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bridging my headunit

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  • bridging my headunit

    i am installing new speakers and a head unit in my friends car. he does not want to install an external amp. instead he wants to use the head unit amp which outputs 50W x 4 channels peak, typically 20W rms. i did the install for him but the sound coming out of the speakers is extremely low with the volume to the max. i dont think i did anything wrong but there is no way the output power per channel is any where near 20W.

    the speakers i'm installing are a bit strange to me, they have 2 sets of inputs, one set says full range and the other say subwoofer boast. blaukpukt make them. because i wasnt sure which inputs to use, i shorted the 2 positives and the 2 negitive on each of the 4 speakers and plugged them into the head unit. does that sound right to anyone?

    also, because I am getting extremly low sound, does anyone know if the headunit can run into problems if i bridge the 2 left speakers (front and rear) and 2 right speakers (front and rear) and leave the other two channels open?

    if anyone has any suggestions, that would be great, thank you.
    http://www.mp3car.com/vbulletin/showthread.php?t=53815

  • #2
    Well I'm no expert, but if they manufacture speakers with 4 connectors, then why on earth would you short them to make 2? Did you try connecting it to just one pair at a time?
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    • #3
      Firstly, if you don't know what you're doing, find a manual or call someone.

      If you're connecting these speakers to a headunit, I'd suggest ONLY connecting to the 'full range' connections.

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      • #4
        bridging channels on a HU is NOT DONE! if you do so, your HU-amp runs @ 2Ohm and it CAN NOT handle that low impedance!

        ask your friend why he doesn't want any amp. if the reason is gving up space, there are enough pretty small amps you can put onder the passengerseat ore something. and it doesn't have to be expensive.
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        • #5
          Originally posted by 2k1Toaster
          Well I'm no expert, but if they manufacture speakers with 4 connectors, then why on earth would you short them to make 2? Did you try connecting it to just one pair at a time?

          he had a pretty nice system installed before this and i uninstalled it. while i uninstalled it, i noticed the positive and negitives were shorted and the speaker wires went into an amp.

          on one of the rear speakers i tried connecting only one pair, it did not make any difference on that speakers so i did not disconnect the rest. i kept the full range connection in and removed the subwoofer bass boast.

          Originally posted by IC-C30
          bridging channels on a HU is NOT DONE! if you do so, your HU-amp runs @ 2Ohm and it CAN NOT handle that low impedance!

          ask your friend why he doesn't want any amp. if the reason is gving up space, there are enough pretty small amps you can put onder the passengerseat ore something. and it doesn't have to be expensive.
          i can understand why you wouldnt bridge speakers into headunits because the output power would double on each channel and that requires more current out of the head unit because now the load is only 2 ohms instead of 4.

          but im thinking if i only use 2 of the 4 outputs of the head unit, there may not be a problem. like i said, if i bridge the left audio into one channel, i would be able to get ~40W RMS speaker, and if i did the same thing on the right audio i would get ~40W per speaker also. thats ~80W RMS out of the head unit, the head unit can output this. i am not sure if everything would go through the way i explained because i am not sure of the internals of the head unit and it might be that if the head unit see's a smaller load, other than 4 ohms, its going to draw more current and something in the head unit can fry.

          i still dont understand on my orginal setup why the sound is really really low and i know its no where near 20 watts, its not even outputing 5 watts i would say. i'm not trying to get max power to the speakers to listen to super loud, i want to to be like a factor head unit of a desent car like a nissan or something. not a crazy loud system with subwoofers, caps, and all.

          my friend doesnt want to invest any more money into this car, he is selling it and he wants some sort of stereo to be installed to help it sell. he had the head unit and speakers laying around and we just went out and bought speaker wire and cramping supplies. he had an awesome system installed but he wants to put it in he next car so i uninstalled that for him. like i said i dont think i need an amp and i really dont want to bridge speakers because i could damage the headunit.

          any other suggestions on why the sound is low when i dont think it should be would be very helpful. thank you.
          http://www.mp3car.com/vbulletin/showthread.php?t=53815

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          • #6
            i attached a picture of my setup. i hacked the male side of the RCA connecter to solder and crimp the speaker wires to plug into the female that came with the head unit. on the manual of the head unit it says use the chassis of the car for gnd, i used the negitive terminal instead. i dont think it makes a difference. let me know if you find a reason why the sound may be so low or any suggestions. thank you.
            Attached Files
            http://www.mp3car.com/vbulletin/showthread.php?t=53815

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            • #7
              from the pic above it appears that you are using the amp outputs instead of the speaker outputs. Which in that case would explain the extremely low sound. There should be speaker outputs coming from the head unit.. green - green/black, purple - purple/black, white - white/black and gray - gray/black those are the standard colors for your speakers.. the RCA's are to go to an amplifier and are not designed to go to speakers.
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              http://mp3car.com/vbulletin/showthread.php?t=75182

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              • #8
                White sounds like right so it's left. Remember this bit of wisdom.

                And when installing an alarm remember "Green means go but you can't go because your doors are locked." Sage words indeed.

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                • #9
                  As said.. RTFM.

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