Car amp turns on but no sound from subs [What To Check]

Many of us have experienced this infuriating situation where the car amp is working perfectly fine, but subwoofers refuse to toss out any bass.

If you’re in this fix right now, don’t worry because we’ve got you covered. Here, we will outline all the possible reasons when the car amp turns on but no sound from subs.

Without wasting any time, let’s look at the areas you need to explore to fix this problem.

Check the Amp’s Power

It is interesting to mention here that your amp might turn on even without receiving the required operating voltage. When this happens, the amp appears to be working, but the subs don’t produce anything. Many amps power on at 6-10 volts. However, they can’t amplify the sound signal and feed it to the subwoofer on this suboptimal voltage.

Check the voltage of the amp’s positive and negative terminals to make sure that this is not the reason behind dead subs. A voltmeter should give a 12-14 voltage reading for a perfectly working amp. If the meter shows anything below 12, you should check the power and ground wires at the fuse block, battery connections, grounding bolt, or any other point in their path where they can get loose.

Some amplifiers have built-in fuse switches that you need to inspect for their continuity after removing them from the amp. If the fuse has not blown, it will give close to zero ohms reading on the multi-meter.

Check the Amp’s Input

If the amp is working fine, but there is no sound in subs, you should also check the amp’s input connected to the head unit. Check the RCA cables used for this connection. If you have a header with multiple RCA outputs, check other ones. If you still don’t get the sound, check another set of RCA cables.

If these troubleshooting attempts don’t solve the problem, it indicates that the problem lies with the header unit rather than the amp. Get a 3.5mm-to-RCA adapter, plug it in your phone and the amp, and play something. If the subs come alive, it shows that your amp and subs are working fine, and a header needs a repair check.

Check the Amp’s Output

After checking the amp’s input panel and confirming that it is working fine, you have to inspect its output as well. Checking the amp’s output is rather easy.

All you need is another subwoofer or speaker for the testing. Start hooking up the test sub or speaker to every amp channel one by one. This trial testing will let you know if there is a problem with the amp’s output or if you have to look into the downstream (the sub and its connections).

The three sections outlined above help you determine if there is an issue with your amp or the header unit. If these tests and checks show that your amp and header unit are working fine, you need to look into subs.

See If The Subs Are Short-Circuited

Short-circuiting is one of the most common subwoofers and speakers problems. If any metallic thing has connected the positive and negative poles at the cone and terminal of the sub, it will immediately get shorted.

Many times users don’t find out about the shorting right away. They only come to know about it when the amp is turned on, but the sub doesn’t produce any sound. Check your subs with other amps and stereo systems. If there is complete silence, it shows that wires have been burned and no electrical signal is being transmitted to the sub.

Inspect the Cone Seal and the Electromagnetic Coil of the Sub

Doing this test is the last resort when your amp turns, but there is no sound from subs. This test is also one of the most detailed and delicate ones we’ve discussed so far.

Here, you will have to open the subwoofer and examine its internal components. First, inspect the cone in the sub and how it’s sealed to the enclosure.

Cone is responsible for producing the final audio output by moving back and forth and consequently pushing and pulling the air. If its seal gets loose or broken, it can’t move the way it should and produce the required sound.

Moreover, you also need to look at the electromagnetic coil of the sub. If the coil has burnt spots or looking out of place, it strongly indicates that it is not creating the powerful electromagnetic field required to interact with the permanent magnet needed for producing the deep-base subwoofer audio.

Before wrapping up, we’d like to share that many times amps are on, but subwoofers don’t produce any sound because of a setting glitch rather than any hardware issue. The majority of aftermarket stereos and even some latest stock head units have separate subwoofer control in the menu. You need to check that setting.

If the subwoofer output is turned off or set at an inaudible decibel value, you won’t be able to hear anything from the subs. Therefore, make sure the subwoofer settings are configured correctly.

It could also be that your subwoofer is bottoming out.

See this video from Sonic Electronix for visual help.

Conclusion

We hope that all this detailed discussion solves the mystery of when the car amp turns on but no sound from subs. Our discussion divulges one important thing that a powered-on amp doesn’t mean a perfectly working amp. An amp can turn on but still suffer from power, input, and output issues and fail to produce any input for subs.

Besides amp problems, subs can also go silent due to issues like short-circuiting, broken cone seal, and a faulty electromagnetic coil. If you have any other queries on this car audio issue, leave them in the comment section. We’ll get back to you with the right answer and explanation ASAP.