Is it possible to do damage that isn't blatant?

[wizbri]

<font color='#000000'>I'm wondering if it's possible to damage a speaker -- with a blast of sound, whatever -- in such a way that the damage is not immediately obvious. It's easy to tell when a speaker has been beset with clipping or distortion. But what about more subtle damage -- does it exist? Something that vaguely degrades the quality of the output?

Or is it an &quot;all or nothing&quot; thing -- either there's damage and it's readily apparent, or there's no damage at all ... ?</font>

 

[Guest]

<font color='#000000'>Yes, it's possible. In my experience, not all damage is catastrophic although fried tweeters tend to stay fried. With woofers there's a little wiggle room; damage need not equal destruction.

My first pair of speakers, c. 1984, were Polk 4A's with a 4-ohm impedance rating driven by a 30wpc Pioneer receiver that got <span style='color:red'>hot</span> every time I listened. I hauled this sorry combination off to college, where both Polks soon developed a rattling sound even at moderate levels and even when driven by a different receiver. The rattle, which I took to be damaged woofers, went away all by itself after a couple months of coddling (no Floyd or Doors past 12:00 on the volume knob) and returned only once or twice, years later, in the presence of high-level sustained bass tones.

The audio rags used to run full-page ads touting &quot;The Genius of Matthew Polk.&quot; I had to concur--after all, the man's cheapest speakers apparently fixed themselves.</font>

 

[RDL]

<font color='#000000'>Speakers usually show damage right away.  Sometimes minor damage will weaken a component of a driver, but damage will usually show its self when played at a moderate spl level.  When damaged, a tweeter will either play distorted sound, or nothing at all.  Bass/midrange drivers are different.  When a bass/midrange driver has been over extended, it may show different symptoms. You most likely will hear a mechanical form of noise produced (vibrations) when the driver is worked to a reasonable spl level.  You may also notice a &quot;buzzing sound in the driver, even at low spl levels.  Usually these symptoms do not go away because the damage to the driver is of a mechanical nature.  

If you suspect a damaged driver, there are few things you can check:

With your hand, gently press the cone (do not press the dust cap). The cone should feel dampened, and should not make any clicking noise as it moves in and out.  Any moderate noise most likely indicates a damaged voice coil.  This test is used for a bass/midrange driver.

Another way to test the driver is to remove the it from the speaker, and test with an Ohm meter.  The Ohm meter will only display the DC (still) impedance of the driver.  Be sure not to touch the cone when it is being tested, for this will change its impedance.  This will range from about 4 ohms - 8 ohms.  If the result is 0 Ohms, then the driver is damaged. This test is one that should be used when a driver makes no sound at all.

These tests have prooven to work in my experience.  I hope this helps answer your question.</font>