Sand bags under a cdp - didn't work well

Last night I started the process of vibration control with the use of sand bags (3) under my Arcam cdp. What I found was that while everything became more focused/detailed it also became more sharp/harsh/forward/aggressive. I didn't know what to expect but it certaintly wasn't this. Van Morrison's voice on trk #5 on Sailing to Philadelphia was abnormally aggressive and in the end I preferred the sound without the bags. Any thoughts as to why things became too sharp & aggressive????