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Magnets and how they relate to power ratings.

Discussion in 'Amps and Cabs [BG]' started by Benjamin Strange, Mar 1, 2006.


  1. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    Howdy kids. I'm modifying my Boogie 2x10, and I've got a few questions. Boogie was kind enough to give me some old EV 10s in 8 ohm versions to replace my 16 ohm speakers, but when I get them home I'm noticing that the old speakers have a much larger magnet on them than the new ones. Michael Wolf at Boogie tells me that these new speakers are rated at 150 watts each (my old ones are at 200w), but he wasn't able to elaborate much on tonal differences between the two.

    I'm a little concerned about the lower power rating, even though my amp tops out at 150 watts per side. I'm more concerned about tone, though. I've refined my tone for a long time with my existing gear, and I'd rather not change it too drastically. How does a smaller magnet effect the tone of a speaker? Also, can I swap the magnets on the speakers without affecting the ohmages or any other parameter? It appears that the magnets are attatched to the voice coil in the same manner, so they might be swappable. Any thought?
     
  2. BruceWane

    BruceWane

    Oct 31, 2002
    Houston, TX
    Magnets don't relate to power ratings at all. That's strictly a matter of how much heat the voice coil can tolerate/dissipate, since quite a bit of the juice that hits a speaker is converted to heat instead of sound energy.

    Magnets do relate to the BL factor, or you might say the "strength" of the speaker in terms of how hard it can push the cone, so it does affect the sound of the speaker.

    And since it's highly unlikely that the cone material and surround material of the different speakers are identical, there will be some difference in sound there, too.

    All you can do is try it and see.

    The wattage difference is not enough to worry about at all.

    ETA - You do know that you're going to end up with a cab that has a different impedence, right? Depending on how you wire it, you'll either have a 4 ohm (parallel) or a 16 ohm (series) cab. You'll get the most out of your amp wiring the speakers in parallel to 4 ohms.
     
  3. BruceWane

    BruceWane

    Oct 31, 2002
    Houston, TX
    I suppose I should actually say that magnets don't relate to power rating much. Depending on what kind of ventilation they provide to the voice coil they do make somewhat of a difference, but I'd say power ratings are much more dependent on the diameter (overall area) and construction of the voice coil.
     
  4. Passinwind

    Passinwind I Know Nothing Supporting Member

    Ermm, the voice coil better not be attached to the magnet! ;)

    You're gonna be messing with the gap-coil alignment if you do manage to successfully swap. Those tolerances are quite tight, I'd be very surprised if you could get away with it.

    Which EV speakers are they Ben? A lot of the OEM versions don't have the big finned heatsinks, but the magnets themselves are the same across a model line. Could this be what you're seeing? I think you might be able to swapthe finned sinks onto at least some EVs.
     
  5. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    Well, looks like it's a success! I decided to leave the magnets alone and just stick the new ones in to see what they are like.

    The new speakers are actually the old EVs Boogie used to put in their cabs. These in particular are the formica cone, which is slightly different than the kevlar cone I had before. It's hard to say how the tone has changed, since I'm not going to have much of an opportunity to let this thing rip anytime soon since my downstairs neighbors hate noise of any kind. Preliminary low volume tests indicate it might sound quite a bit brighter, since I bypassed the internal crossover and am running the power amp straight into the speakers. I usually run my horn all the way off, since I hate those things, but now my speakers are attempting to handle the high end that used to be rolled off. I guess I'm going to have to wire this crossover back in somehow, if I determine that it's too bright once I get this thing turned up.
     
  6. Passinwind

    Passinwind I Know Nothing Supporting Member

    Cool, glad it looks like it's going to work out.
     
  7. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    As Bruce said, the BL factor changes by reducing the size of the magnet, assuming everything else is the same. But if the Formica cone represents less moving mass than the kevlar, the BL may not change at all. It's all theory though - there are too many variables.

    Have you asked the guys at Boogie why they stopped using the old speaker in favour of the new one? Their answer might give you an insight.

    And have you had a chance to give the replacement speakers a decent workout? I'm curious to know how the replacement speakers sound.
     
  8. georgestrings

    georgestrings Banned

    Nov 5, 2005
    "Have you asked the guys at Boogie why they stopped using the old speaker in favour of the new one? Their answer might give you an insight.

    And have you had a chance to give the replacement speakers a decent workout? I'm curious to know how the replacement speakers sound."


    What he said...



    - georgestrings
     
  9. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    Hey, Benjamin, it's good to see you again! I hadn't seen you 'round these parts much.

    Also glad to hear the driver swap worked out. :)

    Tom.