Ran into a Doosy, Can anyone help?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=13379
Printed Date: May 03, 2025 at 9:54 AM
Topic: Ran into a Doosy, Can anyone help?
Posted By: Spectre
Subject: Ran into a Doosy, Can anyone help?
Date Posted: May 10, 2003 at 12:27 PM
Here's what I have: 2002 Pontiac Grand Prix GTP, Factory head-unit, heads-up display, factory speakers and the kicker...... OnStar! Here's what I want to do..... I want to add a pre-amp EQ (PPI EQP), two amps, a sub and replace the factory speakers. I want to keep the factory head unit (the head unit displays stereo information in the heads-up display..... way too cool an option to loose!). I know this can be done using in-line converters. This would all be a walk in the park if it had not been for the OnStar interface. I have found interface kits for adding a new headunit and amp to an OnStar system but viewing the diagrams these won't work using the factory headunit. So with all of your wisdom..... can you give me some advice here? ------------- The Angel Of Death Has You!
Spectres Own The Night!
Replies:
Posted By: DYohn
Date Posted: May 10, 2003 at 12:54 PM
I have never installed in a car equiped with OnStar... but since you want to keep the factory head unit, it would seem that the easiest way to do what you want is to use basic speaker-to-line level converters off the speaker outs of your head unit. Run line level signals to your EQ, amps, etc. This shuld allow all factory interfacing with the factory head unit to stay intact. Am I missing something?
Posted By: Spectre
Date Posted: May 10, 2003 at 1:05 PM
I think that the onstar system interfaces at two points, at the speaker and at the radio, if I interupt the signal to the speaker won't I loose the audio from the onstar? I wish OnStar would provide diagrams but they don't. It's risky at best! ------------- The Angel Of Death Has You!
Spectres Own The Night!
Posted By: vseven
Date Posted: May 10, 2003 at 1:13 PM
I wouldent think it matters if you put your converter right before the speaker. If I understand you your saying that both the HU and the onstar go to the speakers seperatly. So you would be effectivly converting both the factory HU and the onstar into preamps for the amps, right? So just put your converter where there is only two wires going to the speakers, then through your system, then to the speakers. Only problem you may have is if the onstar has a set volume level, ie your HU goes from 1 to 30 but the onstar always outputs at 20 (relativly). In that case I would imagine you need to put two converters for each speaker, and use a Y to combine them both to your amp so you can set the levels independently. This is making perfect sense in my head but that dosn't mean anything. =). Hopefully you understand wat I'm saying. Lemme try this:
Front R from OnStar -> line converter -> Y \___ Front
Front R from HU -> line converter -> Y / Amp
If this is the case its gonna get pretty expensive for 8 line converters with seperate levels (or at the very lease 4 with level controls for the Onstar signal)
Allan.
Posted By: DYohn
Date Posted: May 10, 2003 at 1:46 PM
vseven is right, it shouldn't matter as long as you have grabbed the speaker level signal at a point where it is heading straight for the speakers; ie: straight wire to the speakers. I don't really think any level differential that he mentions should pose a problem, by the way, so I would think you can get by with two (one for frint and one for rear) converters. Now, if this car has a factory "premium" audio system, especially if it has seperate tweeters in the dash or somewhere, you have more problems to worry about. I highly recomend getting hold of the factory wiring diagrams for this car before you simply start swapping things. Or bite the bullet and go let a pro shop do the conversion...
Posted By: vseven
Date Posted: May 10, 2003 at 3:46 PM
I would image there would be a level problem. I say this because I believe the way its setup is the onstar uses the interupt/defeat feature of the head unit to cut it out, just like a aftermarket radio has, then once the radio is no longer powering the speakers it does so. Like I said I believe thats how it works. And if so you'll have one hell off a time trying to get the amps gains correct if your basing it off of two different sources. Hopefully I'm wrong and it just switches the radio to a aux input and the onstar audio gets powered from the HU but from what is described above it sounds like they both wire to the speakers independantly. If you can't trace the wires back try and get some more info from either Pontaic or OnStar. Or see if there is a Chilton/Hayes out yet for that model, usually they have a good detailed wiring on the audio.
Allan.
Posted By: DYohn
Date Posted: May 11, 2003 at 8:36 AM
OK, I did a little research, and if you are keeping the factory head unit, all you need to do is use one set of speaker-to-line-level converters. The OnStar interface is in the radio, upstream of the speaker wires in the wiring harness. If you add aftermarket amps, speakers, etc, the OnStar signals will still work as they do stock with no level problems. I recomend you get the Metra wiring harnesses that plug into yur head unit AND the one that plugs into your factory wiring harness. Us eboth so you can "splice" into the factory wiring without damaging it. Use the Metra wires for your connections. The Metra part numbers should be 70-1858 and 71-1858. If you are adding an aftermarket head unit, you can still keep the OnStar functionality with a specially designed adapter. They run about $100 and plug into the Molex connectors of the factory wiring harness. SoundDomain.com sells one. Cheers.
Posted By: Spectre
Date Posted: May 12, 2003 at 10:38 AM
I REALLY appreciate your help on this guys! So which speakers do I attach the line converter to? Front or back? Would I be able to do both to get front/rear control as well? Since I'm using a pre-amp EQ that takes F/R inputs. ------------- The Angel Of Death Has You!
Spectres Own The Night!
Posted By: DYohn
Date Posted: May 12, 2003 at 5:07 PM
Take the speaker signals for the factory front L-R to one line converter and run RCA's to your EQ for the Front signal. Take the speaker level signal for the factory rear L-R to a second line converter, and run those RCA's to the EQ for the Rear signal. Then, you will need to connect new front AND rear amps to the outputs from the EQ, and run BOTH front and rear speaker wires (new wires) from your amps back under the dash to connect to the factory wiring harness that goes out to your speakers. What you will have done is simply interupted the speaker output from your head unit and sent it to your after market EQ and amps, then back to the factory wiring headed to the speakers. Does this make sense to you?
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