Maybe a stupid question..

Hey all. I am not a electronics guy in the least, all handyman. Question, can I run a new amp and sub, connect to a speaker wire for sound and use the amp for tuning? I know it’s not iideal but I don’t need a screaming system. 2nd question, if I do this does the factory amp still power the remaining speakers so when I upgrade them they are boosted?

 

Yes you can do that if your amp has a line level input. Make sure you use a speaker wire that is on a full range speaker and not a tweeter that may be crossed over. Not sure what you mean by using the amp for "tuning"

 

Basically setting the bass level at a reasonable spot. I know some fine tuning will still be capable with the head unit.

 

Ok yes, your amp output should be adjustable using the line level input

 

Need to get a signal converter to do it right. This is about the best one on the market.
https://www.crutchfield.com/S-6up1m...7XyRK5bKysNOPnPckRowNd7q6Vhe7TbBoCxV8QAvD_BwE

 

If the amp you purchase has line level inputs (its a terminal that speaker wires can be attached) then that would work.

If the amp doesnt then you'll need a "line output converter" *Loc. It allows you to connect the speaker wire from the head unit to it. It has rca output jacks on it that you would then use to connect to your amplifier.
This is normally the better option.

The Loc recommended above is what id use if i had the extra cash for it, but you can get cheaper ones.

 

I think I just did what you are asking. Mine is 15 CM no JBL. I got an factory amp under the passenger seat. There are two harnesses (12 pin and 10 pin I think) connected to the amp. There are line in and speaker out wires. I used a Pioneer powered sub

$180 TS-WX130DA Compact Series 8" x 5-1/4" - 160 W Max Power - Compact Active Subwoofer Black

TS-WX130DA that can let to choose the input type either line level or speaker level signal by switching the switch. If you already have an amp and you can choose input type then set up would be same as mine. I got harness extensions that have breakouts from the speaker wires and connected to the Pioneer. I even connected constant 12v, switched 12v and ground to the breakouts. My Pioneer does not require direct battery connection for constant 12v. I retained factory amp for all door speakers. Pioneer has a wired remote that you can adjust gain, low filter and etc.

 

Not at all a stupid question.
I was asking the same thing in 2014.

Ditch the OEM underseat amp for a proper 5 channel amp.
Add the subs and enclosure of your choice.
Run it, tune it, done deal.

You can try it with the stock speakers, if they don't meet your expectations, replace them.
I ran my 2005 DC with stock door speakers for 8 years powered separately by 2 old school Fosgate Punch 75s (front and rear) and a separate sub amp with a custom made sub enclosure and a 10" Fosgate Punch sub...



OP never stated what year model you have, but 2014 and ^ non-JBL would use this adapter to replace the underseat amp with a proper 4 or 5 channel after market amp.

AutoHarnessHouse



As stated by others, you'd need an amp that supports speaker level input, or some kind of LOC to convert speaker level to RCA jack low level input.