When you are still at the system preference window, you may have to click at the sound and the output tab just under it and select the HDMI option you see there.Go to the Apple logo found at the left corner of the screen and then you click at the system preference you see.
You have to ensure that you have connected the HDMI cable well to the right adapter and also the adapter should be connected well and firmly to the Mac computer for proper functioning.
That’s why we have said in the above paragraph that there is a possibility of you working with the adapter HDMI. It is also crucial to know that not all computers that have Mini Display Port/Thunderbolt are able to work well with audio and at the same time with video from the same cable. The images are perfectly well projected especially if you have done it well and followed the instruction provided. If you are thinking of projecting business presentations, watch movies or play your favorite show, you are sure to enjoy your entertainment and business easily within no time at all. This will enable you to connect to your other device with the HDMI and achieve the desired connection.
In case your Mac pro computer uses the Mini Display port, you are sure to have the possibility of working with the HDMI adapter. The Mac models differ mostly from others as it has to be done with much mini display/Thunderbolt.