Sizing amp to subs

[army5 10+ year member]

I know you want to try and match RMS ratings of both. However here is my scenario: I have 3 8-ohm subs rated at 425rms. I would like an amp that can push close to the 1275 rms at my 2.67 Ohm rating. Problem is all amp specs show 4, 2 and 1 Ohm ratings. Taking this plus typical voltage drop, efficiency ratings and imp rise what would be a good match. My thought is to be a little on the big side and set gains accordingly.

I know this is crude but this is what I've been using to calculate: 2 Ohms / 2.67 Ohms = 75%. Take 75% of rms ratings @ 2 Ohms and then another 75% for efficiency. So for example the ap3001d I would get (2000 * 75%) * 75% = 1125watts. Close enough considering cost and my budget.

So is the above a safe assumption or am I way off? Since amp is pushing less than half of rated would stock electrical with Big 3 and 1/0 ga wire be sufficient?

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[t1990le 10+ year member]

That sounds about right. Try it out and see. If you dont like the amp, sell it to me. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[n2audio 5,000+ posts]

effeciency is accounted for at the input side of the amp. So you don't need to reduce it by the 2nd 75% (maybe it's over-rated by that much??).

If the AP is rated accurately it should do right around 1500 at 3 ohms, 1750 at 2.5. If you want to knock a little off for imp rise from there...1500-1600 at 2.7.

More than your 1100 is the point.

 

[djarmy2004 10+ year member]

From what i hear the Ap amps do rated power. GLWB

 

[army5 10+ year member]

Thanks for the input. So if the amp can manage 1500-1700, that would be anywhere from 75-141 watts over rms across all 3 subs. The subs should be able to manage this if gains are set accordingly, correct?

 

[n2audio 5,000+ posts]

that's not close to an overpowering problem, especially if they're decent subs.

You'd have to do something pretty stupid to really put your woofers at risk IMO