The HD 25 SP are closed dynamic headphones for monitoring, recording and outdoor applications. They are a lower-cost alternative to the HD 25, featuring a simpler headband and a slightly different capsule design. Features:Very lightweight and comfortable, even if used for long periodsHigh maximum sound pressure levelNominal impedance for universal compatibilityTough, detachable steel cableNeodymium ferrous magnet systems and lightweight aluminium/copper voice coils for fast transient response