ATH-IM02 SonicPro™ In-Ear Monitor Headphones || Audio-Technica US
A: Thank you for your inquiry. The "ideal" headphone impedance should be 8x that of the of the source output. iPhone has 4.5 ohms which would indicate the "ideal" headphone impedance should be 32 ohms. The ATH-IM02 is 36 ohms and the ATH-IM01 is 47 ......