Recently I contacted the developer to ask why Hear doesn't work with audio from Safari. The reply I received was crapola.
"Mac OS X 10.9 implemented a new security feature called Sandbox. This term describes applications that are secluded from other programs for security purposes. Safari and included plugins happen to be one of these applications.
Hear and other softwares cannot take control of Sandboxed applications."
If that were true then no "softwares" could capture or control Safari's output, but there are plenty of apps that can. I use Audio Hijack daily to record audio from Safari, mostly from one of the plugins. So if AH can capture audio from a sandboxed app, why can't Hear?
Coreaudio is also sandboxed, yet AH is able to capture any system audio, so the dev's answer is incorrect.
Besides, their direct competitor (Boom) works with Safari, so obviously their assertion that no software can control Safari audio is fallacious.
I tried Boom but didn't like the sound. I prefer Hear although its many options can be overwhelming and seem to need frequent tweaking, such as when changing genres in iTunes.
I dislike all of the the presets and have created my own for headphones, podcasts, tv etc.
There's absolutely no reason for Hear to not work in Safari and it's a major shortcoming, thus only 2.5 stars because of this and the bogus excuse.