After so much talk about the RP-HTX7 it dawned one day that they might be pretty good outdoor headphones. When modified.
So well... The modified set is sitting on the desk next to the MIDI keyboard right now, and it's already played for a few days on the street.
Stock RP-HTX7 are very bass-heavy - so much so the bass gets over midrange. Plus they have that Panasonic thin/stiff character which affects the whole sound, bass, midrange, and treble. Recabled, the headphones show some harmonics which were previously dead in the midrange/treble, gain speed and liveliness, and that "Panasonic stiffness" is mostly gone (though the bass is still elastic/punchy rather than "velvety" as in Denon headphones). A problem of the RP-HTX7 is the searing, fatiguing treble. Solved also, with a little fix from the past :-P
Summary of the modding...
1. Recable to silver-plated twisted pair (AWG 24 main cable, AWG 32 headband).
2. Sunny Bear's mod (two out of three "bass holes" taped over behind the driver).
3. Extra isolation layers (just cotton with some yellow PVC "tablecloth" on top).
4. AKG K-240 cloth over driver grilles.
That last mod killed a bit of resolution sharpness, but made them sweeter and calmer, and removed almost all of that fatiguing harshness. So now they're slightly less efficient, but with a much more pleasant sound. Overall, it's a big change, they're not exactly a different set of headphones, but... Yeah, not like the stock set at all. Quicker, livelier, with a real midrange (though still suffering from a slight lack of definition), no boomy bass, soft treble, and a civilised Austrian tint/distance to the sound. More balanced for sure. They won't replace classic silver K-141, but they're very good outdoor headphones. Isolation is where it should be (getting closer to canalphones' when playing). "Super-RP-HTX7". ClieOS compared them to K-81, and well, there're two things that're wrong about K-81... One - they're supra; two - the driver grille tuning is towards low midrange/bass (square holes). RP-HTX7 driver grilles are tuned for high midrange/treble (circular holes). So unless the K-81 had Kramer holes, they'd never get close in sweetness, even though the drivers are good (high-excursion with good midrange dynamics). Both K-81 and RP-HTX7 are punchy, but K-81 are slamming punchy, RP-HTX7 have a more forgiving kind of bass.
The isolation is just some cotton glued into the cups with yellow PVC "tablecloth" on top. A secondary effect is reducing cup size, so there's less boominess to the bass. Isolation's pretty good, a construction site with excavators working 10 metres away was muted completely with IPod Touch playing at 90% volume. The cups could be larger - the RP-HTX7 are very small headphones, smaller than they seem to be in photos. They're slightly larger than K-81, DN-HP500, the cups are barely enough to fit ears in. This doesn't leave much room for modding or isolation, but the results are nice. The plastic, of course, is thinner and lower quality than on the likes of AKG K-271 Studio.
One pleasant surprise is sensitivity. It's declared at 99 dB/mW, but the AKG K-240 Studio, rated at 96, are way less efficient (by more than 3 dB). So real efficiency must be somewhere around 100-102 dB, and the RP-HTX7 are driven fairly easily. Most players won't have trouble making them shout. The EQ is more towards "loudness", so that helps too.
Musically they tend to go well with rock, metal, synth-pop, anything punchy & powerful. But, they also do saxophones and jazz fairly well. Classical music isn't that great in RP-HTX7 unmodded, but modified it's all right. As usual, a recable and general balancing of the sound makes headphones play anything well.
Between RP-HTX7 and K-240 Studio, the K-240 are more ambiental, the RP-HTX7 catch some microdetail better and have quicker dynamics. RP-HTX7 have a darker, more closed-in sound with a smaller soundstage, whereas the K-240 are all airy and ambiental with a huge positional soundstage. One last problem is the lack of midrange detail (midrange is not as even as AKG midrange), but the right kind of acoustic foam might fix that (dropping another bit of efficiency, but hey, with a headphone amp that's not an issue).