How to get rid of String Buzzing?

[Jayy]

Let me paint the picture for you, because I haven't seen a single helpful post about this concrete issue:
I bought a new bass, a Marcus Miller V9, 4 strings. The thing is that the strings were strung through the bridge, and I prefer them through the body, so I changed that, and also adjusted the saddles so the string height would fit me, i would even say that they are slightly higher now. I did not notice any problem before making the adjustments myself, but it may be because i did not pay really close attention.

But after messing around for a while I noticed that, when strummed with enough force (not brutal force, though) the E and A open strings would produce a clear sound for a second, and immediately produce a buzzing sound that slowly fades away. What puzzles me is that the noise takes a second or so to appear, and that the strings do not appear to touch the frets (I've tried to rise the saddles a big deal). Other things I've noticed is that in the E open string, the string went straight from the bridge up to the string posts, that is, it didn't bend downwards after the nut. I imagined that it was because the lenght of the string was excessive, because when I wind up the string in the string post it is too high. I observed that some significant vibration takes place AFTER the nut when I pluck the open string.
Then I decided to cut the lenght, and although the problem is slightly reduced because now there is a downwards bend of the string after the nut, it still remains.
Other things that I have observed are that the E string does not sit comfortably in the nut: it does not fit perfectly, most of the "thinckness" of the string is not "inserted" into it. Maybe should I widen and deepen the hole? I am also considering on inserting something under the nut to increase its height.

Is someone familiar with this problem? Thank you very much!

 

[Wito]

Other things I've noticed is that in the E open string, the string went straight from the bridge up to the string posts, that is, it didn't bend downwards after the nut. I imagined that it was because the lenght of the string was excessive, because when I wind up the string in the string post it is too high. I observed that some significant vibration takes place AFTER the nut when I pluck the open string.
Then I decided to cut the lenght, and although the problem is slightly reduced because now there is a downwards bend of the string after the nut, it still remains.
Is someone familiar with this problem? Thank you very much!

From the way you describe this, it looks like when you string your bass you start winding from the bottom of the winding post up. It should be done the other way around. You should start from the top of the post and roll your way down, so that the more you turn the tuning peg the lower (closer to the headstock) the string goes. This helps creating a nice witness point at the nut. If the string doesn't "bend towards the headstock" after the nut, that could be one source of vibration. I'd suggest to restring the E and A string the proper way before starting with the rest of the setup.

 

[Wito]

But after messing around for a while I noticed that, when strummed with enough force (not brutal force, though) the E and A open strings would produce a clear sound for a second, and immediately produce a buzzing sound that slowly fades away. What puzzles me is that the noise takes a second or so to appear, and that the strings do not appear to touch the frets (I've tried to rise the saddles a big deal).

Does this happen with fretted notes? If so, does it happen all over the fretboard or is it localized in a particular place?

My first guess is that either the nut is cut to low or the neck is too straight (or maybe even a back bow). The fact that you didn't notice any vibration before restringing the bass makes me think that it's not the nut, but probably the truss rod needs some adjustment. Press the E string at the 1st and 12th fret at the same time. There should be a small gap between the frets and the string in the area between those two points. If there is none, you probably need to loosen the truss rod a bit.

 

[Jayy]

Does this happen with fretted notes? If so, does it happen all over the fretboard or is it localized in a particular place?

My first guess is that either the nut is cut to low or the neck is too straight (or maybe even a back bow). The fact that you didn't notice any vibration before restringing the bass makes me think that it's not the nut, but probably the truss rod needs some adjustment. Press the E string at the 1st and 12th fret at the same time. There should be a small gap between the frets and the string in the area between those two points. If there is none, you probably need to loosen the truss rod a bit.

I forgot to mention that, but yes, the buzzzing only occurs in open strings, not in fretted notes. I've checked the space between the 1st and 12th frets when pressing them and the space is ok.
I've re-strung the strings as you said. That's a life-changing tip, I was doing a bad praxis over and over, from the begining of my musicianship. Thanks a lot! The buzzing is no longer a problem!