That Eden Nemesis NSP410 cab has both 1/4" jacks on the right, and Speakon connectors on the left of the jackplate. As agedhorse pointed out the 1/4" on top is broken - use the one below it if you want to use a 1/4" plug. It would be better to run a standard Speakon cable to it instead, because it locks in place. That Eden jack is expecting a Speakon wired with positive to +1 and negative to -1 (obviously). It's an easy fix and should be a great combination to run together.
get a pair of foam earplugs and roll them up and put one in each of the phone plug jacks to prevent air coming out/whistling.