Quoted from fxdwg:hands down the best, and easiest method, and completely 100% reversible (with ZERO damage) if you decide to sell your pin.
http://www.pinnovators.com/catalog/product_info.php?products_id=48
I used to wire into the speaker in the bottom of the cabinet for all my pins, now I simply order the correct kit for each machine.
Updated link from our new site as of 11/1: https://pinnovators.myshopify.com/collections/stern-subwoofer-kits/products/pinsub-spike-stern-kit
Use this code YDH69A53QCH8 at checkout for for 5% off your first order at our new site. Valid until 2:00 pm EST Nov 6.