[size=24.57px]The T51i.[/size]

 
 
 
 
                                                                   
 
 
 
 

 

Setup

 
My listening setup is a PC running AIMP connected to a Yulong D100 via optical acting as a DAC, connected to a Gustard H10 via XLR connectors. For the testing I reduced the gain to zero in order to switch headphones easier (usually I leave +6 gain for my HE-400s).  My current headphone inventory is HE-400’s, DT990 pro’s, an Ostry KC06A, and now a T51i (which was provided by AVL Electronics). For testing though I will only be comparing between the headphones. Due to my relatively small inventory of equipment I will be testing the T51i’s against headphones which probably shouldn’t be compared to portable closed cans, but it should be fun.
 
 
 
 
 
 Click to enlarge photos, batterys are for scale to see the size differences.
 
                                                                                                                    
 
 
For this review I will first provide you with the general info, followed by the look, feel, and usability of the headphones. Next we will listen to some music. And finally some thoughts on the specific sound signature of these headphones. I would also like to apologies in advance for any inconsistencies or errors as this is my first proper review. Hope this review is helpful.
 
 
[size=15.08px]    The experience and usability[/size]
 
 

Unboxing

 
The t51i’s come in the classic Beyer packaging style. They have large clear pictures of the back and front of the HP’s and come is the easy to open packaging. When you open the box you will be greeted by a nice carrying case, which has a handle and opens with a single Velcro strap (kudos here as it makes packing the HP’s very easy). When you open the case you will see the headphones which are stored within, a 6.3mm adapter, the manual, guarantee booklet, and inside the pockets on the back you will find the 2pin airplane adapter, and a TRRS to TRS adapter, mine also came with an extra O ring which is supposed to help the fit of the 3.5mm jack in certain Apple devices. Pretty useful, nice packaging and accessories overall.
 
 
 

 
 
                                                                                                                                                                   
 
 

Build/comfort

 
The T51i has some epic build quality, it’s pretty much entirely spring steel with a small ring of high quality soft touch rubber/plastic, and height adjustment mechanism. The ear/head pads are filled with very soft and comfortable memory foam which conforms nicely creating a great solid and most importantly comfortable fit, which you can wear for hours with very little adjustment. The material on the ear pads feels like very soft leather or incredibly high quality pleather; which feels very nice. The closed design and good seal also has the benefit of blocking out the majority of ambient noise, about 25-40% of the noise without any music on, and when you play music you can hardly hear any external sounds. The headphones are also very light and compact, but feel incredibly solid. The head phones have 3 angles of adjustment, height, 90 degrees swivel, and tilt which all work together to create their great and comfy fit. The T51i’s cable is pretty nice as it is very light, flexible but feels sturdy this is connected to the drivers with a Y split, the total cable length is 1.2M and is terminated in a 90 degree 3.5mm connector. Accessories; the t51i comes with a nice high quality protective nylon carrying, a 6.3mm adapter, an airplane adapter and a TRRS to TRS cable. A pretty nice set for someone who’s on the move allot, and should pretty much cover everything you would need to do. The carrying case also has extra space to put some other things as well. Some things of note though; when you first wear the HP’s the clamping force may feel a bit tight. Not to worry though as this loosens up very soon and manages the perfect clamping force; same goes for the height adjustment mechanisms as lots of Beyer HP’s it may feel a bit rigid at first but it soon fixes up. Everything about this headphone feels premium and I have no quarrels especially for a headphone of this size, except WHY IS THE CABLE NOT REMOVABLE! I understand that making the cable removable would make it slightly bulkier but the benefits of having a removable cable, especially for a portable Headphone which could get its cable destroyed in many more ways compared to a stationary headphone is a bit annoying. It’s honestly not big a deal though and doesn’t change my opinion of them. But it would be very nice if there next model has a removable cable. Great work Beyer the build quality, comfort, and overall looks of these headphones are immaculate and stunning. 
 
