Disclaimer: I am an audiophile newbie. All I have to go by are my ears, based on what I have listened through so far (crappy stuff, and more recently, the two headphones being discussed).
I have had the Koss KSC75's on Parts-express headband (with Portapro earpads) for approx 1 month. And I have had the Sennheiser PX100II's for approximately 2 weeks. I would consider both to be adequately burned in. I listen to them on an Samsung Galaxy S2 using the PowerAmp app, which allows for custom equalizer settings, and I have created my share of presets for both sets of headphones!
Before I get to my comparison, here's an slightly embarrassing story. A few days after getting the PX100II's, I became disappointed not only with them, but also the KSC75's that I was previously very blown away with. I thought that possibly my hearing was becoming impaired, because I was getting no joy out of either pair of headphones. Despondency was setting it, and depression was imminent. But after a few days, while frantically playing with the equalizer trying to get some life out of the music again, I noticed a button called "Mono".... and I noticed that it had somehow become set to "On". In case you are not aware, "Mono on = VERY bad". One press of that horrid button (that shouldn't even be there!) and I was back to sonic bliss. I told you it was an embarrassing story LOL! Ok, back to my comparison.
After stretching out the headband of the PX100II's to acheive lighter pressure on the ears, they are very comfortable. Because they are a bit heavier, there is more potential for them to fall off the head if you do a quick bow, but it's not really an issue.
The KSC75's on the Parts-express headband are VERY light. And very light pressure on the ears, but still enough clamping pressure that they always feel secure on the head. The portatpro pads help too, because they are soft and comfortable (the stock KSC75 pads are a bit itchier I find).
I'd have to give the nod to the KSC75's here. They are so light that you don't feel them at all, and they stay snugly on the head.
The KSC75's on the Part-express headband are probably more durable than they look/feel, but they don't look/feel very durable! Whereas the PX100II's are built tough, while still managing to be quite light. No comparison - PX100II's.
The KSC75's on the headband can't be folded up, and the drivers don't fold in to become flush, so they are "breakage waiting to happen" if jammed into a pocket or backpack or whatever. The PX100II's however are not only more durably built, but they fold up very compactly - great for portability. PX100II's win big time here.
Ok, this is where it gets difficult for me to articulate. I am fairly new to the world of audiophile, so what I have done is taken to the "Describing A Sound Glossary" here at head-fi for terms that might help me describe what I am hearing from each pair of headphones. These are the terms that I would use to describe both sets.
Bassy - Emphasized Bass.
Laid-back - Recessed, distant-sounding, having exaggerated depth, usually because of a dished midrange. Compare "Forward".
(my note: they are not that recessed or distant sounding, but to me they are a bit when compared to the KSC75's)
Lush - Very Rich/Full.
Smooth - Easy on the ears, not harsh. Flat frequency response, especially in the midrange. Lack of peaks and dips in the response.
Warm - Good bass, adequate low frequencies, adequate fundamentals relative to harmonics. Not thin. Also excessive bass or mid bass. Also, pleasantly spacious, with adequate reverberation at low frequencies. Also see Rich, Round. Warm highs means sweet highs.
I'll add to that: kick ass bass. You can really feel it. That's cool, especially at the gym where there is some external noise, and the extra bass really helps the music make an impact. I love these things at the gym.
KSC75 (on Parts-express headband) sound:
Detailed - Easy to hear tiny details in the music; articulate. Adequate high frequency response, sharp transient response.
Airy - Spacious. Open. Instruments sound like they are surrounded by a large reflective space full of air. Good reproduction of high frequency reflections. High frequency response extends to 15 or 20 kHz.
Imaging - The sense that a voice or instrument is in a particular place in the room.
Open - Sound which has height and "air", relates to clean upper midrange and treble.
Punchy - Good reproduction of dynamics. Good transient response, with strong impact. Sometimes a bump around 5 kHz or 200 Hz.
(good) Soundstage - The area between two speakers that appears to the listener to be occupied by sonic images. Like a real stage, a soundstage should have width, depth, and height.
Spacious - Conveying a sense of space, ambiance, or room around the instruments. Stereo reverb. Early reflections.
Transient - The leading edge of a percussive sound. Good transient response makes the sound as a whole more live and realistic.
Transparent - Easy to hear into the music, detailed, clear, not muddy. Wide flat frequency response, sharp time response, very low distortion and noise. A hear through quality that is akin to clarity and reveals all aspects of detail.
Ok, please keep in mind that I haven't even listened to any higher end headphones yet (although I'm starting to lust after the Beyer DT1350's - please help me Lord!). My point is that I probably don't really even know what the above terms are referring to. But, when listening to the KSC75's, the above terms are what resonate with me - they sound amazing! Having said that, when flipping between them and the PX100II, it mainly just seems to be a "different sound". Both have their own sounds, and both sound awesome, and if I was forced to listen to either pair for the rest of my life, I'd be good with that (well, maybe if I hadn't read about those damned DT1350's!). But yes, I would have to say that I prefer the sound of the KSC75's. The thing that stikes me the most about them is that the instruments seem very "distinct", "separate", "punchy", and "in their own space" (my terms). Not bad for a $20 pair of drivers!
So for me, I'll probably end up listening to the KSC75's around the home the most (but frequently switching to the PX100II's when I need a good kick in the b-ass). But the rig that will be heading out the door with me will always be the PX100II's due to their durability/portability, and fuller bass which really helps at the gym.
Let me know what you think!
Edited by waynes world - 7/27/12 at 10:13pm