Determine speaker power wires polarity - Page 1
Forum section: electronics / beginners

author: jotwerde
author_rank: Contributor
timestamp: October 31, 2018, 07:39:32 pm
content: Someone gave me their speakers of which the power cable (cable from outlet to speakers) is cut at one point.The separate wires of the cable are identical to each other (no distinct color of isolation or cables). The isolation is transparent and the wires are both silver-gray.Is there a way to determine which wire to connect to which?Does it even matter in the case of speakers?Here's an (rather ugly) image to illustrate what I mean:

author: helius
author_rank: Super Contributor
timestamp: October 31, 2018, 07:46:19 pm
content: One wire is the Line, and the other is Neutral. In most cases they can be exchanged without any problem. In particular, equipment marketed in Europe should be perfectly safe because the CEE7/4 plug used in Germany can be inserted either direction.This is a separate issue to the phase of speaker cables; in powered speakers, this issue doesn't crop up.

author: The Soulman
author_rank: Super Contributor
timestamp: October 31, 2018, 08:05:56 pm
content: Quote from: jotwerde on October 31, 2018, 07:39:32 pmTypical power cords are brown/blue on the inside are you 100% sure it is a power connection?Do you have a (internet) picture of these speakers or a manufacturer name and model number/name that we can google ourselvesso that we all can sleep a little bit better?If it is mains connection than it shouldn't matter.

author: johnkenyon
author_rank: Regular Contributor
timestamp: October 31, 2018, 08:09:44 pm
content: In my experience, speaker wires are marked in one of three ways, different colours, white stripe, or moulded ridge on one side.If your wires don't have any kind of colour code (e.g red+black, or black+black with white stripe), then use your fingers to touch the cable - specifically feel the side of each wire opposite where it joins the other wire - you will find one side will be round, and the other will have a ridge.Poor ASCII art:(o)(o>o represents the copper core of each wire the other symbols represent the outer insulation.

author: Audioguru
author_rank: Super Contributor
timestamp: November 01, 2018, 12:02:32 am
content: The mains electricity plug was cutoff, not the speaker connection to its amplifier.Modern plugs are polarized so that the widest blade is the Neutral connection. Then the Neutral wire connects to the non-sensitive power input to the amplifier in the speaker to avoid hum.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: November 01, 2018, 02:03:29 am
content: Look at the main power switch. If only one leg of the power is switched, it is the hot. You might find some markings on the PCB.

author: tooki
author_rank: Super Contributor
timestamp: November 01, 2018, 03:15:25 am
content: Quote from: Audioguru on November 01, 2018, 12:02:32 amOnly on NEMA plugs.European 2-prong plugs do not have any mechanism to enforce polarity (two identical round pins), nor do the most common European 3-prong plugs. (Within Europe, only the UK, Danish, French, and Swiss sockets enforce polarity on 3-prong plugs. However, because the French sockets are normally used with cords that are compatible with both the French- and German-style plugs, the latter of which does not enforce polarity, any appliance sold in Europe must accept either polarity without restriction.)

author: tooki
author_rank: Super Contributor
timestamp: November 01, 2018, 03:18:31 am
content: Quote from: jotwerde on October 31, 2018, 07:39:32 pmSo we are talking about the AC line cord for speakers intended for use in Europe? Then it doesn't matter. (Obviously, if it's a grounded cord, you must determine which is the ground.Can you open the speaker housings? I'd recommend replacing the line cord if possible, instead of repairing it.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: November 01, 2018, 03:48:30 am
content: You need to make sure the hot wire is switched off. That does matter.In the US single pole light switches go on the hot line. If you do it the other way around it's against code. You can be shocked if it's done backwards and your changing the bulb.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: November 01, 2018, 04:01:53 am
content: I guess I am to be the one to ask the OP.Is this the speaker wires from the amplifier or is it your power cord wire to the speaker system that brings power from the wall?If it is the power cord, then there is a right way to connect them (as explained multiple ways above). If it is the speaker wires from the amplifier, then it doesn't matter much.

author: cdev
author_rank: Super Contributor
timestamp: November 01, 2018, 04:12:29 am
content: If you are talking about speaker phasing, not power for amplified speakers, face the two speakers towards each other with the fronts facing one another but not touching, then put the source on mono and the right way to connect them is the way that sounds markedly louder. Its best to use a wire where you can clearly tell one side from the other, just be consistent with both sides, yes it does matter a lot. All speakers sound like crap if they are wired out of phase.Quote from: jotwerde on October 31, 2018, 07:39:32 pm