 
                                                                                                               
                                                                                                                
                                                                                                                
                                                                                                                
 
 
 

Usability

 
The T51i’s are honestly very useful headphones, at this point they have pretty much replaced my in-ears. So far everything I had a use for in in-ears I can do better with these. They have been great at keeping up, the grip is solid which prevents them from falling of my head and because they are on my ears not in them I avoid all the ear pain I get with in-ears. I have been using them all around the house, from simple studying to cooking, I have also been used them for working out: jogging, running, pushups, I have even been doing some kendo with them and they have not even come close to falling of my head (of course YMMV). Also because of their great look and compact size they are pretty much a fashion accessory, from how good they look this is very especially if you commute or travel allot. They also have a 3 button remote to control your phone Volume up Volume down, Pause/Play and they have a microphone on the back, just keep in mind that the volume up and down only work with Apple devices. I also took a few calls using the on board mic, and received no complaints but when compared directly to my note 4’s mic it was a tad less clear but not a problem. The only slight flaw on the remote is that it is very hard to feel for which button is what (maybe next time Beyer), but a little practice fixes that up. Another nice thing is that the swivel and tilt also help if you want to use the HP on one ear only. They are also very neck-able (putting them around your neck lol), which is subtle but a very nice touch if you need to have a conversion in person. The T51i’s also have pretty much zero sound leakage. All in all they are one heck of a commuter or travelers headphone, without a doubt.
 
 

Comparisons between the T51i, dt990 pro’s, and HE-400’s (with Audeze vegan pads)

 
 

 
 Not sure how well it shows, but the HE-400's are giant when placed next to the T51i's
                              

 

Time for some music

 
For the music I just listened to my ordinary while trying to listen to a broad category of music and marked ones out that felt particularly interesting on the T51i’s; weather positive or negative. My thoughts with the tracks names and album info are listed below in no particular order. The info will be Displayed as: Artist/group – Album (date) – Song – extra info “if any” (all music is lossless audio mainly FLAC but also several APE).
 

1. Secret Garden – Songs from a Secret Garden (1996) – Nocturne. This is usually my go to test song for headphones as it has many subtleties, makes use of a variety of instruments, includes vocals as well and has allot of dynamics.  Many HP and earphones I try tend to fail playing it to my liking, and cannot replicate certain aspects of the song.  For example starting at 30 seconds into the song the violin starts to play after this there are very subtle sounds of flapping wings in the background which many other headphones don’t replicate well and make them sound like errors in the track instead of part of it, but the t51i plays them very well. The highs played by the violins, flutes and Chellos are heard nicely along with the great rhythm and depth of the percussion instruments in the background. The vocals also sound very nice on this track as they are mainly on the higher frequencies, and play to the strengths of the T51i.

 

1. Meat Loaf – Back into Hell (1993) – I’d do anything for love duet with Lorrain Crosby – Full unedited version. Time for some Rock, this song sounds great on the T51i’s, it just seems to do everything right, Lee Adays voice is powerful, has great dynamic and feels very clear. The guitars keyboards, and drums all feel very lively and sound great. At the end of the song Lorrain Crosby’s vocals come though perfectly and completes the song. The t51i’s really do this song justice, compared to the HE-400 the only real difference is the feeling of airiness you get from the open cans, but they sound great and it suits the song as well as it makes the bass feel very powerful which contrasts nicely with the vocals, in this case.

 

1. Five Finger Death Punch – Wrong Side of Heaven but the Righteous Side of Heaven Volume 1 (2013) - The Wrong Side of Heaven. This song is interesting, even though it is rather heavy in the lower frequency’s the T51i don’t sound very good with this track (not bad but feels a bit muddy). But when you listen to the track on the HE-400’s you can feel the space and the separation between the vocals and instruments, which falls short on the t51i’s as they are close backed, which removes the airiness and depth from certain aspects of this song and makes the vocals mess with the instruments.

 

1. Halestorm – Halestorm (2009) – Familiar Taste of Poison. This track is played magnificently on the T51i’s Lizzy Hales voice is clear powerful and dynamic, and you can perfectly hear the instruments as well as vocals with no issues. Great marks on this song, it right up there with my HE-400s. One thing of note interestingly enough on this track the vocals feel like they take center stage on the t51i’s compared to my he-400’s where the instruments feel like they are more pronounced and the vocals in the background, it sounds pretty epic on the t51i’s to be honest.

 

1. The XX – Coexist (2012) – Reconsider. This is a very vocal heavy track, but manages to be played perfectly on the T51i’s the males vocals are deep and pronounced while the females is clear and dynamic, overall the song is perfect on the t51i’s maybe just a slight lack of sound stage compared to the HE-400’s.

 

1. Lindsey Stirling - Lindsey Stirling (2012) – Crystallize. This song really plays to the strength of the T51i the mix of dub step and the violin creates a great setting for the t51is to shine and shine they do. The t51i’s great bass and treble reproduction work perfectly this track. The violin sounds great: sharp, crystal clear, and fast, whereas the great bass on these cans helps make this track shine and balances the treble.

