Need Help - BMW's Signal Differential Speaker Wiring, Amps and SVEN4

lloydy · 02-08-2006, 06:15 PM

Please can someone help me with my situaution. I'm half way through installing my carputer.

I have a 2003 (facelift) BMW 318Ci with stock speakers (not HK) without a head unit (now replaced with a Xenarc). My plan was (is) to wire four channels of the PCs sound (using onbaord EPIA SP13000) from a 4 channel output to the stock speakers. I thought I needed just the SVEN4 and the Scosche BMW wiring harness and I was away...

BUT... I just found out that my system does not have an amplifier! I read over on e46fanatics.com that the later models of my car don't have an amp at all - speakers are powered straight from the head unit. When I checked, I realised I don't have an amp. This is was big issue.

So tomorrow I'm going to get a 4x60W four channel amplifier. Is this what I need? Also, I need to know how to use the SVEN4 with it. This was my original set up:
PC -> RCA cables up to where head unit was -> SVEN4 -> Scosche Wiring Harness -> Which plugs into the main harness and then feeds the amp to power the speakers. I looped the antenna power on to the 12v switched so that the amp would turn on with the ignition. And I linked the SVEN4's earth to the earth of the BMW wiring harness.

NOW though - I don't have the amp! So This is my new plan:
PC -> RCA cables into a new 4 channel amp -> speaker wires from amp to SVEN4 -> Scosche wiring harness -> SMWs harness where head unit is.
Im assuming the BMW wiring harness (that usually plugs into the head unit) just links directly to the speakers now. Does this sound like the right thing to do OR should I use the SVEN4 before the amp like this:
PC -> SVEN4 -> new 4 Channel amp -> Scosche harness -> BMW harness

In either case, I don't understand where to ground the SVEN4 to. The SVEN4 has black earth wires on both sides of it (input and output). I believe this is used to balance the audio as BMWs use signal differential speaker cabling. Putting the SVEN4 after the amplifier makes more sense to me as then the earth cable just connects straight to the BMW earth on the harness, "balancing" the audio along the speaker wire. However, I've seen installs with the SVEN4 before the amp. This is where I'm confused.

Please Please Please can someone help me out?

Thank you all so much in advance,

LLOYDY

lloydy · 02-08-2006, 06:21 PM

Another thing,

Please don't say just to replace my speakers and cabling. This is a plan for the future but I'm not up to doing it yet. When I have the time, motivation and of course money to change the speakers themselves I will. Also plannign to add another amplifier and sub.

I know this setup can be done using BMW's soeaker cable as it has been done before. I'm just confused how to use the SVEN4.

I've been following this excellent guide:
http://bimmer.roadfly.com/bmw/forums...1433274&page=2

but this seems to be a case where the SVEN4 is plugged in BEFORE the amp. This way, I don't know where the black earth wire of the SVEN4 connects. Also, surely the balanced signal diff speaker cabling is affected as the audio coming out of the amp is then again unbalanced zas there is no common earth. Oh I don't know... I'm jsut rambling now coz I don't know what I'm doing!! I'm sooo thick. Please help a stupid person out!!

LLOYDY

lloydy · 02-08-2006, 07:41 PM

Found out I don't have a stock amplifier coz I have a European car - apparantly these don't have the amp. The speakers are powered directly from the HU. So now, how do I use my SVEN4? Do I even need it? Are my speakers still using this "balanced" audio or were the banaced signals just used between the HU and the amp?

Will:
PC -> AMP -> Scosche wiring harness -> BMW harness
just work or will I need to put the SVEN4 in there at some point. If I do need the SVEN4, what exactly is it doing?

LLOYDY

3onDubs · 02-08-2006, 08:26 PM

What you are trying to do, basically.........(I feel like I have ADD, so I can't read all of what you wrote)....is connect your PC to your AMP to your SPEAKERS.

This seams very simple. From the PC to the amplifer part is easy and I'm sure you know how to do this. The hard pary is trying to go from your amp to your speakers. You don't really need the SVEN or anything like that.

You have two options in doing this:

1. Run new wires from your amp to your speakers. This will be easy for the rear speakers, but more difficult for the fronts since you would have to run the wires into the door (requires removing the driver dead pedal).

2. Find the Factory wiring for your speakers and just splice the wires comming out of your amp into those wires. In my BMW, I had the amp in my trunk, so the wiring for all the speakers was available in the trunk. This made it easy for me to wire everything because my aftermarket amp was also in the trunk and I didn't have to run any wires through the car. I found a wire guide that tells me which color wires go for which speakers, and I went from there.

In your case, since you don't have a stock amp, I'm guessing that all of your wires might be inside your dash. What I would do is run wires from your amplifier down the drivers side (in our cars we have power wires that run up the passengers side, which is why this is a bad place to run speaker wires). After you run it through the passenger's side, you can go behind the dead pedal and into the dash from behind. Splice these wires into the appropriate wires in the stock wiring harness. This will require you to cut the wires that you will be using, so I suggest labeling the wires, so that reconnecting them will be very easy.

