What speaker cable made a major difference in the sound quality of your speakers??

I have tried too many cables over the years to mention.  I don't chase cables any longer now.  I have had very expensive speaker cables $7K and one day in my system I tried a used $200 cable that was close and better for my budget.  I have also brought an Adcom interconnect torn in to for a digital cable and it bested a very higher priced cable in another persons system.  The same higher priced cable interconnects were better than what I was using at the time ( a good litz copper interconnect).  So no conclusions about what works and does not work based on price for me, just see what works in your system.

I also agree with akg_that jaw dropping - well not a chance but I did place a component in my friends system and it was a night and day difference, and that has happened twice in his system. For some reason his system really hears the changes for the better and it was the most change/improvement I have heard in any system each time.  Cannot explain why though.

Happy Listening.

Crystal Clear Cable, Magnum Opus 99.9999% Silver made a huge difference in my system.

Tara lab's omega gold speaker cable's and Omega jumper cable’s. 

I never believed the cable thing for years. then a friend of mine who owns an audio shop was trying out the Siltech line and asked me to give a few of the models a try I ended up buying the FT12 silver ribbon and I became a believer.. Dam it ! I've had them for years now very happy tried others and never thought to upgrade or side grade whatever. I like the Siltech silver/gold wires.

Canare 4s8. Balanced, dynamic,  detailed, superb extension on both ends of the audio band.  It lets your amp have the best grip on your speakers.  Feels more powerful, punchier than cables twice as big. Details and harmonics come through like you would not believe... for less than $20 a 10ft pair, it is superb, and approved by many audiophiles as it has been sold throughout the years wrapped up under different brand names, at much much higher prices of course.