 

1. Varnus Xaver - From Ravel to Vangelis - Carl Orff's Carmina Burana 7. The organ a pretty interesting instrument, but is one of my favorites. Organ music is usually my got to test music to see how good the bass on a set of cans is and the T51i shines in this track; the organ is reproduced exquisitely with even the lower notes being heard precisely. The only mention other than it being excellent for the organ is that is lacks a bit of the airiness you get from organ music.

 
So far I have about 48+ hours of listening time on these cans. These are just a few mentions, but I have so far listened to pretty much everything under the sun with these cans am I am very pleased overall. Next take a look at the specifics of their sound signature.  
 
 
 

     Sound and Dynamics Comparison.

 
The highs on the T51i are pretty great. They have crystal clear highs, but not piercing or annoying. Compared to the DT990 pro’s they are also very sharp, but unlike the dt990 pros they don’t have any sibilance or screechiness. Whereas compared to the treble/highs in the HE-400’s which need more of volume to hear the upper frequencies, the t51i allows the treble to be heard nicely without needing any extra volume. This is not to say that the HE-400 is bad at reproducing treble which they do great but the very high frequencies tend to have a slight roll off.  Whereas the T51i’s feel relatively stable though out the higher frequencies, especially so for a closed small/portable set of cans they reproduce them incredibly well. The highs are one of my favorite things about the sound signature of these and is definitely placed at the forefront.
 
 
The bass, I was honestly incredibly surprised by this. The bass on these cans are great: tight, powerful, they go low and have a great punch as well as being very clear and dynamic. I was amazed that tiny portable headphones were even capable of doing that, a very pleasant surprise indeed. The bass on these is even better than my dt990 pro’s; the power and clarity in the low end is great. Now let’s compare it to the he-400, (I know that is a really unfair comparison) but the T51i really holds its own here even though they don’t beat the 400’s they definitely hold their own without question and are better in some aspects. No doubt the closed back design helps with this. Overall the bass is very powerful and well-articulated. There is no boomy-ness, they are tight, punchy, dynamic, accurate and clear. Great marks here as well.
 
 
The mids on these cans are good; the only problem is that they seem to be slightly overshadowed by the low end and the and slightly by the highs. I would say that they have a slight dip in the mid frequencies (not in quality just volume). But when there aren’t too many background sounds, the vocal reproduction on these are perfect. All in all even the mids and vocals are great and I am even currently listening to vocal heavy tracks perfectly and I have no gripes, Just that they feel like they are lower (in sound) than the bass and treble (since I tend to particularity enjoy the mids to be more forward, just my opinion). Compared to the dt990 pros listening to vocals on the t51 I actually feels more comfortable, as the sibilance on the dt990 pros are slightly overwhelming (they need the Schiit Vali to tame them a bit); not so on the t51i’s though which feel rather laid back and clear. But when compared to my HE-400’s with the Audeze pads, the t51i’s fall short. The HE-400s have very smooth, airy vocals due to the fully open design, which beats the dt990’s and also passes the t51I (although I only enjoyed the mids on my HE-400 after switching to the Auduze ear pads, before that it felt very dull with vocals).
  
 
The sound stage on the T51i is pretty good, especially for a very small and closed headphone. It feels like there is about 90 degrees of sound space; for example you can hear left, right and center. But when compared to fully open cans like the DT990 and HE-400’s; a small closed can really is not going to beat the competition, although it still manages to hold its own. For example on my HE-400 it feels like the music is coming from outside the headphones whereas on the t51i’s you can tell they are coming from the headphones on your head. Something interesting though is that even though the sound stage isn’t immense the instrument separation is great; I think the Tesla drivers help in this aspect as the headphones feel incredibly fast and responsive at all frequency’s which helps keep each instrument separate and avoids the feeling of sounds messing with each other. It is pretty amazing how fast the HP’s feel. I would describe it as very fast sound decay and very fast drivers which makes the music feel very clean and dynamic; no doubt the Tesla drivers are to thank for that. Something of note, these headphones don’t really need an amp with their sensitivity of 111db/mw (they will work fine from any phone), but an AMP really helps make these cans shine and improves the overall tonality and dynamics of them.
 
