Sooner or later, every guitarist experiences a malfunction of some kind. It could be a result of something trivial such as a loose ground wire. On the other hand, it could be something more serious such as a blown guitar speaker. If you have a blown guitar speaker on your hands, then you can look for the following telltale signs.
The unmistakable “fuzz” or hiss, which comes from any partially blown guitar speaker, is hard to miss once you learn on what to look for. It should be obvious that something within the guitar is amiss if you increase volume leads to even greater distortion levels from your guitar speakers. Fuzzy guitar speakers are often the result of loose or damaged voice coils. You can always check on your guitar speaker if you need the best solution.
Bad speakers may underperform due to a wide range of reasons. For instance, unless the voice coil has really become detached from its cone, you will still get sound though as it will certainly be incomplete. In addition, a lack of high frequencies or even bass is a sure sign that your guitar speakers or cabinets are blown (partially or completely) and need repair or replacement.
Speaker cabinets create their own sound through vibration. Whenever you touch the front of your speakers and do not feel any kind of vibration, the cone is not receiving any form of power. This may come from a malfunctioning component or a wiring problem farther back. In this case, it is may not be the speaker itself with the issue, but the electronic components in the cabinet.
Besides distortion and fuzz, other clear-cut and common audible signs can point major problems. For example, nothing other than rattling coming from your speakers can indicate a fully or partially blown amplifier or speaker.
In the end, the best thing to do is trust your ears. If something sounds off, chances are good there's a problem. While the tips above should give you some insight on what to look for, it all comes down to how well you listen to your gear!