Is this necessary? Fitted some new Alpine mid/bass units that comes with a crossover but how on earth do you find the speaker wires under the dash. I have already wired up the new tweeters to the crossover and installed the crossover in the cavity below these.

Didn't bother in the end. It seems the simplest solution is to pass another couple of wires from the crossover through the front door conduit, but it all sounds great without.