The Science of Pickup Positioning?

Discussion in 'Luthier's Corner' started by freatles, Jan 9, 2014.

  1. freatles


    Jan 9, 2014
    I've been drawing a new fret- & headless bass for myself. Material choices and forms are up to tastes, but pickup positioning peeves me.

    I approach instrument building from physics point of view, so I started by looking at how strings oscillate/vibrate. So there are several harmonic overtone series on the vibrating string added to the fundamental tone.

    Looking at strings vibrate, I cant see the vibration "waves" moving along the string, more or less just the fundamental. I wonder if the waves are, nevertheless, moving up and down the string or stationary?

    So, where would the best pickup position for maximal volume be from the physics point of view (ignoring the P/J -bass traditions)?

    Would this be at the center of the free string, halfway "@ the fundamental"? So just approximate the center for "free string".

    I realize the "response" of the human ear is such that even if the fundamental is removed, ear "perceives" the fundamental from the overtone series somehow. So that would imply that it would be best to position pickups so the first 3-4 overtone are transduced at maximal amplitude?

    Or perhaps the Really Optimal position for pickups would be as long as the string? At the end of the string, or in the bridge as some piezos?
  2. Beej


    Feb 10, 2007
    Victoria, BC
    Each time you fret or place your finger on the board, you are effectively changing the string length, rendering the possibility of finding "maximal volume" a fruitless endeavour. Just build it, and make a jig that suspends the pickup above the strings so you can move it around to determine a position that you like...
  3. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    This is what Leo Fender did when he created the P and J basses. You can see the jig in photos of his old office.
    Perhaps a bridge piezo is the most consistent sounding.
  4. JustForSport


    Nov 17, 2011
    A string plucked anywhere along its length will have waves moving from the plucked position to the end points of the stopped length and back, then to the other end and back, which are (usually) unequal in length and the nodes/ anti-nodes positions will be relative to the stopped length. Since strings are stopped at all different lengths, there are no 'stationary' node/ anti-node positions.
    Even a piezo bridge pickup 'reads' the vibrations from the waves that are moving back and forth from one end to the other.
  5. BawanaRik


    Mar 6, 2012
    New Jersey
    One of the cool ideas that never got the traction is should have was abass I beleive called the rail.

    The pickup slid along two rails and could be moved to suit the mood of the player.

    That being said I still think the right idea is one pickup in the right place. Perhaps under a harmonic.
  6. There are several basses that have sliding pickups in production.
    Warwick's custom shop example:
  7. kohntarkosz

    kohntarkosz Banned

    Oct 29, 2013
    Edinburgh - Scotland
    The Rail was created by Westone in the '80s.


    Gibson got in there before, with the Grabber bass;


    It looks like some Guyatone tried it out as well;


    On a Strat you could flip between 'stock' and 'Hendrix' pickup positioning.

    Something more high end. This is the Spalt vViper bass. Looks like they took inspiration from windscreen wipers.

  8. There is no 'optimal'.

    Music is art. PUs are an expression of what we desire to hear... or have heard in the past. Everything is relative here. Relative to your ear, what you like, the band you play in and the amp and strings you use.

    Check out the classic positions and classic PUs. Most builders have come to realise what they are.;)

    As for Piezos... werl, they have real limitations. What they are really good for is adding detail (high end) to PUs that might be otherwise muddy or a little unclear.

    I'd say, just try putting your PUs in the places that worked for basses that you love and have a similar structure to yours. If you're not happy with the sound, they are a million different options to change the sound with different PUs or strings.

    The world is your oyster! :D

    P.s. I wanna throw in a bid for a neck position humbucker (ie right at the end of the fingerboard). The sound is truly awesome!
  9. tungx


    Mar 8, 2013
    St. Louis
    I had one of those basses! It was a Westone "The Rail". I thought it was a fantastic idea, but the bass just didn't have the tone or sustain that you would get in a decent bass (like my Fender Jazz with a Badass II bridge).

    As for the pickup itself, I was hoping the attached knob would make the pickup assembly glide along a track, but the way it worked was that the knob was for tightening/loosening the pickup assembly, which could be placed anywhere between neck position and bridge position.

    I would love to see another builder run with this idea, but with a bit more quality.
  10. suraj


    Oct 1, 2008
    Mumbai, India
    You can easily try the pickup in several positions and see where you like the sound best. It can be hard to commit to one sound but -


    Another suggestion is to copy positions of basses you like, or something in between two basses that you like..
  11. freatles


    Jan 9, 2014
    Incidentally, I was actually watching a rather entertaining youtube channel last week with this video of the rail

    The replies above crystallize the intuition I had.

    Clearly it seems that I want to come up with a design that somehow allows for several pickup positions.

    While I realize that the timbre of the sound is very subjective experience, I'm still wondering how a "optimal position" can be found for amplitude @ particular "target" tone-series - or actually how to figure this position out on a string with known lenght and mass.

    Perhaps from this one could then combine data for theoretical strings or sets of pitches and see if there are sweet spots? Any observations of prior analysis?
  12. asad137


    Jan 18, 2007
    As pointed out earlier, "under a harmonic" moves as soon as you fret a note.
  13. astack


    Nov 12, 2011
    Washington, DC
    A cool trick to see the upper harmonic vibrations is to use a computer screen or TV as a strobe light. Orient a fretless so that the screen is behind the strings, with the fingerboard perpendicular to the screen. Pluck a string and slide up slowly. At multiples of the refresh rate, you can filter out the movement of the other modes and you see a static wavy string. Move slightly and it kind of collapses back into the a jumbled mess. It's pretty trippy.

    +1 to there is no perfect, not to mention the relative position moves as you fret. You can use that to your advantage to get fatter notes by playing higher up on lower strings, as an example where it's "perfect" when you need that sound. Or another song "perfect" could be that note lower on the neck.
  14. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    why would you want that anyway?

    volume isn't the problem, it's finding an ear-pleasing balance of lows to highs.

    notice how pretty much all the great classic designs (and most of the modern new ones) have their pickups somewhere in the zone between the neck and bridge pickups of a jazz bass?
  15. Jeff Bonny

    Jeff Bonny

    Nov 20, 2000
    Vancouver, BC
    The Rail is an amazing tool to show you how big small increments become when you're zeroing in on a balance between girth and presence. You start to hear an 1/8" as significant. A sliding pickup in some ways works very much like a high pass filter. For me though once I found what I liked I didn't move it much.

    If I were going to design something with a mobile pickup it would be a solidbody with a route from neck to bridge with the idea that you'd cover the hole with a pick guard once you'd found what you heard as the sweet spot. Maybe leave it a little open around the pickup for minor adjustment? I suspect given what the Rail taught me and my taste in non-moving pickup basses like P's and the Jack Casady the pickup on my bass would end up in a mid-body position.

    The science of pickup placement might be interesting but the art of pickup placement is what will get you your sound. As educated as your guess might be it's still all just guesswork until you plug it in and let your ears tell you what's next.
    ZenG likes this.
  16. freatles


    Jan 9, 2014
    walterw - The point was to create a simple model that shows where the maximal amplitude is for one string setting - which one could then use to find optimal amplitude for sets of strings.
  17. freatles


    Jan 9, 2014
    Thanks for the wise words!
  18. As far as pickup placement i really do think certain basses like say warwick thumbs or a Dingwall Z2 have fantastic tone in particular on lower strings and both of them have the "neck" pickups in an untraditional locations.