Worthy substitute for MDR-V6, Sony MDR-7506 is the most used monitoring headphones, after Sennheiser HD 25; it's a good headphones reference. Treble is clear; at normal level, bass doesn't spoil spectrum. These headphones are very comfortable even after several hours use.
Sony MDR-7506 has good sensitivity and good sound insulation. Its only weak point could be its lack of sturdiness for rough users and its lack of performance for high dynamic sounds.
It is no use to try to change capsules; Sony spare parts are more expensive than full headphone.
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