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.
I have made ICs from the Duelund 20awg (DCA20GA600V) Tin Plate Copper Hookup Wire and shielded those cables using tinned copper braid shield connected at the source end only. The cables are balanced/XLR interconnects and they sound good with no noise issues.
I have also made speaker cables from the Duelund 12awg (DCA12GA600V) Tin Plate Copper Hookup Wire and did not shield them. They are constructed using a star quad geometry and bi-wired, so there are 8 individual runs of the 12awg wire to each speaker. Few companies shield speaker cables so I am not sure what you would achieve by shielding the speaker cables. If I were starting a speaker cable project with this wire, I would simply use their Dual DCA12GA 2x12 awg, Tin-plated, Stranded Copper, Oiled Cotton Speaker/Interconnect Cable. The cable already comes as a twisted pair in an outer sleeve, so they are essentially good to go as-is after adding the connectors of your choice. The already twisted and encased wire was not available when I made my speaker cables, so I used their hook-up wire.
A shield can keep RF out, but whether it affects the sound is unknown.
In any case I am assuming that the shield is floated at the amp and speaker, and tied directly to some ground like the safety ground?
And the other good news in that the cotton would make the addition of a shield have a lower capacitance than it wold have with a higher dielectric constant material. So the cotton coming in lower.
Thanks all, for your comments
My speakers (ATC SCM40) are 3-way and have 3 sets of binding posts. At the moment I have the supplied metal jumper bars in place. I had up to this point been dreading having to buy 2 sets of jumpers for my existing cable (TelluriumQ Ultra Black II). But, instead, I can use bare wire. Just have to be careful there are no stray strands which might short the amp.
@mitch2 I am wondering… why not tie the shield at both ends of the XLR?
Ah ok @mitch2 so it is electrically equivalent to tying the shield to the ground, just it is not pin-1 but tied to another place on the devices?