Quoted from Pinballmonkey:Any thoughts to this crossover with upgraded back box speakers? I’m trying to find a subwoofer under $40 for the cabinet as well
Dayton Audio 800-LPF-4 Low Pass... amazon.com link »
800Hz is too high for a subwoofer, you want something less than 200.
Earlier link references this one:
https://www.amazon.com/Nippon-HC-101-channel-Subwoofer-Crossover/dp/B009D9KHZ2