INTRODUCTION
The Sennheiser HD201 is a pair of black and silver coloured budget headphones that made it onto the market in 2006. If you go to Amazon.co.uk and search for "headphones" this is result number one. The fact that they are cheap (£12 when I got them), feature a respected brand name (Sennheiser) and are so well featured at sites like Amazon has made them a very popular choice for mainstream entry level headphones.

SPECIFICATIONS
The frequency response bandwidth of the HD201 is stated as being 21-18000Hz. For those who have a hard time making sense of such numbers, Hz is a unit of measurement used to recognize the pitch of a sound. What it really measures is the actual soundwaves. If you zoom in on a visual representation of a sound wave, you'll see that low frequencies (bass) have "few" and "wide" waves, while a high frequency (high pitched sound) has "many" and "narrow" waves. The Hz is basically the number of "cycles per second", or waves per second. Human hearing is popularly stated as being able to pick up frequencies from 20Hz-20KHz. However, the very top end of human hearing is often stated to be the part of human hearing that we lose first. Also, frequencies that high are incredibly high pitched, and are often not there, or there in very small doses in the music we listen to. Frequencies as low as 20Hz belong to the "sub bass" categorisation and are more often felt (soundwave vibration) than actually heard. Basically, the frequency bandwitch of the HD201, while omitting some frequencies the human ear could potentially hear, is fine for budget headphones. You won't be missing the frequencies that aren't represented. The frequency response is another specification to look at. The best way to explain this is, if you work in a recording studio, you'll want the frequency response of your speakers to be entirely flat, meaning they would play back all frequencies (pitches) at equal volume levels. In the world of mainstream hi-fi, however, the frequency response of speakers is very seldom anything approaching flat. Often certain frequencies are attenuated in one way or another, to make for a listening experience more pleasing to the ear. For instance, often bass frequencies are boosted. The HD201 belong to the mainstream hi-fi category. Their frequency response is very far removed from being flat. This is expected. They don't boost the bass, though. I find the bass response to be crisp and clear. The frequency response is not flat, but it does sound pleasing. These specifications are all fairly standard for headphones in this price class.

BUILD QUALITY
The headphone frame is made of plastic. There is soft padding for the ear pieces and for the underside of the curved bit that goes on your head. This ensures that the headphones are comfortable to wear. The size is flexible and is easily asjusted. The HD201 weights just over 160 grams, so it's a fairly ligh item to bring with you. The one weak point is where the earpieces are connected to the frame. The piece of plastic that connects the two is very thin. It is a robust construction, but this is the weakest point of the design. I've already put the headphones through a fair bit of abuse. I'll throw them into a bag with various other objects, paying no attentiont to the shocks the headphones are subject to, and they haven't failed me so far. I've had them for about a year. On a whole, these are the most robustly made headphones I have ever had, but that is not to say the construction could not be even more robust.

PERSONAL EXPERIENCE
My old Philips headphones broke, as after three years of use and abuse, I accidentally dropped them on the floor and one of the earpieces broke off. That put me in the market to get new ones. I wanted something reasonably cheap that would replace my previous headphones, being equal or greater in quality. This being result number one on Amazon.co.uk when I searched for "headphones", and having received largely very positive reviews on there, they seemed a natural contender. After some basic research, I decided to go for the HD201, which seemed to offer great value for money. I can't quite tell how the build quality of these compare to my old ones, although these are lighter and the design allows for more flexible movement. As such, I think there is a chance these might have survived the fall my previous headphones went through. I've used these headphones for two purposes: listening to music on the move, and for monitoring music while recording audio. Let me just say straight away, the frequency response is not flat, and these are not suited for professional audio mixing and mastering, but for hearing music in yours ears while recording vocals in a silent environment, they do a fine job. I can listen to music reasonably loud while recording with no bleed into the microphone. In other words, you shouldn't have to worry about the person next to you on the bus being forced to listen to your music, at least not when listening at reasonable volume levels. For listening to music on the move, the HD201 do a fine job, although it is limited how much noise gets cancelled out. It does cancel out some, which is very apparent in quieter environments, but if you're in a very noisy environment it will still make you raise the volume of your music. For that particular reason, I tend to prefer Skullcandy in-ear earphones for journeys with public transport, as they filter out noise really well and allow you to listen to your music at a lower volume. I prefer using the HD201 at my end destinations. In a less noisy environment, such as a hotel room, you can sit back and enjoy the details of your music, and this is a more comfortable listening experience than using in-ear earphones. I also feel the sound of the HD201 is more open and detailed.

CONCLUSION
I paid £12 for these on Amazon.co.uk, and for that price I don't think you can do any better. The HD201 does not have a flat frequency response, but for the price, they sound open and detailed. The bass is not overly boosed and sounds crisp and clear. There is no doubt the HD201 offer great value for money!