it's just branding! V6, V9, 7506... the names sell better in different countries that's all. in the 80's audi made a car model named '100' , in the USA that exact same car was named '5000'. same car. marketing.

    Quote:   Did you ever consider 'burning-in' the headphones before you performed any listening tests?   I've had my 7506's for a few months and although I can't exactly remember what they sounded like out of the box I do notice a small difference in the sound now versus then...