I have owned a pair of these headphones for almost a year now, and the sound they produce is quite simply divine. The first time I put them on, I felt the pads did press quite hard on my head, considering what I was expecting from reviews. After a little tweaking of the headband, I found them to be more comfortable and once I had been wearing the phones for a couple of days the pads softened. The result was the most comfortable fit I have ever experienced in a pair, and believe me I have worn many a pair of headphones..
I think after stumbling upon the review below, I felt compelled to leave my feedback as I thought the reviewer seemed truly misguided. The sound these headphones produce, while not completely geared towards a completely flat response (as this was the idea of the 600s) is very truthful. You will find that if you have not been subjected to 'proper' sound, for example in a studio environment, you may think that they sound perhaps different to what you would expect. The average person's opinion is perhaps generally that one wants lots of deep bass and high treble to create an 'impressive' sound. While this may impress, at the end of the day one has to fiddle with equalization controls to adjust the sound for different records, as not all of them will sound good. The reason for this would be that the sound the equipment (speakers or headphones) is producing is not a balanced sound. One will probably, for example find that some records appear 'harsh' on the ears when up loud on a lesser system, and this would be the fault of the listening equipment. There are many other factors that would make this review too long, but the general idea is that if you want to hear exactly what the producer created in the studio, then you want something that matches the 'standard' of sound as closely as possible.
I have been producing, recording, editing and listening to music for many years and these headphones represent what I would consider to be some of the best in headphone sound quality. I actually think that I will never want another pair to replace them.
Decent sound comes at a price, as the materials chosen have to be picked and put together extremely accurately so as to perform exactly as required. Creating accurate headphones is an art, and Sennheiser's many years of experience has clearly lead to their producing headphones of such a high quality. To think that a company with such experience in building accurate devices such as these would place a piece of material in their headphones that degraded their sound is completely ridiculous. Do you really think that a company that invests so much money in developing accurate drivers would sully their reputation and bring down the quality of their high end products by not considering such a thing? I think not. The headphones were designed to be used as they are presented, no changing of cables and ripping out of integral parts will make them more accurate, in any case it will probably do the reverse.
On a brand note, I did have the opportunity to experience Some high-end Sony DJ headphones, which did sound quite good until I compared them to the 650s. The immediate thing I noticed as the harshness of the Sony sound. Playing 'Hunter' by Bjork, I found that the vocals became ear piercing on the Sonys, yet remained silky smooth and accurate on the 650s. All the separate sounds in the track remained clear and were never drowned out, a problem I discovered with the Sony earphones.
(if looking for high quality headphones I highly recommend this track for judging the quality of the midrange, (something often overlooked) as the vocals really push the equipment you are listening to to it's limits and at high levels will really sound painful on anything of a lower quality)
The bottom line is, if you are looking for headphones that will impress the un-trained ear, then go for some of a lower calibre. Perhaps consider some sub-£100 Sennheisers, as these are of a pretty high standard and probably will sound better than most of the other 'high-street' brands. If you are, however looking for a pair of headphones that will give you the true sound of your records and will probably make you hate every other piece of sound equipment you have ever listened to, then buy these. The quality is superb for all genres, and until you have sat down and watched a big budget film with an orchestral soundtrack on these cans, you do not know what you are missing.
** You do not need ridiculous hardware to appreciate these headphones. Integrated circuits today are of such a high quality that even cheap amplifiers (as long as they have the EQ turned off) will produce a decent sound. The only thing one has to worry about is how powerful the amp is. I found that my friend's iPod for example did not really have enough 'kick' to turn these up loud. Not all portable devices have the same output power and I am sure to some 'audiophile' reader's disgust I should point out that I had the opportunity to try the 650's on a sub £10 CD player, and they sounded just as good as they did when plugged into my hi-fi. A lot of this expensive CD player business is just a great big con!