I would like to be very unbiased I have listen to the sennheiser px100 they great phone and I really like they a lot but I do not want to pay 100 dollar for they and so I decide to get the Koss port pro and I will say the difference between they the px100 have less low end bass but very crispy high pitch koss have a excellent bass end but lack a little clarity of the higher pitch the sennheiser be less firm on you head almost do not notice they on you head the Koss have a adjustment to change tension but still should have more range of tension I think but it be still great . I be not go to say one be better than the other because they about equal I have get 4 people convert to the Koss that still enjoy they because of the low cost but the high quality