
These usually have the same signal just with different amplification. I don't think any chipset has the ability to send different sounds to the headphone and speaker exits. You need to have two sound devices though.
Contact the Helpdesk if the above steps did not help.I just tried and it is working just fine. The settings take effect immediately - just close the MIDI setup application. In the right-hand portion of the screen, ensure that Format is set to 48000 Hz and 2-ch 24bit. In the Audio MIDI Setup application, click on the HDMI option in the list of devices on the left. In the list of search results, click on the Audio MIDI Setup application. Click on the search button in the top right corner of the screen and type Audio MIDI Setup. If there is still no audio, follow the next steps, as well. This should produce both audio and video projection. In the System Preferences window, click Sound and under the Output tab, select the HDMI option. Click on the Apple logo in the top left corner of the screen and click System Preferences. Ensure that you have firmly connected the HDMI cable to the appropriate HDMI adapter and that the adapter is firmly connected to your Mac computer. Dana Auditorium is one location where this may happen. We have noticed that some combinations of Mac computer + HDMI adapter + classroom projection system may produce valid video projection but no audio. Potential audio problems when connecting a Mac to a projector using HDMI There is, however, a list of Mac computer models that do support both audio and video over the HDMI cable with the appropriate adapter. There is no definitive list of these computer models that do not support audio over the video cable. Roughly, this includes Mac laptops made before Mid-2010.
Right now, we are aware of certain Mac computers that cannot output audio over the HDMI cable.
However, not all computers that have Mini DisplayPort/Thunderbolt can send the audio over the same cable as video due to incomplete design by the manufacturer. For Mac models that have Mini DisplayPort/Thunderbolt, it is possible to use an HDMI adapter to connect to some of our newer classrooms and project a much higher quality image.