Eli5: What does frequency range and impedance do to headphone/earphone quality?


Eli5: What does frequency range and impedance do to headphone/earphone quality?

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The nominal impedance has more to do with efficiency than quality. Basically any given speaker, from a tiny headphone to a big concert rig, has two things impacting how hard it is for the amplifier to move it: The mechanical resistance from stiffness of the suspension + weight of the driver and the electrical resistivity of the motor. Nominal impedance is a rough indicator of the electrical side. The higher the impedance, the less wattage an amplifier connected to it generates and (other factors equal) the less loud the speaker will be. If we assume all else is magically equal doubling impedance will roughly halve volume. It also impacts amplifier compatibility. This is less an issue with headphones but basically amplifiers are certified to run down to a minimum impedance and have different ratings at different impedances.

For total efficiency it should actually have an efficiency rating listed in DB, I just wanted to give an idea of what impedance means in a speaker there.

Frequency range is more directly related to quality. Ideal human hearing runs from 20hz – 20,000hz, though sensitivity varies across that band and it drops off more on the higher end for adults and especially men.

Doubling the frequency covers an octave. So 20-40, 40-80, 80-160 are all octaves. If your driver only produces sound at a significant volume down to 50hz, you’re missing more than an octave of the source material. Speakers (headphones and full sized) tend to slope off fairly gently on the low end, but on the high end they often “break up” and the response chart goes crazy, so you’ll see some things stating their range up to say, 30k as an indicator that it’s smooth all the way up the human audible range and that breakup doesn’t happen until a ridiculous frequency.

Reputable brands will cover a decibel range with their frequency response if not a full chart. So if it says 20-20k (+/-3) that speaker is claiming to cover the entire range of human hearing with a maximum variance of 3 decibels. Which is….really good, actually, but it’s just an example.

Hopefully that gives you something to run on.