I think it's the sound what's meant to be "old-school"-out of the pack, they do not sound like new, bright flats, as many can. They are rather flexible, instead of the stiffer, old-style flatwounds that many do still use (because they still do sound good.) But they are not super sloppy or hard to control-if you have used the lighter gauges of the Dogal Jaco flats, you are probably not that far off (well, I have not used the Dogal, but am familiar with other very light sets.) I think the mixed reviews are because of the unique feel, and the confusion regarding their cobalt content-they are not an overpriced Slinky Flatwound with funny, random gauges, but rather its own, new product, different from Ernie Ball other flatwounds offerings. I honestly love both feel and sound, but we are all unique individuals with different needs and own preferences.
If used with four in-line, bass side tuners, I would highly recommend that you do not cut the D and G strings too short, leaving more string length than usual, as the lighter gauges + plus silks make them more slippery than the norm. Make it longer, so you can lock in place the string bent into the tuning machine post with an additional length of the string on top of it. I had no trouble, but the G did slip when I first installed these flats, and today, after installing some Hipshot HB3 tuners in lieu of the Mexican tuning machines, I also had to do the same with the D, as it started to slip as well while getting the string up to pitch. It does look odd as I ran out of string length, but it's now safely locked in place, so I don't mind it too much.
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I only needed to do the "string lock" with the D&G; the E&A are thick enough to not slip out of the tuning post.
The Hipshot tuners are great as usual! I will also install an incoming Xtender tomorrow- looking forward to seeing how it will work with the Smoothie Flats E.