How to Test a Subwoofer With a Multimeter?

How to Use a Multimeter to Check Blown Subwoofer?

Using a multimeter to check the blown subwoofer is a handy diagnostic tool for audio technicians. When the subwoofer becomes damaged, it can be difficult to tell from visual inspection alone. With a multimeter, you can measure the resistance of the voice coils and other components inside the speaker to determine whether they are still functioning correctly. Testing a sub is especially important for subwoofers, which are designed to produce low-frequency sounds that require a more significant amount of power than other components.

How to Check a Sub With a Multimeter?

You can quickly test the subwoofer with these simple steps:

• Disconnect your sub from the power source
• Disconnect all other connections
• Take your speaker out of the enclosure
• Get access to your subwoofer’s voice coil
• Connect your multimeter to voice coil terminals
• Turn on the multimeter to check Ohms ⁽¹⁾
• Evaluate your ohms to see if the sub is blown or not

1. Disconnect Your Sub From the Power Source:

Before you connect the multimeter to the affected subwoofer, ensure you have disconnected the subwoofer from any power source. Disconnection will prevent any damage to both the multimeter & subwoofer itself. Additionally, having an electrical source connected while taking readings can provide false results. Disconnecting the power source before connecting any electronic device, like a multimeter, is essential. Doing so will prevent any potential damage and ensure accurate readings.

2. Disconnect All Other Connections:

You will have to take your subwoofer out of the subwoofer box. Therefore, it is essential to disconnect all the cables and audio inputs to ensure you can easily remove your sub.

3. Take Your Speaker Out of Your Subwoofer Box:

Removing the subwoofer from the subwoofer box is essential for a few reasons. First, it allows you to connect directly with the speaker and measure impedance more accurately without disruption. When measuring through a speaker’s connection terminals, acoustic loading from the enclosure can affect the impedance, making it harder to show the accurate reading.

Taking the speaker out of the box eliminates this issue and gives a more accurate measurement. Additionally, when taking measures from inside the box, you risk creating an electrical ground connection with other components, which can do inaccurate readings.

For removal, start by carefully removing the screws or bolts that hold the subwoofer in place. If necessary, use a screwdriver or wrench to loosen any tight bolts. Once you remove the bolts and screws, gently remove the sub from the box by pulling it toward you. Be careful not to drop or damage the subwoofer in any way.

4. Get Access to Your Subwoofer’s Voice Coil:

You must get direct physical access to the voice coil to check its electrical resistance or other electrical parameters. When checking the resistance of a voice coil, it is necessary to ensure that you are measuring the actual resistance of the coil- not just the resistance caused by other components in the circuit. By taking access to your voice coil, you can be sure that any readings taken with a multimeter accurately reflect what is happening within the coil.

5. Connect Your Multimeter to Voice Coil Terminals:

You must first obtain a set of test leads to connect your multimeter to the subwoofer’s coil terminals. These are specially designed pieces of wire with clips at both ends to allow for easy attachment to the multimeter and speaker connections. Wire with clips is an easy way to hold the connection firmly.

Once the test leads are ready, attach the leads one by one to each terminal on the subwoofer’s voice coil. Be sure to connect the red lead (+) to the positive (+) terminal and the black lead (-) to the negative (-) terminal. (Positive and negative terminals connection is essential for an ideal checkup of the subwoofer.) Next, set your multimeter to a DC Voltage setting and similarly connect its test leads as you did with the speaker connections – one lead on each of the two terminals.

6. Turn on the Multimeter to Check Ohms:

To do so, ensure the multimeter is in the proper mode, and you set it to measure resistance in Ohms (Ω). To check for any fluctuations in resistance, use the “Ohm” or “resistance” setting on your multimeter.

7. Evaluate Your Ohms to See if It Is Blown Subwoofer or Not:

The ohm level of a blown voice coil will depend on the quality of the speaker and its type. Let me make it easier for you to evaluate your sub’s ohms level:

• A voice coil must work adequately with between 1.5 to 8 ohms of resistance for most subwoofers (This number can vary depending on the speaker’s size and type).
•  If your subwoofer is not functioning correctly or has been damaged, its voice coil resistance may be higher or lower than usual.
• If you get an OK reading, there will be a problem other than the subwoofer.

So, What’s a Multimeter?

A multimeter ⁽²⁾ is a device that enables technicians and engineers to measure voltage, current, and resistance. It is an essential tool for accurately troubleshooting and repairing electrical systems, as it can help diagnose problems in circuits, wiring, and other components such as speakers and amps. Multimeters are often used with oscilloscopes or other specialized equipment to analyze a system’s electrical signals further. Multimeters measure AC and DC voltage, current, resistance, capacitance, and other electrical properties.