I was thrilled with the option of getting my hands on a pair of the renowned Sennheiser PC-66 headphones, but before ordering, I researched the internet and found once and again that the volume was very low using the USB connection even at maximum settings. As a thorough buyer I emailed Sennheiser tech support regarding this problem before buying and they replied that it was a non issue and that I would have no problems.
Well I did have problems and even after tweaking everything that can be tweaked the volume is inappropriately low to listen to music pleasurably.
I had to return the headsets to the retailer and lose $20 attributed to re-stocking fees. I did inform Sennheiset regarding the deceptive
information and they really have ducked the issue.

Don't buy these headphones.

Sound is okay. Does not even compare with Sennheiser 580s or 650s. Works fine with glasses as the earpieces are not huge. When I am done, I switch back to speakers for general gaming.

I use it to play FPS games.

Using it with the included USB sound hub is the best option - microphone is very clear and people can hear what I am saying. I wish I could get a boom like this one to use over the phone. Random Ppople ask me what headset I am using at times because I come across so clearly.

As a bonus, it is also recognized in the PS3 as a headset, but I have not tested it much as nobody has a headset on the PS3. I'll test it with Rock band later so i can guitar/sing.

I purchased this item specifically for Voip phone services (I am a subscriber of Vonage Pro).
I bought it after trying two VERY bad products from HP and Logitech (bith in the range of $35-40). This product was apprx $100 but the quality and the comfort are on a totally different level.
My voice sounds perfctly load and clear (typically that is the problem) to the point that most of the times (including calls to international cell phones) people can't even tell that I am on a Voip line.
The quality of received sound is absolutely flawless.
I am so happy with this product that I am actually sold into all Sennheiser products: I am about to purchase the Sennheiser PXC450 noise-canceling headphones and expect nothing less than zen noise reduction excellence.

Hi. I'm a professional musician, and I also sing online at a karaoke website. I've gone through honestly a dozen different microphones and several different headsets and mixers to get the kind of sound I want out of my recordings. Mind you, I'm picky about the way my voice sounds. I want the simplest solution with the best quality. This headset fills the bill. The sound is easily as good as a standalone headphone set, and here's where it becomes a gem-- the microphone. The microphone is of a very hight quality condenser microphone such as used in wireless recording microphones you see on performance headsets in videos. I know what I'm talking about, my voice sounds fantastic on this system. And now I can get rid of my mixer, microphone stand, large microphone, and run a thin little line into the laptop, so I'm also portable!

Sennheiser is well known in the music world for its superior recording equipment, and they've learned well-- I can tell you there is not a better headset on the market for singing directly into the computer. I'm so happy I'm done looking for this perfect solution!

Bottom line: buy these you won't be disappointed!

Using on Win7RC, plugged USB adapter in and it installed and came right up. Very simple to use. The sound is much better than any other headset I have used. Others I am talking to (Ventrilo & Skype) can hear me much better than my last 2 headsets. These were $30 - $40 more than I payed for either of my older headsets, so they should work better. Overall I am happy with them.

I have purchased several headsets for use with on line communication such as voice over ip. I have recently begun to teach technical classes with a product that allows both voice communication and visual presentation. None of the headsets were comfortable for the extended times required in a "classroom" environment. The Sennheiser PC 166 has proven to be an excellent tool for the job. It is comfortable to wear for extended periods, and the quality of sound both sent and received is by far the best I have encountered.