Are Car Speakers AC or DC


Car speakers cannot operate themselves, and to function correctly, they need an amplifier.

Speakers are just transducers. To produce sound, speakers take an amplified electrical signal from car amplifiers and then convert it into mechanical energy, which moves the speaker cone back and forth.

Although all of us use the car speakers daily, many wonder if speakers are AD or DC? Well, let’s find out.

As a general rule, all car speakers are AC because the alternating signal from the amplifier powers them. It is the change in polarity of the current which produces sound.

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Tip: To verify whether car speakers are AC or DC, you can set a multimeter to ~ AC VOLTS at the output terminal of the amplifier and play a tone. You will see voltage fluctuation in the terminal.

If you do not have a multimeter at home, I recommend using a Crenova, which is easy in daily usage and can measure not only all the electrical parameters but also a surface temperature.

The Amplifiers use a DC input power source, and they have built-in transformers which convert DC into AC. 

Why Do Car Speakers Use AC Rather Than DC?

AC is a type of current that alternates its direction of flow, and frequency is the number of cycles per second and is expressed in Hz. DC, on the other hand, flows in one way and does not change its directions. 

A direct current will not make any sound because it moves the cone either in or out.

In contrast, the alternating current will move the cone both in and out due to a change in the direction of the current. That makes AC suitable for speakers. 

How Are Car Speakers Powered?

An amplifier powers the car speakers via speaker wire. The amplifier has a negative and positive wire at the output, which is input to car speakers. 

These wires send amplified signals to speakers at various frequencies. Then the signal is transferred to the mechanical energy and is passed through a voice coil. 

The current from the amplifier induces an electromagnetic field inside the voice coil. Since the magnet is fixed and with a change in frequency, the voice coil moves freely. 

Both speakers and amplifiers have positive (+) and negative (-) terminals. Therefore, always connect the positive terminal of the amp with the positive terminal of the speakers and the negative one with the negative ones. 

If you interchange and connect positive with negative terminal, then the output of all speakers will be unsynchronized and unpleasant to our ears. 

Let me show you the waveforms of speakers A and B.

Case 1 – When the same terminals are connected. 

car speakers connected with correct polarity

In this case, speakers A and B positive terminals are connected to the positive polarity of amp and negative vice versa.

output from speakers in correct polarity

The output of speakers A and B is synchronized and in phase with each other. Therefore, the resulting output is higher in amplitude without noise when all speakers are connected in the same way. 

Case 2 – When positive and negative polarities are interchanged 

car speakers connected with reverse polarity

In this arrangement, I connect positive and negative terminals of speaker A with the positive terminal of the amplifier and the same with negative. 

Just interchange the wiring of speaker B – positive of the speaker with negative of amp and so on. 

noise from speakers in reverse polarity

The outputs from speakers A and B are out of phase resulting in noise. 

What Voltage Do Car Speakers Run At?

Car audio equipment is designed to operate at lower impedance than home audio appliances. 

Car amplifiers have to supply enough voltage to car speakers to get power output (sound) at realistic listening levels. 

Most car speakers have lower impedances around 4 ohms. So to deliver 100-watt output from standard 4-ohm speakers, it takes peak to peak 60 volts. To achieve this, the amplifiers are set at +30 V and -30 V.

According to ohm’s law 

P = E2/R                    E = Voltage and R = impedance

The power doubles each time as you lower the resistance by half. 

As we know, there is a limited amount of voltage available in the car stereo, approximately 13.8 volts.

Therefore we have only 13.8 volts to apply to our car speakers, and if the speaker is of higher impedance, it will not be able to produce sound.

The Head unit’s internal amplifier cannot drive even up to one-ohm resistance. So we need power amplifiers to amplify the signal. 

The amplifiers have internal step-up transformers. A step-up transformer converts lower voltage alternating signal to higher voltage signal by stepping it by.

For example, if you have a 1:2 step-up transformer, it will convert 12 volts into 24 volts. 

Do car speakers use alternating current?

YES, the car speakers use alternating currents to produce sound. 

The voice coil in the speaker is nothing else than an electromagnet. The electromagnet is a coil of wire usually wrapped around a piece of magnetic metal such as iron.

Unlike permanent magnets, electromagnets can reverse their polarity with a change in the current direction, between north and south pole polarity. 

As we pass alternating current from the amplifier, an electric field is induced, constantly pulling the cone inwards and outwards. Repeated motion of the cone creates sound waves in the air. 

This cone’s motion depends on the frequency output of the amplifier, and several frequencies are played simultaneously, all at the same time ranging from 20 Hz to 20 kHz.

The more complex a sound wave is, the harder it is for the speaker to produce sound. 

To maintain the quality of sound, more than one speaker has to be connected to the system.

This type of system does an excellent job of splitting the frequency spectrum among different speakers. This reduces the workload from the speaker and helps produce accurate sound quality.

The splitting of frequencies and sending them to different speakers is done by using crossover networks. The most common crossover network is two-way crossover.

There are two types of filters in the two-way crossover – low pass filter and high pass filter.

The output of the low pass filter goes to the speaker responsible for producing low-level frequency signals. The output of the high pass filter goes to the speaker responsible for high-level frequency signals. 

Can I Convert AC Speakers to DC?

You can convert the AC speakers into DC speakers, and to do this, you must know electronic circuits and soldering skills.

For this task, I recommend you take help from a professional. The converting process, although not too complicated, is time-consuming. 

To do this, you need a rechargeable lithium battery of 12 volts for car speakers, soldering equipment, multimeter, loose wires, and clips. 

  • First, remove the speaker and circuit from the case carefully.
  • Now on the circuit board, you will see various capacitors, diodes, a transformer, IC, etc. 
  • Locate the ac source on the circuit board with the help of a multimeter. Usually, this point is located near the big capacitor and then solder two wires at each end. You will use these wires to connect the positive and negative terminals of the lithium battery. And now connect the speaker to the circuit board. 

When the battery is connected, you can check the circuit by giving any sound input to the speaker. Of course, you will hear some noise, and you will have to adjust volume, bass to fine-tune the output. 

Conclusion 

As we have gone through a lot of detail regarding car speakers, you get an idea of how your car speakers work.

All car stereos use speakers which operate on AC and being powered by AC.

The proper wiring of car speakers with an amp will result in good sound quality and makes your journey memorable. 

Martin

Welcome to ImproveCarAudio! I am Martin, and I love to write about everything related to car sound systems. I strive to provide the most accurate and helpful information about car audio through extensive research, as well as my experience with car audio installations.

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