I have owned a vast number of Me Electronics products, ranging from the famous M9 to the M11+. Yet neither of them have been as unique as their Sound Preference model: the SP51.
With the SP51, you are able to tune your IEM’s to your preferred sound signature.
 
Want Monstrous Bass?
Got it.
Want Some Extra Clarity?
Got it.
 
It really is almost like magic. However, it is as simple as taking the back port and replacing it with something else. Each port has different amounts of bass and is differently coloured. The “Extreme Bass” port is black, while the “Enhanced bass” is gunmetal, and the “neutral” port is silver.
 
Interesting right?
 
 Build Quality:
Quite amazing actually, especially for the price. The housing is made entirely out of quality metal. The cable is covered with Teflon and clear plastic and is very flexible, while keeping microphonics and tangling out of the way. I wish all IEM cables were like this…
 
Comfort:
Fairly Average at best. The comfort of an IEM is different for everybody, and is also dependent of the type of tips you use. ( I personally use the funky double flanges the M11+ provides, and I get a very nice seal ) For example, using the smallest single flange tips when you have large ear canals isn’t going to get you a good seal.
 
Isolation:
Once again, only average and can be completely dependent on the seal you get.
 
Sound:
Notes:
Used Sansa Fuze with 320 kbps with no amplification and equilization to try to keep it as accurate as possible.
 
Okay, this is the big one: Sound.
I will go by ports, as each one of them sounds quite different.
 
Extreme Bass:
When it said “extreme bass”, it wasn’t kidding. The base on these is absolutely ridiculous. Bowel enducing, impactful, almost painful bass. Whenever there is even a touch of bass, it starts farting out  earthquakes of deep bass. It comes out when uncalled for almost everytime. Really, despite the monstrous bass, I really couldn't find a way to really enjoy the extreme plates.
 
Enhanced Bass:
This is when things get good. A large amount of bass is cut from the extreme bass, giving it more balance.The bass suddenly tightens up. The treble is nice and clear but unfortunately there is lots of sibilance that comes with the treble. Most of the time, it is fine and out of the way, but when it shows up, things end up very bad. Listening the Lil' Wayne's extremely squeaky voice in " 6 foot 7 foot" was nearly unbearable.  Despite the sibilance, I feel that this is still very good sounding with a slight V- Shaped sound sig with slightly recessed mids and vocals and a powerful low end and treble. If only it were less fatiguing...
 
 
Neutral Bass:
Well, yes, the bass is very neutral on these and clarity is very decent. Mids are much less recessed and bass is well contained. The sibilance is much lessened. These (obviously) are the most balanced of the three, offering excellent clarity. However, if you are looking for tip-top clarity, these aren't your top choice. These are decent, but if clarity and balance is all you are looking for you are better off with something like the HiFiMan RE0 and the Sunrise Xcape or maybe even Mee's own A151. In the end, these still are quite clear, but it isn't at the top of the competition.
 
Verdict:
Yes, these can be muddy bass monsters, but at the same time these have the ability to have great clarity. You can think of these as an "all rounder", or a "starter IEM.". You can learn which your favorite sound preference is, or that more bass isn't always better. In the end though, while these do perform extremely well, won't be in the top of the competition. 

Let me begin by saying that this is my first review, so try to be nice! 
 
Let's begin with build quality....
 
The twisted cable  is covered in a nice, thick, clear black cover that should fight against abuse very well.  The black metal housings should handle a lot . One thing I didn't like about the build is it's strain reliefs. It tends to get slightly loose. It shouldn't affect the durability much since it still covers the cables, but it can bother you.  Overall, the build is excellent, except for the strain reliefs..
 
Comfort and Isolation
 
Comfort was sort of a weaker part of the M9's. The stock single flanges are actually very comfy, but all existing isolation disappears and sound quality is slightly decreased. Very deep insertion is required for the best sound. The double flanges or the Sony Hybrids improves the sound and isolation, but neither of them have the same comfort as the stock single flanges. 
 
 
Microphonics
Yeah, it's still there, but isn't quite noticeable. No microphonics when worn over the ear however.
 
Sound
 
The M9's seem to do quite a difficult feat. They achieve a mainstream sound signature that non-audiophilics love, while still being able to appeal to audiophiles.
 
Bass:
Can be a tad bit excessive sometimes. Every once in a while, the bass shows up when uncalled for.  Should satisfy bassheads.
 
Mids:
The M9's is quite satisfying in clarity, though the mids might feel recessed or pushed back.
 
Treble:
Unsurprisingly, the highs of the M9's is its weaker point. Although of the astounding detail put out from the M9's, they can be quite harsh at times.
 
Soundstage:
Excellent, thanks to the M9's vented design.
 
 
[size=medium]In conclusion...[/size]
 
[size=medium]Mee might have released new and possibly better IEM's that probably beat the M9's in just about every way, but with the lowered street price ( I've seen newegg go as low as $10! ) these still can't be beat. It pretty much destroys anything near it's price range, ( like the Skullcandy Ink'd or the JVC Marshmallows ) [/size]
 
 
Thank you  taking your time and reading my review, however amateur it may be, and I hope this helps..!
 
( Used Un-rockboxed Sansa Fuze with 320 kbps quality and no less. )