There is a thread in here about this topic, but the thread is closed and this really needs a re-up.
Here we are many years later and the exact same problem still exists! I just had an install done after being out of the game for 15 yrs. Exact same problem so I changed the wiring myself.
On another topic..... for those of you, like me, who have been out of it for a while...... DO NOT ALWAYS TAKE A SALESPERSON'S advise. Some things have changed! Kicker makes a shallow mount sub (COMPVT). I bought one while being told it will pound as hard as any other sub. Wow was he wrong. I had some Kaptions thrown in up front on a 65W RMS amp. I couldn't even hear/feel the low's it was so bad! High's everywhere but no low's. Bought 2 of these subs and the J2 1000.1 amp and have never looked back since.... mainly because I'm afraid that by turning my head to face the rear of the vehicle I'm worried my eyes will bleed from the bass being thrown around.
JL is still the king of Bass. That much hasn't changed!