i have HDLs and WP6s. with my transparent ref. xl ss they did improve things. the differences were small but noticable. smoother treble, more ambience. you could see more into the soundstage. it seemed to strip away a level of grunge.
later, as i got use to the HDLs i pulled them out to see if i could tell the difference. the first time it didn't seem to make much difference. then later i tried it again and it was like the first time; small but worthwhile improvement.
recently i replaced the ref.xl ss speaker cable with the opus. the HDLs don't really help the opus much if at all. i have had them in and out of the system. possibly a slight improvement.
so my conclusion; the HDLs are worthwhile for ref.xl or below, not for the opus. i may sell my HDLs. i do like tweaks and might continue to experiment as my system evolves.
later, as i got use to the HDLs i pulled them out to see if i could tell the difference. the first time it didn't seem to make much difference. then later i tried it again and it was like the first time; small but worthwhile improvement.
recently i replaced the ref.xl ss speaker cable with the opus. the HDLs don't really help the opus much if at all. i have had them in and out of the system. possibly a slight improvement.
so my conclusion; the HDLs are worthwhile for ref.xl or below, not for the opus. i may sell my HDLs. i do like tweaks and might continue to experiment as my system evolves.