Doing what I described above will require you to have a pinout description of your wiring harness and a description of what color wires go to which speaker so that you will be able to know which wire to splice into.

The only problem that I see with this setup is that our cars have 10 speakers. You will not be able to amplify all of these because they ask for different frequencies. For example, the tweeters will need a different frequency than the mids. The ohmage on all the speakers is strange as well...If I recall, some are 8 ohms and others are 4 ohms. You might not be able to amplify all of the speakers, but I suggest amping the following at least: 2 front woofers, 2 rear woofers, and 2 front tweeters. You might be able to use an after market crossover for your front woofers and tweeters, but I would suggest getting new speakers because of the ohmage problems.

I have some speakers that will fit your car if your interested...5.25" kenwood excellon components (with crossovers) and 6.5" coaxials.

lloydy · 02-09-2006, 12:30 AM

OK - I think you're right - I won't need the SVEN4. I have a Scosche wiring harness which means I don't have to cut any of the wires anyway. Also, I think my only access to the speaker wires is where the head unit was.

So I think my plan is to buy a 4 channel amplifier and run speaker cable up to the head unit area to power the speakers.

What I don't understand is why I can't just send an amplified signal to FL, FR, RL, RR and it all work. These are the only wires I have to work with anyway. All that came into the stock radio were these four pairs of +/- RR, RL, FL, FR wires (also obviously the power, ignition, earth, illumination and antenna wires). I thought the speaker sets themselves (the mid range and tweeters etc) did all the frequency separation themselves. I thought when the amplified signal came to the speaker set, the bass speaker would take the low freqs, the mid range speaker take the mid freqs and the tweeters take the high freqs. Aren't they all just connected? How would I even go about separately amplifying the indivdual speakers?

If you are right it looks like I'm going to have to run all new cable to each speaker. But also, if you are right about this, then how on earth did the stock radio power all those speakers just by using the 4 pairs? It couldn't have, surely!

I will see how it pans out tomorrow. I will upgrade all speakers and cabling later on in life. Just want to get it working using the stock speakers for now tho.

Also please note I'm a UK car owner - meaning I have righthand drive. Using "drivers side" and "passenger side" will get confusing!

Thanks for your help,

LLOYDY

3onDubs · 02-09-2006, 02:16 PM

No problem...I forget that your car is probably very different from mine. You might be right about the speakers having built in crossovers because when I used to have my stock speakers amped (I had it done at a stereo shop, so I don't know the details), but there were no crossovers installed. If your headunit had only four wires going into it, then you should be able to only amplify those four channels off of your amplifier. The scoche harness should allow you to do this....I was thinking of a more complicated solution, but you should try just amping those four signals and see how your setup sounds. You will know immediately if it works as intended when you listen to your system.

The battery in my trunk is located on the right side when I am facing my trunk....that is the reason that the power wires are run through my passenger side (or your respective driver's side). Take a look at your trunk to see where your battery is and run your speaker wire on the opposite side...if that makes any sense.

I had originally thought that the BMW amplifier did all of the crossing over, but now I see that this is not possible since yours doesn't even have an amplifier...unless your headunit has built in crossovers (which is highly unlikely), then the speakers themselves have built in mechanisms to filter out the wrong frequencies...in which case you would be ok with just amping the FL, FR, RL, and RR channels directly in your dash.

lloydy · 02-10-2006, 10:25 PM

Thank you very much for your help. I bought a 4 channel (4x50W) amplifier and this did the job. Just incase anyone else wants to know, this set up is extremely loud without distortion. I didn't realise the stock speakers could go that loud! All seems well now.

I put all my cables down through the centre of the car. I now have a "ground loop" somwhere as I have an engine whine coming through my speakers. I have grounded the amps etc perfectly and my speaker cables are not close to any power cables so Im unsure of the problem. Also, whats even more strange is that the whine is only coming from the rear speakers and not the front speakers even though the amplifier each of the four speakers. It's a £100 ($150) Sony amp so it isn't a crap one.

EDIT: Forgot to mention for future reference, I didn't need the SVEN4 after all. This is probably why they don't sell them in the UK - you don't need it! All you need is a new amplifier. So my Sven4's now for sale...

Oh well, I'll try to figure that one out another time...

LLOYDY

3onDubs · 02-13-2006, 12:41 PM

Are you using a soundcard? I had engine whine when using a soundcard and was unable to get rid of it. It is possible to get rid of it with a ground loop isolator, but I was ready for an upgrade anyway, so I ended up buying a digital sound processor and ran digital cables from my pc to my sound processor. My entire setup is now noise free and I am getting the best possible sound out of my pc.

lloydy · 02-14-2006, 07:43 PM

I have just pruchased a ground loop isolator from eBay. I hope this does the trick! Renegade brand - fits in between sound card and amp RCA leads.
Cost £9.99 delivered.

LLOYDY

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