If making your own up buy new 2 pole speakons, I had an issue with farty speaker noise at volume, tried swapping out basses, inst cables, checked inside from socket to speaker eventually ordered a new speaker from the States only to track it down later to a dodgy 20 year old 4 pole peavey PA cable I butchered to make up a bass cab lead. It is easy to see if a 1/4 jack is clean or damaged but not if the little wire fingers on a speakon are opening, mucky or jammed.
I believe in speakons but as above don't skimp