To start, I purchased these for two reasons. I am a live audio engineer, so I use these for mixing monitors and as my personal monitors when I sing Tenor as part of my group.
 
These have two speakers per ear. Low/Mid and High. 119db @1mw with an impendance of 21 ohms which means your iphone can drive these quite poorly.
 
My initial View:
I have been wanting a pair of custom in ears for quite some time and was looking at all of the different brands for around one year or so. I tend to take my time when it comes to anything that I may not be able to return. After much time, reviews, and a choice I decided to go with the UE5's over the UE7 or UE11. The vocal in-ear as they are so called.
 
So off I went to my audiologist to have my ear molds done. Julie Glick is an authorized UE audiologist. She contacted me herself rather than through her secretary, she is amazingly nice and her $75 mold cost at the time was cheaper than most other audiologists ($100). Did I mention she was a UE authorized audiologist?

Ten minutes go by and voila the innards of my ears lay in front of me in pink form. Sent my molds in and two weeks later my custom molded UE5's arrive in the mail. I am super excited at this point. I open the box and a black magnetically closed matte box greets me with a simple UE logo on it. Once past the "How music is meant to be heard" card I arrive at the metal box that holds the in-ears. Molded foam is caressing the metal box and my excitement grows. My name is on the box, my serial number is  on the matte box along with my name (again) and the initials of the person who inspected them. I open the box and am greeted by my all black UE5's with the Batman Logo on them. They also come with a tiny brush and loop wire to clean them with when your ears get dirty.
 
Allright now to the good stuff.
Sound:
As mentioned in the beginning of this review, I am a live audio engineer so most of the auditioning I did with this was done with live audio and later on pre-recorded music. The sound quality of these are simply natural. Garbage in garbage out, quality in quality out. These in-ears are the perfect balance of Lows, mids and highs.
 
For live shows these were powered by a shure wireless beltpack for live shows and various consoles when mixing.
 
The low end is round and hard hitting but not too boomy and it does not muddy or dull the mid and high end. The mids are where these really get their shine. They are so warm and clear that it really is disgusting. My voice comes through  with such clarity and realism that it feels as if I am literally in my own ears (sorry for the pun). The high end is where the headphones came to a screeching halt in my opinion. When I began to hit high notes and the music driven my ears became fatigued extremely quickly and my . It got to a point where I would only put one in my ear and use the floor monitors to compensate.
 
Music sounds good on these. But it all depends on the mix that you have. IF you a great track to listen to then these will bring out that shine but if it is a good or an ok mix then you will hear all of the flaws. I realize that I did not want to listen to half of my music with these as it really showcased their flaws and made them truly sound like a**. A lot of my music is uncompressed but most is ripped at 320kbps.
 
In comes the FIIO E11.
I used these with the FIIO E11 and holy WOW! This amp did the one thing that I thought I would never do, bring these everywhere with me. They have brought the lows and the mids to life. Once you boost the EQ aka bass to level one the FIIO the low end is absolutely stunning. These are absolutely my favorite in-ears by far that I have used ( I've wasted much money looking for the correct par). The soundstage is SO much larger with this amp that it boggled my mind once more. Remember the sibilance I mentioned earlier when being driven? It has all but disappeared. The high end is now like warm velvet during a winter storm. AMAZING in case you missed my horrible metaphor. I have now vowed to never use these headphones without proper amplification again.
 
Final thought:
For the money, customer service and quality that you receive these are well worth the money. Speaking of customer service, I have used these countless times and have not had any issues with them. Before I forget the cables are part of this. They are detachable in case you accidentally destroy one of them and are very quiet when rubbed against clothing or body. The quality is quite good with ample insulation. The cable is 48 inches long.

