My only regret is that I didn't buy these earphones earlier. I had reasons for hesitating: $250 is a lot to take a gamble on something that didn't really have any informative customer reviews online, and as an EDM guy I was concerned about the bass rolloff at 40hz. Massdrop solved the first problem for me by dropping them at $99, and it turns out the second was never a problem to begin with.
(KDE stands for Koss Dual Element [referring to the two dynamic drivers per ear. That makes the full official name the Koss Koss Dual Element 250...Per Koss: "The larger 20 mm transducer is low frequency dominant and ported, while the 13 mm transducer focuses on mid and upper frequencies in a side-firing angle."]).
I think a lot of potential buyers could be put off by the unusual design, and by looking at it I can't blame you for thinking "that can't be comfortable," or "there's no way that will stay on my ears without having to adjust it every two minutes." Everyone's ears are different so these may well be issues for you. For me though, I've been surprised at how comfortable and stable they are. They'll stay in place better than most earbuds for me; it's just not something I've needed to worry about. (The exception is if you lean your head sideways, ear facing your shoulder. They won't fall to the floor, the earhook will catch them, but that one specific angle is their sole weakness.)
SOUND QUALITY
"That's great, but how do they sound," you ask?
If you take the general sound signature of the PortaPro and refine it, fixing the PP's limitations and compromises, bringing detail and clarity up to impressive levels, you would have the KDE250. I can't decide if this is the best mid-fi earphone ever made, or a respectably average TOTL 'phone.
The highs and mids are excellent (the relative levels are close enough to flat, everything is smooth up and down the spectrum), but for me the bass is the star of the show. It turns out hardly any music ever has anything below 50 or 60 hz, not even electronic dance music. I do occasionally come across a track that has meaningful elements lower than the Koss can reproduce and I can tell something is missing, but it's not often at all. Some months I don't come across any. I feel silly for ever having doubted.
I've never come across an IEM that can thump like the KDE250, the bass is powerful, clean (doesn't impede the mids whatsoever), and reproduces more texture and low end detail than any dynamic driver I've heard (I'm a planar magnetic guy through and through, but the dual dynamic system Koss designed doesn't give up anything to my preferred tech).
The KDE250 does have weaknesses, of course. The soundstage is unusual; when I haven't listened to it for awhile, it sounds okay to the sides and in the front, but it has almost no vertical element at all. This sensation does go away as my ears adjust to it. It's not anything I'd call a problem, as much as an idiosyncrasy. I'd classify it as an "open" earphone, but it's much more isolating than most open earphones or earbuds. That can be good or bad, depending on your needs. Personally I prefer open earphones 90% of the time; I hate going out in public when I can't hear my surroundings at all. Like most earphones, no matter how loud you crank it, there's just not enough sound for someone else to ever hear, no matter how uncomfortably close they might be.
The KDE is also rather fragile, my first pair broke after being pulled off and falling 6 feet to a hardwood floor. Koss really ought to have included a strong shirt clip, which would have saved them. They did replace them with a new pair within a week though, thanks to their famous lifetime warranty.
COMPARISONS
Vs. Audeze iSine 20-
I'll be clear up front here: the iSine 20 is the better sounding earphone. It's better in almost every way, and I don't think anyone is going to be confused about this. And it SHOULD sound better, it costs 4-5x as much as the Koss! But is the iSine in a different league? I'd say no. I judge (with EDM playing) the Koss to get you fully 90% of the way to the iSine; their sound signatures are very similar. If you can afford it, get the Audeze and never look back. If bang for your buck is your chief concern, get the Koss and spend your savings on lottery tickets or something, whatever, why should I care?
One important difference between the two is that the Audeze is very unforgiving of a poor source. It's wasted on 128kbps mp3s, and it makes my LG V20 sound just BAD. It makes all of the smartphone's flaws stand out as glaringly obvious. The Koss, on the other hand, is extremely forgiving of less than perfect sources. It sounds good enough jacked to my phone for me to be able to focus on the music, instead of the clinical sound quality, yet it still scales up well when paired with a quality desktop rig (mine is a Schiit Magni 3/Momby).
Vs. Sennheiser MX985-
This is a much more even comparison. They're both on about the same level in terms of quality, they just do it in different ways. I've always thought of the MX' as a cross between the HD600 and HD800; it's got a lot of the former's warmth, and some of the latter's clarity-detail. The 985's biggest weakness is its lack of bass punch, which happens to be the 250's strength. The two couldn't be more different, but they complement each other nicely.
Vs. Blue Demun-
I very much like the Blue Demun, but the Koss is an entire tier higher up. Not a useful comparison. Trying to compare it with a VE Monk+ would be twice as silly.
CONCLUSION/DENOUEMENT
I personally made the decision to live with the (very small, very inoffensive) limitations of the KDE250, and I'm selling my iSines to use the cost difference elsewhere in life. But there is no wrong answer here, if you have a KDE250 -OR- an iSine 20, you have an excellent sounding pair of earphones, and I'm confident you will enjoy them!
