| I've never heard of them referred to as "softs" but like Maladoit1 says, they are probably just a lighter gauge set of strings.
I think that it's a personal preference as to which gauges are better for slapping. For example, Les Claypool is rumored to use two A strings and two G strings (making his E and D strings much lighter than even super-light gauge strings) on his four-string.
All things being equal, lighter gauge strings will feel "floppier," may be easier to press down, and will be under less tension than the heavier gauge strings, which will feel tighter.
You can slap with any string but overall, flatwounds sound a bit mellower than roundwounds. Thus, most people stick with roudwounds for a punchier slap tone, but you can really do anything you want.
Finally, keep in mind that some basses (but not all) will require a basic setup after you change string gauges. |