I bought these headphones!! I already own the KZ ZS10 Pro X and Shure SE 215!! I play electro-acoustic guitar in venues!

The KZs have the well-known issue of overanalysis in the sound and sharp treble... which gets tiring during long playing sessions!! The Shures are good headphones (with perfect isolation), very reliable though, but their mids are very harsh (scratchy) all night and there is almost no treble!!

The Sennheiser IE 100 Pro come in and sit exactly in the middle... they have all the positives of the Shures but with clearer and more distinct treble... and they don't have that fake KZ sound! You hear all the instruments more naturally and in a sound as close as possible to the natural one... at this price they have no rival!! You put them on and forget about them, they are super light...!

I think they have no rival in this category up to (100 Euro).

The cable broke within a month without much use and the higher quality replacement costs as much as the in-ears themselves. Nevertheless, as earphones they have much better sound than both the Audiotechnica M40x headphones and the equivalent Shure SE215, which are terrible.

So: Use in two fields; both for listening to music on the phone, and (mainly) for monitoring during live music performances.
I characterize it as an absolute tool, and I will explain the reasons.
The correct requirement for in-ear monitors should be sufficient listening at mild volumes; this is achieved thanks to the very satisfactory isolation it offers, and indeed with good to excellent detail. You can get absolutely decent sound at lower volumes, thus protecting the eardrum from strain. If you are a singer, because your voice will sound to you internally as well due to the speaker and skull vibrations, it needs to be boosted to balance out.
It gives a warm sound, if adjusted with a bit of care, you feel like you are singing in a stadium. VERY SMOOTH headphones....
Very important note: the silicone tips must be the size that "seals" the ear canal, to achieve isolation from external sounds. If they are not "tight", not all the hertz are delivered, you lose bass.
I hope I helped....

vfm for professional headphones! Of course, their use is for demanding gaming that lasts up to 6 hours. In the first few days, my ears needed to get used to them, but now after 3 weeks of use, I don't even notice that I'm wearing them. Amazing isolation from external sounds, as for their quality, everything indicates that they will last a very long time. 10 out of 10 from me!

I have used many headphones for professional use on stage. They have by far the best sound of all! I am absolutely satisfied

Well, these headphones have amazing sound compared to other much more expensive ones. Nice clean and fast bass, and warm highs. You can't call them flat, I would say they sound more like a V shape. The sound stage is not crazy, but it's there, at least in my opinion. (tested on a mixer and mobile)
*You have to wear them correctly and with the appropriate ear tips for your ears, otherwise you won't get what they offer!

What you pay is what you get, and let's not forget that SOUND is a subjective matter, so it would be good to try them out if you have the opportunity before making a purchase. For me... Pure disappointment... They lack bass! We fell for the BRAND NAME and even more so for the fact that they claim the product belongs to the PRO series. Unfortunately, I was taken in by various reviews and simply... WASTED MY MONEY!

I can't imagine better at this price. I prefer them over the other headphones on my ear. I would recommend them without hesitation.