I know that I seem to be the only one posting replies here, but I thought I would try to further clarify the "headphones" comment.
I remember hearing a similar effect one time while at a private concert of Chris Issac. I was seated center stage not more than 8' from Chris. The speakers for the small auditorium were actually on plane with me to either side. The amplification was not turned up particularly high and I could hear the actual acoustic guitar and his voice in the natural while also hearing the amplified signal from the pa system. When I moved to behind the plane of the speakers the sound became very typical. But the magic returned once I re took my seat.
This is a very similar effect to what I am hearing from the Janszens. Take that for what it is.
I remember hearing a similar effect one time while at a private concert of Chris Issac. I was seated center stage not more than 8' from Chris. The speakers for the small auditorium were actually on plane with me to either side. The amplification was not turned up particularly high and I could hear the actual acoustic guitar and his voice in the natural while also hearing the amplified signal from the pa system. When I moved to behind the plane of the speakers the sound became very typical. But the magic returned once I re took my seat.
This is a very similar effect to what I am hearing from the Janszens. Take that for what it is.