Definition: Excessive woofer cone excursion

Could someone describe and/or explain the meaning of "excessive woofer cone excursion"?

The reason I ask this is I am looking to into purchasing a pair of Bryston's 7B-ST amps. These amps are rated at 500 watts a channel. My Paradigm Studio 100's are rated up to 350 watts of input. As I understand it, I could drive my Studio 100's with the Brystons as long as I keep the listening level at a point which does not cause excessive woofer cone excursion. But what exactly is excessive woofer cone excursion?


Excessive woofer cone excursion is when the cone extends forward or backward beyond it's intended mechanical motion limit. I've experienced that in my subwoofer, and it's very audible when it occurs. Almost sounds like a hard object is hitting a softer one, and the cone is going to pop. Similar to your car's suspension bottoming out when you hit a dip in the road, not a pleasant thing. It never happens when I'm playing music, only on movies with excessive LFE.

In your case, using two Bryston 7B-STs might be a bit of overkill, but not in the negative way you think. They're probably more power than you need, but I think what will end up happening is that you'll never tax the amps, so you'll always get clean amplification feeding your Paradigms. I think your Studio 100s are rated for amps up to 350 watts, and 210 watts maximum input. You might find that the Bryston 4B-ST at 250 watts per channel is all the amp you'll need.
Gunbei's definition is certainly correct, although perhaps too conservative, as the effect described is "bottoming out" the woofer and is akin to fully extending or compressing the suspension on your car. If you've ever done that you have an idea how bad it is; it would probably be considered abuse by the manufacturer. I had a dealer once tell me that if you can see the woofer moving at all, that's excessive. Perhaps the truth is somewhere in between. But the point is that woofer excursion is more a function of damping factor and distortion than mere power. If the amp has a high damping factor then it will be able to control woofer excursion better, per watt, than an amp with low damping. It's the ability of the amp to swing enough current to start and stop the woofer and return it to it's starting point quickly. The bottoming out is a result of the woofer continuing on its trajectory after the music signal has ended. Subwoofers are prone to this because so many have too-small voice coils and/or cheesey amps in them, and because it is easy to overdrive them when all of a sudden Trex stomps by or somebody in Houston "lights this candle." I have seen and heard big amps drive reflex loaded woofers (like the Paradigm)(they travel more) to high levels without hardly any visible woofer excursion. The Bryston has a pretty good damping factor, I think, but you should check. Anything over 500 is good. My guess is that with a clean input signal the Bryston will drive the Paradigm to concert levels and neither piece of equipment will show any strain. Your ears are likely to be the first to give out!
Hi Dan - don't worry in the least about using these large amps with your Paradigm's. You obviously already understand that as long as you don't abuse your speakers then they'll hold up just fine. "Too much" power is not nearly so much of a problem as too little power, in which case the amps may be more easily driven into clipping & produce damaging harmonic distortion at much higher than rated power levels. THAT is what usually damages voicecoils.
I have always preferred amps with power ratings which are much greater than spec'd for my speakers; better damping & control, with headroom that is never taxed even by the largest transients, clean, smooth, effortless. Rarely I have really pushed the envelope, & no matter how loud it gets there is no speaker-damaging distortion (the ears however - now that's another issue). Indeed your ears will be the limiting factor even if you really like it loud at times.
It's actually easier to damage speakers by having to little power.
RWWEAR is right. You can never have too much power...clean power that is.
My speakers are rated at a senstivity of 93db. My amplifiers can pump a minimum of 1200 watts/channel of good clean Krell power into them. Can't hurt them unless I forget to take my psychiatric medicine and go off the deep end.

Don't worry about having too much power; go for it!

Richard Diamond
Thank you for all of those who responded.

Dan S.