Q: “My son recently decided to use one of my woofers as target practice for a toy and ended up putting a 1/4″ diameter hole in one of them. It still seems to work fine so I’m wondering if I need to have it repaired?”
A: You don’t say exactly where the hole is. A delicate part of the surface of a woofer is the surround area. A tear or hole in that material is very likely to get worse over time until it starts to really degrade the performance of the speaker. This is also one of the parts that’s integral in keeping the speaker’s voice coil centered in the magnet’s gap. When it degrades it makes it easier for the speaker to go askew, which can cause the voice coil to rub up against the magnet, which causes distortion and leads to failure. Any damage to a speaker’s surround should be fixed immediately.
The center dome of a woofer is mainly used as a dust cover to keep things out of the magnet/voice coil assembly. A hole in this part probably won’t change the sound of the speaker much, but should be repaired to avoid long term damage.
Finally, the main part of a speaker – the cone area – will often be relatively unaffected by a small hole, depending upon the size of the speaker of course. That said, there are some potential problems. If your speaker cabinet is not ported (which is increasingly rare these days), then the hole in your speaker will act as a port. In this case it can have a pretty significant impact on the sound. And because that’s the only opening, air will be getting forced through it pretty hard, which is likely to cause it to rip further, and can create some strange sounds as air “whistles” through the small opening. If your cabinet is ported then a small hole will have a less effect, both in terms of air pressure in the cabinet as well as the inconsistency in the surface area of the speaker.
Sometimes speakers can operate with a small hole in the cone for years without problem. The extent to which the sound will be altered depends on a variety of factors – you can be the judge. It’s also relatively easy to affect repairs on such a hole. If the speaker material is still attached you can sometimes glue it back to close up the hole. Use as little glue as possible. Too much and the extra mass will potentially cause the speaker to move off center in the voice coil when under stress, the result of which can be distortion and failure.