author: tooki
author_rank: Super Contributor
timestamp: November 01, 2018, 06:00:25 am
content: Quote from: JustMeHere on November 01, 2018, 03:48:30 amRepeat after me: in Europe, the polarity is not enforced by the plugs, so every device with a plugmustbe made to be safe regardless of polarity. This is why in Europe, devices with plugs must be double-insulated. (The only way a device can be sure of polarity is to be hard-wired.)The OP is in Bulgaria, which is part of Europe which uses the German-style socket, which does not enforce polarity even for grounded plugs. So any appliance used there MUST be designed to be safe with either polarity.For all intents and purposes, the Americas are the only place that still relies on polarized 2-prong AC plugs for safety in any way. (I suppose the Australian plug enforces polarity, not sure if they allow devices to rely on it, though.) But since more and more products are designed for world compliance anyway, they just properly double-insulate anyway.And why are you even bringing up light switches and sockets? We aren't talking about house wiring, where things must be done accurately. This is a plug-in device, which must comply with different standards separate from household code.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 01, 2018, 09:46:17 am
content: that doesnt matter...

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 01, 2018, 09:56:32 am
content: Are you talking about signal leads from an amplifier, or a mains lead to powered (active) speakers?Kinda important as if you get this one wrong you'll destroy them.Active speakers will also have some other signal input socket, such as a Cannon XLR or 1/4" jack. They will also have a rating plate stating the allowed mains voltage range.

author: jotwerde
author_rank: Contributor
timestamp: November 01, 2018, 06:54:28 pm
content: First, I wanna thank everyone for taking the time to post a reply.Quote from: IanMacdonald on November 01, 2018, 09:56:32 amQuote from: tpowell1830 on November 01, 2018, 04:01:53 amMains, thought this was illustrated in the image (by showing the plug at the one end). Am I maybe misunderstanding something?Quote from: JustMeHere on November 01, 2018, 03:48:30 amI live in Europe.Quote from: Audioguru on November 01, 2018, 12:02:32 amIt's aType Cplug (can be seen in the pic, maybe did't make it clear/good enough, sorry). No blades at all.Quote from: johnkenyon on October 31, 2018, 08:09:44 pmQuote from: The Soulman on October 31, 2018, 08:05:56 pmIt's the cable with the speakers at one end and the plug intended to be plugged into the wall socket on the other. It has to be the power connection.But the wires are both similar (look and feel).Here's a pic (or two):From tooki and Mechatrommer's answers I gather that it's safe in this case to connect the wires to either ones of the others, right?

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 01, 2018, 07:15:13 pm
content: If it is the common CEE 7/16 Alternative II "Europlug" (Type C), thenQuoteThe fact that it happens to be powering speakers is irrelevant to the discussion if you are talking only about the power mains cord/plug.That is what caused confusion at the beginning of this discussion.

author: Zero999
author_rank: Super Contributor
timestamp: November 01, 2018, 08:52:53 pm
content: jotwerde,Please attach the image, rather than using a hosting site. I was at work on my coffee when I saw this and the site was blocked by the firewall, so I didn't respond.Yes, the polarity of the mains is unimportant. It's AC and goes through a bridge rectifier, resulting in DC of the correct polarity.

author: jotwerde
author_rank: Contributor
timestamp: November 02, 2018, 08:02:40 am
content: Quote from: Hero999 on November 01, 2018, 08:52:53 pmCorrected the images. Was using the wrong sharing link, sorry.I don't like using attachments, using a hosting site and embedding the image is cleaner (at least when done right).Thanks for mentioning the bridge rectifier. Very insightful.

author: Zero999
author_rank: Super Contributor
timestamp: November 02, 2018, 10:48:53 am
content: Quote from: jotwerde on November 02, 2018, 08:02:40 amNow I can't see anything, as the firewall is blocking the image.It's possible to embed an attachment in a post. Attach the image, as usual, post it, click the attachment's thumbnail to open the image, copy the image location (the procedure for this, depends on what browser you're using), edit the post and paste the image's URL into the post between  tags.See the following thread for more information:https://www.eevblog.com/forum/chat/how-to-include-images-in-a-post/msg298580/

author: jotwerde
author_rank: Contributor
timestamp: November 03, 2018, 10:04:03 am
content: Quote from: Hero999 on November 02, 2018, 10:48:53 amOk, thanks, I'll keep that in mind for future posts.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 03, 2018, 12:03:47 pm
content: I just saw your drawing in op. Its kinda strange. How can 1 wire for each speaker?

author: bob225
author_rank: Frequent Contributor
timestamp: November 03, 2018, 12:22:44 pm
content: It seem like there is some confusion, so you want to know what's live and what's neutral ?Its a AC input the plug is not polarised or earthed so polarity shouldn't matter (like a electric razor)does the item have a fuse on the rear of it ? if so that will be live, trace it with a meterThe biggest question no one has asked, why was the plug chopped off in the first place?that sort of lead screams cheap Chinese cable ( copper coated aluminium )

author: jotwerde
author_rank: Contributor
timestamp: November 03, 2018, 02:15:25 pm
content: Quote from: Mechatrommer on November 03, 2018, 12:03:47 pmOops, that's a mistake. My fault.