1987 town car, common ground head unit

I have an 87' Lincoln Town Car with the factory optioned JBL Upgrade. I believe it to be the same Common Ground system as the Prem. Sound and Base Model. I have a Kenwood X997 powering four kicker 4 ohm 3 way speakers individually from the 52x4 internal amp. I am attempting to "amp integrate" the factory JBL amp using the Kenwood preouts. I want to turn this into an 8 speaker setup by powering the 6.5 in 8 ohm (2004 mustang) door speakers and adding another set of 8 ohm speakers to the rear deck. I conveniently had a set of 4x1 monster rca cables that had been cut so intend to use it as signal thru the factory radio output to amp input harness. This factory harness I refer to has 1 speaker negative wire coming off of it that previously ran into the head unit. I have the single common speaker negative wired to the same ground as the kenwood head unit, and I plan to splice all of the positives from the rca to the factory amp signal harness. For testing purposes I initially spliced only one positive from one of the rca channel to the right rear speaker. The rca negatives are clipped off and left alone. I hooked up a single 4 ohm 3 way speaker to that rear channel and i am not getting sound. This amp was just tested by a professional and determined to have power and sound output. The amp makes a constant buzz every other second and a pop is audible when the speaker is hooked up. The speaker began to smoke after as well. I don't know how to test proper speaker output, but I did have varying voltage from 0 and switching to 9-14 volts intermittently then back to 0. I already have four speakers wired off the head unit so I am not looking for that suggestion. I am determined to make this work properly to utilize the factory JBL setup which is known to be high quality. To reiterate Kenwood RCA + Output wired to the positive amp signal. The negative rca outputs are clipped and left disconnected. The factory 1 wire speaker negative from the amp signal harness is grounded with the Kenwood. This is exactly what an amp integration harness does so I expect if done correctly it should work. Still not working properly.

skratpiece wrote: I am determined to make this work properly to utilize the factory JBL setup which is known to be high quality.

I am uncertain how to respond to this without sounding mean or biased. If the JBL setup is indeed such high quality then why do you need to upgrade at all? I doubt you will find anyone here who agrees with that statement. At least if it is working it is fine and should be left alone, otherwise a complete audio system would be the answer most of us would give. Personally a properly setup aftermarket system with 6 speakers (4 speakers 2 tweeters) would far exceed any output you would possibly gain by trying to make that combo work. Again I am not trying to sound mean or biased, but considering where you are posting your question, this answer should have been expected.

If you read the instruction booklet that comes with most aftermarket car audio it specifically states that it is not designed for use with a common ground system in any way. In fact MOST of the car audio we deal with can be severely damaged in a common ground system.

To master and control electricity is perfection. *evil laugh*

so you want to add factory speakers from a 04 mustang and install them in your towncar? where do you propose these will fit? not only that but you should understand that more speakers dont equal better sound because they need to be properly placed and set up to blend with the other speakers. seeing that you want to mix factory and aftermarket speakers, this plan will most likely sound horrible. please trust the people who do this stuff everyday. dont read too much into the name on a factory system anymore than you should think that a race car sponsored by Lowes is made out of wood, anything aftermarket that JBL actually produced during that time probably was far better than anything in that car. that "JBL" system only sounded good in 1987 when car audio was still in its infancy. car audio system designers didnt care about signal processing or speaker placement or any of that stuff that makes todays factory systems far exceed anything that was in a car in 1987. the only thing that JBL system had over the base system was a little more power than the standard system, you are going to do all this work for nothing.

Guess I Shouldn't have bothered attempting to ascertain any technical expertise. I shoulda just asked my grandma how she felt about the matter. Common ground systems are integrated daily. My theory is simple. Send proper signal to the amp using preouts. This is the same idea as any other amp integration, but because nobody here knows anything I get these type of responses.

To further elaborate and attempt to get this thread back on track. I have attempted to wire signal to the amp using preouts, and using a scosche fai-3a with common ground converter. The fai-3a has been reported to work, but I have not heard it work yet using the suggested wiring diagram. I will review my wiring tomorrow. I may also attempt to eliminate the common ground loop wire and run negative signal to each wire seperately. The reason I haven't attempted thus far is because I suspect there is a posibility that the amp is only supposed to be wired according to the way it came though I am willing to bet that it should work.

maybe no body knows how to do it because the people who originally knew how to do it realized that it wasnt worth doing so they stopped doing it in favor of a better way. the people who post on this forum post to make peoples audio systems better and to educate other people about the right way to do things. not here to tell people how to rig stuff up or to just go along with whatever people come up with in their heads. my guess is that this isnt the first time you have been told the same thing from other people and at some point it should become evident that what you are trying to do is not going to give you what you want. it might work electrically but it will be the worst possible way to go with your system. first, you are using the RCA outputs to send a signal to an amplifier that probably uses a high level signal output with a common ground. low level signals were not really used back then, the RCA outputs probably dont have enough power to register with that amp. try using that common ground adapter on the speaker wires from the radio and send that to the amplifiers inputs.

Can you tell me if either of the 2 following harnesses would plug into the wires you unplugged from the rear of your factory radio? http://metraonline.com/part/70-1770 http://metraonline.com/part/70-5510

soundnsecurity wrote: in favor of a better way.

I guess better is in the eye of the beholder or in this case the original poster.  If better equals using what you have and is near free I reckon that might be better to some, even if the result is less than what is possible with other methods. Even if the majority of people know other ways are "better" it sounds like that is not the better this OP is seeking.  I will now bow out since I know nothing of that topic. Good day folks

To master and control electricity is perfection. *evil laugh*