no sound coming from external speakers, that are plugged into jack on my macbook pro haven't touched any settings, or downloaded any new software. I just started up my computer and the headphones jack that power my external speakers aren't working?! I get no sound at all. Yet, when I unplug it from the jack, the sound from the computer comes on (3 sec) later. I've been reading the different posts and trying to follow the steps that are given, but it's not working.
You can try setting the sound output manually from system preferences. Does you external speaker get listed here upon plugging in?