Question about Alpine MRP-F300 Car Audio Amplifier

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Subs have almost no sound coming from them

My subs have very little sound, can't even tell their on unless you put your hand directly on them. The amp is a brand new 4 channel Alpine f-300, that i have bridged for 2 channels. These subs did the same thing with a previous cheap amp. I have the filter set to lp, and i have tried every setting and dial on the amp, none seem to make much if any difference. My head unit does have the subwoofer mode turned on, and i have gone through and adjusted every audio setting on it. They do seem to make a little more noise if i turn the bass all the way up on the head unit, but then my full range speakers distort easily and i can't get much volume out of it. The subs and the amp are both 4 ohm, i even ohmed out the subs and they checked out. I have checked and repositioned my ground. I even tried hooking up other subs and got the same results. All in all i have tested combinations of 3 different amps one of which is brand new, and 4 different subs with all the same result, just a barely audiable beat. The only other thing i can come up with is to pull the head unit and run new RCA's, but since i am getting a tiny bit of sound, i wouldn't think they would be the problem, because that would mean they are sending a signal, like their supposed to. Though other than trying that i'm out of ideas...

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  • meow_mix_666 May 10, 2009

    Actually i did get it working today, and it was the rca's. I have 2 of the same amp, one for my subs and one for my full range speakers. Both of my amps have a set of rca pre-outs on them. And since my full range speakers, use the speaker level input wires to get their signal, i ran a set of rca's from that amp, to the amp from my subs and sure enough they both started pounding. So i just abandoned the old rca's coming from the head unit, and saved me the trouble from ripping my dash apart again. Though still one sub pounds harder than the other, i'm not sure what would cause that.

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  • 655 Answers

Hello meow_mix_666,

If you have tried different amps and different subs with the same result, I'd definitely suspect that you are not getting enough of an output signal from the head unit. Checking the RCA's and perhaps using a different set of preamp outs would be a good idea.

One other possibility that you may not have considered is to check the phasing. I've run into speakers that had the markings reversed and running the subs out-of-phase on a 4-channel bridged would make a huge difference in the bass.

Hope this helps.

Posted on May 10, 2009

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Posted on Jan 02, 2017

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Mitco39
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SOURCE: Alpine mrp-350 amp

1) If you bridge on a non bridged amp your sound will be horrible as they sine waves comming out of the two teminals will be different... I suggest removing the bridge. 2) The gain knob is to adjust when the amp will reach its max volume with respect to the sterio;s volume. 3) the LP filter is a Low Pass filter and its purpose is to eliminate the higher frequencies that do not sound all the well when played over subwoofers.

Posted on Mar 26, 2007

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SOURCE: Car amp's stopped working. Putting out a heart beat sound through subs but no bass.

could be low current ,disconnect all power including ground for 20min N.B most amps will seem to be shorted at output but this is normal due to damping ratio.

Posted on Aug 09, 2007

etirbynnor
  • 655 Answers

SOURCE: The subs aren't pushing out bass.

Hello crobins2,

The Kenwood KAC-6202 2-channel is only rated for 60 watts RMS per channel into a 4 ohm load. That just isn't much power for a pair of 12" subs. Even the bridged output is only 200 watts into 4 ohms, still at the low end for a sub, much less to share between a pair of subs.

Assuming that your subs are 4 ohm, you could probably get more sound by driving just one of them on the bridged terminals. But to get the best power with what you have, connect one sub to each channel, set the filter switch to the far right (LPF), set the operation switch to stereo (both channels driven), set the filter frequency (Hz) to 100 or lower, and adjust the input sensitivity as far clockwise as possible without causing distortion.

But, to do the subs justice, you really need at least 300-400 watts to share between them.

Hope this helps.

Posted on Sep 27, 2009

  • 53 Answers

SOURCE: 2 alpine type r 15's 4 ohm dvc and 2 american bass


Option 1 (parallel) = 0.5 ohm load
Voice coils wired in parallel
Recommended Amplifier: Stable at 1/2 ohm mono This set up will blow your mind as your amp will put out 1800rms at 0.5 ohm

4_4ohm_dvc_05ohm.gif

Posted on Oct 19, 2009

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