I got tired of smashing up my tailpipe tips while off roading and had a local muffler shop install turndown's on my factory exhaust right behind the muffler ($40) and yes, it has drone. Mainly at startup and at highway speeds. And I think the factory muffler is probably quieter than this system. It's not unbearable but it is there. But it's worth it to move the tailpipes out of the way.
I think that any turndown will add drone as the sound it going down and bouncing back into the cab rather than escaping to the outside.
If you live in a State where you have a vehicle inspection annually (like here in Texas) it will also not "legally" pass inspection with a turn down.