Haven't heard the KTX, is that the same driver as the KSC75 and the PP?
I believe that the biggest weakness with the SHP9500s is the mids, not the bass as some people think. Ironically, the biggest strength with Koss headphones tends to be their mids. The PortaPros, KSC75s, and SportaPros are somewhat A-shaped headphones. Their treble is veiled and their bass rolls off rapidly below 100 hz, but from 100hz to 2000hz, those little Koss phones can trade blows with much more expensive headphones. There is a savoriness to their mids that kept me coming back to them for 10 years.
So I can see how someone could prefer them. I don't think they're better though. The treble is simply in another league on the 9500s. The bass impact is very fixable with a good amp, and it is going to scale better, coming from a 50mm driver, compared to the quarter-sized Koss drivers that can't move as much air. (The corollary to that is that Koss cans are very non-fatiguing so... there is that).
Sorry for the delayed reply.
I believe the KTXPRO1 has the same (or at least similar) titanium-coated drivers as the KSC75.
I know the Porta Pro has different drivers made of different materials, but I have not heard it.
The KTX and KSC sound very different.
The only two things I like more about the KSC are the soundstage (since it rests away from your ears) and clarity. The rest of the sound comes off as lo-fi to me, especially in the bass, which hardly sounded better than cheap earbuds. (Though it's worth mentioning that the one I had was refurbished. It's entirely possible that a brand new one would sound better.) Pressing the pads against my ears did not improve things either. But, er..."veiled treble"? The KSC is bright and sparkly. That's one of the things it's famous for.
The KTX has a different enclosure and has far superior overall sound, in my opinion. The bass impact (along with higher frequency impact such as drums) is also
way beyond the SHP9500, which, in my tests, did not sound any different whether I drove it from the headphone outputs of my laptop or a Schiit Magni 2 Uber amp. (However, if you were to equalize the headphones, you could obviously increase or decrease their bass impact to an extent.)
Anyway, I was talking about the KTX, not any other Koss models. (I have owned others that are more expensive, but still easily prefer the KTX.) Since it's only $10, I highly recommend it to everyone. It sounds better to me than
many headphones that cost hundreds!
I've been thinking a lot about the 880 beyers. The 250 ohm and the 600 and the 770 pros in the 250 ohm. I'd read about the treble being so bright, does that change with amplification? Does better or different amplification reduce that?
I had the DT 880 Edition (aka Premium) 600 ohm. I think it's clearly better than the SHP9500, but not by a large amount. They sound fairly similar. Both are a little bright to my ears, but not a major problem.
What I'm most concerned with is sound quality. Neutral, clear and detailed reproduction of my source material with a wider sound stage. I really enjoy the 9500's for these reasons but am wondering aloud here if clarity, detail and sound stage can be increased by a large margin for $500 or less; beyond what the 9500 is capable of. Inversely if a large margin of improvement can not be had for less than $500 I'd rather spend the money on source material. If the 9500 sounds better than the 880/250 that's info I want. What sounds better? What other set of cans has what the 9500 has but in spades, and at what cost.
If you want the best (as in most accurate) sound you can get for under $500 (which can also compete with or even outperform headphones that cost thousands), go for used STAX. It sounds worlds better than the SHP9500—markedly greater than a mere 5% improvement.
http://www.head-fi.org/t/676272/the-entry-level-stax-thread
The 95% figure depends very heavily on what type of frequency curve you prefer.
If you like headphones a bit warmer, a bit darker, then the SHP9500s may be less than 95% of the way to your ideal. And I think that's part of where the upgrading itch comes from. If a headphone matches the frequency curve you want, it's pretty easy to be content there. If it's very different from the frequency curve you want to have, then the incentive to look up a tier is greater. Perhaps the people that go all the way up to the Stax and Audeze are the ones that couldn't find the frequency curve they could be content with in anything they tried along the way?
Well, I'm sure you know there's more to sound than just frequency response. Impulse response (like the timing of transients) and distortion are factors, among others. And different driver technologies are going to sound different regardless. (Even when equalized to have the same FR.)
Personally, I'd say the SHP9500 is only maybe half as good as the best headphones. At its price, though, it's the best circumaural open-back I've heard.
My V-MODA Audio Only Cable (which is the same as the one you linked to) sounds...a little
bad. I used it as an interconnect on various systems and it blatantly reduced the sound quality compared to other cables. Made things sound more etched and nasty. But when used as a headphone cable, it wasn't so bad. I talked with a guy who designs cables about this particular one. He's one of the skeptics who insists most cables sound the same...and even he admitted it's a poorly-made cable that acts more like a resistor than well-made ones, and wasn't surprised at all when I reported its negative effects. But at least it's cheap and looks cool. Just a few of my thoughts on the matter.