800W to 450W RMS Sub?

[gatorgrizz27 10+ year member]

I have a Boston G-510 sub rated for 450W RMS. I am debating between either an amp rated for 500 w or one rated for 800w. I hooked the sub up to the 2 rear channels on my component amp (240W) just to get an idea, and it hardly moved. It is in a sealed box, .5 cubic feet, so I think it can handle more power. It would also only see 800W if the volume knob was all the way up, correct? I just want to make sure it wont destroy it by running the 800W amp, because I don't feel that 500W will be enough. Thanks.

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[AndonD454 10+ year member]

get the 800 amp.. odds are your sub can handle more than 450 rms. not sure about 800, but the sub wont see that. first of all, youre right, with gain set correctly, youd see 800 only when the volume knob was at the max you set it for.

btu keep in midn that youll also get an impedance rise from the box, lowering the amt of power youre gonna end up wiht..

regardless.. headroom is never a bad thing.. you never knwo when youll end up switichin that sub out for an 800 rms sub and wish you wouldve just paid the little extra cash for the bigger amp.

 

[gatorgrizz27 10+ year member]

Why would the impedence rise? Isn't a 2 ohm load a 2 ohm load regardless of the enclosure? I believe the sealed box will require more power to move the cone due to the air pressure but I thought the wattage stayed the same?

 

[helotaxi 5,000+ posts]

Why would the impedence rise? Isn't a 2 ohm load a 2 ohm load regardless of the enclosure? I believe the sealed box will require more power to move the cone due to the air pressure but I thought the wattage stayed the same?

Impedance isn't a constant. The nominal imp. is pretty much the lowest you will usually get from a driver but it will rise depending on frequency and the enclosure. The peaks in imp are usually greater in a ported box.

As far as power to move a sub, it takes more power to get large excursion out of a ported box compared to a sealed one unless you feed it frequencies well below the tuning freq of the emclosure. The inertia of the air moving in and out of the port damps the cone much more than the fixed amount of air in a sealed box.

 

[AndonD454 10+ year member]

its like posi trac on the rear end of a plymouth... it just does...

but dont worry about it. for your concerns youll get 800 rms to the sub and youll have everything at 2 ohms...

i was just giving you the reason behind part of your overall power loss.. think of it this way.. yeah in a perfect world youg get 800 watts from your 800 watt amp to the sub.

but its not a perfect world and voice coils are almost never EXACTLY where they say they are, electrical systems arent always as stable as they should be, wires arent wlays as connected as they should be, boxes take power away because they affect your subs performance, blah blah you get the point.

EDIT: helotaxi broke it down for ya

 

[gatorgrizz27 10+ year member]

Alright, thanks for the impedence explanation, just wanting to make sure the 800W amp won't murder my sub as long as gains, lpf, etc are set right. Thanks.