advantages of inductors

Discussion in 'Home Theater Projects' started by Camm, May 17, 2003.

  1. Camm

    Camm Extra

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    I am looking at building some more speakers and was wondering what the difference of air core and copper foil inductors was. Also the differences between the caps. Im not really that dumb but I have only used the air core and Bi-polar so educate me please:b
     
  2. Dan Wesnor

    Dan Wesnor Second Unit

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    There is very little, if any, noticable difference between round wire and flat wire air-core inductors. However, with iron core, there will be some energy storage that can cause smearing.

    But with capacitors, it depends on how good your hearing is. There really isn't much difference between 10% and 5% capacitors, so don't worry about that. However, bipolar caps sometimes behave non-linearly over large voltage swings, like those seen in a speaker. They also may not discharge properly, causing smearing. Typical caps used in speakers (Dayton, Solen) are good enough for most applications, although a number of people with good ears and a reasonable mind (a rare combination - most people only imagine they have good ears [​IMG]) think Sonic Caps are a good choice for certain situations. I use them, but only on top-quality projects and then usually only on the tweeter. Very few pople I trust have said that Hovland caps are better than Solen.

    If you'd like a long dissertation on these subjects, and can afford the phone call, call Jeff at www.soniccraft.com, and he'll talk capacitors until you hang up on him.
     
  3. Mark Hayenga

    Mark Hayenga Supporting Actor

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    Iron core, steel laminate, etc inductors use core materials that have a high magnetic permeability. This higher magnetic permeability increases the inductance relative to an air core inductor, but it has some drawbacks.

    The first is called hysteresis. Simply put, the iron 'remembers' which way the magnetic field was oriented through it last. When you apply current in one direction through the inductor, all the little magnetic dipoles of the material go from being randomly oriented to being 'lined up' in one direction. When you stop the current, they more or less stay lined up. The iron 'remembers' where it was last - this is bad. When you apply current in the opposite direction, they have to go from being lined up in one direction, to being lined up the other direction (180 degree reversal). This behavior is non-linear and creates distortion.

    The other bad thing about 'cored' inductors is that the magnetic permeability of the material may vary with frequency. I'm not certain, but I believe this is why iron core inductors are not recommended for frequencies >1kHz. Varying the magnetic permeability directly affects the inductance, which is a bad thing.
     

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