Speaker cable vibration?

After trial and error, I discovered that a certain 'edginess' and lack of coherence I was hearing from my speakers was due in part to the physical vibration of the speaker cable and connectors. As music was playing, I felt the connectors where they connected to the binding posts, and they had significant vibration, in direct relation to what the drivers were doing. Also, to a lesser degree but in the same vein, the speaker cable itself was also vibrating.

I then tried damping the the cable and connectors with very DIY items from Home Depot -- pipe insulation and felt washers for sinks. The result was a much tighter, smoother more natural and direct sound.

I am in the middle just now of receiving different speakers after selling off the ones I was using. I have wondered if poor binding post insulation was the culprit, and will find out more definitively once I try the new speakers and see if vibrating binding posts are still an issue.

I bring this up, because:
1) The issue seems significant in its affect on the sound
2) I haven't read/heard much about this before (I would think any significant source of vibration would have been jumped on by the tweak companies by now)
3) Why haven't speaker cable companies addressed this
4) Curious to hear from others

The sound has been improved, but looks-wise, I've got speaker cable wrapped in pipe insulation. Not very WAF to say the least. I do know of one company -- Acoustic Revive -- that I think has some sort of insulation in their connectors. FYI my speaker cables are thick Synergistic Research with WBT 0645 banana connectors.