As a mastering engineer, I love when I receive a song that is mixed correctly because it makes my life so much easier and makes me less likely to eat and drink my life away (though I’ll probably still do that anyway).
The one thing I’ve noticed that all good mixes particularly from genres such as dance and rap (both drum and bass heavy dependent) have in common is that they are mixed really, really, really low. While I do recommend most amateur mixers try to get their mix between -6 and -3, the best mixes I receive particularly in EDM and Trap are mixed with a peak volume of between -20 and -15.
Why is this volume level the sweet spot? Because when a mastering engineer hits the song with high powered compressors and limiters there will be enough room for the song to “breathe”, particularly for the bass and kick to have adequate headroom. When a dance song has a peak volume of -1 and it is mastered, 99% of the time, the kicks and bass wont hit hard because “the life” will be squashed out of them by the mastering. This is because there is no headroom.
What does headroom mean? Let’s say we have a room (0 db) with an elephant (song) in it and the room only allows one inch of room between the walls and the elephant (headroom). If we drop some magic potion on the elephant that makes it bigger (mastering) he’s going to destroy the room (squash the song). This is what happens to a song with little headroom (i.e. songs mixed with a peak volume of -3 or higher). If we take a mini elephant, say with 5 feet of room between it and the walls and drop our magic potion on it, the elephant will be as big as possible without destroying the room.
This is what mastering will do for a well mixed song. It will make it as big as possible without sucking the life out of it and most importantly making the drums knock!