Question: how many ohms are apple headphones?
Answer: Apple earbuds are 23 ohms... my fave studio headphones, Audio-Technica ATH-M50s, are 38 ohms... one of the most common studio headphones, Sony MDR7506, are 63 ohms. So, more "pro" headphones are higher impedance, but that just means that you will get less power (lower volume) on a low-voltage audio source.