I am trying to connect an analog subwoofer to the line out of my MacBook Pro 17. Apparently, contrary to the smaller models, the 17 inch's line out minijack switches between analog or digital, depending on software control from OSX. When you plug in some earphones, contrary to all other computers I have used, there is a lag between the moment in which the electrical connection is made and when the signal is sent to the phones (and loudspeakers muted).
That leads me to believe that there must be a way to tell OSX not to mute the speakers and to play audio through the minijack at the same time. But I have not been able to make it happen.
As soon as the analog external device (let us call it "headphones") is detected, in the "sound" system preferences, the choice switches from "Internal Speakers" to "Headphones", both of type "built-in".
I have examined options like installing Audio Hijack Pro, with the SoundFlower plugin and the Griffin iMic DAC dongle to trick the MBP into sharing a sound source between the speakers and the "line out" of the dongle, which may work, as the article in http://forums.macrumors.com/showthread.php?t=725870 suggests, but sure looks like a square peg in a round hole.
All I would need is somehow to find a way not to turn off the speakers while the signal is also routed to the minijack (as it happened to someone else, who considered it a fault), so I may send an audio signal to my subwoofer.
I wounder if there is anyone who can illuminate me with a simple software only solution that may be a batch file to enter in terminal (and another to bring things back to normal) or an app that may do the trick.