Very slow access from iMac

I have a WD My Book Live external drive of 3Tb.

The drive es being connected to a router to access from both computers.
I have a PC and iMac. I´m having a lot of troubles to access from iMac. I mean it is extremelly slowly to access to the WD drive.

From PC sometimes have troubles, but most of the time the access is good.

From WD support could not give a solution, not even a reasonable answer.

Anybody can help me?

Thanks a lot!


What did they tell you? And how is your Mac communication with your router? What are the wireless specs for it?