Audio devices generally work solo. A MacBook, for example, only has one audio jack which means you can only connect one set of headphones or external speakers to it however, there are simple ways to get around it. Devices that connect via the audio jack can be forced to work together with a cheap hardware but the audio jack isn’t the only way an audio output device connects to a Mac.
USB and Bluetooth powered audio devices connect just as easily with a Mac. If you need them to work with the built-in speakers, or any other device connected to the audio jack, it’s fairly easy. There’s a built-in tool on macOS that lets you combine and output audio to multiple devices.
Output audio to multiple devices
Connect all the audio devices that you want to use to your Mac. On the Mac, look for and open an app called Audio MIDI Setup. This is a stock app on macOS and you should be able to open it from Spotlight, Launchpad, or the Applications folder.
Once you have the app open, you’ll notice that all the audio devices that are connected to your Mac are listed in a column on the left. At the bottom of this column, there’s a plus button. Click it, and select ‘Create Aggregate Device’ from the menu.
This will add a new device to the left column. Select it and the pane on the right will list all the audio devices that are connected to your system. Check the box next to each device you want to output sound to.
Next, open the Clock Source dropdown and select one of the audio output devices. Next, look at the devices listed under ‘Subdevices’. You can change the order of these devices. Move the device that you select as the Clock Source to the very end.
Note: You may have noticed that I’ve added the same device i.e., a Bluetooth speaker twice. The speaker in question is both an input and an output device and in order to add it, I had to select all instances of it. You will likely have to do the same. If you’re using just a speaker with no mic, and you only care about outputing audio, you can instead create an aggregate Multi-output device. The process is much simpler; all you have to do is select the option from the plus button, and select your output devices.
When you’re done, right-click the aggregate device in the column on the left, and select the ‘Use This Device For Sound Output’ option.
Play audio, or video with audio, on your Mac and the audio will be routed to all the devices you selected to create the aggregate device.
If you want to use multiple audio input devices at once e.g., multiple mics, you can use this same trick but set the aggregate device as the audio input device.
I tested this out with a Bluetooth speaker and the built-in/in-line speakers on a MacBook and it worked flawlessly. This should work with just about any audio device you have as long as it can connect to your Mac. The exception will be where you cannot connect multiple devices e.g., you may not be able to connect multiple Bluetooth speakers to a Mac at once. In that case, you’re limited not by how many devices audio can be routed to, but how many can be connected.