amp & 15's to factory radio

And are the speakers in phase!

i have 2 dual voice volfenhag 15's my in line converter is adjustable (tried all levels) tied into two rear speakers my amp is a stretch daddy 1300watt 2 channel all gains adjusted the wires are 12 gauge.

pleses help......

Start fire in car and run.

Nice ride, shame about the tunz. No offence intended. The only way that amp will make that much power (which is a real stretch at best) is to get struck by Lightning. The amp if it has a 30 amp fuse can put out about 450watts rms. The amp is way too small for the subs, you will damage the subs - could be a good thing though, the subs are even worse than the amp. How have you wired the subs to the amp? What are the impedance of the subs? I'll try to help you with this mess and get you the best you can from them but I really think a new setup is in your future. I'm not trying to knock your purchase, just poke some fun at it. Let's get this solved for u.

Comedy. 

Power and ground wires should be 4 gauge for best results on the power side. 

The wires from each sub should be in parallel, that is positive to positive and negative to negative for each sub with one sub per channel on the amp, this will result in about 450-500watts per channel.  The reason this amp is "too small" for these subs is because you will turn the volume up causing clipping, kinda as safe as jumping on a trampoline in a room with low cellings.

As for setting the gains, turn them completely down on amp and converter.  Next turn stereo volume to around 85% of max.  Turn the line converter up until the subs play at level that you can somewhat hear.  Then adjust the gains on the amp until you hear distortion and turn it down a few clicks.

The last possiblity is that the box you have is too small, and from looking at the T/S of these subs you are gonna need some decent air space, a good portion of your trunk.  If you use a ported box, forget about your trunk.