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Discussion Starter #1
I've always set up my amps by the dmm/test tone method, using the rated power of the amp and the calc. on the12volt.

My JL amp is rated at 45w x6 at 4ohms on 12v. But the birthsheet for it says 79w x6 at 4ohm on 12v. I usually set it by the voltage chart in the manual, but would it be alright if I set the amp for say 55 or 60w per channel? According to the birthsheet the THD isn't much higher at 79w
 

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As long as the amp isn't getting too hot and isn't distorting, you should be fine. It's always best to measure the distortion with something like an oscilloscope if you really want to get the most out of your amp, though. The impedance of each speaker varies between frequencies and between speakers and you need a very specific load impedance to hit maximum output power.
 

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Doesn’t matter… The only difference you’ll notice is on your head unit volume control or any external gain control for sub amp.
 

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Doesn’t matter… The only difference you’ll notice is on your head unit volume control or any external gain control for sub amp.
^this! who cares. the difference between 45 and 75 watts is less than 2.2dB. barely audible.

you wont be pushing an amplifier to max constantly anyway.
 

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^this! who cares. the difference between 45 and 75 watts is less than 2.2dB. barely audible.

you wont be pushing an amplifier to max constantly anyway.
If it’s barely audible then you may not even notice it on the head unit volume control setting.
 

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If it’s barely audible then you may not even notice it on the head unit volume control setting.
more than likely. might be a click or two lower, depending on the HU.
 

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Discussion Starter #10
The amp is a JL e6450........its old as hell, I don't think the sheet is a factory one. I think its from the test equip the shop that sold it to me has. I haven't been able to find it since I got the amp, but it did say 79w x 6 at 12v and the THD% was still under the rated level. I do actually have the birth sheet from my RF P600.2 in my hand. And the amp is rated 600w x 2 at 2 ohms, but the birthsheet says 238 x2 at 4 ohms and 737 x1 at 2 ohms with less than .1%THD
 

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Discussion Starter #11
the birthsheet was just a printout on a piece of white paper that said the amp name and rated specs vs. the actual specs and it had the shops name on it also.
 
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