Mac OS simple sound mixer

Ever wanted to play sound through multiple audio devices on your Mac OS X system? It cannot be done with the normal Mac controls, but to my surprise there is a decent sound mixer built into the base Mac OS.

Step by step instructions: Play sound on multiple devices, including Internal Speakers, on OS X | Best Mac Tips

I have this setup for my 90 year old mother, so we can all watch TV at once:

• HDMI from Mac to our Panasonic TV
• Headphones plugged into the earphone jack on the Mac
• Closed captions turned on for TV

The result is that we can turn her volume way up, while we listen over the TV’s internal speakers. The headphones, even at maximum volume, may not be quite loud enough for her. In that case, I will add a $25 earphone amplifier into the system.

Still missing: I cannot find Bluetooth headphones that are loud enough for her.

Second, I don’t know of anything similar for her phone.