Ohm rating for headphones.

Discussion in 'Homesteading Questions' started by Windy in Kansas, Feb 3, 2005.

  1. Windy in Kansas

    Windy in Kansas In Remembrance

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    I need to replace the headphones on a radio/tape player that I've had for about ten years. While I'm sure I have the owners manual, I haven't a clue where it might be.

    I bought some replacement headphones today that were 16 ohm. I figured that they were as standard as the old 8 ohm ones were of old.

    When I got home with them I discovered that each the right and left speaker of the old earphones have 24 ohm marked on them. In the store I only noticed 16 ohm and 32 ohm, so I am at a loss as to what I should do. Any suggestions?

    Do you add the resistance of each together and with the ones I have get 48 ohms? I am kind of thinking that the 24 of each still gives 24 ohms. Hm?
     
  2. Cosmic

    Cosmic Well-Known Member

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    In simplex terms, today they are probably color coded. The jacks / plugs will have a ring of color. If they don't match, they won't work.

    Is true with most stuff related to stereos / computers. You can attempt to do home brew fixes. Better to get the proper match in the long run. Maybe a return with some attention to what is really required.

    Had this problem in my last computer upgrade, bummed me out and I am technically versed. Sometimes is best to go with the flow and not know to much. :haha:
     

  3. BobBoyce

    BobBoyce Well-Known Member

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    The main thing in figuring impedance is whether the headphones are mono or stereo. If stereo, then each left and right are independent, and would be 24 ohms each. If mono, they would typically be in parallel, and instead of doubling, the impedance would be halved, ie 12 ohms total impedance. All in all, how impedance is calculated can be a little more complex. For the most part, in low power devices it's not near as critical as in high power applications. I'll explain a bit just in case you would like to learn the dynamics behind it. I'll not go into THD (total harmonic distortion) or other factors, just the impedance factor.

    Because audio equiptment uses nominal impedance (actual impedance of a speaker varies as sound frequency varies) the actual rated value is typically calculated at or near the center frequency of the speakers dynamic range.

    Dynamic range is the range of frequencies that an audio component can reproduce without the response (ability to reproduce the sound) suffering too much.

    If the headphones are rated at 16 ohms, while the speaker impedances are 24 ohms each, it's probably because the speaker manufacturer rated their impedance at the center frequency of the bare speaker acoustical response range, ie the speaker in free space with no enclosure. The speaker manufacturer has no way of knowing how the speaker will be used, so that is the only rating they can honestly make.

    Meanwhile, the manufacturer that builds the headphones have altered the speakers acoustic response behavior by installing them into an enclosure (the headphones). Since this alters the total dynamic range of the assembly, the center frequency point shifts, shifting the nominal impedance as well.

    The lower the nominal impedance, the higher the nominal current will flow through the speaker at a given voltage, hence the higher the wattage consumed. In low power applications, it's usually better to use the same, or a higher impedance rating than design, to prevent damage to the output amplifier of the device. This prevents the replacement speaker or headphone from attempting to draw more power from the device than it was designed to deliver.

    I hope I didn't confuse you too much. You should be just fine with what you have as long as it's the right type (mono vs stereo) for the device you are using it on.

    Bob
     
  4. Windy in Kansas

    Windy in Kansas In Remembrance

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    Thanks for the help, advice, and education. I went ahead and opened them and am using the now, and they work just fine. Whew! The end plug was shaped the same, one was gray as was the wire and phones, while the other was all black.

    Since the plug was the same indicating stereo, I was brave enough to try them.

    Thanks for the prompt reply. I knew someone here would know.