Wiring a sub in a BRZ
 

So I'm getting ready to build my sub enclosure now and finally get one of my subs into the car, the question I have is on connecting it to the stereo. Since the BRZ doesn't have line outs I'm obviously stuck with speaker level inputs till I replace the headunit. Now from what I've read the rear speakers don't have full range going to them and thus aren't good to get the signal for the subs, that little box in the trunk under the floor panel on the driver's side I've read is the amp for the door speakers which do have a full range signal, so I'm guessing that would likely be the best spot to wire the sub into, my question is which wire are which on that amp?

I just did this and used a line-output converter from www.davidnavone.com. N-HRL4 I think it's called. It's a 4-ch but I'm only using two for now. If you have the inputs on your amp, you can skip this.

I also purchased a pair of forward/reverse harnesses (10-pin) from SVXdc (he's a member). This harness is the same on both the HU and the factory amp, but some of the wires are labeled differently. There's also a 6-pin plug (same size as HU, but less wires) that is just for power/ground but I skipped this. The LOC has power/ground/remote but I skipped all these as it's only used to turn on the amp (I tapped the factory remote lead instead).

Since SVXdc has the 10-pin already wired for the HU, the wires labeled for the rear L/R are actually the front speaker L/R output from the factory amp. Really the only ones you need to break away are the ones labeled front L/R and remote on his harness.

He gave me a breakdown of the harness pins, too:

BRZ OEM Amp 10-pin harness and socket:

1 VFL+ (output to left door speaker +)
2 WFR+ (output to right door speaker +)
3 FL+ (input from HU's front left + channel)
4 FR+ (input from HU's front right + channel)

5 VFL- (output to left door speaker -)
6 WFR- (output to right door speaker -)
7 (NC)
8 AMP (+12V remote turn-on from HU)
9 FL- (input from HU's front left - channel)
10 FR- (input from HU's front right - channel)

Ok, nice, that's exactly what I was hoping I could do since the amp will be mounted on the driver's side wall of the trunk, and I already have a line-output converter from a previous build so I can just put that under the floor panel and have a short RCA cable to the amp, too bad my amp is a behemoth so I can't actually fit it under the floor, at least not without removing the spare tire.

Actually I wonder, is the input from the HU actually a powered signal, or is it a line level signal? It would make sense that it was just line level, but with factory stereo systems you can never tell.

Do people keep spare tires still?

I always drop the weight. I pay for roadside anyway.

If you don't have them already, Monoprice sells 1.5' RCA cables for under $3, IIRC. I bought a 1.5' and a 3' just in case, and ended up needing the 3' to cross the trunk cleanly.

Luckily, my JL 250/1 was the perfect height for going under the trunk floor, but man is it close. I trimmed the foam and made little channels under it for wires to run.

For my amp ground, I used one of the studs that the factory amp is mounted to.

Only the front door speakers run through the trunk amp (at least in USDM cars). As far as I know, they are not amplified until after that box.

I think I still have a short RCA cable laying around since from that build where I had the line-output convertor I had it right next to the amp so it had a short run.

It's not so much the height that's the issue but the width/length, it's about 17" x 10" I believe, with the attached mounting tabs it barely even fits standing up on it's side in the trunk, i'm almost thinking it would be nice if I could get it up on the bottom of trunk deck, but not sure if that would be worth the hassle.

If they aren't amplified then a line-output convertor shouldn't even be necessary, just splicing an RCA cable into them should in theory work.

Damn that's a beast!

I was tempted to mount up above the trunk as I've seen some others do. There's one guy who made a cool hinged base. I don't know if I'll keep my current amps, so I didn't want to go that far just yet.

I bet SVXdc could answer this properly. Not sure how active he is on here, but he's also on NASIOC.

I do, even if I never really use it it's nice knowing it's there, especially for long road trips, like in the summer I'll be driving to Baltimore MD from NH, so I would want the spare for that trip, so I prefer to just figure out a way to make everything fit without losing it.

That it is, and it'll be overpowered for how I'll be setting things up in the BRZ too since in my last car it was powering a pair of 12" 4ohm subs in parallel, now it will only be powering a single one of those subs, but at a higher impedance, still at 4ohm it's rated at 456 watts RMS and the sub is rated for 350 watts RMS (1400 watts peak), though the sub is a beast and I've always heard people say that that sub was very underrated so it should be fine.

The HU pushes a few watts to all channels and the amp just amps the fronts a bit more. At least my volt meter measured the same output on all four HU outputs before the amp. Use a speaker level converter. I did at first, got a DSP that handles it now. Don't overthink it. ;)

Also, just use scotch locks to tap the wires, no need to pay for a harness, not that that isn't super easy in the connector aspect, just unnecessary expense in my view.

Ok, line-output converter it is then, and yeah, I planned on just using scotch locks, I have a bunch of them in one of my tool boxes.

:word:

I almost went that route, but couldn't bring myself to splice into the factory wiring. If it wasn't such a new car, I probably wouldn't have cared.