change from rounds to flats, re-setup necessary?

[OneDrop76]

If I change my bass from round to flatwounds, will I need to have a setup done on my bass since the tension is different? I really want to try flats, cause I play a lot of reggae. I was also told they feel a LOT different when playing. Is this true? I'd prefer to use a lighter attack and let the amp do its job, as I am a recently converted guitar player. So if the tighter strings facilitate this, that's fine with me.

[AGCurry]

Any time you change to a different set of strings - unless they're just like the ones you take off - you may have to adjust your action. Usually, it's just a matter of small adjustments at the bridge.

Flatwounds do feel different from roundwounds, but if you can play on one you can play on the other.

[skinnypete]

I recently switched to Flatwounds and had to adjust the trussrod and the intonation slightly. It's no big deal so long as the bass' setup is in good shape initially. If it is out of whack with round wounds it will be even more so with flats because the difference in tension is considerable.

[bassontherun]

+1, minimal adjustment. On the positive side, on one bass that I changed from rounds to flats, I was getting less buzz, so I was able to lower the action a bit. Others have been about equal. Enjoy the flats!! To me they are easier on the fingers, but you'll have to decide if you like the difference in sound. If you have the scratch, try a few sets (including some tapewounds). Like rounds, they will have a variety of tones.

[Dave Siff]

I recently changed from rounds to flats on two of my basses, and didn't do any tweaking. They probably need a slight tweak, but the action and playability didn't really change and the intonation is fine. Granted, one of the basses has a rockwood neck. But, the other is a MIJ Fender Precision. The flats went right on there and the neck didn't act up at all.
As far as flats being easier on the fingers, I'll take issue with that. I found out the other night that if you dig in hard enough, flats will do a number on you. About halfway through my band's set, I noticed a rather large blood-blister had formed on the index finger of my picking hand. It burst during our second-to-last song, spewing blood onto my bass, strings and pickups. A true rock-and-roll moment. I've got another gig Thursday and I am rockin' some NewSkin liquid bandage!