Rating: 
Summary: not worth the headache
Review: The Sennheiser active headphones are among the most uncomfortable headphones that I have ever tried. The head band is brutally hard on my pate after only 10 minutes and the ear pieces feel "wiggly" and loose - like they will slip off momentarily. The sound reduction system seems to work to a limited extent, although no where near as well as I had hoped. When I sit next to my noisy tower computer (I unfortunately have no choice in this matter) and plug in the headphones to my small radio, the active sound reduction clearly limits the volume of unwanted noises. However, instead of cancelling repetitive, background noises, it seems to trade one set of humming frequencies for another, albeit slightly less offensive, set of sounds. I think that until I can afford to fork over the big bucks for the Bose headphones, which I have also tested to greater satisfaction, then I am better off with my existing giant radio earmuffs (Peltor Worktunes) which are annoying, sweaty and bulky to wear, but are overall more versatile, comfortable, and effective than the Sennheiser headphones.
Rating: 
Summary: Makes Life More Enjoyable
Review: These Sennheiser HDC 451 noise suppression headphones are absolutely wonderful. I wear them everywhere -- indoors or out -- even when I'm not listening to music. Nothing I've owned has improved my quality of life more.These Sennheiser headphones eliminate redundant noise -- high or low, up to 20 db -- but leave other sounds undisturbed. Indoors, this means an abatement of unwanted utterings from dishwashers, air-conditioners, or other appliances; even people talking -- or the TV playing -- in other rooms. Outdoors, this translates into a reduction in noise from lawnmowers, leaf blowers, cars driving by, or planes flying overhead; even the sounds of kids playing or dogs barking emanating from down the street. On planes, the Sennheisers significantly reduce the rumble from engines -- and the incessant hissing from personal air vents overhead. And let's not forget sleeping -- which is now, for once, truly feasible. With noises canceled out, my CD's (or DVD's) sound appreciably better -- particularly in the highs which are definitely much clearer. As the ultimate benefit, the open-air design of these Sennheisers allows me to use them everywhere, indoors or out; something not possible with a more encompassing closed-ear style (such as those from Bose which are significantly more expensive). I've used these headphones, for example, when visiting amusement parks, or when attending indoor or outdoor sporting events -- all of which were made surprisingly more enjoyable (and much more pleasant) by eliminating unwanted noise. I've even found that, while wearing these headphones, I can still carry on a normal conversation -- or listen to music or the television -- when the sound's source (person or machine) is located in the room with me or nearby. The Sennheiser's earpieces are covered with a durable cloth (not foam); and they swivel on universal joints to insure a comfortable fit. These remarkable headphones have but one shortcoming. They surprisingly tend to amplify wind noise, making them unusable on windy days or outdoors when riding about on a bike or horse. Can a set of noise canceling headphones make music sound better -- while simultaneously improving one's quality of life? You bet! If you're in the market -- these Sennheiser HDC 451's are definitely the one's to get.
Rating:
Summary: Makes Life More Enjoyable
Review: These Sennheiser HDC 451 noise suppression headphones are absolutely wonderful. I wear them everywhere -- indoors or out -- even when I'm not listening to music. Nothing I've owned has improved my quality of life more. These Sennheiser headphones eliminate redundant noise -- high or low, up to 20 db -- but leave other sounds undisturbed. Indoors, this means an abatement of unwanted utterings from dishwashers, air-conditioners, or other appliances; even people talking -- or the TV playing -- in other rooms. Outdoors, this translates into a reduction in noise from lawnmowers, leaf blowers, cars driving by, or planes flying overhead; even the sounds of kids playing or dogs barking emanating from down the street. On planes, the Sennheisers significantly reduce the rumble from engines -- and the incessant hissing from personal air vents overhead. And let's not forget sleeping -- which is now, for once, truly feasible. With noises canceled out, my CD's (or DVD's) sound appreciably better -- particularly in the highs which are definitely much clearer. As the ultimate benefit, the open-air design of these Sennheisers allows me to use them everywhere, indoors or out; something not possible with a more encompassing closed-ear style (such as those from Bose which are significantly more expensive). I've used these headphones, for example, when visiting amusement parks, or when attending indoor or outdoor sporting events -- all of which were made surprisingly more enjoyable (and much more pleasant) by eliminating unwanted noise. I've even found that, while wearing these headphones, I can still carry on a normal conversation -- or listen to music or the television -- when the sound's source (person or machine) is located in the room with me or nearby. The Sennheiser's earpieces are covered with a durable cloth (not foam); and they swivel on universal joints to insure a comfortable fit. These remarkable headphones have but one shortcoming. They surprisingly tend to amplify wind noise, making them unusable on windy days or outdoors when riding about on a bike or horse. Can a set of noise canceling headphones make music sound better -- while simultaneously improving one's quality of life? You bet! If you're in the market -- these Sennheiser HDC 451's are definitely the one's to get.
