Right. Because, bass perception is highly variable and this is even on top of recording levels. The same music that seems to have too much bass will sound just right at a lower volume. This is where the Loudness switch came from, to turn bass up a lot so it sounds right when listening at a lower volume.
What this means is you have two choices. One, you can mess around constantly tweaking level from one song to the next and every time you change the volume. Or two, you can listen to a lot of stuff just like normal and make a mental note how things sound. Then after a while if it seems on balance it would be better a little more or a little less make a very small - very small - adjustment.
That is what Duke recommended, and that is the way I did mine, and it works great. Nothing ever is perfect, but overall everything sounds great.
What this means is you have two choices. One, you can mess around constantly tweaking level from one song to the next and every time you change the volume. Or two, you can listen to a lot of stuff just like normal and make a mental note how things sound. Then after a while if it seems on balance it would be better a little more or a little less make a very small - very small - adjustment.
That is what Duke recommended, and that is the way I did mine, and it works great. Nothing ever is perfect, but overall everything sounds great.