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4 channel amp for 3 speaker system in a truck???

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  • 4 channel amp for 3 speaker system in a truck???

    Hi Guys...

    I need some amp advice as I slowly work towards my truck PC.

    Just ordered Pioneer P7600MP head unit, 2 Infinity 4"x6" Kappa 462.5cfp (plates), and 1 Kicker S8L7 8" Sub. Everything is due on the 12th and I will be installing this coming weekend.

    The 8" Sub says it can go 900w RMS at 2ohm (these guys come in 2 and 4ohm and I ot the 2ohm...perhaps I made a mistake?).

    The kappa's say 90w RMS at 4ohm.

    These components are going in an 87 s10 STANDARD cab truck and I will be doing some peel & seel or dynamat.

    I need an amp (I guess a 4 channel ?? ) for the system and frankly I am confused by all the selection choices. The source of my confusion comes mostly from the ohm impedence ratings.

    As the Kappa's are 4ohm and the S8L7 is 2ohm...I need an amp that will make the most out of what I ordered and really need suggestions.

    I know asking such a general question is like asking what color I should paint my house and is very subjective but I have tried to read up and research (google, here, crutchfield etc..) but am confused and just want to order an amp and be done with it!

    I don't want to compete, I am only looking for some decent tunes that will not cost me a fortune.

    Hoping to spend no more than $250 if possible.

    Thanks fellas

  • #2
    This is what I've found so far in my research. I am not an expert, just learning like you...

    2ohm speakers with draw/suck/pull/consume twice as much power as a 4 ohm.

    The standard in car audio is 4 ohm so your headunit is likely 4 ohm and unless specified, assume any amp you look at is only rated for 4 ohm.

    To drive the sub you need a amp that is stable at 2 ohm (meaning it can provide enough power to a 2 ohm speaker with overheating or distorting).

    I just bought an Alpine MRP-F240 ($250 CDN). It is 4 channels and 2 ohm stable which I think would work for you. In addition, it is physically smaller than most amps - important to me so I could fit it under the seat.

    As an advanced topic, the amp is also bridgeable. Which means you can combine 2 channels together to drive one speaker at double the power (but the same ohm/impedance). So you could use channels 1 and 2 for the Inifitys and bridge channel 3 and 4 to drive the sub. However, this more advanced and you can probably get good results without bridging (and leave one channel unused).

    For more info:


    • #3
      You shouldn't have bought the two ohm version in general. Your best choice at this point is to look for a 3 channel amp that is 2ohm stable (not sure if anyone is making such an amp) OR and this might be the more likely choice, a 4 channel amp that is 2ohm stable when bridged (that means it will need to be listed as 1 ohm stable in stereo).

      One of these combinations should exist, I just haven't looked at what was availible in quite some time.


      • #4
        Thanks fellas.

        So...I am now even more concerned. The Kappas are 4ohm rated....does this mean I can't run them at 2ohm? Also, does the inverse hold true...meaning, can I not run the 2ohm S8L7 at 4ohms?

        Does anyone know of an amp that can do 4 ohm front channels and 2 ohms when bridged for the rear single 8" sub?

        Man....I am not wanting to deal with an RMA and restock fees....What a hassle.

        Any reccomendations gladly accepted.