Mate, if its live all the time its possible you will fry something else.

Please get the ignition live checked and draw a new feed from the back of the head unit if its not something you're able to do yourself, take it to an i.c.e shop, they'll do it in 3 minutes or whereabouts are you based?

Make sure the fuse on the permanent live is as close to the battery as possible, underneath the bonnet, not in the car

Check both the fuses too, the one on the live and there should be a small blade fuse in the amp?

Don't put that tannoy speaker in until its all fixed

Check the rca leads are working ok and they've not split thru the coating anywhere, or the connectors are fooked, and the same for the speaker cable also, pop the sub out the box and check the soldered connections for the speaker wire