Tannoy DC6T special edition losing base??

Hi I have recently bought tannoy DC6T special editions and I am powering them with marantz pm6004....

My issue is I'm losing bass an sound in one speaker I thought it was the speaker that was faulty so I've swapped them around and now the good speaker has lost it's sound!!

After discovering it's not the speaker I'm guessing it's either the amp or less likely the wires (these are decent wires costing £40 a metre )

Any ideas as to what is causing the problem will be greatly appreciated as I can't find a solution I've rewired the amp and speakers twice but to no avail

Huge thanks in advance
Mark