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Speakers and pickups and magnetism...

Discussion in 'Pickups & Electronics [BG]' started by secretdonkey, Oct 14, 2004.

  1. secretdonkey


    Oct 9, 2002
    Austin, TX
    I bet this has come up before, but a quick search didn't turn anything up.

    Anyway, I'm sure I'm not the first to notice that speaker cabinets, especially big sub enclosures, make great table-like surfaces on which to open your bass case, change strings, etc.

    My intuition has always told me to avoid doing this, however. Knowing that the pickups contain magnets, and that speaker cabinets (especially big ol' subs) have EVEN BIGGER magnets, it occurs to me that the pickups could potentially be adversely affected by proximity to (relatively) powerful magnets. Maybe not from the occasional case opening on top of a sub, but over time, with prolonged and repeated exposure, perhaps?

    So, is my intuition right or wrong?
  2. rickbass

    rickbass Supporting Member

    From a viewpoint with no technical expertise, I think your concern is much ado about nothing.

    After all, Sears Silvertone/Harmony made a guitar-amp combo where the speaker was housed in the case of the guitar. In other words, you took out the guitar and plugged it into the case which housed the amp and the speaker. When you were through playing, you put the guitar back into the case, (which housed the amp and speaker).

    Those things are now collector's items and they still work today, 30+ years later.

    But as I implied - I'm no expert. I have had two biggedty-ass stereo speakers about one foot away on each side of my TV for years and it hasn't affected anything.
  3. luknfur


    Jan 14, 2004

    I've read magnets can loose significant power over time - especially 10 to 20 years. Never heard of any issue with pups being in proximity of stronger magnets and wouldn't be suprised if they may not even become stronger. Large speaker magnets in close proximity of one another I can see may cause a problem with speaker performance.
  4. phatcactus


    Apr 2, 2004
    Chicago, IL
    I've read that the power of ceramic and alnico magnets will deteriorate if they're forced together with like poles facing each other for a length of time, but neodymium magnets don't suffer from this. I don't think any arrangement would cause magnets to become stronger, as I'm under the impression that their strength is determined while the magnet is being made. Anyone care to verify anything I've said?
  5. DubDubs


    Aug 23, 2004
    Los Angeles
    Well if you think about it the gigantic speaker magnets are right next to each other wich almost nothing seperating them so a small magnet on the outside of the cab shouldn't do anything at all.
  6. luknfur


    Jan 14, 2004


    My "wouldn't be suprised if they would increase the strength" comment was really a bit of a quip and reflection that I didn't know one way or the other. At any rate, never heard any such cautions about keeping a bass away from a cab and if something like that were an issue, we'd probably all know about it by now.

    There's plenty of info on the net though as out of curiosity I just skimmed through one site on magnets - probably just enough to have obtained a misconception.

    What was cursorily extracted was that a small magnet is influenced by another magnetic field, the stronger the other field the more the influence. It seems a stronge magnetic could in effect increase the strength of a smaller one as it could cuase the poles to be more pure - which makes for a stronger magnet. On the other hand, it could decrease the strength depending on how long the exposure to the stronger force was if the end result was a partial change in polarity.

    In as much, forcing two pups of like poles together for an extended period would in deed tend to weaken their fields becuase it would in effect force some of the polarity to change.

    The comment on the Neo mags also flows constently as they apparently are inclined to retain their existing polarity better than other magnets.

    What I had read before was old pups could be inexpensively remagnatized but I think that's done via electric current.
  7. Tim__x


    Aug 13, 2002
    Alberta, Canada
    You're actually not wrong, the way to make magnets is to expose them to a very powerful magnetic field, usually from a big electromagnet.
  8. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    You can destroy or enhance a small permanent magnet by placing it in close proximity to a larger magnet. However, you need to keep in mind that distance and time are important.

    The magnetic field strength decreases rapidly as you move away from the magnet. If I can remember all the way back to my college electromagnetics course, I seem to remember that magnetic field decreases proportionally to the square of the distance. Bottom line is that even a few inches or a foot away from the speakers magnet will render its magnetic field harmless to your bass' magnet.

    Also, time of exposure will determine the amount of damage caused. The weaker the magnetic field, the longer the exposure needs to be to cause any damage. Unless you are planning on sticking your pickups to the speaker magnet and storing them that way, I don't think that you have anything to worry about.