Ferrofluid Vs Ferropaste! (Large Magnets and Speakers)

Discussion in 'The Steam Vent' started by Pogre, Nov 12, 2017.

  1. Pogre Audioholic Ninja

    Pogre
    Joined:
    Jul 29, 2016
    Messages:
    4,025
    Likes Received:
    1,136
    Location:
    Mesa, Arizona
    I stumbled across this one watching science videos and thought it was pretty cool. One of his experiments involves a speaker and shows the application quite well. I always wondered how ferrofluid worked in a speaker.

    • Like Like x 2
    • Informative Informative x 1
  2. KEW Audioholic Spartan

    KEW
    Joined:
    Jul 12, 2009
    Messages:
    6,335
    Likes Received:
    2,213
    Location:
    Jowjah
    Fun stuff!
    KEW,
  3. Pogre Audioholic Ninja

    Pogre
    Joined:
    Jul 29, 2016
    Messages:
    4,025
    Likes Received:
    1,136
    Location:
    Mesa, Arizona
    Really cool how the ferrofluid stays in place when you put a couple of drops in there. Think it changed the way the speaker sounds? I'm guessing yes, but I really don't know.
  4. KEW Audioholic Spartan

    KEW
    Joined:
    Jul 12, 2009
    Messages:
    6,335
    Likes Received:
    2,213
    Location:
    Jowjah
    I'm really guessing, but I think the idea behind the ferrofluid is to more efficiently conduct heat away from the driver (as compared to air). Guessing the ferro part is to prevent the fluid from spattering all over creation.
    But that is speculation, and I am not sure how the fluid gets cooled in turn.
    The fluid would increase the resistance compared to air, but depending on it's viscosity, it might not change the sound too much.
    This would be an argument for warming up your speakers if it did! Fluid viscosity is often temperature dependent!
    KEW,
  5. Swerd Audioholic Spartan

    Swerd
    Joined:
    Sep 3, 2004
    Messages:
    5,056
    Likes Received:
    3,019
    When in doubt, look it up on Wikipedia
    https://en.wikipedia.org/wiki/Ferrofluid#Loudspeakers

    After a general explanation, there are shorter sections dealing with applications for ferrofluid:

    Loudspeakers
    Ferrofluids are commonly used in loudspeakers to remove heat from the voice coil, and to passively damp the movement of the cone. They reside in what would normally be the air gap around the voice coil, held in place by the speaker's magnet. Since ferrofluids are paramagnetic, they obey Curie's law and thus become less magnetic at higher temperatures. A strong magnet placed near the voice coil (which produces heat) will attract cold ferrofluid more than hot ferrofluid thus forcing the heated ferrofluid away from the electric voice coil and toward a heat sink. This is a relatively efficient cooling method which requires no additional energy input.

    Heat transfer
    An external magnetic field imposed on a ferrofluid with varying susceptibility (e.g., because of a temperature gradient) results in a nonuniform magnetic body force, which leads to a form of heat transfer called thermomagnetic convection. This form of heat transfer can be useful when conventional convection heat transfer is inadequate; e.g., in miniature microscale devices or under reduced gravity conditions.

    Ferrofluids of suitable composition can exhibit extremely large enhancement in thermal conductivity (k; ~300% of the base fluid thermal conductivity). The large enhancement in k is due to the efficient transport of heat through percolating nanoparticle paths. Special magnetic nanofluids with tunable thermal conductivity to viscosity ratio can be used as multifunctional ‘smart materials’ that can remove heat and also arrest vibrations (damper). Such fluids may find applications in microfluidic devices and microelectromechanical systems.
    • Informative Informative x 3
  6. KEW Audioholic Spartan

    KEW
    Joined:
    Jul 12, 2009
    Messages:
    6,335
    Likes Received:
    2,213
    Location:
    Jowjah
    Wow! I use Wikipedia all of the time, but wouldn't think to use it for technical stuff.
    Those are quite nice explanations of how it works!
    The relation between magnetic force and ferro-fluid temperature was something I did not know!
    KEW,
    • Agree Agree x 1
  7. Swerd Audioholic Spartan

    Swerd
    Joined:
    Sep 3, 2004
    Messages:
    5,056
    Likes Received:
    3,019
    Wikipedia is great! Before I retired, I used to use it all the time at work. For nearly all modern science stuff, I think it's better than the latest textbooks.

    For example, I had to write a roughly 5 page solicitation for clinical trials of a new experimental anti-cancer drug. It is believed to work by blocking the binding of two proteins called TP53 (tumor protein 53) and Mdm2. The document was meant only for people who do basic science and clinical research in cancer, but I still had to briefly explain how the proteins work in normal tissue and in cancer, how the new drug is believed to work, and how it might be tested in cancer clinical trials. It had been many years since I read about TP53, and if I ever knew anything about Mdm2, I had completely forgotten it. Wikipedia quickly got me up to speed on the basics, and in less than an hour I could follow the latest publications on that subject. No textbook is quite that good.
    • Like Like x 2
    • Informative Informative x 1

Share This Page

  • RBHsound.com
  • BlueJeansCable.com
  • SVS Sound Subwoofers
  • Experience the Martin Logan Montis
  • CEDIA