This is an IEM that can take time to understand. Most who appreciate it are those who have tried a lot of other IEMs, and have been in this hobby for a couple of years or more.

My own introduction to IE900 began a month or so after its launch. I visited a listening session hosted by TAS and was absolutely unimpressed by IE900 back then. At that time, the only IEM I had was Moondrop Blessings 2, and I genuinely thought that Blessings 2 was better than 900.

Over the years, whenever visiting TAS, I kept listening to it, or rather Pritam kept making me listen to different songs on it on different devices, and bit by bit, my admiration for it kept growing. After 3 years there finally came a point where I felt that I had to have it. And after buying, the only thought was "How did it take me so long?"

So what is special about this IEM?
IE900 is precision incarnate. A single DD that has been so magnificently tuned that it produces some of the most accurate timbres of real instruments I've ever heard. I was especially impressed with how Pianos sound on this, having heard the sound of a Steinway, the way IE900 produces it is incredibly lifelike.
The soundstage is also very underrated. You won't immediately notice anything brilliant about the stage, but eventually you'll start to realise that nothing feels closed in while listening to this. Everything has its proper place and space and creates a perfect atmosphere.
The bass is no overpowering, but it is quality and very noticeably, while the treble is lifted and clear.
Mids, particularly lower mids take somewhat of a backseat in this IEM, but that is perfectly fine as the market is loaded with mid-heavy warm IEMs.

Listening on IE900 is like listening to a solo musician's performance- clear and precise, compared to listening on Thieaudio Monarch which is like listening to an orchestra- lush and layered.

So what are the cons?
The cable is typical thin Sennheiser cable. Although it sounds great, it does not have the best feel.
MMCX connectors are probably more durable than 2 pin (less risk of breaking), but the rotation motion is actually a hindrance rather than a help while trying to wear these.
Since the IEMs are very small, people with large ears like mine might find them not snug enough. I bought the largest size of tips I was able to find (Azla Origins with 14mm+ dia) to make them fit on me tightly.

Sound wise, the only thing I'd put somewhat of a negative on is that these are not tuned for EDMs, so if you're someone who listens to electronic music a lot, these might not be best for you.

Also need to mention that my first unit suffered from the right earpiece dying on me one fine day. Contacted TAS and had a full replacement in under a couple of weeks. Excellent service by the TAS team!

Overall a must have IEM for a serious audiophile in his collection.

I didn't expect this kind of sound from this tiny device. Unboxing was underwhelming compared to fiio iems. The tips are okay if you put it correctly. They need to be put very lightly inside ear canal, not too deep, otherwise the tip will collapse and won't sound good. Sound is more detailed than anything I've ever heard. It doesn't sound fatiguing at all. Like i said, it sounds smooth. The azla sednafit light is the tip to go for. I've tried the spinfit cp100+ as well, but the sednafit light sounds the best. Thanks to mr pritam for helping me get the perfect iem for my taste.

Kudos to Pritam sir for the recommendation. A well balanced IEM with a high degree of musicality. My favourite IEM for when I simply want to lose myself in the music and enjoy the show.

Amazing what can be achieved with a single driver.

No Words for me to say about this IE 900 IEM. Even if I say more it will be very less. That much perfection in sound.

Firstly, I thank my new friend Pritam ( The Audio Store Co-Founder ). He helped me by asking about my taste in music and came up with the best for me. He was a polite person who never tried to sell anything until customer requirement needs it. Very honest in delivering the Info. Thank You, my friend, for the best recommendation. 

IE 900 Wherever you search for review it will 9.9 Rating or 9.5 from Audiophiles. Any website or Video everyone says is the best. It is exactly the same as mentioned on sound. 

Sennheiser has come with their experience on this IE 900 IEM. They are very well built material Aluminum when you put them in-ears feels like nothing was there. Such a good comfortable if you carry on your hands feel noting weight. The first impression of me was comfort. 

Then I started playing with Iphoine 12 + 3.5 Jack + Apple Dongle Jack. It's a very simple setup not used any Dac/Amp then I started playing Dangreos By MJ. I can't really explain my experience with the first impression. 

The instrumental part was Awsome!! Drums have kick bass. Guitar strings will make you simple :) Sound Stage will be like Auditorium. Vocals are a blessing Gift for this IEM. The bass is mindblowing and you keep repeating the song for that kick and experience. 

You play anything it sounds exactly the same as how the musician thought to deliver the end of the listeners. That all will be delivered without any other expensive AMP DAC. That's the beauty of IE 900. 

The big joke is it's a 7 MM Driver don't how they designed this IEM. It can be done only with the experience of 75 Years as a sound engineer like Sennheiser.

Great Job by Sennheiser Team. I really bow for their work.