Sincerely,
In Love

[size=small]So this is my first portable amp that I have purchased. Prior to this I have used my receiver headphone out, outs from too many mixing consoles to name and my portable champ my iphone. Needless to say that the iphone is the worst out of all that I have used, sounds like booty to honest.[/size][size=small][/size]
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[size=small]First Impression (looks):[/size][size=small][/size]
[size=small]The amp is tiny. It fits with room to spare in the palm of my hand. The amp has a matte finish from which fingerprints will be attracted to in disgusting ways. The two click buttons that are on there (EQ aka bass and Hi/Lo settings) feel a little cheap. I was actually afraid that I was going to scratch the plastic finish as I have to use my nails to switch anything because of their size. The buttons are tiny and it is hard to tell when you are in the first EQ setting or on the way there. EQ zero and two are easy as they are at their respectable extremes.The volume button is smooth once past the "click" of on. It's made of metal which gives a nice tight smooth grippy feel when turning the volume. This thing weighs 2.3 ounces and I gotta tell you that I thought it shipped without the battery. It is that light. I had to open it to make sure that the battery was actually in there.[/size][size=small][/size]
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[size=small]Sound:[/size][size=small][/size]
[size=small]Turned the amp on with nothing plugged in and all I heard was the fact that I was plugged into an amp. Being around much more powerful amps it is nice to know that the operating noise that I get from a $6000 QSC amp is the same that I get from a $59 headphone amp. Immediately, I began listening to uncompressed music as the "Garbage In Garbage Out" rule applies more than ever when amps are involved. Ask the off key singers.[/size][size=small][/size]
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[size=small]I used my custom molded UE 5's from Ultimate ears. I will be purchasing the Hifiman HE-500's as this amp is more than capable of pushing them. My UE's have an impedance of 21 ohms which my iPhone can play with not much success. The first thing I noticed is the sound stage. It is much wider than using no amplification. The center feels very focused.[/size][size=small][/size]
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[size=small]Low End (bass) - The amp on EQ setting zero plays music as it was mixed which is typically what you need on a well mixed album such as Bob Marley's orignal mix of Could you be loved. On EQ setting one is where the punch of the low end comes in. Forty hertz from Linkin Parks Numb come through clear enough to rattle my ear drums. It is enough to fill out your needs without blowing you out of the water. The EQ two setting should not be used. The low end seems to remain the same while the low mids (150 - 300) get a boost. The only thing that I found this setting to sound good with is one reggae song. It does not sound bad but does muddy up the sound.[/size][size=small][/size]
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[size=small]Mid - This is where this amp impressed me. Mids that are implemented well are silk on one's skin, like apple filling to your pie if you get my drift. The way this amp pushes the mid levels is truly amazing. I had to keep checking to make sure that this small amp was what was reproducing the sound. I can't say enough about the way that the mids make me feel. GREAT!![/size][size=small][/size]
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[size=small]High - This is generally where everyone wins or loses in my book. Consider the high end the pie crust to my apple pie. Too much of it, and it takes away from all of the hard work that the low (crust) and the mids (filling) have done. Too little and it gives you a taste yet leaves you wanting for more. I am on the side of not enough on this amp. If it had just an 'nth more I would probably never take this amp off from my headphones. The high end is there not sharp, not dull but could be brighter.[/size][size=small][/size]
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[size=small]Hi/Lo (Outside casing) - Important to note that there are two Hi/Lo gain settings. One on the outside which in my opinion widens the sound stage slightly larger and boosts the mids yet keeps the high end sharp without cutting into your brain. At the same time it would be nice to have a touch more highs to make the sound better rounded. The bass sounds untouched. That being said switching from Lo to Hi does not kill you with POWER!!!! It gently raises the levels without hurting your ears by introducing sharp highs or ear splitting high mids. Good to have but not necessarily that important when on the lo setting (internally).[/size][size=small][/size]
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[size=small]Hi/Lo (Inside Casing) - Also important to note that on the Hi level on the inside that your battery life is cut from ten hours to somewhere around four. All listening prior to this was done using the lo setting. On the high setting the amp sounds so much bigger but not in an obnoxious way. Music of all kinds sound much more full bodied and in your face. The bass boost on EQ 1 is where its at. You have no need to go above this simply because of how growly the low end sounds. Depending on how well the mix you have is kick drums punch you in the face and the mids and highs soothe you.[/size][size=small][/size]
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[size=small]My negatives to take away: Could use more high end, and ACTUAL level two for bass that could punch out your teeth rather than a mid booster. Wish they didn't use plastic that attracted fingerprints. Bigger buttons on the side for the EQ and gain settings.[/size][size=small][/size]
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[size=small]Overall, my opinion on this amp is that it is absolutely AMAZING for the price. Great first amp that has WAY more power than I will ever use (until I get my HE-500's).[/size]