While most modern soundbars rely on an HDMI cable to connect to HDTVs and 4K TVs, there are still plenty of soundbars on the market with legacy audio inputs that will work with older TVs—and yes, that includes many CRT (aka “tube”) TVs that are decades old. By connecting an aging TV to a soundbar, you can give your older set a massive audio boost, complete with thumping bass and even virtualized 3D sound. And if your ancient flat-screen or tube TV has the right outputs, hooking it up to a new soundbar will be a snap. Here’s how to get started. 1. Look for optical or RCA audio outputsThe first …