Base System Powered Sub Install w/ Trunk Wiring and LOC

I wanted to move this write-up to this sub-forum. A lot of people have had questions about adding bass to their base systems and I feel kind of shady posting links to my build page to show them the write-up.

I was less than impressed by the bass in the stock system. I'm not really an audiophile but I wanted a little more bass in the system without having to sacrifice a lot of trunk space. A powered sub met my needs just fine.
Here is some info on the install.

So there are no RCA outputs on the back of the stock headunits. So, until they come up with a replacement headunit, you need to either purchase a powered subwoofer with a harness that lets you tap into the rear speaker wires or buy a Line Output Converter (LOC). The LOC will allow you to splice into your speaker wires and convert their high level output to low level output (RCA). The powered sub I installed came with a harness I could use but the wires weren't long enough to run to the speaker wires, so I purchased a LOC and used that. If you go to Amazon and search Line out converter you will see plenty of options. I went with a relatively cheap Rockford Fosgate LOC just because it was the last piece I bought and decided to keep everything one brand. It works fine and the system sounds great to me.

All of the wires you need to splice into are in the trunk. There's a 12v switched source along with both sets of rear speaker wires. They are running along the roof of the trunk near the back of the rear seats on the right side. They are wrapped in a black material that you can easily pull apart to expose the wires. You will want to expose them closer to the rear seats where they enter the trunk before they Split into a Y.

I spliced these wires with the wires from the LOC without cutting them. If you've never done that before (I hadn't) here is a pretty good article on it. http://www.rx8club.com/series-i-inte...utting-228546/
Hopefully you can see it in the pic but the speaker wires will be two sets of twisted wires.
White-Green is Left speaker positive
Brown-Yellow is Left speaker negative
Brown-white is Right speaker positive
Brown-Blue is Right speaker negative
The smaller gauge Blue-white wire is the 12v switched.

There is a conveniently located bolt between the seats at the floor of the trunk for your ground location. Just remove the bolt and sandpaper the paint off.
The power wire can be run through a grommet in the firewall on the passenger side but I believe this means removing the front tire and wheel well cover. There are some good pics of that here on the forum. I ended up going through a grommet on the driver's side and routing it straight up and under the plastic cover at the top of the engine bay. Not an easy thing to do and probably not the best way but doesn't require taking the wheel off.

If you are installing a sub in the EcoBoost then you will also want to pull the plug on the mic above the ceiling liner. All you have to do is sit in the back and pull the roof liner down. It's held up by two magnets. Once you pull it down you will see a black box with a wire running back behind it a few inches. Disconnect the wires there and you'll be fine. Otherwise, you will hear a ton a bass distortion coming through your sub.

If anyone has any questions just let me know. Hope this helps someone!

Fantastic info, thanks Edwin.

Two questions:

The power wire can be run through a grommet in the firewall on the passenger side but I believe this means removing the front tire and wheel well cover. ... I ended up going through a grommet on the driver's side and routing it straight up and under the plastic cover at the top of the engine bay.

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I'm confused what this power wire is. You say there is 12V in the wiring harness alongside the speaker wires. Aren't I just tapping into that? Why is there a separate new power wire, that you seem to be running from the trunk up into the engine bay?

If you are installing a sub in the EcoBoost then you will also want to pull the plug on the mic above the ceiling liner.

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What is this mic for? Some automatic EQ feature? Do you know if the V6 has the same thing?

filmamigo said:

Fantastic info, thanks Edwin.

Two questions:



I'm confused what this power wire is. You say there is 12V in the wiring harness alongside the speaker wires. Aren't I just tapping into that? Why is there a separate new power wire, that you seem to be running from the trunk up into the engine bay?



What is this mic for? Some automatic EQ feature? Do you know if the V6 has the same thing?

