    Also does anyone know how to test the polarity of a tweeter, I tried using the AA-battery test and the dome didn’t move at all.

    This is driving me nuts so any constructive help would be greatly appreciated!!
  25. I am dubious about being able to check the polarity of a speaker with a multimeter. Measuring DC up to 20V doesn't sound right because audio is a sine wave, thus AC... the polarity will be constantly changing.

    What you need to have is the polarity changing at the same time as the other speakers. Whilst Renault are historically bad, they aren't going to mess something up like running cables to speakers, they will have a coding system for the wires and they will be routed according to CAD software.

    Speakers are a head ache because you can't even test for continuity to the wires, there is continuity all of the way through a voice coil so both the positive and the negative side of the speaker will ring through to the head unit positive.

    I have only changed the front speakers in mine because the rears really aren't going to make much difference, only adding a bit of sound fill. I'll check what coding system I used when I get home, but I found a guide out there which described the colour coding system.

    As for the tweeters, there are unlikely to be cross overs in the system so there will be a direct feed from the positive door speaker to the positive tweeter. In this instance you can test continuity, disconnect the positive speaker cable from the speaker, place your probe on the wire and see which tweeter wire rings through (tweeter should be disconnected).

    If you do it this way the two front speakers (plus tweeters) will be in phase with each other and that is what matters the most, you don't go to a gig and stand with your back to the people playing.

    You can determine whether or not the rear speakers are in phase with your fronts by the ear. It will be obvious, and if you cant tell then surely it doesn't matter. Bass is the easiest to hear with phasing, so crank the bass up high on the speakers, set the fader to the front speakers only. Slowly move the fader to the center. Does the bass get higher, stay the same or get lower?

    If the bass gets lower your rears are out of phase.

    Hope this helps.

    Edit: If I remember correctly, I looked a dacia speaker cable adapter. This adapter identified which end of the plug was positive and thus determined which wire was what.
    Space Cadet likes this.
  26. have you tried bypassing the cars cabling for the speakers and wire it up yourself just to test them and see if it sounds any better?
  27. Assuming you know the pinout for the head unit, pull the head unit out, disconnect the speakers and use the multimeter to check resistance from the wires coming out of the head unit through to the speaker terminal connections. This will give you the definitive answer on what is positive and what is negative for each wire, as you're checking from source to destination.
  28. Thanks mate, much appreciated.

    Just to confirm, I haven’t tested the speakers using a Multimeter, only the cables and I followed various identical guides on t’net. But as mentioned all the cables which I got a positive reading on are all the same colour, so unless this is just total randomness hopefully the test worked correctly and they are all in fact positive.

    I don’t think Renault have totally messed-up, I think possibly it’s just that the fronts are all in the same phase but possibly out of phase (with positive cables to negative terminals) and the rears are all the same phase and in-phase (with positive cables to positive terminals).

    If you could find that guide it would be really appreciated, thanks.

    With regards the tweeters, as far as I understand from various sources there is no external crossover either in-line on in the head-unit itself, the tweeters apparently have the ‘resistor’ (or whatever it’s called) built into the back of the tweeter itself and therefore the tweeter and main speaker receive the same signal from the head-unit (theoretically the standard main speaker also plays some of the high-range as it doesn’t have a resistor on it). This seems to be backed up by the Pioneer set I have bought as both the tweeters and main speakers have the resistors built into the back of them.

    Working on the basis that I’ve found all the correct positive cables and I know the polarities of the new front and rear (2-way) main speaker I can easily connect them and hopefully in-phase, if for some strange reason they are out of phase then I can easily swap them over. Thanks for the bass tip; I will try this to double-check!

    It’s been good to talk this through because other than the front tweeters I think I’m ok with it all, it’s just now how do I know whether the tweeters are in-phase with the front mains? There is no marking on the tweeters to suggest which terminal is positive or negative.

    The new Pioneer set speakers have the same female socket in both the main speaker and the tweeter, if the sockets are the same polarity in both (which logically makes sense) then my current wiring needs to be swapped for the tweeter and also the main door speaker.

    I’ve just made myself a bit doubtful about all this and if there was a definitive way of test the tweeter polarity I’d really like to try it so I know for 100% certain. My hearing isn’t fantastic so I don’t want to rely on it for testing if I could do it mechanically/electronically somehow.

    Thanks regarding the Dacia adaptor idea, in theory though this would just connect my positive cable to the negative terminal again. As I’ve got to join new cables with tweeter plugs onto the existing main door cables and new cables with traditional spades onto the rear main cable will make sure I get the polarities correct first before soldering.
  29. Thanks, no I’ve not tried that and as I’m still using the standard head-unit it would be impossible for the time being. It’s probably on the cards though me getting a new-head unit so rather than using new cable I will just check the continuity of all the cables then and where they definitely go.

    I’ve done installs in the past with new complete uninterrupted speaker cable running from the amps to the speakers, its satisfying knowing for definite that you have everything the right way around.
  30. Thanks, as above really - its something I will double-check when/if I get a new head-unit.
  31. I'm surprised there are no marking on the tweeters for polarity. Traditionally you will get a black (neg) and black/white stripe (pos), but sometimes you get random colours which doesn't help. In standard form, the bigger spade will be positive with the smaller spade being negative on speaker connections.

