Diagnosing a Blown Speaker
Test 1: Listening A blown voice coil produces: fuzzy, distorted sound at all volumes. Rattling on certain notes. Complete silence. These symptoms are worst at low volumes where distortion is more noticeable relative to output.
Test 2: DC resistance Disconnect speaker from amplifier. Set DMM to resistance (Ω). Measure across speaker terminals.
| Reading | Diagnosis |
|---|---|
| ~80% of rated impedance | Good (3.2Ω for 4Ω speaker) |
| 0Ω or very low | Short — voice coil fused/melted |
| Infinite (OL) | Open — broken voice coil wire |
| Intermittent | Damaged coil, intermittent contact |
Test 3: Physical Remove speaker from enclosure. Press cone firmly but gently at edges. Movement should be: smooth, even resistance, no noise.
Scraping sound = voice coil rubbing on pole piece. Usually indicates: impact damage, overheating causing coil to deform, or ingested foreign object.
Test 4: Excitation Connect 9V battery momentarily (< 1 second) across terminals. Cone should jump firmly. Weak movement suggests partial damage.