Question about Rockford Fosgate Punch 401S Car Audio Amplifier

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Frequencies I have a lpf on my head untit and i have an lpf on my amp. The amp is powering subs and I know the lpf is supposed to be on. My question is which lpf should i use the head unit one or the amps or both, and what frequency should they be set on? one more thing the head units lpf has a -24Hz to +6 Hz for 50Hz, 63 Hz, 80hz, and 100 Hz.

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  • ronnieyannon Apr 24, 2009

    Thanx for the help.

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Hello again ronnieyannon,

It's probably best to allow the amp that is powering the subs to control the frequencies going to the sub(s). I would not use the lpf on both the head unit and the amp in any case. The control settings are not completely precise and you could end up with a lot of tweaking between the units to get the sound you want. I'd send full range to the amp and with it playing something with a lot of bass, set the 401s to "LP", the crossover slope to near maximum, and then adjust the frequency until it sounded best to me. Starting on page 11 of your manual are the Rockford-Fosgate recommended adjustment procedures, including setting the gains and the filter frequency.

Those numbers for the lpf on your head unit sounds like it allows you to decrease (-24dB), as well as increase (+6dB) the bass at the specific frequencies of 50, 63, 80 and 100Hz. You probably don't want to decrease the bass boost for subs. And the 401s will allow a boost up to 12dB and is variable from 50-250Hz.

Hope this helps.

Posted on Apr 24, 2009

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