Solid Bass In-Ear Headphones with In-Line Mic and Control Red. With newly designed drivers and in-line mic and control, the ATH-CKS550iS Solid Bass in-ear headphones give you portable, smartphone-compatible headphones with superb bass reproduction. The powerful 9.8 mm Dual Magnetic-Field Drivers feature an extra magnet in front of the driver to create a concentrated magnetic field that helps produce full, textured bass. Audio-Technicaâs specially designed Multiple-Transition Diaphragms add to the expansive bass response, as does the new Bass Venting System, which provides excellent air damping.