(KDE stands for Koss Dual Element [referring to the two dynamic drivers per ear. That makes the full official name the Koss Koss Dual Element 250...Per Koss: "The larger 20 mm transducer is low frequency dominant and ported, while the 13 mm transducer focuses on mid and upper frequencies in a side-firing angle."]).
I think a lot of potential buyers could be put off by the unusual design, and by looking at it I can't blame you for thinking "that can't be comfortable," or "there's no way that will stay on my ears without having to adjust it every two minutes." Everyone's ears are different so these may well be issues for you. For me though, I've been surprised at how comfortable and stable they are. They'll stay in place better than most earbuds for me; it's just not something I've needed to worry about. (The exception is if you lean your head sideways, ear facing your shoulder. They won't fall to the floor, the earhook will catch them, but that one specific angle is their sole weakness.)
SOUND QUALITY
"That's great, but how do they sound," you ask?
If you take the general sound signature of the PortaPro and refine it, fixing the PP's limitations and compromises, bringing detail and clarity up to impressive levels, you would have the KDE250. I can't decide if this is the best mid-fi earphone ever made, or a respectably average TOTL 'phone.
The highs and mids are excellent (the relative levels are close enough to flat, everything is smooth up and down the spectrum), but for me the bass is the star of the show. It turns out hardly any music ever has anything below 50 or 60 hz, not even electronic dance music. I do occasionally come across a track that has meaningful elements lower than the Koss can reproduce and I can tell something is missing, but it's not often at all. Some months I don't come across any. I feel silly for ever having doubted.
I've never come across an IEM that can thump like the KDE250, the bass is powerful, clean (doesn't impede the mids whatsoever), and reproduces more texture and low end detail than any dynamic driver I've heard (I'm a planar magnetic guy through and through, but the dual dynamic system Koss designed doesn't give up anything to my preferred tech).
The KDE250 does have weaknesses, of course. The soundstage is unusual; when I haven't listened to it for awhile, it sounds okay to the sides and in the front, but it has almost no vertical element at all. This sensation does go away as my ears adjust to it. It's not anything I'd call a problem, as much as an idiosyncrasy. I'd classify it as an "open" earphone, but it's much more isolating than most open earphones or earbuds. That can be good or bad, depending on your needs. Personally I prefer open earphones 90% of the time; I hate going out in public when I can't hear my surroundings at all. Like most earphones, no matter how loud you crank it, there's just not enough sound for someone else to ever hear, no matter how uncomfortably close they might be.
The KDE is also rather fragile, my first pair broke after being pulled off and falling 6 feet to a hardwood floor. Koss really ought to have included a strong shirt clip, which would have saved them. They did replace them with a new pair within a week though, thanks to their famous lifetime warranty.
COMPARISONS
Vs. Audeze iSine 20-
I'll be clear up front here: the iSine 20 is the better sounding earphone. It's better in almost every way, and I don't think anyone is going to be confused about this. And it SHOULD sound better, it costs 4-5x as much as the Koss! But is the iSine in a different league? I'd say no. I judge (with EDM playing) the Koss to get you fully 90% of the way to the iSine; their sound signatures are very similar. If you can afford it, get the Audeze and never look back. If bang for your buck is your chief concern, get the Koss and spend your savings on lottery tickets or something, whatever, why should I care?
One important difference between the two is that the Audeze is very unforgiving of a poor source. It's wasted on 128kbps mp3s, and it makes my LG V20 sound just BAD. It makes all of the smartphone's flaws stand out as glaringly obvious. The Koss, on the other hand, is extremely forgiving of less than perfect sources. It sounds good enough jacked to my phone for me to be able to focus on the music, instead of the clinical sound quality, yet it still scales up well when paired with a quality desktop rig (mine is a Schiit Magni 3/Momby).
Vs. Sennheiser MX985-
This is a much more even comparison. They're both on about the same level in terms of quality, they just do it in different ways. I've always thought of the MX' as a cross between the HD600 and HD800; it's got a lot of the former's warmth, and some of the latter's clarity-detail. The 985's biggest weakness is its lack of bass punch, which happens to be the 250's strength. The two couldn't be more different, but they complement each other nicely.
Vs. Blue Demun-
I very much like the Blue Demun, but the Koss is an entire tier higher up. Not a useful comparison. Trying to compare it with a VE Monk+ would be twice as silly.
CONCLUSION/DENOUEMENT
I personally made the decision to live with the (very small, very inoffensive) limitations of the KDE250, and I'm selling my iSines to use the cost difference elsewhere in life. But there is no wrong answer here, if you have a KDE250 -OR- an iSine 20, you have an excellent sounding pair of earphones, and I'm confident you will enjoy them!
