How to Tell If a Subwoofer is Blown?by William Lynch
Your stereo's subwoofer is dedicated to low-pitched audio frequencies, or bass. Playing music too loudly and forcing excessive sound through the subwoofer may cause the speaker voice coil to separate from the speaker cone, damaging performance and resulting in what's known as a blown speaker. If you suspect your subwoofer may be blown, there are a few simple ways to diagnose the problem.
Pressing on the subwoofer can indicate whether it's blown. A functioning subwoofer has suspension that allows for movement. Use both hands and gently press on either side of the subwoofer's speaker cone. If the cone is rigid or locked in place, the subwoofer is definitely blown. Even if the cone moves, listen for scratching noises and be sensitive to any movements that are too loose or sluggish, as they may all be signs of a worn suspension.
A blown subwoofer damages sound quality, producing cracks, pops and general static. To test the subwoofer, start audio playback at a low volume. Gradually increase the volume and bass, listening for any disturbances in sound quality. Even distorted sound without excessive static may indicate a partially blown subwoofer.
Use a digital voltmeter to measure the subwoofer's voltage. Hook the voltmeter's leads to the subwoofer's positive and negative terminals located on the rear of the speaker. Each subwoofer will have its own specific ohms reading. If the voltmeter produces a reading far below expectation or if the reading fluctuates wildly, the subwoofer needs to be replaced.