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1. The blue-white small gauge wire in the trunk is the 12v switched source you will need to use to have the sub power off when the car is turned off. This wire is actually what powers your backup camera so the sub will power down as soon as the car turns off. There will be a separate hookup on your sub for this and any sub install kit will come with some switched power cable for you to use to splice into this wire. The power cable running from your sub to your engine bay is the actual power source and will be a thicker gauge wire that comes with the sub install kit. This will actually attach to the battery.

2. The mic is only in the EcoBoost. It is used to enhance the sound in the cabin. Although, I think it is more of a noise cancelation feature than an attempt to pump engine noise inside. Either way, it needs to be unplugged for aftermarket subs. Otherwise the car will vibrate like mad at low rpms from a ridiculous amount of bass being pumped in.

Any other questions just let me know.

What's your impression of this setup? Does the front door speakers become overpowered by the sub? Im interested in adding a powered sub but also thinking about replacing the door low, mids and tweeters. This seem to be a good option as the 400a package is pretty good but just needs better speakers. Thanks for the write up.

Blacksheep said:

What's your impression of this setup? Does the front door speakers become overpowered by the sub? Im interested in adding a powered sub but also thinking about replacing the door low, mids and tweeters. This seem to be a good option as the 400a package is pretty good but just needs better speakers. Thanks for the write up.

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This will upgrade the bass to a respectable level but it definitely won't overpower the door speakers. I would like to replace the speakers in the door once there's some better plug and play options out there. The speakers in the front aren't terrible, they just aren't as crisp as they could be. I think it's the mids that are lacking up front.

Thanks for the write-up. Is that the Rockford Fosgate 10" or 12" subwoofer?

It's the 10, Im not entirely sure the 12 will sit upright back there, I remember measuring back there after looking at the dimensions before I bought it. I recommend looking at the dimensions first if your looking to go for a 12".

I have not touched speaker installations in many years. So the self powered sub still needs to be connected directly to the battery? I wish you could just tap both into the switched power wire in the trunk. I am too old and too lazy to tear my car apart and run power wires through the car panels and firewall.

Cueball said:

I have not touched speaker installations in many years. So the self powered sub still needs to be connected directly to the battery? I wish you could just tap both into the switched power wire in the trunk. I am too old and too lazy to tear my car apart and run power wires through the car panels and firewall.

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Yep still needs to be connected to the battery unfortunately. You can always buy all the equipment and then have best buy or some one do the install.

Edwin said:

It's the 10, Im not entirely sure the 12 will sit upright back there, I remember measuring back there after looking at the dimensions before I bought it. I recommend looking at the dimensions first if your looking to go for a 12".

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Just ordered the JBL 12" powered sub. It is 1" taller than the RF sub you have, and thanks to the picture, I think it will fit.

Yeah you'll be perfectly fine with an extra inch. I wanted to put mine as close to the corner as possible, you can see in the pic the ceiling comes down a little near the walls but I'd say I have about 2-3" left. Enjoy the JBL. :cheers:

how are you liking the sound of this sub? just ordered one today. saw it had pretty good reviews

HTX said:

how are you liking the sound of this sub? just ordered one today. saw it had pretty good reviews

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I think it sounds great. It fits perfectly into that corner of the trunk and can get loud enough to put some decent bass into the cabin which was exactly what I was going for. I will say that with this setup you won't get a ton of bass at lower volume but to me that's not really a big deal. I had a 650 watt system in my last car but this little powered sub doesn't have me missing it.

Edwin said:

I think it sounds great. It fits perfectly into that corner of the trunk and can get loud enough to put some decent bass into the cabin which was exactly what I was going for. I will say that with this setup you won't get a ton of bass at lower volume but to me that's not really a big deal. I had a 650 watt system in my last car but this little powered sub doesn't have me missing it.

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Awesome. that's just want im looking. I want to add a little bass to the cabin without shaking everything lol

HTX said:

Awesome. that's just want im looking. I want to add a little bass to the cabin without shaking everything lol

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Haha. I know what you mean. This should be work perfectly for you then.