Phase

Speakers are a complex electromechanical machine that vibrate and move air to produce sound. Sounds simple. But what many people do not understand is just how a speaker receives a signal from the radio or amplifier which powers it.

All electronics in a vehicle will operate on 12 Volts DC, or direct current battery voltages. But, a speaker will not operate properly if DC voltages are applied to a speaker. So what happens? The amplifier, whether internal to the radio or a separate amplifier connected to the radio, will convert an audio signal from the radio to a very low AC voltage.

For a speaker to make sound, it must move IN and OUT. But to do this, the audio signal that is given to the speaker through speaker wires must change polarity. Or more simply, the voltage waveform of the audio signal must switch between (+) positive and (-) negative polarities very quickly. When a this happens, the speaker will move in for (-) negative signal and move out for (+) positive signals. This is a simplified overview of how a speaker vibrates in and out, producing sound. This is a very important concept in mobile electronics.

POLARITY: is the part of the voltage waveform that is currently active. The part of the waveform that is (+) is considered positive polarity, and the part of the waveform that is negative is considered negative polarity. You might notice that speakers connections are marked (+) positive and (-) negative so that you connect the (+) positive speaker wire to the (+) positive speaker connection and that you connect the (-) negative speaker wire to the (-) speaker connection.

In reality, a speaker is NEUTRAL or doesn’t have a (+) positive or (-) negative to it. The marks on the speaker indicating (+) positive and (-) negative are there so that you connect ALL of your speaker the same way. WHY? Well, polarity. When all speakers are connected the same, all (+) positive speaker wires connected to (+) positive speaker connections, etc., then all speakers will move out at the same time and move in at the same time. When all speakers are connected the same, the speakers are said to be “in polarity”. What happens if speakers are “out of polarity”? Lets say there are (4) four speakers in a vehicle, (3) three of which are connected the same, but (1) one is connected “out of phase”. That one speaker will move opposite of the other three and cause problems. The amplifier that is powering the four speakers will, internally, see an “out of phase” problems. When an “out of phase” problem exists, the overall sound from the speakers will sound different. What happens inside the amplifier is that the AC voltage waveform powering the “out of phase” speaker will be opposite of the other “in phase” waveforms. When this happens, the “out of phase” waveform signal will CANCEL out one or more of the “in phase” waveform signals powering one of the “in phase” speakers. When two waveforms cancel each other out, a flat waveform exists. Speakers will reproduce this flat waveform in the form of dull or lifeless music.

Many amateur installers or listeners cannot tell when a speaker is out of phase. To these people, the music reproduced by the speakers sounds odd, but they do not know how to solve the problem - finding the speaker “out of phase” and flipping the wires until the speaker is “in phase” with the rest of the speakers. When this happens, the sound immediately improves and the amp is not fighting itself internally.

AC Voltage Audio Waveforms