Why are pickups "pointed"?

[xtian]

To any of the luthiers: Why are pickups made with a small, focused pole?

We have magnetic, piezo, and LightWave pickups now. All of these focus on a very small area of the string. Is there a type of pickup that works by focusing on a larger area of the string?

It seems that if a pickup were like a strip of tape, it could be laid on the body parallel to the string. It would no longer matter where the "sweet spot" was, because the entire space would be covered. And anyway, doesn't the sweet spot change as the string length is changed (ie - an open string is going to have a particular sweet spot that is going to be in a different place from a string that is fretted at the 9th fret, for example)?

Thanks for the help!
- Christian
Budapest, Hungary

[DP Custom]

One reason is that, the more the pickup is sensitive to an elongated area of the string, the more likely it is that the higher harmonics will cancel themselves out...leaving only the very low harmonics and the fundamental...the result is a very "dead" sounding tone....

Dave P.

[John Davis]

Originally posted by DP Custom
One reason is that, the more the pickup is sensitive to an elongated area of the string, the more likely it is that the higher harmonics will cancel themselves out...leaving only the very low harmonics and the fundamental...the result is a very "dead" sounding tone....

Dave P.

So it's like everything starts vibrating at the same frequency, and the pickups end up not "picking-up" anything?

[ChlkDstTtr]

It helps to understand it if you know a little more about sound waves (this works with light too, but that's another subject).

If you look at the image I've attached you'll see a long wave on the left which I've divided into 2 wave lengths A and B. These are opposite wavelengths (A's peak is B's trough, and B's peak is A's trough). When you combine these together (the middle wave) you'll end up with the wave on the right (which happens to be a strait line), which on a musical instrument is no noise at all.

The range of the pickup does pick up many wavelengths, but since you're picking up a small area it is likely that the wavelengths will build on each other rather than cancel each other out. However the more string you pick up the more likely the wavelengths will change (that's why a pickup at the bridge sound differnt than a pickup in the center, and still different than a pickup all the way up at the bottom of the fingerboard). This change will allow certain frequencies of the note (because one note is made up of many frequencies) to cancel each other out and you'll end up with a dead sound.

I hope I didn't confuse anyone.