[dns7950]

Sorry if this has been posted a million times, I've searched a ton of threads and haven't found what i'm looking for. Basically, I want to install an aftermarket stereo + subwoofers and amp in my 2005 330xi with Harman Kardon stereo. I'd like to keep all the factory speakers working, and keep the steering wheel controls. I would love to be able to replace everything but I definitely can't afford it right now (laid off). Everything I have is stuff I bought ages ago and took from my last car. So I read on this thread: aftermarket headunit in e46 with HK?
that if I install a new head unit directly, the speaker outputs will kill the Harmon Kardon amp. The stereo i'm using is the Sony MEX-GS820BT, so it's a high power head unit, 48W RMS per channel. I bought a line output converter (Scosche SLC4) from Crutchfield, since they also mention that it is needed for Harman Kardon stereo on their site: Upgrading the stereo system in your 1999-2005 BMW 3 Series sedan
and I was hoping the instructions from Crutchfield would tell me how to install everything, but the Crutchfield installation instructions are kind of useless and don't mention a LOC at all... So my question is, how do I install the LOC to keep the factory Harman Kardon speakers working? I was planning on installing my subwoofers and amp (2 Infinity Kappa 1200Ws and a Zapco ST-1000XM II) by just running an RCA from the sub out on the head unit, so I don't need the LOC for that, just for keeping the HK amp from frying. I'm assuming it taps into the wires right before the HK amp, but which wires are those? Anyone know which wires are the high level ones I need to plug into the LOC? I also can't find instructions for keeping the steering wheel controls, I purchased a Metra ASWC-1 Universal steering wheel control, does that plug into the "remote" jack on the back of the stereo, or is that for something else?

 

[markusmarkus]

First, the signals that run from the factory head unit to the factory amp are called balanced differential signals. They are used in both the HiFi and the HK set ups. Second, the Sony head unit has both speaker level and line level outputs. The Sosche adapter is used to decrease the voltage of the signals coming out of the head unit to levels that are acceptable to the factory amp. I suggest you install it using the Sony’s line level (aka RCA) signals as the line level signals’ voltages could be too high for the HK amp. Crutchfield should have given you a wiring diagram with the Sosche adapter. Call them and ask for the wiring diagrams.

Now, how to attach the other amps to your system. Basically, it depends on the amps. Do they have speaker level I inputs? If not, you’ll need to tap the car’s wiring harness that runs from the Sosche adapter to the HK amp. Search this forum for the chassis harness wiring diagram. It’s posted somewhere.

 

[dns7950]

First, the signals that run from the factory head unit to the factory amp are called balanced differential signals. They are used in both the HiFi and the HK set ups. Second, the Sony head unit has both speaker level and line level outputs. The Sosche adapter is used to decrease the voltage of the signals coming out of the head unit to levels that are acceptable to the factory amp. I suggest you install it using the Sony’s line level (aka RCA) signals as the line level signals’ voltages could be too high for the HK amp. Crutchfield should have given you a wiring diagram with the Sosche adapter. Call them and ask for the wiring diagrams.

Now, how to attach the other amps to your system. Basically, it depends on the amps. Do they have speaker level I inputs? If not, you’ll need to tap the car’s wiring harness that runs from the Sosche adapter to the HK amp. Search this forum for the chassis harness wiring diagram. It’s posted somewhere.

Thanks for the reply. Like I said, for the Zapco amp I can just run an RCA from the sub out on the head unit like normal. It's the line output converter I was confused about, can't it just take the speaker level inputs from the harness and turn down signal level before it gets input to the amp? I only have one RCA cable from the amp installation kit, so I'd rather use the speaker level connections that are already there to connect to the line output converter if possible. I'm not sure what voltage the input on the amp is supposed to be, but from what i've read it seems like line level is too low and speaker level is too high, so something in between? I just still don't know how i'm supposed to find which wires are the ones giving the signal to the HK amp that I need to adjust.
I'm really surprised there isn't more clear info on this, I would have thought lots of people would be installing aftermarket stereos. Do you know which speakers are powered by the amp in the trunk? Is it just the rear deck 6x9 "subwoofers" or is it all speakers? If it's just the rear deck 6x9s maybe I should just install it and not care if the amp gets fucked, I definitely won't be lacking bass with 2 12's, lol. Just would like to have all the speakers working if it's possible.

 

[Kneedspeed]

The key idea you need to know is factory amp doesn’t have RCA input so you need the speaker wire output from the new aftermarket head unit to be reduced in gain for factory level input to the factory HK amp. Here’s specifics:

1. Install new head unit using an a. adaptor harness that will connect e46 to aftermarket connector (Scoche has one, also can search on Amazon) and b. antenna adaptor, c. Steering wheel control adaptor... you seem to be clear on this part so I won’t belabor... (btw, I also installed a Sony BT receiver without a CD changer DSX-A415BT 4x55W ... it’s very good amp pairing for the non-HK speakers... I got mine from Germany 99 euros, so it came with the e46 harness adaptor and the lights are orange red to be sort of of OEM looking);

2. Now install the LOC...you need to know the four speaker level wires you need to splice ( left front, right front, left rear, right rear) the LOC into plus where to ground all four. I’ll presume you have some understanding of basic wiring (stripping wires and grounding). The downside is splicing factory wires in case you have regrets later. Attached is wiring diagram for the Scoche SLC4 LOC.

