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Bridging an amp for subwoofer wiring

Discussion in 'Audio & Video' started by double_b, Sep 14, 2014.

  1. Sep 14, 2014 at 10:49 AM
    #1
    double_b

    double_b [OP] Well-Known Member

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    I have an Alpine PDX F-4 that I currently have channels 1 and 2 driving my front components. I built a sub box with a RF Punch and want to use channels 3 and 4 of the amp to drive the sub. I have a Pioneer NEX4000 HU so I have subwoofer output connected to channel 3 and 4 of the amp. I then ran the positive from channel 3 and negative from channel 4 to the + and - of the RF sub (I have it wired for a 4 ohm load according to RF directions). I got nothing. Yes I turned on the sub in the HU settings.

    The Alpine instructions are a little unclear to me. They show two different wiring diagrams for a 3 channel setup. I assumed the top one shown below would be what I want since I have a subwoofer out from the HU. Obviously I don't think that is right.

    Can someone let me know how I need to wire it to bridge channels 3 and 4 to drive the single 10" RF sub?

    [​IMG]
     
  2. Sep 15, 2014 at 5:02 AM
    #2
    Lurkin

    Lurkin Well-Known Member

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    Sounds like you have it right. First thing I would do is double and triple check my wiring. If that doesn't help, I would start switching 1/2 and 3/4 channel inputs and outputs to see if the problem follows the inputs, outputs, or amp.
     
  3. Sep 15, 2014 at 7:48 AM
    #3
    Indy

    Indy Master of all I survey.

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    Start simple. Use both wires from output 3, sound? Do the same with 4. If either doesnt work youve found your problem.
     
  4. Sep 15, 2014 at 8:23 AM
    #4
    adrenalnjunky

    adrenalnjunky Well-Known Member

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    can you do two things - post a pic of your current connections at the amp, and any chance you can pull your sub out and show us the wiring there? Is this a SVC or DVC subwoofer?

    do you have a multimeter - can you disconnect your speaker wiring and check the ohm load there -make sure that the woofer is showing good?
     
  5. Sep 19, 2014 at 3:53 PM
    #5
    double_b

    double_b [OP] Well-Known Member

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    OK, so I got to work on this a little today. I am definitely getting sound out of all 4 channels of the amp. I verified this by plugging the front components into those channels and I got same sound as channels 1 and 2. Well, after I turned off the LPF on those channels.

    I also switched around the RCA wires to make sure the subwoofer RCA was actually connected to the HU. It is.

    I then just hooked the sub directly to just one speaker connector of the amp(not bridged like I explained in my original post. I got sound, low volume sound anyhow, and I tried that in both channel 3 and 4.

    It is a RF P3 shallow mount with DVC. The only way I got sound was to put the + and - on one side of the speaker. When I would wire it like RF shows in the instructions, + from one VC to the - of the other I get no sound.

    I feel like I have both the amp and the sub wired like both instructions show but obviously I may not.

    I just wanna get the damn thing hooked up and get some low end damn it!! haha
     
  6. Sep 19, 2014 at 10:17 PM
    #6
    adrenalnjunky

    adrenalnjunky Well-Known Member

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    Post a pic of exactly how the sub is wired, and exactly how you're wiring it to the amp. Show all of the end plate of the amp so we can see all the connections.

    Also - do you have a ohm meter - sounds like you may have an open voice coil on one side of that P3.
     
  7. Sep 20, 2014 at 10:12 AM
    #7
    Indy

    Indy Master of all I survey.

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    Since you're getting low volume on the rears, have you set the gains?
     
  8. Sep 22, 2014 at 5:22 AM
    #8
    double_b

    double_b [OP] Well-Known Member

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    I can't post a pic of how it's wired because I don't have it wired up currently. I tried several different ways then left it unhooked for now.

    After looking again at RF's wiring wizard it looks like I cannot wired the sub for a 4 ohm load which is what the PDX-F4 needs when bridged. Could that be the issue?

    Here is the screen shot of the wiring wizard.
    [​IMG]

    I was thinking the PDX could do a 2 ohm load, and it can, but not in bridged mode.
     
  9. Sep 22, 2014 at 5:28 AM
    #9
    adrenalnjunky

    adrenalnjunky Well-Known Member

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    Ahhh - I didn't even think about that - You have a P3D4, and no, you can't wire it to a 4 ohm overall load, either 2 or 8. You could wire it to an 8 ohm load, and see if that at least gets it playing for you. Optimally, you'd need a P3D2 (dual 2 ohm coils) sub to series the coils together for a 4 ohm load.

    Or use your 4 channel for the doors, and pick up a little monoblock that is 2 ohm stable.
     
  10. Sep 22, 2014 at 5:33 AM
    #10
    Lurkin

    Lurkin Well-Known Member

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    One other way to run it, if you don't want to reinvest in a sub, is to run one VC off ch3 and one VC off of ch4. This will give you your 4ohm load to the PDX.
     
