Paul, I am ntentionaly not going in the dive into the techniques how I did it. This is kind of irrelevant. What is relevant that the state of that absolute blackness exist? I recorded a video when I examined it in details a week ago, but I decided not to post it. In the video I described how to identify the state absolute blackness and distincted from endless amount of gray shadows of bass. To make it very brief and simple here are the main concepts. Any version of gray bass emanates something toward to listener. The absolute black base does not emanate anything. It completely free from any radiation and kind of might be described as rowuk's vacuum. 

However, vacuum is a passive force but my observation that absolutely bass does radiate something. The fourth that it sends is a strange sense of endless fear. The depths of this blackness should be high that it's become literally  like a singularity of the black hole into which you do not want even to look. However, this fear is not the fear of the black hole itself but a fear of losing our own attachment to anything that we know. So the black hole become a bottomless well of uncertainties which obviously make us uncomfortable.

So, listening music, we are traveling over our reality and the presence of absolute black bass remind us that there are spaces in our soundstage where our control collapses and uncertainty become. This became slightly difference listening. This new listening is stopping to become an esthetical or ethical ceremony and become rathe and explorative philosophical journey. I have three level of bass blackness in my listening room and when I activate them then I clearly see that philosophical value of my music has direct correlation with the blackness of my bass. It is one of many aspects of audio which highlights my beloved transformation between physical and spiritual