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Physics of bridging an amplifier - was: Damping Material
thelizman
wrote:
Kevin Murray wrote:
If a speaker
bottoms out it will sound like crap and the listener will turn down the
volume.
This inherent "built-in protection" protects the speaker from mechanical
damage
resulting from excessive V-A.
If the speaker "bottoms" meaning striking some part of the basket it is often
already damaged.
You would think, anyway. What most often happens is the listener ignores
it, thinks its part of the source, or because the subs are in the trunk
they don't even notice.
That's common; an overload condition isn't "heard" until the driver quits.
Thats why as an installer I was such a fan of
Alpine's (or was it JBL's?)old soft-clip design. The speaker never
bottomed out per-se, it just got harder to push.
It's also worth pointing out that IME 75% of the time a speaker blows,
its not the voice coil that went bad, but the mechanical portion of the
speaker which couldn't handle the abuse. Spiders and surrounds come
unglued, get worn out, or the cone itself becomes warped. I've even seen
some speakers where the leads get ripped out of the speaker terminal in
subs that have high Xmax, but don't cut the leads long enough. Power
handling in a voice coil is rarely a problem. Thats why I tell people
not to worry about an amp thats too big, you can always turn it down
when things start to go "thwack!".
--
thelizman "I didn't steal the FAQ either"
FWIW; in speaker testing the most common failure mode is melting voice coil
glue. I drive every woofer to its maximum SPL capability using a ramped sine
wave ( a demanding but non-purposfully threatening) that has characteristics
similar to musical programs.
Using a Crown Macro-Tech 5000VZ I've blown up dozens of woofers but have only
damaged suspensions on a few occasions. It's true that this represents a lab
condition and not repeated abuse over a long time. But, thinking about it,
nearly all woofers have more Xsus (linear suspension stroke) than Xmag (linear
motor travel) so it's hard to imagine a situation where a limited stroke motor
woukd tear out a suspension with more travel.
Not saying that it doesn't happen; I'd just like to know more about the
circumstance.
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