Sound quality awful, but All Night Long instead!
585491
Sounds horrible, like it was recorded in someone's bathroom. The sound full cuts out on the first song for a half a second. If you was some Junior, then buy the All Night Long album, much better!
2184004
I tried to like these, but their sound quality is so poor--even with the great price for replacement iPhone headphones.  The product's phone functionality works fine, but they are a failure as headphones.  Maybe I got a bum pair that made it through a quality screen in error.  The highs are hissy, their are non-existant low-mids, and their is a background hiss.  My cheap, off-brand cassette player from 1984 would give Griffin Tunebuds a run for their money in terms of audio quality.

I have had great luck with cheap, neodynium magnet, sound-isolating headphones from J-Labs, Sony, and Skull Candy.  I assumed that I could get a phone headset and decent headphones in one package for $20-$30 in the Griffin Tunebuds, but I basically got a serviceable headset.  I am not going to return them, but you can bet I won't be listening to music with them.  I am listening to them as a write this--wow, so bad!
2319796
I am giving this 1 star only for the quality of the sound not the artist.

Huge TTD fan, i have all his albums, even the awful jazz one with his new name.

Borrowed this cd to check out the sound with cool edit and wow was it terrible!

Let's say most cds are maxed out at 100% in terms of RMS well this one is normalised at about 30%.

Please take my advice and avoid this stinker, his greatest hits released by Sony is fine, stick with that one folks.
547560
Product is subpar, sound gets distorted at high volumes.
3384759
I'm disappointed in the sound quality.  Guess I'm going to have to buy a sound bar or something to get the best out of it.
4331154
While the sound quality was nice, it was so quiet, I could barely hear it! I connected it to a stereo, if I turned the volume up to a level that I could hear, it became very distorted and sounded awful. The point of headphones if your hearing isn't that great is to be able to turn up the volume loud enough for you to enjoy without bothering your neighbors. I had to return them because they were useless for me.
881931
Absolutely appalling sound quality. I listened to some hard rock and some 70's prog-rock and was thoroughly disappointed with these. The kind of mid-range response you'd expect from a pair of dollar store headphones. The sound is so tinny in the mids and so hissy in the highs it was painful. The low-end was actually ok, so one star there - and a second star for comfort. Shame on you Sennheiser. I am definitely returning these and springing for the Bose in-ears.
2524804
I bought these earphones to talk on my iPhone. But the sound quality is terrible! I can hear fine, but those on the other end report that the sound quality is so poor that they have to guess a half of what i'm saying. Two stars - for the sleek design (i have them  in red) :)
3645072
The sound is terrible: quite tinny and voices in particular constantly resonate (around .8kHz), even at low volumes. Also clearly has an EQ which emphasizes bass range, while I had expected a flat frequency response. Fold down to mono is also quite poor, especially with audio that was originally 5.1 or higher.
4675135
sounds very tinny and volume so low, you can hardly hear it. The distortion is awful. Then all distortion is awful.
2883639
I ordered these headphones for my Nexus One. I cannot begin to say how disappointed I was with these. I assumed (given the price) that these would be comparable to my exceptional CX300s, but boy was I wrong. The sound quality is absolutely abysmal! There is little or no high end on these, and mids are completely muffled. At the end of the day, you're left with a boomy, overly bassy sound emanating from this pathetic excuse for a Sennheiser headset. Not to mention, (like many other reviews did), the build quality feels very cheap. I never expected Sennheiser to produce crap like this.

The CX300s are typically found in the $25 range and sound exponentially better than these earbuds. For $35, this is a complete ripoff.

Oh, and by the way, I tested them with my laptop also just to make sure that my N1 wasn't giving me trouble w/ the headphone jack. The sound was still bad. Thankfully, I returned this item and Amazon was very friendly about giving me the refund.

Summary: DO NOT BUY!
4202219
Sound quality is so bad. I am extremely disappointed.
4349189
I probably shouldn't complain too much given the price of these headphones but they are the worst sounding things I've ever owned. I use them at work and as such I literally have them on the lowest volume setting possible but they still distort constantly. I'm just super let down with the terrible sound quality, on the plus side due to using them at such a low volume the battery life is much better than advertised. The box said they were rated for 4 hours of battery life (the description said much more than that or I wouldn't have bought them) but I'm actually consistently getting around 7 hours of horrible sounding music
2866081
The sound quality was rather worse than my 3 year old sound bar. Sound was rather muffled in a weird way in no way I could fix via the settings. There was no on-screen-displays, and the remote buttons needed to be hard pressed in order to do something. At least my sound bar still sounds great...
3292096
Stereo sounded worse after I used it. Trust the negative reviews as my end result had way too much treble.
3912724
In the past I've used just inexpensive earphones ... I thought I'd splurge and get some that sound better.  So, based on reviews, I purchased these as well as some "Audiophile Elite" earbuds: https://www.amazon.com/gp/product/B01D6MZ0YO/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1
The ones from Kyoo-Up came in a fancy package and look nice, but I was really shocked and disappointed by the sound.  These earbuds are completely lacking in treble, leaving only mid-rage and base sound.  That means that both music and voices sound dull and muddled and simply awful.  This is not a small thing...when I say they're lacking treble, I mean UTTERLY lacking in treble.  Also, when using them with my cell phone, people complained that they heard a buzzing sound and bad audio.  So there's a problem with the microphone on these as well.  By contrast, the "Audiophile Elite" ones have a great sound so I now wear those all the time.  So be warned...stay away from these Kyoo-Up despite the nice packaging.  By the way, the Audiophile Elite don't have a microphone  they're just for listening.
4019199
Eh...sound isn't very good...severely lacking depth.