How to run 4-channel amp with a seprate powered sub to door speakers? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 3 Old 06-19-2020, 02:47 PM - Thread Starter
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How to run 4-channel amp with a seprate powered sub to door speakers?

Hello,
I have a 2013 Jetta (no Fender system, no CD changer). I'm planning on doing my first install. I bought 2 5.25"s for the front, 2 6.5"s for the back, and a small 8" powered sub for the trunk. My back door speakers are Kenwood 1696 with 100W RMS and 320W peak. The front doors have Rockford Fosgate R1525X2s with 2-40W RMS and 100W peak power. For the powered sub I bought the Fosgate B8P. I keep reading that I'll need an amp for the door speakers as they won't sound good without an amp. 1. How would I run a 4-channel amp to my door speakers while also running speaker wire to my powered sub? 2. I bought an 8 gauge wiring kit for the powered sub, what would I need to wire the amp? 3. Would I need to run speaker wire from the amp to all 4 door speakers, or can I somehow send the amplified signal back behind the head unit and connect it to the 4 speaker wires? I'm 16 and it's my first install, so please explain in simple terms. Thanks in advance!
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post #2 of 3 Old 06-19-2020, 09:55 PM
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Quote:
Originally Posted by Raymo41 View Post
Hello,
I have a 2013 Jetta (no Fender system, no CD changer). I'm planning on doing my first install. I bought 2 5.25"s for the front, 2 6.5"s for the back, and a small 8" powered sub for the trunk. My back door speakers are Kenwood 1696 with 100W RMS and 320W peak. The front doors have Rockford Fosgate R1525X2s with 2-40W RMS and 100W peak power. For the powered sub I bought the Fosgate B8P. I keep reading that I'll need an amp for the door speakers as they won't sound good without an amp. 1. How would I run a 4-channel amp to my door speakers while also running speaker wire to my powered sub? 2. I bought an 8 gauge wiring kit for the powered sub, what would I need to wire the amp? 3. Would I need to run speaker wire from the amp to all 4 door speakers, or can I somehow send the amplified signal back behind the head unit and connect it to the 4 speaker wires? I'm 16 and it's my first install, so please explain in simple terms. Thanks in advance!
So a bunch of thoughts about this, having spent many years at a giant autosound company (and actually my old business partner supplies Rockford, so good call on your purchases).
- I would first of all ditch the rear speakers. I am dead serious. They are a historical accident because cars were very noisy, radios had little power, and back seat passengers could not hear the sound. Now they serve no audio purpose-well except to fill in some bass to cover up the poor sound of crappy front speakers. Nobody sets up front/back stereo at home, it's dumb. I've ditched them in every car now for a long time, never missed them a bit. Plus now you need just a 2-channel amp
- Then you just wire the rear speaker outputs to the subwoofer inputs, and the head unit fader will essentially become a subwoofer level control.
- Yes the fronts must have an amp WITH an adjustable highpass crossover to really shine. I like Alpine but you can't go wrong sticking to Rockford. The wire gauge would depend on the amp-they can tell you if the owner's manual doesn't already.
- Your sub has adjustable lowpass crossover? What is the model number? (Because I don't find "B8P").
- Don't get one of those exact-fit CarPlay radios, my old biz partner knows the factory, those have had a lot of problems. A new generation was supposed to fix that but stalled due to COVID.
- Then you need to tune the crossover, that is a whole different thread as I'm not up on the latest for that. The bass-ic thing ha ha is to start with the both crossovers at 80 Hz, and flip the polarity ("phase" or "0/180"). Whichever position has more bass is correct. Then usually you want to spread the crossovers apart and somehow measure.
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post #3 of 3 Old 06-19-2020, 10:34 PM - Thread Starter
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Wow I had no clue. I might leave the rear door speakers on and just turn them down from the head unit as I'm planning on selling the car in a couple years. I will cancel the rear door speaker order though. Thanks for saving me money!

As per the woofer, it's actually the Fosgate P300-8. Since it's a small car I thought that the bass will be adequate if I throw it in the trunk.

If I was to keep the stock rear speakers but use them as the bass connector, should I just snip the wires for now?

Thanks for all the help 🙂
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