You could splice the four wires near the aftermarket head unit wiring but then again it’s easier near the factory amp in the trunk because you’ll add a subwoofer and amp (but u might not care if you’re using head unit RCA output). The splice wires for the factory amp harness (sorry dont know the ones from the head unit, can’t just go by color need pin #) are given in the video below.

The entire process including how to access the wiring harness in the trunk, how to find the factory amp, which pins/wires from the factory amp harness to splice to the LOC, and how to install the subwoofer is captured in this YT video... although the author doesn’t show all of the LOC steps so clearly, it should help:

3. Install subwoofer and its amp as in the Video above. Sounds like the difference is you plan to run the RCA line input from the head unit to the subwoofer amp, whereas the video uses the LOC to convert wire to RCA input.

Don’t forget your grounds. And you might want to add a fuse if you’re going to patch the battery at all. Good luck!

 

[Jaynyce0027]

Great thread! Lots of good information. I will save this for future use.

Sent from my SM-G970U using Tapatalk

 

[markusmarkus]

Make sure you solder all wire splices! Also, shrink tubing is your friend.

 

[dns7950]

Make sure you solder all wire splices! Also, shrink tubing is your friend.

Don't have a solder iron unfortunately, been meaning to pick one up for a while but wanted to get a good Weller one that's out of my budget right now. Solder iron is over $100 and posi-connectors are a couple dollars, gonna have to make do with the twist connections. I've never had a twist connection fail before, only downside is looks IMO, but it's gonna be hidden anyways so I don't care.

Also, i've been doing more research trying to figure out how to wire this and i'm more confused than ever. In that video linked, he sure doesn't explain very clearly. He shows every wire that you apparently need to tap into, but doesn't specify which is which for the first couple wires pointed out. Can see he has a paper with it written down, but doesn't show it clearly. I managed to find a different video that shows it better I think.

. I still don't quite understand what's going on though, these videos are showing people using a 2 channel line output converter, I was under the impression that I would need to splice into all 4 channels to adjust the gain and then have the outputs going to the amp, and all the speakers would be driven by the amplifier. Are some of the speakers just driven directly by the head unit instead of the amplifier? I bought a 4 channel LOC thinking I would need all 4 channels. Are the people in the videos even putting the outputs of the LOC back into the factory amp, or are they just cutting into the rear for their aftermarket amp? Would the amp be safe with the high power aftermarket outputs for the front going to it? I don't know what i'm doing.

I really wish there was a simple guide for dummies, because this is all giving me a headache. I would have thought there would be a clearer guide considering these cars are 15+ years old and there must be tons of people who have installed aftermarket stereos. At the point where I'm not sure if I should just suffer with the shitty factory stereo while my nice aftermarket one gathers dust until I can afford a professional installation, or if I should just plug in the deck, cross my fingers and see what happens.

 

[Kneedspeed]

So I watched your video. Your confusion between 2- and 4- channel LOC has to do with each video trying mainly to achieve two different things.

in the video I posted, this is mainly about installing a new aftermarket head unit that has 4- channels of outputs ( frontL, frontR, rearL, rearR) and you need to decrease the gain for the factory amp. You’re splicing the 4-ch LOC in SERIES with the 4 speaker wire outputs from the new head unit. By in Series, I mean you actually will sever (not merely splice into) the correct wires before they go into the Connector to the factory amp. The cut wire side coming from the head unit will go into the matching INPUT of the LOC. The cut wire side going into the factory amp connector will be connected to the OUTPUT side of the LOC. On the LOC, you set the output switch (if there is one) to “factory gain” or else turn a knob for the gain. The video guy there then installs a subwoofer amp and subwoofer as Part 2, where he merely needs the outputs for left and right (usually rear). Those can be pre- or post-LOC since the subwoofer amp has its own gain adjustment. Often a LOC will have RCA outputs in addition to wire outputs, so post LOC is convenient to that. (With your aftermarket head unit, you can bypass all this by running a long RCA output from the head unit to the Subwoofer amp.)

In your video, the guy is only adding a subwoofer to the existing harness going into the factory amp. So he only needs a 2-channel LOC that takes wire inputs (from a Right and Left channel, usually the rears) and has RCA outputs to the subwoofer amp. He then splices (don’t sever old wires here) new wires with the head unit wire outputs for rear R and rear L and connects to their respective LOC inputs.

This is a bit confusing if you’ve never dealt with separate preamps and subwoofer, phono, and headphone amps.