[Mickelin]

Haven’t seen any of these, so hopefully I’ll get it right. I salvaged my JL Audio sub, amp and LC2i from my previous car and will attempt to install in my ”new” G21. Just realized there are two 12V batteries: one under the trunk and one on the right hand side. Guessing the best option is to connect to the right hand battery. I have the Harman Kardon sound system, so will tap into the booster harness for the signal. Not sure about the wires. There is a black/white, blue/gray, black/green and a yellow/purple. Anyone know which is which? (L+, L-, R+, R-) Would rather not have to dismount the seats to trace to the underseat woofers. I will use the ground point in the left side bay. Finally, I will need to find a suitable remote signal in the right hand side fuse box. Any tips on which one to use?

[Mickelin]

Watching a Bimmertech under seat sub replacement video I have confirmed that the black/white and blue/gray are the right side sub wires. How to determine polarity without access to the speaker?

[Mickelin]

No replies despite 100 views. Guess I am on my own. Oh well, I’ll keep posting, maybe it will help someone else.

Removed the seats to verify the pairs. Driver side sub wires are now confirmed as black/green and purple/yellow, passenger side blue/gray and white/black.

Still unclear which is + and -, but at least they will be in phase. Guess I will have to try both ways and see which sounds best.

[Mickelin]

Based on this diagram that I found, I’m guessing that the purple/yellow and the black/white are the + leads. 50% chance I am right…

[Throatpunch]

Originally Posted by Mickelin

Watching a Bimmertech under seat sub replacement video I have confirmed that the black/white and blue/gray are the right side sub wires. How to determine polarity without access to the speaker?

Multimeter and lowest voltage setting. Positive will yield + voltage and if u have it reverse it will be - negative values

[Mickelin]

I have now Finished the install using a custom made harness, an Audio Control LC2i converter, a JL Audio JX250/1 amp and a JL Audio CP108LG sub. My assumptions about the wires above were correct. The bass improvement is fantastic. I now have solid and clear bass at all volume levels. I will now code in the B&W DSP profiles and see what the HK system is ultimately capable of.

[Mickelin]

Coded the Bowers & Wilkins profiles into my HK system. The Concert and Stage profiles together with my new sub and some eq tweaking sound fantastic!

[lolamorena]

Originally Posted by Mickelin

Haven’t seen any of these, so hopefully I’ll get it right. I salvaged my JL Audio sub, amp and LC2i from my previous car and will attempt to install in my ”new” G21. Just realized there are two 12V batteries: one under the trunk and one on the right hand side. Guessing the best option is to connect to the right hand battery. I have the Harman Kardon sound system, so will tap into the booster harness for the signal. Not sure about the wires. There is a black/white, blue/gray, black/green and a yellow/purple. Anyone know which is which? (L+, L-, R+, R-) Would rather not have to dismount the seats to trace to the underseat woofers. I will use the ground point in the left side bay. Finally, I will need to find a suitable remote signal in the right hand side fuse box. Any tips on which one to use?

Hello. I am thinking about installing a kicker hideaway sub powered with the battery in the trunk. You said you powered yours with the battery on the right. Is that the one in the front of the car under the hood?

[Mickelin]

No, there is no battery under the hood. There is one in the right side of the trunk, one under the trunk floor.

[lolamorena]

Originally Posted by Mickelin

No, there is no battery under the hood. There is one in the right side of the trunk, one under the trunk floor.

Hey, would you happen to know what color wire is a 12v wire good to tap into on that harness that goes into the Amp?

[Mickelin]

The amp should be connected straight to the battery!

[alpineg20]

Originally Posted by Mickelin

I have now Finished the install using a custom made harness, an Audio Control LC2i converter, a JL Audio JX250/1 amp and a JL Audio CP108LG sub. My assumptions about the wires above were correct. The bass improvement is fantastic. I now have solid and clear bass at all volume levels. I will now code in the B&W DSP profiles and see what the HK system is ultimately capable of.

Thanks for sharing the details on your install. I am getting ready to install a sub in my ride. Did you connect the + and - from both under-seat subs to the LC2i?

[djv112]

I am trying to do this very similar setup but using the PnP harness:

2022 G20 M340i x with HK system + Technic Top HiFi (Option 688) Add-a-Sub Harness for RAM/Booster audio systems - Booster T-Sub Harness/LOC150i

I am getting waaay too much base with the eq down and both gains down so i think something must be wired incorrectly. I am plugged into the booster (lower one with angled fins) which I believe is correct. I'm tempted to just cut into the under seat subs wire and use my line level in on my amp as i'm not sure what else could be wrong. I originally had the ground on the connection to the frame but moved it to the batter which improved it but something is still very wrong with the signal...

Any thoughts?

[djv112]

Here are the connections.

[snekjumpr]

Originally Posted by djv112

Here are the connections.

One thing I’m seeing is that the speaker input plug is not fully seated into the LOC.

When you say both gains are lowered, I’m guessing you mean the gain on the LOC too? Did you try setting volume to 75% and raise the gain on the LOC until the light starts to flicker?

[djv112]

Good catch! I reconnected the speaker block and it is flush now. I have the gain on the LOC and amp all the way down and still getting the extreme noise even at low volumes. I suspect the LOC and will try a different one tonight to see if that solves it. Thanks!

[djv112]

So after replacing the LOC with one from Amazon everything was good, faulty part shipped by Technic wasted a lot of my time!