Hi guys I've run a small cabinet shop (customwoodcreations.info) choose misc/gallery for enclosure builds. Anyway I traded off some labor for a Rockford 4600x and a kicker 12a 8ohm sub. Is there a way to wire the sub to match the 4ohm amp? Is the 8 ohm sub cutting my amps power by half?

 

If the sub has only one voice coil, then no, there's no way to show the amp a lesser load. If the sub is a dual voice coil model, than the coils can be wired in parallel to drop the total load to 4 ohms at the amp.
Are you able to determine the model number of the sub? Is it easy to remove from the enclosure?

 

Either that, or find a 2nd, identical sub.

 

The only problem with a 2nd identical sub would be that he's splitting the amp's output of 120W into 2. 60W per sub isn't going to be worth the trouble. In my opinion.

 

Its a single voice coil. I have the amp hooked up to my Droid x from the headphone jack it sounds very impressive. The amp is 4 channel and there are 3 wiring configurations.
The way I'm interested in shows the front channels bridge to one sub and the rear channels bridged to the other sub creating 180 watts per sub. If you only have two inputs from your stereo where do you get the other 2 low level RCA a y-splitter or active crossover?

 

If the amp doesn't have a summing switch (internally sums one input to both FR & RR inputs) you can use a Y splitter.
As for 180W...
4 x 30W @ 4 ohms (12.6V - 0.08% THD)
4 x 60W @ 2 ohms (12.6V - 0.3% THD)
2 x 120W @ 4 ohms (12.6V - 0.3% THD)

And that's at 4ohm- you're looking at 8 which would produce less power (although I'm unsure if their power supplies were regulated or not back then; it may make more power than thatat 14V).

 

Power supply was unregulated and you should get 40-50watts RMS per channel. We sold a buttload of them back in the day.

Yes technically your woofer is consuming half the power but it is not going to hurt anything so if you like it, great.