Flatwounds, never tried them ....a few questions

Most are generally stiffer than rounds, however there are quite a few brands that are compareable to rounds in stiffness. Thomistik-Infelds are the loosest flats on the market. You will probably have to add relief into the neck if you switch to these, unless you have played with extra light guage rounds like 40-95 or 45-95 guage. D'Addario's are medium tension and if you go down a guage size you may not have to mess with the truss rod.
Example; If you generally use 45-105 in rounds, get 45-100's in D'Addario's.
GHS flats are a bit stiffer and RotoSound and Fenders are the stiffest!
LaBella's in a lighter guage aren't too bad and the sound they give is well worth it, but at $36.00 a pop make sure they are what you want. D'Addario Chromes and Half-Rounds are the most reasonably priced for the sound. They are not like old-School flats, but they are nothing like rounds either. I hope this helps.

P.S. Half-rounds are sanded down roundwounds which are then polished. They sound like flats with more sustain or rounds with less highs and treble. They do have a nice unique warm tone and they do offer a good alternative to flats and rounds.

 

-I didnt have to change mine, but I changed when the weather changed; it was gonna need to be changed anyways

-Flatwound and slapping dont mix

-My set of flat are the Webstring "Detroit Bass" stainless steel flats, in medium gauage. They play and sound just fine, I'm even thinking of gaing to a heavier gauage.

 

No offense, but you couldn't be more wrong about that. All of Larry Graham's most memorable slap lines with Sly and the Family Stone were done on flats. Two of the most popular non-Sly slap lines in history, "Brick House" and "Boogie Oogie Oogie" were done on flats. Will flats get you that hi-fi modern slap sound like Marcus or Vic? No. But do not sell flatwounds short when it comes to slap, because they can sound amazing.

To answer the other questions, you may need to adjust the truss rod for flats, and you may not. Depends on the bass.

If you want deep-sounding flats, my advice is to buy pretty much any flats on the market and let them go dead and never change them until they break. Except for Thomastik Jazz Flats. I could never get them to go dead after 2 or 3 months of usage, and I found out recently from a friend who looked inside them that they're rounds in flat clothing. The outer wrap is flatwound, but on the inside they are most definitely roundwounds.

 

Wow, those are a good price. Have you used any other flats that you could compare them to?