The Sony MDR-7506 Headphones are closed-back, over-the-ear style folding monitoring headphones with a mini-plug connector and 1/4" screw-on adapter. At over 60 Ohms, they require decent amplification but can certainly still be used with smartphones. They have a high sensitivity rating and are designed for use in a studio setting. The 40mm diameter driver produces decent bass punch without being overwhelming. They are cushioned in a way to be worn comfortably for long periods of time, though please note these do have a coiled cord which not everybody loves. Overall, these headphones are a good choice when detailed listening is required.