prevent speakers from blowing

The best advice for "keeping a speaker from blowing" is

1.  do not overpower it (I agree with the other posters that in your setup you are probably fine)

2. make sure it is installed in the proper size and type enclosure.

1. You will be fine. Just back down over do the gain so you wont blow it( I would leave any bass boost features on the amp or cd player off also). In fact you might be getting cleaner sound with a higher wattage amp because it dosnt have to work as hard to drive you sub if you have the gain set properly!

2.The best advice for "keeping a speaker from blowing" is  do not overpower it (I agree with the other posters that in your setup you are probably fine)

#1 is correct. 2 is WAY off (except about the box, thats excellent advice). An oversized amp is DEFINATELY safer for a sub. The lower the gain is, the lower the THD, and consequentially, the less thermal damage to the voice coil. And again as #1 stated, leave all EQ enhancements OFF, they just reintroduce the distortion. Just be sure your gain has been properly set.

Over-powering any speaker is dangerous.  THD has nothing to do with thermal damage, unless it is very gross (like 20%.)  Please read my long post about loudspeaker power ratings.

https://www.the12volt.com/installbay/forum_posts.asp?tid=25066&KW=loudspeaker

I guess it's time for my tirade about the myth of under-power... OH, and here's a link for you from another professinal:  http://www.bcae1.com/2ltlpwr.htm

On Dyohns comment, i must disagree...  First of all THD does affect thermal capacity as the peaks of a distorted signal (negative arc AND positive arc) are a flat line pulse of DC, which is like effectively hooking the coil to a battery. Heat is created plain and simple, much like the coil (filament) in a light bulb. As for it being "grossly" distorted, take a look at the average schmoes self installed set-up; Head unit bass=maxed, amp gain=maxed, amp EQ/bass boost=maxed..... i would call that grossly distorted, indeed. And secondly, an "overpowering" amplifier isnt ACTUALLY supplying too much wattage if the gain is set properly. E.G., a 350 watt sub on a 400 W amp thats around half gain is not getting 400 W. It's getting 350 (give or take), just at a substantially lessened THD.  Generally speaking, though, your long post is quite accurate and will definately help educate the masses.

Simplemitch, an amp's gain controls are used to match a headunit's outputs to an amp's inputs.  Simply stating that an amp set at half gain will not produce full power is incorrect (too broad a statement).  That all depends on how strong a signal that amp is recieving.  Yes, it's sometimes possible to turn down the gain to produce less power, but say you have an Eclipse head unit with an 8v preout- setting the gain halfway will most likely send the amp into clipping at or before half volume on the deck regardless of the amp.  Or you have an oldschool deck maybe 5-6 years old with a laughable 1volt preout (just pulling a number out of the air), and you set the amp to half gain, you won't get anywhere close to that 350 watts.