    Edit: Confusing myself now on colour coding. Believe its opposite to what I originally said, black / white being pos and black beging neg.
    Last edited: Aug 3, 2017
  32. To make things more interesting, I've found a note I made on the speaker polarity from a guide (which I'm yet to find).

    The note says Green / Brown are + and White / brown are -
  33. The concept would be that you don't put the meter across both wires but only from one to ground or the chassis, meaning to only get the +ve or -v voltage.
    crowdie likes this.
  34. Thanks guys!!!

    There are no markings whatsoever on the tweeters and because they have a female socket with two identical pins inside I cant tell which is pos/neg. There aren't the traditional big/small spades...

    So if the green-brown wires are positive then perhaps my front tweeters and mains are in fact wired correctly and possibly therefore my rears are out of phase....??

    But I've tested the wires for polarity, but have I actually done it the right way??? - "The concept would be that you don't put the meter across both wires but only from one to ground or the chassis, meaning to only get the +ve or -v voltage."

    ....So I connect the black/negative probe to the chassis and then the red/positive probe to one wire at a time to see which is which. I totally understand this, but wouldn't the negative wire be grounded anyway???

    Would I get a different reading doing it this way to 'my' way?

    I genuinely really appreciate your help, thanks again!.
  35. That makes more sense, cheers!

    Speaker wire negatives aren't the same as typical electrical negatives, they return to the head unit. I believe the term is floating, so no they wouldn't be grounded.

    You may well do, I'd be inclined to re do the rests this way and see what happens.
  36. Again, thanks.

    In the meantime I’ve spoken to a very helpful mobile car stereo guy near me (was hoping to book him for tomorrow but he is fully-booked for weeks and therefore gave me loads of free advice!!), he agreed that I’d tested the speaker cable polarity the wrong way and to do it with the black/negative probe to the chassis.

    May be this will produce completely different results to ‘my’ way and I may find all the car speaker cables are in fact correct!? – or perhaps just the rear are incorrect which would explain why my old rear speakers sounded so flat.

    He also said that it’s impossible to test a tweeter’s polarity and was surprised that there wasn’t any marking on mine. But he also said as long as they’re in-phase left to right that it doesn’t matter whether they’re in phase to anything else (not on a ‘normal’ system at least) because without the markings or posts you can’t tell which way to wire them.

    So, I feel a bit more positive (no pun intended) now about it all, I will test the speaker wire polarity again tonight and see what I come up with.

    And the cables that go into the plugs that in-turn fit into the sockets on the back of the tweeter have got to be fitted one way or t’other, in which case I’ll keep them the same orientation as the cables that go into the main speakers and assume that Pioneer wired their sockets the same way around for both the tweeters and the main speakers (which makes logical sense).
  37. Right, I fitted all the speakers last night.

    I first tried to test the polarity of the speaker cables again using the new multimeter test, but it gave the same reading on both wires.

    'My' way of testing them gave the same readings as before and seemed to tie-in with the guide that Crowdie kindly PM'd me, i.e front green-brown wires are positive.

    Serves me right for working late at night in the dark but when I said that all the cream wires were positive, actually the rear creams were positive and the front greens positive and all the whites front & rear were negative. This ties-in with the guide and logic that all whites are negative.

    So I soldered on all the correct speaker plugs and spades, bolted on the speaker spacers and fitted the speakers....

    I think the rears are out of phase with the fronts! - so obviously somewhere my logic or meter readings are out, I knew they would be!!

    What the mobile audio guy told me yesterday though was not to worry too much about matching the colours of the wires and testing the polarity of the wires or speakers because there will always be something out. But what they do is hook everything up and then test the speaker polarity using an AA-battery on the speaker cables in the connector at the back of the head-unit and if need be pull the pins out and swap them over. This then allows for any crossed wires, or incorrect coloured wires etc etc.

    So next job for me will be to pull the standard head-unit out, which I started to do last night. Does anyone please have a guide for the connections on the back of the head-unit (standard 250 model)?

    Or, I may just bite the bullet and put a new head-unit in while I've got the old one out, but then this means having to get all the new loom connectors which looks like a mine-field.....

    So, I'm getting there. Slowly!
  38. In the end I ordered a new head-unit and connectors. Because I had the old head-unit out I was able to test the speaker polarity at source in the connector-block and bonza - one of the rear speakers was out of phase. It was wired using the same colours as the other rear but for some reason somewhere in the car's loom there must be a mix-up. Anyway I pulled the pins out of the connector-block and swapped them around then triple-checked all speakers and thankfully they are now all correct!!!!!!
  39. I was playing with my system yesterday and I figured I'd try the test out of interest. All four wires read +5.7V against ground, and the more I think if it the more this is to be expected.

    The speaker signal is sinusoidal, it will be both positive and negative on ALL wires at difference points in time so I can't see this test being an effective way of measuring polarity.

    Short of getting an oscilloscope I'm not convinced you can test the phasing with a multimeter - it's not what they are designed to do. Your best bet would be to trust the manufacturer wiring, its a lot more likely to be right than any of these tests.

  • Share This Page

    1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
      By continuing to use this site, you are consenting to our use of cookies.