Bose After market sub add on - wiring question

**zeven13** · 08-17-2008 09:36 PM

Helped a buddy with an '03 put his subs in today. He has no clue about audio stuff and has the car torn apart for some other add ons.

Setup is:
2 Alpine 12" R's
Alpine V12 amp
1 Farad cap

Power wire is run. Fuse blocks mounted. I tapped the wires, but had to guess which they were.

1. Where is the best place to attach the ground in the trunk?
2. He has a capacitor... do I run the power wire from the positive on the battery to the negative on the cap and ground from the positive?
3. I tapped into the radio outputs into the Bose Symph II pins 6-8 and power wire 25... can someone confirm this is correct? I have the Bentley wiring diagram, but would like a confirmation.
4. Would an LOC make a difference if I'm using the Lo inputs from the radio? Obviously I'd have to retap into the output wires, but I don't see the advantage of using the LOC.

Thanks a4mods.com for the basic writeup that got me this far.

**B6 Dude** · 08-17-2008 11:21 PM

Originally Posted by zeven13

...
2. He has a capacitor... do I run the power wire from the positive on the battery to the negative on the cap and ground from the positive?

STOP! -- I'm not an audio person, but from general electronics you should connect the positive on battery to positive on the capacitor (then to the positive on the amp). Ground to neg on cap to neg on amp. Connecting it backwards can cause a violent failure.

And keep the cap as close as possible to the amp.

I would expect with a large cap like that should come pre-charged or they should give you some procedure to slow charge it (before wiring it up). Use the instructions or call them, as this is not to be taken lightly.

And verify everything I tell you.

**Greg9** · 08-18-2008 06:30 AM

They usually give you a resistor or a 12v light bulb in order to charge the cap. These run a 12v so your not going to blow anything up but you can still make a pretty good spark and shock yourself, so pay attention to what your doing.

**zeven13** · 08-18-2008 07:18 AM

Whoops. I actually typed that wrong. After seeing your STOP message, I quick looked to see what I had done. I went positive from battery to positive on cap and negative on cap to ground. The cap is connected to the amp, so there is no concern in distance.

**koolade9** · 08-18-2008 11:25 AM

Originally Posted by zeven13

Whoops. I actually typed that wrong. After seeing your STOP message, I quick looked to see what I had done. I went positive from battery to positive on cap and negative on cap to ground. The cap is connected to the amp, so there is no concern in distance.

He's referring to the length of power wire between the cap and the amp, essentially the cap is in-line with your amplifier. 12v & gnd connect directly to the cap, and 12v & gnd come off the cap to your amp. Once you have everything wired up, as soon as you make the final connection, or flip your circuit breaker, that spark is typically enough to discharge the cap. Goto the battery where you connect your 12v lead for the stereo, and disconnect 12v from the system, this is where you'll charge the cap/amp (The amp has a few smaller capacitors as well, and you're essentially charging the whole system) With the car running, (and stereo off) use a volt meter to measure the car's voltage (remember that as a reference point) Use a 40-50ohm resistor (if they didn't give you a charging plate) in between the battery to your 12v lead (don't hold the resistor with your fingers unless you like burnt fingers), and use a multimeter to read voltage from the system 12v side. You'll watch the voltage climb as the cap/amp charge. It'll take a few minutes to charge...ideally, you'll get your system voltage to equal the car's voltage (that reference point from earlier). You'll probably get within .25v from that #, voltage will stop increasing and hover around that point. Boom, you're charged. Now take out the resistor, and connect the 12v to the battery. You're done.

To answer your other questions:

1. Where is the best place to attach the ground in the trunk?
-there's quite a few places depending on where you mount the amp/cap. Just find a factory bolt and use that...strip down the paint around that bolt to bear metal to get a better connection. Once you bolt it, spray a quick shot of clear-coat or paint to keep the area from rusting.

2. He has a capacitor... do I run the power wire from the positive on the battery to the negative on the cap and ground from the positive?
-already covered above

3. I tapped into the radio outputs into the Bose Symph II pins 6-8 and power wire 25... can someone confirm this is correct? I have the Bentley wiring diagram, but would like a confirmation.
-if you pull out your radio, there's a pin-out diagram on the back, use that to locate your low-level output leads and remote lead (radio turn-on)

4. Would an LOC make a difference if I'm using the Lo inputs from the radio? Obviously I'd have to retap into the output wires, but I don't see the advantage of using the LOC.
-you won't need a speaker level converter if you're using the low-level outputs off the back of the radio.

Hope this helps...

**zeven13** · 08-18-2008 12:14 PM

Won't need to charge the cap as described, should be good to go from his previous usage of the system. We literally pulled it out of his VW and put it into his Audi. The sub enclosure contains the amp and cap. The cap to amp connections are internal to the enclosure. I think the intention was for a clean look. My buddy bought the amp/subs/cap as a package deal.

As for the other...
1. I was asking which bolt most people use to ground. I know how to ground the sub. I found 1 or 2 that would work, but nothing was really a direct hookup. Still looking for someone to give useful advice.
2. cleared up
3. partially confirmed
4. no bonus in using a LOC

**koolade9** · 08-18-2008 02:41 PM

Originally Posted by zeven13

Won't need to charge the cap as described, should be good to go from his previous usage of the system. We literally pulled it out of his VW and put it into his Audi. The sub enclosure contains the amp and cap. The cap to amp connections are internal to the enclosure. I think the intention was for a clean look. My buddy bought the amp/subs/cap as a package deal.

As soon as you re-connect power to it, the spark will discharge the cap. At best, it'll just lose some of it's charge, thus it's effectiveness...

Originally Posted by zeven13

As for the other...
1. I was asking which bolt most people use to ground. I know how to ground the sub. I found 1 or 2 that would work, but nothing was really a direct hookup. Still looking for someone to give useful advice.

Originally Posted by koolade9

-there's quite a few places depending on where you mount the amp/cap.

...so where's your amp located then?

**zeven13** · 08-18-2008 07:52 PM

also in the enclosure with an access cover on the connections

**B6 Dude** · 08-18-2008 09:16 PM

Originally Posted by Greg9

They usually give you a resistor or a 12v light bulb in order to charge the cap. These run a 12v so your not going to blow anything up but you can still make a pretty good spark and shock yourself, so pay attention to what your doing.

Actually, if you've ever seen a reversed cap rupture or blow up at 5V, you'll know why I used the word "violent".

BTW, car batteries can source a LOT of current, so connecting a large uncharged cap directly to a car battery will draw a lot of current, generate a lot of heat, and melt/burn things.