Speakers do not break on their own. Something external has to cause a speaker to break.
The system is being played too loud
All components have limits and exceeding the limits of either the speakers or the amplifier/receiver may result in speaker failure. Unfortunately speaker parts are like glass - they may not break the first time from abuse but once they’re broken, that’s it. The broken parts must then be replaced. If any parts are melted or smell burnt, that indicates way too much power is going through that part.
"But my speakers are rated for 200 watts, yet my receiver rated at 50 shouldn’t even have enough power to do damage..." is a common question we receive. Ironically, you are more likely to damage a speaker when using a low power receiver than a high power one. Here is the reason why. If the receiver is asked to produce more power then it can, it will start to distort. The term is clipping. This is the number one cause of speaker destruction and the number one cause of tweeter failure.
So how do you prevent clipping? Keep the volume within the limits of both the receiver and the speakers. To get a better understanding of watts and dB’s, we must understand how volume works.
Keep in mind audio intensity is not linear, but logarithmic like the earthquake Richter Scale. In plain English that means when you double the amount of power going to a speaker, you don’t get double the sound out. Doubling the power only provides a 3 dB increase - noticeable but not overwhelming.
Low level listening takes only 1 watt or so of power. But to get 4 times the perceived volume it takes 100 times the power. Thus, you can see how the power on a 100 watt receiver disappears very quickly.
On most receivers, full power is usually achieved when the volume control is at the halfway or 12:00 o'clock position. If you have a receiver who’s volume control is read as a negative (-) this indicates how many decibels you are away from full blast. To get a 3 dB change (say from -23 to -20) takes DOUBLE the amount of power. To get a 10 dB change (say from -20 to -10) takes TEN TIMES the amount of power.
When you turn the volume knob past the full power point, the amplifier distorts. Sound that is harsh, strident, brittle or unpleasant in any way is an indicator of a distorting amplifier and is your signal to turn down the volume.
So why is the extra room beyond the volume control there? Ah good question. Many sources, such as the radio, tapes, or recordings made at lower levels may need the extra boost to be played at higher volumes. A loudly recorded DVD or CD will have a lower maximum limit than a softly recorded cassette.
The wide dynamic range of today’s action/adventure movies also plays a role in damaging speakers. Explosions and other sound effects are recorded at a MUCH higher level than dialog and average sound effects. If you set the system volume to a pretty high level during normal scenes, it’s going to be way too loud during the bang-bang, boom-boom scenes. If you want your system to play louder than it currently does, without distortion and speaker damage, you will have to get a better, more powerful amplifier/receiver (see The Truth About Power Ratings) and/or more efficient speakers. Generally, with digital sources such as CD, DVD and satellite or digital cable, you want to follow the full blast rule from above.
The system is being improperly used
Some listeners expect the system to be heard over the sound of running machinery, vacuum cleaners, chain saws or a room full of drunken revellers. Or they try to connect musical instruments or microphones, their speakers break and they wonder why. This kind of usage exceeds the limits of safe operation of just about any gear intended for home use. Years ago we encountered a customer who kept reporting that his BIG expensive speakers were breaking over and over again. We finally found out that he put them on the porch of his house and played them while cutting firewood with a chain saw. I am not making this up. Cross my heart. He was using his home speakers as a public address system.
If you want to have a party and play really loud music, borrow a receiver and another set of speakers from a friend (invite the friend to the party), use Y cables to connect both receivers to the same CD player and run two systems. You’ll get more even sound coverage and (probably) avoid breaking something.
Hire a DJ, or get yourself some PA speakers. PA and DJ speakers are very efficient. Notice, they have horns on them. They’re the way to go if loud is your top priority. Keep in mind just because a speaker is more efficient or can play louder does not mean it sounds better. A megaphone plays loud, but it sure doesn’t sound too good. At Polk, we do not use horns because we feel they present a unnatural, harsh and very in-your-face sound.
A malfunctioning amplifier or receiver
If you’re reasonably certain that you’re not asking more of the system than it can safely deliver and if the speakers continue to fail, the odds are good that there is something wrong with your amp or receiver. One way to check is to turn on the system but play no music. Take off the speaker grilles and observe the woofer(s). If they are moving or are pushed out or pushed in rather than at rest in the neutral position, then your amp is putting out a DC voltage and that is a BAD thing. Get the amp/receiver fixed. If you are ever in doubt about the proper functioning of your electronics, have a qualified service centre check it. Better safe than sorry.