Subwoofer help

I’m installing a NVX powered sub under the seat, I’m using the high level inputs getting signal from the front dash speakers.

No matter how I connect them I only get very slight sound from the sub. What an I doing wrong, can I not connect them there? Any help would be greatly appreciate.

thanks
Dusty

 

I found the problem, I relocated the connection point to the capacitor and plugged the speaker in reconnecting the door speakers. I was unaware the door speakers would quit if you unplugged the dash speaker. Anyway it thumps now but I’m still not happy with the over all sound.

I used this same sub in another small car, it had a sony head unit which allowed numerous adjustments to the sub and it really sounded good. Only being able to just adjust the bass with the prius head unit you can not find that sweet spot. Yes the sub it self does have five adjustments but I still couldn’t get what I was looking for. Thanks for the response.