I now need to revise the last post because when I first started test the polarity of CDs I was using an Adcom GDP-575 and was finding over 90 % of CDs to be inverted.  I thought that it was more likely that the Adcom CD player was inverting but when I started using an NEC CD-730 CD player that...

P.S. Inverted acoustic music doesn't occur in nature and is harsh and irritating beside having other bad attributes.   Best regards,   George

The headphone diaphragms move in response to a positive electrical signal when they should be moving out, and move out when they should be moving in when they receive a negative electrical signal.  If they were speakers it would be as if the red and black wires were reversed at the rear of both...

It seems to me that the AKG K701 headphones are inverted but the Sennhieser HD650 headphones aren't inverted.   George S. Louis

Some Stax electrostatic headphones invert polarity, the AKG K701 headphones invert polarity, some Maxell Studio Series headphones invert polarity, and many active noise cancelling headphones such as the great sounding Aiwa HP-CN6 invert polarity when the active noise cancelling circuit is on...

The Musical Fidelity Xcan-V2 tube headphone amplifier inverts polarity. George S. Louis, Perfect Polarity Pundit