Connecting an extra speaker or two to ... a wired connection using a 3.5-millimeter port. Why would you do this? Isn't the point of Bluetooth going without wires? Yes, and no.

We should also be aware that backward compatibility with 3.5mm headphones is completely up to the handset manufacturer at this point, even though they will need to provide a DAC and speaker ...

However, installing some systems still requires lengthy speaker wires running back to ... use Bluetooth only or offer a basic option like a 3.5mm audio jack and Coaxial input.