I didn't try it with Duelund cables but I DIY speaker cables with similar construction and providing a shield improvement the sound quality (mostly blackness and image). The shield having equivalent gauge is used as the ground lead. The added capacitance will provide a path to ground for high frequency noise. Give it a try to see if you like it.
Duelund shielding
I have some Duelund dual DCA12GA on order for speaker cable. I'm seeking a richer, warmer tone and this unique cable is well recommended. I am wondering though if anyone who is using it has gone to the effort of shielding it.
As far as I can tell, the cable is tinned copper and only wrapped in cotton. There is no shielding. I've also noticed that vendors such as Audiolund are repackaging it with added shielding.
Has anyone tried buying a metal braiding and shielded the raw cable themselves? Did it improve the sound?