Thread: EQing bass
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Old 05-12-2018, 09:40 AM   #18
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Join Date: Dec 2012
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Originally Posted by Judders View Post
Even on a well set up bass, the frequency response doesn't follow a neat pattern, especially the part involves playing the same pitches on different strings.
There is actually a predictable pattern to it, but it's complex and about impossible to compensate. It has mostly to do with the way that the harmonic series sets up along the vibrating length of the string and the position of the pickup relative to that.

The fundamental always swings the full length from the fret to the bridge. If any part of it is moving one direction, the whole string is moving that direction. The only nulls are at the fret and the bridge, and the widest excursion is at the exact center between them. On an open string, that's over the 12th fret, but if you fret at the 12th, the center is now where the 24th would be.

If we look only at the first harmonic - an octave above the fundamental - we find a null at the fret and the bridge, but also at the center point. The string swings one direction on the bridge half of the string and the opposite direction on the fret half, and not at all right in the center. It swings the furthest at the quarter points - the 24th fret on an open note, and the 36th fret when we play at the 12th.

Our pickups stay in one place, but the nulls and peaks of the different harmonics move around as we change frets, so the pickup...well...picks up a different balance of harmonics depending on where you're fretting. That IS a noticeable change in frequency response.

As the pickup moves closer to the bridge, this effect has less noticeable impact in the sound. A pickup right at the bridge (a piezo under the saddle for example) should be as close to perfectly even all the way up the fretboard as you can get. But this also changes the relative mix of the harmonics because the widest swing of the fundamental is much further away than that of the higher harmonics, so that they seem to be swinging about the same distance. That's a large part of why a bridge pickup seems to be brighter than a neck pickup, and a piezo pickup is so ugly andbright and brittle on the top end.

I'm not going to comment on the OP. I've found that for most things rock you can just pound it into an SVT and be done with it.
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