Pros: Durability, Comfort, Portability, Style, Versatility, Isolation
Cons: Price keeps going up, not as good a value as it used to be
The HD 25-1 is more than a great sounding headphone, it has stood the test of time, and proved to be one of the worlds most durable and versatile headphones. There's many detailed reviews of this classic headphone, so I won't go too much into the details. In short, all I can say is the hype and praise these headphones have received is well deserved. After owning these, I began noticing professional DJ's and Sports Announcers on TV wearing these all the time. Funny I never noticed that before, but I can see now that they use them for a good reason. I think the reason these are so well regarded is more so because of their design/comfort/durability/versatility vs their sound quality (which is great too).
The sound signature of these is quite balanced, with a slightly above average bass response, likely due to the above average isolation they provide. The sound stage is about average for a closed headphone in this price range, but the separation on more complex compositions is impressive to me. They are very sensitive and easy to drive, which makes them ideal for portable use. They get loud enough to be dangerous, even from portables. Like most higher end headphones, they also benefit from high end amplification, but it's by no means required to reach their potential. Due to their balanced sound signature, these will please lovers of any genre of music. They are equally suited for gaming or movies also. Gave it 9/10 due to the average sound stage, there's other closed headphones that do better in this regard.
The reason Sennheiser built a reputation off this model is the design and versatility of it, it is a true feat of engineering. The plastic is of high quality, making them light and durable. The clasping force is moderate, and combined with the Velour ear pads, I notice no discomfort at all when wearing them all day, even with my glasses on. With the leatherette ear pads they come with, you will get warm after 1-2hrs, but you get a slightly better seal, which improves bass impact slightly. I think the added comfort of Velour more than makes up for the unnoticeable decrease in bass impact. It's easy to get the right seal on all head sizes/shapes. Once there on, they stay there, even when running/exercising. The split headband helps keep them from moving.
They look good when there on, not overly stylish or big, a more minimalistic look. The cable is just the right length too (1.5m), and conveniently terminated to a 90 degree 3.5mm connector, with a screw on ¼ inch adapter too. For those who care, mine say Made In Ireland. Because these are so modular, you can easily take these apart and customize them with custom paint jobs or after market cables if that's your thing. All the parts are easily replaceable, and easily available, which is something no other headphone achieves in this price range with this sound quality and comfort/durability. For many, this headphone is the last one they ever purchase, simply because it won't break, sounds great, and is so versatile. For those who manage to break something, a replacement is easy to find. That's why you see so many professionals using these on a daily basis.
I highly recommend this headphone, for anyone. It will be the last headphone you buy. I can honestly say I was skeptical of the hype these had, but after owning them, I quit using all my other closed headphones in favor of this one, not just for the sound quality, but the versatility it provides. It's like a good ol' Acura; it might not look the most flashy, or perform spectacularly well in any one area, but it does everything well, takes a beating, and never lets you down. Gave it 9/10 due to the constantly raising price of this model.