  11. Sep 22, 2014 at 7:29 AM
    #11
    double_b

    double_b [OP] Well-Known Member

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    Yea, I would return it and get the P3D2 if I could but I am past my 30 days(Amazon) is past. I am considering a small monoblock. I like the size and price of the Precision Power iON series. But I hate to spend any more money. lol

    Would this give me the full 200 (more likely close to 250) RMS that the bridged set up would? Or will this configuration be only 100RMS since it is not bridged? This seems too easy of a solution, what are the drawbacks? haha
     
  12. Sep 22, 2014 at 7:42 AM
    #12
    Lurkin

    Lurkin Well-Known Member

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    This will give you the ratings for 2 x the individual channel. Not sure if the bridged rating on your amp is exactly 2 x stereo channel rating or not. I did this on an older setup I had for the exact situation you are in, I thought I had a 2 ohm stable bridged channel, but was only 4 ohm stable, so had to hook each VC up to a seperate channel. Worked fine for me, and I could not find any documented reference that said this was a bad thing (several comments, but no actual facts to back it up).

    Reality is that as long as the 2 individual channels are set to the exact same settings, so that there is no deviation in the two signals going to the VCs, then you are fine.
     
  13. Sep 22, 2014 at 8:12 AM
    #13
    adrenalnjunky

    adrenalnjunky Well-Known Member

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    It can be done - but you run into issues there, cause you're using independent channels to power each voicecoil - you'd have to electrically match the gain on each channel to make sure you don't have voltage differenitial on the outputs -otherwise one coil would be fighting the other.

    Looks like your amp is rated at 100watts per channel into either 2 or 4 ohm, so you would be giving the sub the same 200 total that bridging it would provide.
     
  14. Sep 22, 2014 at 8:13 AM
    #14
    double_b

    double_b [OP] Well-Known Member

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    Cool, thanks. I did a quick Google search on it and Crutchfield states just what you are saying. Can wire the VCs independently as long as channels are exactly the same. I don't have an ohm meter, can I assume since it is just channel 3 and 4 of the same amp it will be the same?

    Also, I am assuming that the connection for each VC is on the same side. In other words, the + and - post next to each other is for one VC and the other VC is on the other side of the speaker and by the wiring diagram above they are "bridging them together" hence using + and - from each side of the speaker?
     
  15. Sep 22, 2014 at 8:23 AM
    #15
    Lurkin

    Lurkin Well-Known Member

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    I assume that you will still use ch 3 & 4 for the VCs. Inputs should be the same, since most amps only allow an input from the HU for 1 and 2, then for 3 and 4. Gains are also usually the same, either one gain setting for all channels, or one for the Front and one for the rear. As for what is + and - on your sub, I don't know, but you need to make sure you get that right. The +/- on each VC must be consistent.
     
  16. Sep 22, 2014 at 8:29 AM
    #16
    adrenalnjunky

    adrenalnjunky Well-Known Member

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    typically VC connections are grouped per coil on either side of the woofer - quick search of the current P3's on the web shows that as well.

    As for the channels being the same - looking at the manual for your amp - there only appears to be a single gain shared between channels 3/4 - so you should be good there.

    Good luck!
     
  17. Sep 23, 2014 at 10:54 AM
    #17
    double_b

    double_b [OP] Well-Known Member

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    Thanks for all the help guys. I ran the wires from channels 3 and 4 last night and hooked them up independently to the VCs. I got sound, albeit low rumbling since it was just the sub laying on the seat, I had taken it out of the enclosure.

    Have to carpet the box and put the sub back in and hopefully I'm good to go. Like I said even though it wasn't really loud volume coming out of it I know it's because it was the bare sub, no box.
     
  18. Sep 23, 2014 at 11:15 AM
    #18
    Lurkin

    Lurkin Well-Known Member

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    I would search up amp gain tuning, get yourself a cheap DMM, and set the gains appropriately. I would suspect your volume issue is in the tuning. Even without a box, the cone will move quite well if it is powered sufficiently.
     
  19. Sep 23, 2014 at 4:36 PM
    #19
    double_b

    double_b [OP] Well-Known Member

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    Well I guess I'm destined to not have a subwoofer in my truck. Finished the box, hooked it up and it's barely playing, soooo low volume. I don'y know what else to try. I tried switching the + and -, turned the gain all the way up. Oh well. It was a nice idea anyhow. It can be for decoration back there.

    So mad right now.

    Maybe I'll take it to a shop and let them screw me over.
     
  20. Sep 24, 2014 at 4:18 AM
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    ike3000

    ike3000 Well-Known Member

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    have you tried playing around with the crossover settings between the HU and amp? try turning off the crossover on the amp and just use the HU, or vice versa
     

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