I have a late 2013 rMBP 15 without a dGPU. I connect it to my TV via HDMI. I also have an Apple bluetooth trackpad connected. When the lid/screen is open, the sounds comes out from the TV just fine. But when I close the lid to make it go into clamshell mode, video continues to play on TV, but audio switches to the rMBP's speakers and no sound comes out from the TV. Now when I use my friend's late 2013 rMBP 15 WITH the dGPU to do testing, using the same TV and same HDMI cable, even after I put his rMBP in clamshell mode, the sound continues to come out from the TV. Am I correct in assuming that the lack of dGPU is what causes the audio to switch back to the rMBP's speakers after it goes into the clamshell mode? Or is there some other setting I can change or is there something wrong with my rMBP? Thanks in advance!