Plugging a speaker into the rear audio port of a Dell computer fails to play the audio on the speaker. Plugging the same speaker into the front audio port with a headphone picture plays the speaker like it ought to.

The problem seems to be that the rear audio is either speaker or microphone, while the front audio is only headphone or speaker and no microphone.

This is true on my i5 and my i7 which are both Dell computers with the same setup and the same result.