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    jeffandpamsmith's Avatar
    jeffandpamsmith is offline Junior Member



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    Help connecting subwoofer RCAs on head unit to amp.

    This is my first post, so be gentle. I tried reading and searching, even called Alpine, and I'm still not sure (Alpine guy didn't sound sure either).

    Head unit is Pioneer Premier FH-P800BT, amp is Alpine PDX 4.100. Installing in a Smart Cabriolet (you know, the 8 1/2 foot car - don't laugh - its a great car). Speakers are one pair component Focal Access 165 A1, and JL Audio 8" W3V3 4 sub (yes it fits, and you can't even see the box without trying hard)

    I'm doing this myself, and am trying to "measure twice - cut once" ... so to speak.

    I have everything figured out and wired so far (I think) but the last step is hooking up the Pioneer sub out to the amp. I can't figure it out from the Pioneer manual, nor the Alpine.

    Channels 1 and 2 on the Alpine are for the Focal speakers. Channels 3 and 4 on the Alpine are going to be bridged for the sub. Both the Smart aftermarket place where I bought the stuff online, and Alpine say to hook the + speaker lead from the sub to the + output on the Alpine for channel 3. Then hook the - speaker lead on the sub to the - amp out for channel 4. They both say I don't need to do anything else to bridge the amp.

    I didn't know to ask, but the Pioneer has 2 sub out RCAs, and the Alpine has RCAs in for both channel 3 and channel 4. Since the channels are bridged, how do I configure the RCAs?

    Do I need to use both sub outs on the Pioneer to get all the sub signal? If not, which one do I use - L or R? Then on the Amp, do I need RCAs in to just 1 channel (either 3 or 4) and is so, which? Or do I hook up both sub outs on the Pioneer to both channels on the amp?

    Alpine waffled (and this was their tech guy). He agreed on the output from amp to speaker/sub, but seemed to wander around on the RCA issue...saying that only 1 would probably be needed, then talked about using a "Y" connector to get both input RCAs into 1 amp channel, but didn't specify amp channel 3 or 4. Then he said I could run both, but prob didnt need to. I'm confused and don't want to power anything up till I hear from someone who knows more than me.

    The sales place in CA (I'm on the other coast) was hard to get to talk to their installers, but I will call them tomorrow, I want to learn more if I can.







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    Einzee's Avatar
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    Re: Help connecting subwoofer RCAs on head unit to amp.

    You will use both sub outs on the Pioneer and connect them to the Alpine Amp. This is done like this because the "Left & Right" each have a signal OR the RCA outs are mono and it is safe to just use both of them so each input on the Alpine gets the maximum signal. The Amp will combine that signal into one output and then onto the sub.



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    Re: Help connecting subwoofer RCAs on head unit to amp.

    Rats (I only ran a 3 wire RCA - but can easily get another) but thanks.

    Follow up question on amp and head unit grounding: a sticky thread here says ground the HU directly as the factory grounds are often poor. I had it hooked up thru an adaptor to make the Smart plug wires fit the Pioneers, but after reading here ran a better wire to the black (ground) wires to the "main" ground. Question is: Alpine says ground all items to the same ground to prevent probs, Pioneer says use diff ground "in case on ground comes loose" (or some such). In the Smart the battery and main ground are all inside the car under the passengers feet, I can connect all to the obvious big bolt very easily, should I?

    Also, I pre-emptively did the "Pioneer RCA plug ground wrap around with bare wires to better ground the jacks" in the "whine" sticky, don't know if its still needed with this unit but figured it couldn't hurt...true?




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    Einzee's Avatar
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    Re: Help connecting subwoofer RCAs on head unit to amp.

    Quote Originally Posted by jeffandpamsmith View Post
    In the Smart the battery and main ground are all inside the car under the passengers feet, I can connect all to the obvious big bolt very easily, should I?
    I dont see a problem with using that particular spot as long as the original factory connection is not compromised by the terminals that you install.

    Quote Originally Posted by jeffandpamsmith View Post
    Also, I pre-emptively did the "Pioneer RCA plug ground wrap around with bare wires to better ground the jacks" in the "whine" sticky, don't know if its still needed with this unit but figured it couldn't hurt...true?
    I havent researched that issue and cannot offer advice.



    Stupid questions make more sense than stupid mistakes!

    It is best to remain silent and be thought of as stupid, rather than opening your mouth and removing all possible doubt!

    Quote Originally Posted by Twistid View Post
    Try taking the positive wire from your battery and run it to the engine block, see if that should fix things...
    Quote Originally Posted by PaulD View Post
    THE FUSE AT OR NEAR THE AMP PROTECTS THE AMP. WIRES DO NOT NEED "PROTECTING" WITH A FUSE SINCE THEY ARE NOT POWER PRODUCING DEVICES.
    Quote Originally Posted by shake this View Post
    Which one sounds better (short small diameter or long large diameter)?

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    Re: Help connecting subwoofer RCAs on head unit to amp.

    Hmm. Won't that reduce your mileage putting a sub in one of those things? And are you sure it has the torque to pull a sub?

    Okay, done laughing at the car. But yes, run both the outputs on the stereo to the amp for channels 3 and 4. And that'll work for the place to run power/ground.




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    Icon32 Re: Help connecting subwoofer RCAs on head unit to amp.

    I'm piggybacking on this thread because I have a similar scenario. I have the FH-P8000BT head unit. This will drive two 6.5" Pioneer door speakers in the front, and two 4" Pioneer speakers in the rear (mounted in the headliner.) To boost the bass I'm putting a small sub in the rear, connected to a Pioneer GM-3300T amp. Only the sub will run through the amp.

    My question is how to wire this. As noted above, the Pioneer installation options are limited (two) and unclear.

    I'm thinking I will use the harness connections to wire the four full range speakers (ie, a "normal" car radio install) and set the hi-pass. Then I will use the two RCA subwoofer outputs to feed into the amp, set the corresponding lo-pass, and then bridge the two amp outputs to drive the single sub.

    Is this the correct way to do this?

    TIA




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