What Happens If Speakers Are Wired Backwards?


Speaker wires are used to connect an amplifier to the speakers so that the audio signal can be transmitted between the devices. Speakers must be wired correctly if you want to ensure the best sound quality from your audio system.

What happens if speakers are wired backward?

Wiring speakers backward, causes them to be out of phase. Phase cancellation results in certain frequencies being reduced in the output, and it is detrimental to the audio quality. It also negatively affects the stereo imaging of the speakers.

When the polarity is reversed, the performance of the speakers is significantly altered.

Wiring speakers backward is an easy mistake to make, particularly if the wire is not identifiable by its color, or labeled clearly. In this comprehensive guide, we’ll look at the issues surrounding speakers when they are wired backward, and how you can avoid them.

Wiring Speakers Backwards

The reason that it’s important to wire speakers correctly, is linked to speaker polarity. Polarity is created when the wires are used to connect a speaker to an amplifier, so that sound can be played back through it.

The correct speaker polarity is achieved when the positive terminals on both the amplifier and the speaker are connected, and the negative terminals are also connected.

  • When speaker wires are wired backward, this creates what is known as inverted polarity, which is also sometimes called “reverse polarity”. This causes the speaker to move outwardly when it should be moving inwardly, and vice versa.

Reverse polarity leads to phase cancellation when more than one speaker is being used. Sonically, this causes certain frequencies to be canceled out and has an undesirable effect on the audio quality.

Wiring speakers backward won’t cause any damage to the devices, nor is it a dangerous practice. However, it will almost certainly have a negative impact on the way the audio sounds as it is outputted by the speakers.

  • If you notice that your speakers don’t sound particularly good and that certain frequencies seem to stand out significantly over others, there’s a good chance that you’ve accidentally wired your speakers backward.

By swapping the speaker wires and connecting them to the opposite terminals, you can easily rectify this issue and enjoy the full quality of the audio playback that your speakers and amplifier are capable of.

What Color Is Positive & Negative Speaker Wire?

Speaker wire is different from other cables which transmit audio signals in several ways.

Firstly, it is much thinner than an instrument or microphone cable. It is also often color-coded, which makes it easier to remember which wire is positive, and which is negative.

The vast majority of speaker wires are color-coded as follows:

  • Red for positive
  • Black for negative

The color of the speaker wire should match up with the color of the plastic outer coating on the terminal of the amplifier.

By simply connecting the colors to their relevant terminals, you ensure that the wires are positioned correctly.

In some rare cases, speaker wire may not be color-coded. If this is the case, there are some additional ways to check that you haven’t wired them up backward, which will negatively impact the sound they produce, as I explained earlier.

The first way to check that your positive and negative speaker wires are hooked up to the suitable terminal is by simply listening to the audio. If you notice disruptions, dynamic inconsistencies, certain frequencies sounding weak, or interference, there’s a good chance your speakers are wired backward.

Color-coded speaker wire is very easy to find and doesn’t usually cost much money, so I would recommend investing in some if you are struggling to determine whether your current set of wires are connected backward or correctly.

Check out this article to see which thickness of speaker wire you need.

If you remember that most of the time red is the positive wire and black is negative, you should be able to easily connect the wires to the amplifier terminals and be confident that they are set up correctly, which will ensure maximum sound quality and minimize potential problems. 

Check out this useful YouTube video that explains speaker polarity.

Is Grey Speaker Wire Positive or Negative?

Speaker wire has two strands, which are different colors. This makes it easier to ensure that the positive and negative wires are connected to the appropriate terminals on both the amplifier and the speaker.

As I previously explained, most speaker wire manufacturers use the universal color coding of red for positive, and black for negative. It’s quite rare to find speaker wire which isn’t color-coded in this way, but it is still possible.

  • If speaker wire isn’t colored red and black, the chances are it will be colored grey and black.

This may lead to confusion, especially if you’re used to using speaker wire with the traditional color-coding which is also shared by most positive/negative electronic cables and devices.

If you have one grey wire and one black wire, the key thing to remember is that black is always negative. Grey, in this example, has simply been used in place of red, and consequently, it is the positive wire.

  • This means that you should connect the grey wire to the positive terminal on the amplifier, while the black wire should be hooked up to the negative terminal.

Doing so will ensure that reverse polarity doesn’t occur and that the signal can be transmitted as intended.

If for some reason you have two wires which are both grey, the only way you can tell which one is positive and which is negative is by using your ears.

Connect one wire to the positive terminal of the amp, and the other to the negative terminal. Listen out for any inconsistencies or weak spots in the output.

I have written an article on using speaker wire for 12v power. You can read it here.

Then, repeat the process by connecting the wire ends to the opposite terminals. If you notice an improvement, this is likely to be the correct way to wire up your speakers.

If you notice a lessening of audio quality, the wires a likely to have been wired backward.

If you have ever wondered why some speakers have 4 terminals be sure to check out this article.

What Happens if You Connect Positive to Negative on Speakers?

Connecting positive speaker wires to negative terminals will lead to several issues. Thankfully, these issues are quite easy to notice, and therefore you should be able to rectify the problem and identify it quickly.

The most common result of connecting the speaker wire backward is that the bass response becomes weaker. When the polarity is reversed, bass frequencies suffer the most. This is a result of how bass tones are produced by a speaker cone.

Low-end frequencies are produced as a result of the air pressure in the small area which surrounds the speaker. An out-of-phase signal causes the bass woofer to move inward when it is supposed to move outwards.

This will cause the kick drums, bass guitars, sub-bass, or lower tones of a vocal track to be essentially cut out of the speaker’s output.

There may be a very small amount of bass frequencies still produced, but on the whole, the audio will sound like it is missing its low-end thickness.

The second thing that is likely to occur when you connect positive speaker wires to negative terminals is that the stereo imaging will be messed up. This means that the panning of the various instruments or other elements of the audio will become chaotic.

  • Reversed polarity causes the stereo information to be skewed, so the speakers have no way of knowing which sounds are meant to be panned to which side of the stereo field. This creates a narrow, lifeless effect.

Another likely side effect of wiring your speaker wires in reverse is the diminishment of high frequencies. The focus of the treble frequencies is diminished when phase cancellation occurs.

Much like the effect that backward wiring has on the bass frequencies, it should be quite easy to notice when the treble end is being affected by this problem.

Finally, and perhaps most significantly, wiring the positive to the negative on a speaker will cause phase cancellation. This is every musician and recording engineer’s nightmare, as it can destroy the frequency output produced by the speaker.

Phase cancellation is a strong sign that your speakers are wired backward, and can be rectified by simply swapping them over.

Related Questions

What gauge speaker wire should I use?

If your need long wires to connect your speakers to an amplifier, it’s recommended that you use a thick variety. 12 or 14 gauge speaker wire is suitable for this. If the wires are kept short, you can use 16 gauge wire to form the connection.

What is the difference between speaker wire and electrical wire?

Speaker wire is designed for transmitting audio signals which have a very low voltage. Electrical wire, on the other hand, is often designed for higher voltage currents and it is a more multi-purposed wire.

Does speaker wire affect sound quality?

Speaker wire should not impact sound quality, as long as it is in good condition. The only time it may have a negative impact on sound quality is if the ends have become damaged due to wear and tear.

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