Rating: 
Summary: Certainly better than the Airline Headset
Review: This is meant to be a lightweight headphone set which can make travelling with them a little easier and travelling itself more comfortable. It reduces external noise, but one should note carefully that 10dB is NOT all that much. Is it an improvement? Yes. Does it completely block external sound? No, not by any means. In fact, the best way I can describe it, it's the equivalent of taking a thick towel and wrapping it once around your ears. You will still hear outside noise, but it's muffled. I bought this for airplane use, as I travel frequently, but can't yet say how effective they are in blocking that horrible engine droning. I'd imagine they'll help, but not too much. They come with a handy airplane headphone converter jack as well (plug it into the armrest). As far as sound reproduction, I'd advise these headphones if you have a programmable/custom equalizer function on your CD/MP3 player (I use these with my portable, which adequately powers them). Otherwise, you're likely to find the bass rather weak and the treble not quite bright enough. The midrange is, however, superb. With an equalizer you can easily correct this. The headphones are also extremely comfortable, and because the noise reduction feature operates on its own set of AA batteries, you can use it even without turning on your CD player. The bottom line is that these headphones are good but a little pricey: if you need to buy one set of good headphones, look elsewhere. If you can afford the luxury of a lightweight pair and still reserve a sturdier one for home use, by all means check these out. Lastly, if total noise reduction is what you seek, check out non-open-air headphones. Keep in mind that such headphones can leave you very much in your own little world, sometimes even if you'd rather not be!
Rating: 
Summary: Good but pricey, still hear external noise
Review: This is meant to be a lightweight headphone set which can make travelling with them a little easier and travelling itself more comfortable. It reduces external noise, but one should note carefully that 10dB is NOT all that much. Is it an improvement? Yes. Does it completely block external sound? No, not by any means. In fact, the best way I can describe it, it's the equivalent of taking a thick towel and wrapping it once around your ears. You will still hear outside noise, but it's muffled. I bought this for airplane use, as I travel frequently, but can't yet say how effective they are in blocking that horrible engine droning. I'd imagine they'll help, but not too much. They come with a handy airplane headphone converter jack as well (plug it into the armrest). As far as sound reproduction, I'd advise these headphones if you have a programmable/custom equalizer function on your CD/MP3 player (I use these with my portable, which adequately powers them). Otherwise, you're likely to find the bass rather weak and the treble not quite bright enough. The midrange is, however, superb. With an equalizer you can easily correct this. The headphones are also extremely comfortable, and because the noise reduction feature operates on its own set of AA batteries, you can use it even without turning on your CD player. The bottom line is that these headphones are good but a little pricey: if you need to buy one set of good headphones, look elsewhere. If you can afford the luxury of a lightweight pair and still reserve a sturdier one for home use, by all means check these out. Lastly, if total noise reduction is what you seek, check out non-open-air headphones. Keep in mind that such headphones can leave you very much in your own little world, sometimes even if you'd rather not be!
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