Anyone else experience buzz with flats, but not with rounds, on the same bass?

[Killed_by_Death]

When I first got my BTB, I checked it over on every fret for buzz & there was none.

Cut to a string change (EB Cobalt Flats) & the 7th fret on the A is buzzing with any kind of accents.
Actually, I have to play lighter than normal for it not to buzz.

Raised the action to 1/4", still there, but not much.
(action measured from the 21st fret top to the bottom of the string)

The truss rod was adjusted so there's minimal relief, less than 0.012", but more than 0.010".
(at one point it was less than 0.010", but didn't seem to make a difference)

An added little tick comes in now, because I'm getting buzz on the E string now, which I hadn't noticed before.

My mind is telling me it's the switch from rounds to flats, so I put the A from my other bass on there, and lo & behold, no buzz, unless you really hit it hard.
(that's a new round wound, not sure what brand, but the ball ends are brass - red - black - silver, E - G)

Then I put the EBCF on the other bass & it's fine on that one, with the action at 3/32" on the 24th fret.

So, tomorrow morning I will go ahead and swap all the strings.
Right now I just want to rest & stop shaking my head

 

[petrus61]

Yes, when going to less tense flats. The Cobalts are pretty bright from what I understand, so that could have something to do with it. Also, rounds tend to get worn on the bottom where they meet the fret. If you threw on a brand new set of same exact rounds and kept the same relief, you might hear way more buzzing than the broken in set because of this.

 

[Killed_by_Death]

Now I'm glad I posted here, because you've got a point!
Maybe I'll just put it back like it was, raise the action to 1/4" on E & A, then check back later about lowering it again.

add:

changed my mind again, definitely putting the flats on the SRX now, because I play it more

odd that the cheaper SRX has flatter frets & it's in worse condition (rusted frets)

 

[Badwater]

Wow, that's pretty extreme for string height. However, I had a similar experience when changing from round to light flat ECB84. But was easily fixed by raising up the action just a few hairs to 3.2mm on the E. Initially the action was lower than 3mm with the rounds. Still, even with the low action, flats visually looks a lot higher than it really is. I find myself measuring it from time to time, thinking it go higher.

One major factor could be the break angle over the bridge. With string through this should not be a problem. With some top load bridges where there is almost no break angle, it could contribute to flabby flats. Also, the heavy high tension gauges can also cause big string movement vs the lighter gauges, thus requiring higher action.