How to Tell If Your Speakers Are Blown
Three different failures all get called blown, and they sound different. Here are the battery test, the multimeter reading, and what is worth repairing.
A blown speaker usually announces itself as distortion that gets worse with volume, a rattle or buzz on bass notes, or no sound at all from one driver. The quickest test is the 9 volt battery check: touch a battery briefly across the terminals and listen for a pop. No pop and no cone movement means an open voice coil, which is a dead speaker.
Most speakers people call blown are not blown. They are disconnected, wired to a dead amplifier channel, or fitted with a torn surround that costs twenty dollars to fix. Working through the checks in order saves a lot of money, and takes about ten minutes.
What blown actually sounds like
There are three distinct failures and they sound different from each other.
A burnt voice coil gives you silence, or a very quiet thin output with no bass at all. The coil has overheated and gone open circuit, or it has swollen and jammed in the magnet gap. This is the one that is genuinely dead.
A partially damaged coil, or a coil rubbing against the magnet, gives you distortion that scales with volume. Quiet passages sound fine, loud ones sound gritty and fuzzy, and the harshness sits on the note rather than around it.
A torn surround or a split cone gives you a buzz or a flapping sound on bass notes specifically, while midrange and treble stay clean. This is the most common failure in older speakers and the least serious.
Distortion that appears at all volumes and on every source is more likely an amplifier problem than a speaker one.
The physical checks, in order
Take the grille off and look at the driver in good light.
- Check the surround, the flexible ring joining the cone to the frame. Foam surrounds crumble with age, usually between 10 and 20 years, and you will see cracks or a gap. Rubber surrounds rarely fail.
- Look at the cone itself for splits, especially near the center dust cap and around the outer edge.
- Press gently on the cone with your fingers spread wide, pushing both sides evenly. It should move smoothly and silently. A scraping or crunching sound means the voice coil is rubbing in the gap, and that speaker is finished.
- Check that the cone returns to its resting position on its own. A cone that stays pushed in has lost its spider.
- Look for a burnt smell near the magnet. That one needs no further diagnosis.
The battery test
Disconnect the speaker from the amplifier first. Take a 9 volt battery and touch the positive terminal to the speaker’s positive tab and the negative to negative, for no more than a second.
A working speaker gives an audible pop and the cone visibly jumps outward. Nothing at all means the voice coil is open circuit. A weak or crackly response means the coil is partially damaged.
Keep the contact brief. This is a DC voltage on a component designed for AC, and holding it there will heat the coil.
The multimeter test, which is better
Set a multimeter to ohms and touch the probes to the speaker terminals with the speaker disconnected.
You should read somewhere between 3 and 7 ohms on a speaker nominally rated at 4 or 8 ohms, because DC resistance always reads below the nominal impedance. Our explainer on what ohm means for speakers covers why those two numbers never match.
A reading of infinity, OL, or no continuity means an open voice coil. A reading close to zero means a shorted coil, which is worse, because a shorted speaker can damage the amplifier driving it. Disconnect it and leave it disconnected.
Rule out everything else first
Before condemning a driver, swap it. Move the suspect speaker to the other channel. If the fault follows the speaker, it is the speaker. If the fault stays on the same channel, it is your amplifier or the cable.
Check the cable at both ends, since a single strand of copper bridging positive and negative inside a terminal will silence a channel and looks perfectly normal from a distance. Check the balance control, and check that a home theater receiver has not been set to a speaker configuration that switches the channel off entirely.
In a car, the wiring is the likelier culprit than the driver. Door speakers live in a hinge loom that flexes every time the door opens, and broken strands inside the rubber boot are extremely common. Our guide on how to fix car speakers covers those tests.
What can be repaired and what cannot
A perished foam surround is a genuine repair. Refoam kits cost USD 25 to 40 a pair and the job takes an afternoon, which is worth doing on any speaker with decent drivers and worth doing on vintage speakers regardless.
A torn cone can be patched with tissue and flexible adhesive if the tear is small. It will never be perfect, but it stops the buzzing.
A burnt or rubbing voice coil is not economically repairable outside of professional recone services, which cost USD 80 to 200 per driver and only make sense for expensive or irreplaceable speakers. For a mass market bookshelf speaker, a replacement driver is cheaper.
Why it happened, so it does not happen again
Most blown speakers are killed by clipping rather than by too much power. An underpowered amplifier driven past its limit produces a squared off waveform carrying far more sustained high frequency energy than music does, and that is what cooks tweeters. A clean amplifier with headroom is safer than a small one played loud. The full explanation sits in our piece on what RMS means for speakers.
The practical version: when the sound turns harsh as you raise the volume, that harshness is the damage happening. Turn it down.
Frequently asked questions
Can a blown speaker still make sound?
Yes, and that is the common case. A partially blown speaker often plays at low volume and distorts badly as you turn it up, or buzzes on bass while the midrange stays clear. Complete silence usually means the voice coil has gone open circuit, which you can confirm with a multimeter reading of infinity across the terminals.
How do I test a speaker with a multimeter?
Disconnect the speaker, set the meter to ohms, and touch one probe to each terminal. A healthy 8 ohm speaker reads around 6 to 7 ohms and a 4 ohm speaker reads around 3 to 3.5. An infinite reading means an open coil and the speaker is dead. A reading near zero means a short, and you should keep it disconnected because it can damage your amplifier.
Is it worth repairing a blown speaker?
It depends on what failed. A crumbled foam surround is worth repairing on almost any speaker, since a refoam kit costs USD 25 to 40 and restores full performance. A burnt voice coil needs a professional recone at USD 80 to 200 per driver, which only makes sense for vintage or high end speakers. For an ordinary modern bookshelf pair, buying a replacement driver is cheaper.
What causes speakers to blow?
Most often an underpowered amplifier being pushed into clipping, which sends sustained high frequency energy into tweeters that were designed for brief peaks. Other causes are genuine overpowering, a DC fault in the amplifier, physical damage to the cone, and simple age, since foam surrounds break down after 10 to 20 years whether the speaker was used hard or not.