Is My Speaker Blown?

Is my speaker blown, or is it the cable? Rule out the chain first, then four checks on the driver (push, look, meter, sweep) tell you which fault you have: open coil, rubbing coil, shorted turns or a damaged cone or suspension. Each has a different fix.

The faults behind "blown"

• Open voice coil. Coil or lead-out wire burnt through. No sound; meter reads open.
• Rubbing coil. Heat has deformed the coil or former, or the suspension has sagged, so the coil touches the gap. Scraping, worst on low notes.
• Torn cone or surround. Over-excursion, impact or age. Flapping, buzzing or air noise.
• Spider damage or failed glue joints. Cone off-centre or rattling.
• Shorted turns. Overheated windings fused together. Plays, but weak and distorted, with a low resistance reading.

Causes are covered in why sub drivers fail.

Rule out the chain first

1. Swap in a speaker cable you know works.
2. Try the cab on another amp channel, at low level.
3. Check the Speakon or terminals inside the cab for loose or broken wires. See Speakon wiring.
4. Check the DSP preset: a mute, a wrong filter or a limiter set far too low can look like a dead driver.

Silent or distorted on a known good amp and cable means the fault is in the cab.

Four checks on the driver

1. Push

Amp off and disconnected. Press the cone gently and evenly with flat hands. It should travel smoothly and silently. A scratch or grind means a rubbing coil; a cone that sits crooked or doesn't return to rest means suspension damage.

2. Look and smell

Tears in the cone or surround, a pushed-in or lifted dust cap, glue lines come away. A burnt-varnish smell around the vent or dust cap points to an overheated coil.

3. Meter

Resistance across the terminals, driver disconnected. A healthy 8 Ω driver reads its Re, below nominal: the WM1850/8 is specified at 6 Ω, the B&C 18SW115 at 5.3 Ω. Compare against the maker's figure.

• "OL" or infinity: open coil.
• Near zero, or well below Re: shorted turns or a short in the wiring.
• Close to Re: coil intact; carry on to the sweep.

Method in testing a driver with a multimeter.

4. Sweep

If the coil reads normally, play a quiet sine sweep from around 30 Hz up. Listen for scraping or buzzing at particular frequencies. Rattles also come from loose panels, screws, grilles and ports, so feel round the cab while it plays.

Recone or replace

Most "blown" faults are in the moving parts (coil, cone, spider, surround), which is what a recone kit replaces. If the basket and magnet are sound, a recone can bring the driver back; whether it is worth it depends on kit and labour cost against a new driver. See reconing explained.

If you replace, match size, impedance and cut-out, and check the new driver's T/S data suits the box. See the replacement guide and replacing a speaker driver. Our two 18s for comparison:

Stop it happening again

High-pass below the cab's working range, keep the amp out of clipping, set peak and RMS limiters from the driver's rating, and keep cabs dry. Most coil failures are heat; most cone and suspension failures are excursion. See amp matching and Xmax and excursion.

Safety: switch off and disconnect the amp before touching drivers or terminals. An 18" cab is heavy (the WM1850/8 driver alone is 20 kg), so get help to lift or tip it.

Sources: Re values from the Wavemark WM1850/8 spec sheet and B&C Speakers' 18SW115 data (8 Ω), checked 11 October 2026.