speakers bottoming out

Just purchased a pair of soliloquy 5.3's and was wondering if someone could explain just why speakers bottom out. Of course this occurs at high volume and under a fairly heavy base attack. What exactly is a speakers rating supposed to tell the owner (i.e. watts recommended) Is it even a problem I wonder?
"Bottoming out" happens when the driver tries to exceed its excursion limits, typically (as you noted) while trying to reproduce low bass at high volume. For each octave lower you go in bass, the driver has to move four times further to reproduce the same volume (in a sealed enclosure). In a vented enclosure, such as the Soliloquy, the driver excursion actually decreases at resonance, then increases dramatically below resonance. Powerful bass signals significantly lower in frequency than the system resonant frequency can drive the woofer into over-excursion, resulting in mechanical "bottoming out". In addition, there is a tradeoff between midrange extension and efficiency on the one hand and bass output (including long excursion for high volume) on the other. The Solioquy 5.3 is intended to work well with fairly low powered amplifiers, and so the design trades off some bass excursion capability for higher efficiency.
Okay as far as wattage rating - perhaps a speaker can handle 100 watts at 1 kHz. That would be the thermal limit - any more and the voice coils melt. Somewhere in the low bass power handling becomes displacement limited - in other words, at some frequency 100 watts will cause the speaker to bottom out. I get the impression that the Soliloquy is tuned to a lower than normal system resonance for its 5 1/2" drivers. It will probably be displacement limited to less than 100 watts somewhere in the half octave or so above resonance, back up to 100 watts thermal limited at resonance, and then below resonance the displacement power handling limit will plummet to maybe just a few watts at 20 Hz or below. The specifics are speculation, but the pattern holds for many reflex enclosures.
What are you playing to bottom out the speakers? I have had the 5.3's for several months and have not had this happen. My amp is rated a 100 watts rms. The speakers are supposed to handle 200 watts rms (I think).
You're playing them too loud, so you need a bigger speaker, or else turn the volume down. IF YOU CAN GET A CATALOG LIKE THE SOLEN ONE, you can usually look up the maximum excursion limits of the woofers (if they're spec'ed and in the catalog). Dynaudio drivers have a progressive non linear suspension, SO THEY DON'T BOTTOM. This is not necessarily good if you operate them near their excursion limit very often, though, because dynamics are compressed. YOU'LL ALWAYS BE ABLE TO EXCEED THE EXCURSION LIMIT BEFORE THE THERMAL LIMIT OF A WOOFER, if the driving signal is low enough in frequency...or ESPECIALLY if it's concentrated enough around the box alignment's least damped cone motion frequency, which will vary from one speaker to the next.
It could also be your amp is too SMALL! Contrary to popular belief, most speaker problems, suchas your bottoming out, or blowing speakers is caused by too LITTLe of an amp. You may need more clean power! Also, do you have the bass cranked up or the "loudness" button on? These will bottom out speaker cones and should only be used at LOW volumes!! Finally, if it's heavy duty Rap and the like you're playing, it may be you're playing it too loud for your speakers to handle. Stuff like Rap has a ton of bass and is much like turning up the bass all the way. Hope this helps! --Tom
I've had the same problem with my transmission line woofers a few months ago. They would take incredible low frequency passages until one day I noticed a frightening pop come out of my woofers (Vifa 25OOO8). My system is located in a very dedicated enviroment in my house(basement. As the summer progressed my wife and I dicovered that the humidity level was getting high. So we elected to install a 65 pint per day dehumidifier and Bye-Bye went the woofer poping. I would like to thing this wasn't a fluke, and hope maybe you can get bck to the reason you are in this hobby. E-mail me with your results. Joe Ritota