cnwahlheim

I am thinking of disconnecting my factory subwoofer and adding an aftermarket sub and amp to the OEM setup. I would need to tap into the signal wire that originally went to the sub for the input to the amp, but am not sure if I should tap into it before or after the factory amp. Does anyone have experience with this?

Vlad_Type_S

iTrader: (3)

Dude, when I started kicking around this idea, I had the same exact question! I think that the answer depends on your ultimate goal.

If you just want to add a sub and leave the rest of the system alone, you have two options (like you already said lol):
1) Tap in before the amp. This would require you to cut the factory harness, solder on some RCA connectors, and run the signal wire to the aftermarket amp. This is cheap, but labor intensive.
2) You can get a line-output converter product such as the Scosche LOC80-2. (The first one that popped up with a google search.) This would hook up to the sub speaker wires after the factory amp (conveniently accessible from inside the trunk! ) http://www.crutchfield.com/p_142LOC8...che-LOC80.html
This would be the easiest way to simply add a sub. The inputs to that converter are high impedance, so the factory amp isn't working hard at all to drive it. This was my first misconception: if I tap in after the factory amp, the factory amp is wasting power to drive that signal. Because the impedance is so high on these converters, very little power is wasted. This option is more expensive, but much easier.

Finally, the only reason to NOT do this is if you eventually want to upgrade your entire audio system. The reason is that you're kicking some money down the toilet installing this line out converter when eventually, you'll bypass the entire factory amp with something like an AudioControl Matrix. But realistically, you're only kicking down like 20 bucks and I'm sure you can flip your equipment for half price.

Any other guru's care to chime in? I'm a self-taught installer so I am willing to wager there are aspects to this question that I am not considering.

cnwahlheim

Thanks for the detailed response. I may eventually upgrade the entire system, but for now, I am pretty happy with everything except the subwoofer. Which route did you eventually choose?

cnwahlheim

Also, how do you determine which wires, pre-amp, are the output for the subwoofer?

Vlad_Type_S

iTrader: (3)

I've been reading so much about it on this site that I've decided to go full blown with an infinite baffle build and a really nice component system. I've been inspired reading some of these amazing audio build threads. I'm still at a stock setup because I'm saving up and paying off other debts. These cars are an expensive habit.

If I were just adding a subwoofer, I would definitely go with the line out converter option because of how easy it would be to install; you don't have to mess with any other part of the system at all.

I'm not sure I understand your question. If you mean, what would serve as the input to the line output converter, the answer is the speaker level subwoofer signal after the factory amp. The best way to access this signal would be to get at the factory subwoofer connector under the rear deck. Once you get all the trunk trim off, it should be fairly obvious. Just unplug the connector to the subwoofer .

To get at it, I recommend cutting off the factory subwoofer connector with like 6 inches of slack on the connector, just in case you ever need to reattach it. That way, you can put back the factory sub if you needed to. I recommend soldering and heat-shrinking your connections when possible, that's the most resilient way to connect wires in the face of the harsh automotive environment. If you decide to use any sort of crimp/splice, I encourage use of some sort of dielectric grease to prevent rust and corrosion.

cnwahlheim

Thanks, Vlad. Sorry for not wording my question about the input wiring more clearly. I was trying to ask, when I am looking at the wiring harness that goes into the amp from the OEM head unit, how do I determine which wires correspond to the subwoofer? Are they labelled in some way?

Regarding whether to tap into the wiring pre- or post-amp, I agree that is sounds much easier to tap in after the amp, but does that mean the signal has been subjected to processing? Would I get a more "clean" signal tapping in before the amp? I am wondering because I would prefer to have more control over the crossover points and have fewer "boosts" at various frequencies.

will1018

In my opinion, I would definitely go the LOC route. I initially wanted to install a single sub and didn't research at all. Having no idea what I was doing I ended up cutting off the entire harness for the oem amp. I was an idiot haha. I ended up having no sound in my car for 3 weeks till I finally got an amp to power the rest of the speakers. I also had to get a line driver, which i didn't like, so my head-unit is completely useless. my whole system is currently running off of a aux cord connect to my equalizer, haha. I essentially screwed myself over and forced myself to upgrade my entire system. The lOC makes life a lot easier. the best part about it is that you dont have to remove the rear deck. I mean it would make it easier but you can get away without having to. All you do is unhook the + and - wires from the stock sub cut off the oem harness then solder or twist the wires to the wires coming out of the loc then you run a RCA cable from the LOC to your sub amp and your good to go. the best part is you still can control the sub volume from the headunit.

heres one a friend of mine used in his car, Its cheap and it got the job done.

http://www.sonicelectronix.com/item_...AX-ALOC10.html

Gregerst

iTrader: (1)

I think vlad has summed it up pretty good. The easiest route would be to unplug the factory sub and use the wires to connect to the high-level or speaker-level input on your sub amp. A lot of amps, but not all have these. If it doesn't than use a LOC. The signal after the factory amp is crossed over at 80hz but shouldn't matter as you generally want to play your subs at or below that freq.

I hate cars

Preamp is the cleanest signal. Post amp will have a hiss but since you're only adding a sub and the hiss will be cut by the lowpass filter there's no good reason to go preamp.

If you end up adding aftermarket front speakers and amplification you would want to consider preamp since the hiss will then be audible.

cnwahlheim

Thanks so much for all the great information!!