I upgraded my dads 40yr old thorn speakers which belonged to on old vinyl player, had two 25w mids and a tweeter. Gutted the boxes and partitioned the bottom half to house a down firing sub. Top half with a modern mid driver and tweeter.
Inside i used capacitors connected to the positive terminals of each driver to filter the audio range and a coil of wire transistor for the sub.
Jaycar helped me through which capcitors and such to use for each driver inside the box. Low range will blow the tweeter if not filtered.
Any speaker wire will do, wouldnt use usb cable.