One logical explanation may be that the HRS was damping or modifying some resonance in your rack that affects the CD player's performance even though it's on a different shelf.
HRS Isolation Voodoo, anyone experienced this?
I was auditioning an HRS isolation platform for my turntable. When I took it back, not only did I notice a huge difference in the performance of my turntable, but also in the CD player 2 shelves below the turntable. I cannot believe that. How can this be so? I never used the platform under the CD player but somehow the Platform influenced the performance of the CD player as well. I was shocked. How can this be? Amazing VOODOO of some sort. Now everything sounds somewhat not right. I can't believe it.