The RMS and peak ratings that manufacturers assign to subs mean exactly ****. There are too many variables involved to say what kinda power a sub will take on a daily basis before it burns up something important. For example, sub company x suggests you use a 1.0-1.5 sealed box or a 1.5-2.5 vented box for sub x, so the RMS power rating for this sub is based on these box specs. If you build a larger box in an attempt to gain SPL (and i've never seen a sub company recommend the right size box for SPL only applications), the sub will most likely need far less than the suggested RMS to start cooking. Just use those numbers as a guideline as to which amp to match up to the sub, and always buy an amp that leaves you headroom (extra clean watts and less chance your sub will see any clipping) incase the sub will take more than the suggested RMS in the enclosure you choose. Audiobahn suggests that I give my 1200Q 750w of constant power, but it sees a lot closer to 1kw on a daily basis, and it still takes a half hour of hard play to even begin getting hot.
The bottom line is to make sure it doesn't distort, overheat (*overheating will cause distortion before it really begins to damage your sub. make sure you listen for it any time you play your system for an extended period*) or see any clipped signal, and you can enjoy your sub to its fullest potential for years.
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