Inside the Z7, you'll find 70mm ALCP Film drivers, capable of delivering detailed and natural music to your ears. Rated at 70 Ohms, you can listen to these straight into a phone or laptop and coax great sound out, but plugged into a headphone amp is the best way to go. The Sony Z7 has already been extensively reviewed, so check out Head-Fi to hear what others have to say about the headphone, and Innerfidelity for measurements.