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Discussion Starter · #1 · (Edited)
I also cross posted this in the car audio forum. I ask that the moderators (You know who you are Alfred) leave it here as well as I think it can help out members of this forum.

After searching, I wasn't able to really find a tutorial on how to add a subwoofer to the stock sound system.

For reference, I have a 2007 S60R with the HU-850 head unit and PA-300 amplifier.

I am comfortable with wiring but am not a professional so take what I write with a grain of salt. If anyone has any comments on something I did wrong or an easier way to do, I will gladly edit it into this write up. A special thanks to Vio who gave me some advice on the install and got me started.

First, here is a parts list:
Kenwood Excelon X500-1 - - Mono amplifier, 300W @ 4 ohm
Boston Acoustics G312-44 12" Subwoofer with dual 4 ohm voice coils
12" Sound Ordnance Bass Bunker Sealed Enclosure - 0.95 cubic feet
RCA female-female adapter pair - I clearly overpaid for this but didn't want this part breaking. I'm sure these can be picked up for $3 somewhere.
Wiring Kit - Free with amplifer :)
Adapter Harness for use with stock sound system

EDIT: Wish I had known this at the time, but this clearly seems to be a better adapter. Better Adapter Harness

It eliminates the need to modify the amp and add in the female-to-female RCA adapters. Nice find!

First, let's start with the adapter harness, pictured below:





This allows you to unplug the cable coming from your stock amplifier and get RCA outs to your new amplifier. It also splits out a power signal and ground. I hooked up the power signal to the subwoofer amplifier so it would only turn on when the stock amplifier was on.

To start, we will remove the stock amplifier, which is located under the front passenger seat. Start by moving the seat all the way forward and removing the plastic covers at the end of the rails. Under each cover is a 13mm bolt. Undo these.





NOTE: I know my car is filthy. Yours may be similar. This would be a good time to clean under your seat :)

Also remove the blower duct under the seat. After the bolts are out, move the seat all the way to the rear. Remove the plastic covers at the end of the rails and once again you will find 13mm bolts. I loosened these, but did not take them out completely. This allowed me to tilt the seat forward enough to get to the amp. I suppose it may be easier to undo them and move the seat, but I will let others chime in.



After these have been loosened, move the seat all the way forward again.

In hindsight, I guess it's less work if you loosen the front bolts first, but life goes on...

Next, undo the lower molding by the doors so you can get access to underneath the carpets.





At this point, it is a good idea to unplug your battery so undo the negative terminal and place it aside.

Now, we are going to work on taking the stock amplifier out. There are 2 bolts holding the unit in. You can see the first in this photo:



You can't see the second in this photo, but it is down where the carpet is ripped up.



These bolts are 10mm.

After these bolts have been removed, you can shimmy the amplifier out and unplug the 3 connections.



The adapter harness is great, but the design of the connector was clearly done by someone who has never used it... The original connector is angled to avoid the fins of the heat sink. The adapter harness is not and will not fully go in. For this reason, some slight modification needed to made to my stock amplifier. Nothing my Dremel MultiMax couldn't handle...



It's tough to tell from this photo, but I notched out lip and fins above the connector. It will all make sense once you are in there.

Once you have the modification done, it's time to do some wiring. Start by connecting a wire to "power on" lead from the adapter harness. You will connect this to the power on terminal on your subwoofer amplifier. Make sure you cut enough wire. Remember, you can't go wrong with solder :)



Next, use your female-to-female RCA adapters to connect your supplied RCA cables. I connected to the rear speakers out, but I'm not sure it would make a difference if you connected to the front speakers out.



At this point, I taped off the ground lead as I wouldn't be using it. You can also plug in the amplifier cables.

I found it easiest to run the wires with the backseat removed. It pretty much just pops out.



I also popped out the strip of leather along the rear pillar. This also just pops right out.



From here, it should be pretty obvious how to run the wire into the trunk. Here's what it looks like in the trunk now.



Next, I mounted my amplifier on the side of my enclosure. This is temporary until I have the patience to mount it in a better spot.

I ran the RCA cables and power on wire across the bottom of the trunk right behind the rear seats.



After the wires were run, I connected them to the amplifier. I also connected the speaker wires at this point between the amplifier and enclosure.



Next up are the connections for power. Connect the supplied power cable with the in-line fuse to the battery as pictured below:



Make sure to add in the fuse so you're not left scratching your head the first time you power it on.

Use the supplied crimp to connect the giant 4 gauge wire to your amplifier.

I grounded my amplifier to a screw in the chassis besides the rear fuse box like so:



Once again, use the supplied crimp to connect this giant wire.

And here is the final product (until I mount the amplifier elsewhere)



Put everything back together and enjoy the nice low end you just added :)

Hope this helps everyone.

-Patrick
 

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good work
 

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cant wait to do that to mine
 

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quick question, does your new amp power the door speakers as well or just your subs?

I used to have two 12" arc audio subs and twin arc amps with caps running at 8 ohm running through an eclipse deck, best subs I have ever heard/felt in my life...long story short all were stolen and I have been hesitant to get back into the aftermarket audio world....

I have thought about dabbling again but have been scared of how complex the R seems to be....I would like to keep my door subs and still maintain the sound quality but add low end response. Did this work out for you or are you losing some of the response over the full range of sound?

I would imagine that the amps are "tuned" for our cars or in other words they are setup to power through specific ranges without crossovers....Have you found this to be true? Do you need an aftermarket crossover setup at all? EQ?

On a side note the lasers in eclipse decks are probably the best for playing cds. Frigging things are amazing...you can literally scratch a cd by rubbing it on pavement and then play it with no skips...
 

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Hack Moe D
 

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good job, came out nice. now your car is slower more weight!...jk jk but seriously :p
 

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