HiFi Adventures - Blow a Speaker
The Repository->Blow a Speaker
How to Blow a Speaker
I suppose most of us are under the impression that the way to blow a speaker was to send it more power than it can handle. This is only partly true, as I found out. There are actually two ways to blow a speaker.
Method #1: Too much volume
This is probably what most of us think of when it comes to blowing speakers. Is it caused by having too powerful of an amp? Not necessarily. What happens here is that you drive a speaker louder than it can go for too long of a time. Did you ever notice that, on low notes, the woofer in a speaker moves in and out? They are supposed to do that--but only to a certain distance. If you ask a speaker to move farther and faster than it was built for, the cone will rip apart, and you'll have to either re-foam or re-cone your speaker. If you try to play music out of it at that point, it will make an ugly scraping sound because the voice coil (the part under the dust cap) is rubbing against the magnet. This type of "blowing" normally happens to woofers, because it has to travel the largest distance, but it can also happen to mids, tweeters, planar and ribbon drivers as well.
The problem here is that speakers can only go so loud. Using a more powerful amp will not make the speakers any louder if they are already at their peak. All the more powerful amp will do is push the speakers beyond what they were meant to do, and eventually push the voice coil farther than it was designed to go, and rip, out it goes. By the way, if a you really do have an issue of the sound not being loud enough, and the speaker is at its peak, the solution is either to buy/build a speaker with higher sensitivity, or add more speakers. This is why ampitheaters aren't driven by a single speaker, but several; it's too much work for just one speaker to do.
Method #2: Not enough amp
This is the scenario that puzzles people. You may have heard it before, though. If you are at a party or live venue, and the sound system just isn't carrying over the sound in the room, someone keeps turning the volume knob up. But if the amp doesn't have enough power to do what you're asking it, it will try anyway, in an ugly distorted manner. Yes, that's the amp distorting, not the speakers. The sound waves the amp is trying to produce are too big, so it literally "clips" the tops of the waveforms off, and the end result has a sort of "buzzing" sound. The speakers can handle this for a while, but eventually the buzzing sound wears them out, and causes the voice coil to heat up. If you drive a speaker for long enough with this "clipping/buzzing" sound, the coil will heat up to the point that its parts melt together, and the speaker pretty much fails to work anymore. There's really nothing you can do here but buy a new speaker. This kind of speaker blowing is common in the tweeter and midrange drivers, as they usually bear the brunt of the buzzing sound. I like to call this the "cheap car stereo" method, because it is that sound you hear when someone has a crappy car stereo, and they try to blast it for the neighborhood to hear, and it just sounds fuzzy. It's actually not the speakers that are distorting, it's the amp--and eventually, it will melt the coils in the speakers. Maybe that will get the jerk to stop blasting his music.
So can too powerful of an amp really blow speakers? Actually, the chances of blowing a speaker are far more likely with the combination of too weak of an amplifier for too large of speakers (as in the case of method #2). Using a very powerful amp with less-powerful speakers is actually a safe bet, as long as you are listening to the music at normal listening volumes, and not trying to broadcast down the block.