Installing Amp in 2013 Passat with Factory Fender Amplifier

Hey all, I'm doing an amp install tomorrow, 8/5, and am trying to figure out what the best input method is going to be for the amp in my car. Here are the specs and parts I have on hand; Vehicle: 2013 VW Passat with Factory Fender amplifier and Subwoofer in trunk *this will be important for my question Amp: Kicker 2019 Model CXA400.1 running at 1ohm Sub: Rockford Fosgate Shallow Mount 8 inch running at 1ohm Kicker LOC: Capable of 55 watts in and 8v out Kicker High Level Inputs: basic high level inputs with RCA cables on the end So here are the options I have because the amp can do high and low level inputs. 1. Connect the Kicker LOC before the factory amp ensuring I get the full frequency spectrum 2. Connect the Kicker LOC after the factory amplifier using the subwoofer outputs in the trunk as the inputs for the LOC. 3. Connect the High Level inputs before the factory amplifier 4. Connect the High Level Inputs to the subwoofer outputs in the trunk after the factory amplifier I do like the range of the factory amplifier sub so it's frequency spectrum is something I am happy with if that makes a difference. I have never dealt with a factory radio or factory amp before and am just a guy who installs his own stuff but I want to make sure I get it right so any advice would be awesome. Thanks all! Bryce

1 vote for option 2

Is there any reason why you feel that would be the best choice? Just looking to understand more

After doing some research on The Google on the LOC vs High Level Inputs it seems like a lot of unqualified people like myself jumping in and clouding the arguments between knowledgeable folks so it's kind of hard to pick a part the factual information from the BS ya know especially when adding the variable of using the outputs of factory amplified subwoofer outputs. Anyways,long story short, @i am an idiot, I figure you either were an idiot when you joined back in 2006 and are a knowledgeable beast now after all these years or that is sarcasm and you knew it from the start, either way I figure you know what you are talking about so I'm headed with option 2 so thank you! If you see this and get around to an explanation for my knowledge that would be great. Thanks!

I always recommend using a line out converter, especially for the diy guy. Especially now days with the lack of repair options for factory radios and amplifiers. There is a much greater chance of grounding a speaker wire that you ran 15 feet from behind the radio to the trunk. I know in your case you will not be running it that far, but there is still many places you could run it somewhere that it may get pinched. Grounded speaker wires can take out a deck or an amplifier. If you use a line out converter with just the 6 inches of wire that came on it, a lot less chance of a grounded wire. If you pinch the rca cable, no damage other than the cable.

Oh so it didn't have anything to do with the actual properties of an LOC vs High level inputs on those subwoofer outputs?

Ok so a couple updates and I'm still using this thread because I feel it may still be relevant to the input choice I used so be patient with me. I was impressed with the sub that I had, it was something I had previously and fit without much work in my factory vw box so I wasn't out much here. Basically I wanted more bass but the sub couldn't handle any push for extra power *or so I thought but we will come back to that... So I got an insane deal on a JL Audio 10TW3-D4 which I have wired at 2 Ohms getting I would guess 300 watts rms based on my gain setting on my amp. Now finally I don't have to worry about distortion or anything and can just let whatever song comes on just play. The thing that brings me back here though is that songs that I know the sub sections of well from previous installs/cars seem to be quiet in some spots of the songs on this setup and then other parts of the same songs with lower drops hit hard and sound great! It seems to be that the "higher" bass lines are quieter as if they don't go through the subwoofer as much or something but the "lower" bass lines are as expected. I have my stereo set to 7/8 of the way up on the bass setting which should be supplying plenty of input to my LOC, I have my gain on my amp to about 7/8 as well, Low Pass Filter is at about 85, and Bass Boost I have on an adjustable remote that is about 3db out of 6db although I have increased too. Is it possible that because I'm using the subwoofer outputs from the factory amp that they are only feeding it like say 50 hertz and down for example instead of what I'm used to sending which is like 80 or a little more so I'm not getting the opportunity to play those higher notes through my amp? What's a possible solution?

I should mention that in the wiring schematic for audio the factory amplifier mentioned bass speakers as well as subwoofer so I know it on paper has them defined somewhat differently at least but what that means in the amplifier I don't know. I'm just a guy who likes good audio lol and I don't like it when only my rap bumps and my rock doesn't bump at all and my sweet JL sub is just sitting there

Any thoughts?

You could try setting your amp's crossover higher since the factory sub is already crossed over. It doesn't have to be as high as it goes, just set it around 200 and check for a difference. An RTA would help pinpoint what frequencies are getting to which speakers. If you don't have one, there's an app called RTA analyzer that may work for you (haven't tried it). I'd test at a lower volume level. If your factory sub is crossed over at a lower frequency, then perhaps you could use a processor (instead of a simple LOC) to sum inputs from other speakers as well for a broader range. Then feed that to your amp.My ex once told me I have a perfect face for radio.