This is probably the best article for a beginner about impedance with respect to headphones.

I haven't managed to find an explanation of why the impedance of headphones is just a single, real number (like 250 Ohm). I thought impedance is a complex number, so it should have real (resistance) and imaginary (reactance) part. Maybe the imaginary part is just zero. All I know is that impedance varies with frequency.

  • \$\begingroup\$ Try this: electronics.stackexchange.com/questions/83829/… and note that speaker impedance is normally dominated by the winding resistance of the coil. \$\endgroup\$
    – Andy aka
    Commented Jul 17, 2015 at 12:58
  • \$\begingroup\$ I've seen a Behringer musical bass amp where the "headphone" jack was wired directly to the speaker output. That certainly is under 2Ω! \$\endgroup\$
    – rdtsc
    Commented Jul 17, 2015 at 13:22

1 Answer 1


Impedance does vary by frequency. However, for many things it doesn't vary very much by frequency within the expected operating frequency of the equipment, and a single number is much easier to handle than a frequency response graph. So people quote a single average number.

In fact, your linked article admits this:

Headphone impedance can vary by a factor of 10 or more over the audio band. The SuperFi 5 is rated at 21 ohms but varies from 10 ohms to 90 ohms.

That's quite a lot of variation! It also explains why this causes variation in the audio quality when driven from different sources.

  • 1
    \$\begingroup\$ Ok, impedance varies with frequency, that's why it's usually specified as a single number at given frequency. My other question was why it's a single real number instead of a complex number (we know impedance is a complex number). \$\endgroup\$
    – user216094
    Commented Jul 17, 2015 at 14:50

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.