Trouble blinking leds with TIP31 Answered

Hello everybody, I am trying to make a blinking circuit to hook up to the LED strips in my car so they blink in sync with the bass. 

I have made a circuit following some instructable here, I can't recall which it was. Anyway, I'm pretty sure the schematic is correct, because the leds blink.

Now two problems arise: I have hooked them up to the subwoofer out of my radio ( a Kenwood kdc something), and after enabling it I was told to put a speaker coil in series to increase the resistance, in order not to fry the channel. Is this right?

Next, the leds don't quite blink, but they pretty much stay on all the time, with very little variation, I suppose because the sub out gives out quite a high voltage, so the transistor does not open the enough for the leds to blink properly. I was thinking of putting a resistor/potentiometer in series with the signal coming from the radio, in order to reduce the voltage and have a better blinking effect. What do you think?

Thanks in advance, peace :)