Stock Stereo Not Usable For Sub?

[countrydude]

I've got an audio install problem that has me scratching my head with no ideas for cause/solution. I should mention I'm not really any kind of expert so that doesn't actually say much. Anyway... Here is my situation. I am installing a subwoofer in my 2010 TC using the stock stereo (basic model with bluetooth for phone calls, CD player, and an AUX input), amp under one seat and sub under the other. I tapped into the speaker wires at the back of the stereo using a line out converter since my amp only has low level inputs. After wiring everything else up and then testing it out I realized there was a problem: With the speaker balance set to the center the amp got very little signal but if I faded it left or right the signal would increase and the more I fade it to one side the stronger the signal gets. I fiddled with all the knobs making sure I there isn't a setting I missed or messed up and double checked all wiring. Eventually I concluded that I wired the LOC incorrectly and one of the inputs was out of phase so pulled out the head unit again and switched one of the positive and negative wire pairs to the LOC. That didn't work and now I have no idea what to do from here. Any one else have any problems like this? Does the head unit put out signals that happen to be just perfectly out of phase? 

[mrtn]

That does not sound right. There’s no phase delay correction in a cheap OEM head unit. Did you check the output like it was before? Do the original speakers work fine with the head unit?

[countrydude]

The door speakers work fine. Not sure what you mean by "Did you check the output like it was before?"

[Beta Don]

I *think* I know what's happen here  -  I assume your sub is mono and not stereo?

 

Wiring a mono sub to a stereo radio, you need to run the sub off either the right channel output or the left channel.  When you wire it into one wire from each channel, all the sub will 'see' is the difference between the channels  -  If the two stereo channels are outputting the same basic signal, the sub doesn't get any input at all, as there's no difference between them.  When you shift the stereo off balance, side to side, you're creating a difference between the left and the right and the mono sub sees that difference and amplifies it

 

Hope this helps,

 

Don

[mrtn]

But the line converter should melt the speaker signals together for mono sub output.

[Don Ridley]

I agree this appears to be a mono/ stereo problem. Check the LOC for a mono output setting. Check sub for mono or stereo inputs or configuration.

 

I am sure a Google search will identify this problem and possible solutions.

[countrydude]

My amp is a two channel that I have bridged down to one for the sub. It doesn't have a mono setting but I think the system automatically puts the two together when set up bridged. I had this system installed in a different car and didn't have any issues so I don't think it is an amp problem. Although the headunit driving it previously had a dedicated pre amp output...

This is the amp I have: https://www.manualslib.com/manual/460658/Diamond-Audio-Technology-D5-300-2.html?page=11#manual  Maybe there is something I missed?

The LOC I have is super basic and only has level adjustments for each channel. I have the set equally but I fiddled with them when I was trouble shooting and it did really affect anything. 

 

Thanks y'all for the help so far!

[Beta Don]

The fact that the sub amp works fine when you have the balance set all the way to the right or left, but not when you have it set balanced in the middle pretty much tells you all you need to know.  Try running the sub off of the left or right channel ONLY and see what that gets you

 

Don

[countrydude]

On 11/16/2017 at 9:23 AM, Beta Don said:

The fact that the sub amp works fine when you have the balance set all the way to the right or left, but not when you have it set balanced in the middle pretty much tells you all you need to know.  Try running the sub off of the left or right channel ONLY and see what that gets you

 

Don

Holy shit, Beta Don dropping knowledge and uncovering a clue revealing a twist in the plot! I tested each channel on its own by unplugging one cable at a time from the amp and here is what I got:  

 

Unplug right channel cable with fade to left; no affect.

Unplug right channel cable with fade to right; no affect.

Unplug left channel cable with fade to left; sub cuts out!

Unplug left channel cable with fade to right; sub cuts out!

 

Now WTF does that mean?? Both door speakers work fine...

[Don Ridley]

Assuming the amp is OK, you are need to check the wiring and amp in small steps to verify all is correct.

1. Disconnect wires from the amp and connect one set of wires to a spare speaker to verify it works. Fade right and left and verify that works ( sound should fade completely on one fader side). If that works connect the other set and do the same test.

2. If the wiring is ok, configure the amp for 2ch operation. Not mono, not bridged. Connect one set of wires to one amp channel and connect your spare speaker to the output like you are adding another set of speakers. Fade like before and verify that works. Then connect the other set and perform the same test.

3. If all of that works, you are ready to check the bridged and mono amp settings and your sub speaker.

 

The wiring, amp or sub speaker is the problem.