Matt M. & LuisV, I picked up an i-simple interface so that I can use my cell phone as music source. I’m waiting on the perfect power switch.
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In the mean time, I’m swapping out the door speakers. Behind the 6-1/2″ speaker grill is a 1″ gap then a 5-1/2″ speaker. The interior panel held away from the inner door structure. I mounted a horn on the 5-1/2″ speaker to direct the sound in to the cabin instead of in to the door. See picture. You’ll never guess what the horn is made from-a Home Depot $4 plunger cut to size.
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If I were to do this again, I would mount a 6-1/2″ speaker to the interior panel and place the filler behind the speaker.