Employing a second medium of sound volume resistance? I have a Macbook Pro 2012 and a pair of headphones (without their own sound volume adjuster). These headphones are awfully loud and even with quarter bar sound level, I have to turn the audio volume slider in apps all the way down to get a decent volume level. My ears aren't super sensitive or anything, I think it's just these headphones.
Is there a software that I can download which will act as a virtual cable type thing where the app will feed audio data to the virtual cable (VC), the VC will then allow me to edit the sound (in my case I want to alter volume levels) and then output to my headphones.

This isn't something that you can do in the default Mac OS (I don't think so anyhow). I'm asking if anyone has heard of something like that.
There is actually a somewhat hidden step between 1/4 bars and muted. To select it, first set the volume to zero by holding the volume down key and then press the mute key.

Another way is to run osascript -e 'set volume output volume 0.5'. set volume output volume 0.1 and set volume output volume 0.9 are equivalent to set volume output volume 0.5.

You can decrease the volume level by using Soundflower together with AU Lab:


Download Soundflower from http://cycling74.com/soundflower-landing-page/ and download AU Lab from https://developer.apple.com/downloads/.
Select Soundflower (2ch) from System Preferences > Sound > Output.
Open AU Lab, set the input device to Soundflower (2ch), set the output device to Built-in Output, and press Create Document. You can then control the volume level from AU Lab and by changing the volume level of the built-in output from System Preferences.