Post Party Blues: The Blown Speaker Test
It's almost inevitable. You've got the neighborhood / the office / the baseball team / the PTA in for some holiday cheer, and the sounds of the season are so good on your Axiom speakers that your guests (or your kids!) keep turning it up . . . and up . . . and up . . . until they crank it a notch too far. How can you tell if damage has been done? Do you need to do the Blown Speaker test?
Guru Alan Lofft gave this step-by-step guide to checking for damaged drivers to message board member hawk1061, whose wife may or may not be guilty of said damage . . .
Lots of speakers get blown at parties when users "crank it up" in the spirit of the occasion, especially when drinks are flowing.
Try playing a CD, one with cymbals, vocals and good bass in stereo, turn the balance control all the way to the left, and listen to each driver of the left speaker, with your ear fairly close (use a moderate volume level) while covering the other two drivers to make sure you are isolating each driver. Usually, the driver will work fine or it won't issue sound at all.
If the voice coil is warped from heat or overdriving, you might hear a distorted scraping sound. Repeat the test for the right speaker, turning the balance control all the way to the right.
You can also use the battery check to check the woofer/mids: take an AA battery, and connect the leads to the input posts on each driver. If the driver is working, the cone will make a "click" and move either inwards or outwards, depending on the polarity you used to connect them.
This will not damage the drivers. If there is no movement of the cone, then the drivers are gone or fused.
By the way, quality amplifiers have good protection circuitry, but that's used to protect the output stage of the internal amplifier, not to shield your speakers from clipping damage.
To check if a subwoofer is damaged, you can try gently pushing in the cone of the driver with your hand (with the subwoofer switched off)and fingers applying equal pressure. You should not hear anything if the subwoofer is undamaged.
If you do hear a scraping sound, then the voice coil has become warped or fused from overheating/clipping and is scraping against the magnet assembly as you press the cone in and out.
Some General Advice: If you're really planning on playing stuff super-loud, then you need an outboard amplifier for at least the front three channels, and preferably larger floor-standing speakers like the M60s or M80s. Either that, or use the M22s, get an outboard amp and a center, and control the maximum volume level. The M22s are great little speakers and will play remarkably loud and clean when supplied with clean unclipped power in an average living room or slightly larger space, but a much larger room demands bigger more capable speakers and a big amp.
There you have it - the word from the expert. Hope you never have to do the blown speaker test, but you may want to bookmark this page, just in case!