Bi-Wire with two pairs of speaker cables

"....If the plating or base metal was poor, there could very significant sonic effects....."  

leales.

Do you think that the designer/manufacturer of high-quality loudspeakers would knowingly use something that degrades the sound?

Poor plating or base metal also applies to spade lugs and banana plugs.

Do you think that the designer/manufacturer of high-quality loudspeakers would knowingly use something that degrades the sound?

Stuff happens.

We once got a new batch of NE5532 chips that had 10x the current draw. My company replaced 7 million Philips capacitors that did not meet the life spec. Of those replacements, several tens of thousand had to be replaced because if the bung was over the negative rail trace, it sucked out the electrolyte, shorted the buss and occasionally started a fire.

I bought two pair of audioquest type 4 no frills from audio advisor. I had them terminate the speaker ends of the two pair with spades. On the amp end, one pair is terminated with spades, the other with bananas. This way, I am able to avoid doubling up spades at the speaker terminal of amp. Instead I place one spade per terminal and one banana. Works out great. The cables are not fancy, just plain white jacket, with speaker and amp ends clearly marked. I think for the money, audio advisor does a great job with the AQ type 4. These Type 4's are highly regarded by Stereophile and have gone unchanged since inception back in the 80's. Why change something that works. Probably the best balanced affordable cables in existence imo. 

Just replaced my Morrow Sp3 internal Biwire (old version) with two runs of new Sp3 for an external Biwire. I did this after running the old Sp3 to the woofers and new to the Mid/highs and liked the results. Bottom set still breaking in but good and improvement so far.