Some folks in this and other threads have asked about the ADP and how it compares to the HD650 and DT880 classic cans. Specific concerns have been brought up about ADP mid-range distortion. The ADP has significant amounts of distortion in the midrange. This is due to the T50RP driver and is common to most other T50RP based cans. Distortion may be very driver to driver dependent. Some sample T50RP drivers have quite a bit of distortion, some are better behaved. Here are distortion plots for the ADP And comparatively for the DT880 (250 ohms) And HD650 As can be shown, the ADP has much higher distortion numbers in the midrange, the DT880 has a distoriton peak between 2 and 3 kHz, and the 650 shows better behavior. Higher distoriton numbers in the DT880 and 650 in the bass area are expected given they leak sound, while the ADP is a closed sealed pad headphone. In terms of performance, the HD650 is technically superior to the ADP in the mid-range and treble region (distortion / fidelity). I've had the pleasure to listen to both HD650 and ADP cans. HD650s are more resolving and scale better. HD650s are also more open souding and less fatigue prone. The HD650 is more comfortable. If the ADP is able to provide seal (there Fostex inherited construction variations here too), bass will be superior on the ADP. If it fails to provide seal, ADP will sound fairly poor.