 
 
Everything about these headphones feels premium, from the materials, to the comfort and even the sound; it hardly makes any compromises except for a few nitpicks. All in all though I would easily recommend these to anyone who is looking for the perfect set of portable cans and would also make the perfect gift for any one, audiophile or not. The T51i’s now have a permanent place on my desk at all times, whenever there is too much ambient noise, or I don’t feel like sound leakage, I pop the T51i’s on and have no worries about ambient noise or sound leakage. I will update this review with any relevant information as I use the T51i’s and get more time with them. Good listening to all, and if you have any opinions, thoughts or anything to add please feel free to inform me and I’ll add it. I know this wasn’t really a fair comparison but the t51i’s really held up well and I am amazed that such small portable headphones were capable of such a large sound, one hell of pair of headphones no doubt, portable or otherwise.
 
I give them a solid 4.5/5 stars. 
 
 
Thanks for reading, I know the review was to long. Sorry about the horrible photography skills. 

Introduction
I was first introduced to the Beyerdyamic T51i’s when I entered the market for a Hi-Fi portable can I could listen to on my morning commute and at school. After searching through countless competitors including the B&W P5/7s, B&O H6s (which I owned for a short while) and countless other headphones, I decided to settle down on three main criteria that I was looking for to have in this headphone:

• Great Soundstage
• High Level of Portability
• Clarity

The above three requirements perfectly exemplify my beloved SoundMAGIC HP100s’ and although I knew going in I wasn’t going to get as good of sound out of a portable can as I would out of my full sized headphones,  a sound signature that is close would be a winner.  Before I purchased the T51i, I ended up buying the Koss SP330 on ear around a month ago and loved everything about it. Did they sound as good as my SoundMAGICs? No. Not even close. But for the price, they had everything that I wanted. The only issue I have with them was comfort. After about an hour, I have to take them off because of unbearable pressure on my jaw that cause my teeth to ache. Knowing that the T51i was another on ear headphone, I was initially cautious of buying it for fear of the same issue. However, I heard numerous reviews about them having exceptional sound quality and couldn’t resist their alluring design. I decided to pull the trigger and hopefully see what all the hype was about.
 
First Impressions/Opening
When the headphones arrived in the mail, I carefully unboxed them to see what was in store for me. After opening the carton, I saw that the headphones were recessed in a small black nylon carrying case with a Velcro strap. Included inside of the case was the manual, warranty card, a 3.5mm to ¼ inch headphone adapter, airplane adapter as well as a TRRS to TRS adapter for the headphones. The actual headphones themselves surprised me quite a bit. Unlike the photos which gave the appearance of a weak aluminum headband, the headphones felt quite sturdy with a solid brushed metal headband and earcups with soft black leather padding on the underside of the headband as well as the earpads. The cables from each earcup while thin, were connected to each cup by a strong, thickened rubber and each cable terminated to a single solid Y cable fashioned around the shape of a round, durable rubber cylinder eventually terminating into an L-plug.  Each earcup proudly displays the Beyerdynamic logo as the swiveling mechanisms allow for the folding of the headphones for ease of portability. I found the headband sliding mechanism to be quite stiff, not allowing for minute changes in the position of each cup. Whenever I wanted to adjust a cup, I often found myself taking of the headphone, and fiddling with the sliding mechanism, often times missing my intended notch.  Weighing in at 174g, they reside at a perfectly portable weight. However, as the headphones are made mostly of metal, the earcups are heavy, and it is definitely noticeable compared to my SP330, most especially when worn around my neck.  Also, the comfort issues that I dealt with in the SP330 are extant in the T51i’s. The clamping force out of the box is strong and the headband requires stretching in order to relax the tension on the head
 
Sound
                The most accurate description for the T51s would be a warm, detailed sound which provides rich, lush bass and clear highs with a forward sound signature overall. However, I did find the soundstage to be lacking for my tastes, especially considering the SP330 has a slightly larger soundstage and is a fraction of the price. I also found that vocals and guitar solos in songs lost their sparkle and instead sounded veiled and muffled. As in my previous review, I’m going to include a panel of 6 songs from different genres in order to evaluate my feeling s on how these headphones reproduced each song. As a point of reference, I’ve “burned in” the headphones for around 15 hours or so and all music is either being amped from my Sony STR-V220 A/V Receiver or my Fiio E17k.

1. Com Truise – Cathode Girls

 Com Truise’s 3^rd track of his debut album Galactic Melt is a quintessential example of modern electronic music and a perfect example of a genre where the Beyerdynamics excel. The T51’s lush bass and clear highs really make every element of this song stand out. Each synth drop resonates as you hear the drums in the background thunder and the cymbals clash.  

1.  Meiko – I’m not Sorry

Meiko’s beautiful, full voice in this lovesick ballad is unfortunately not done full justice by the Beyerdynamics. Her vocals are slightly muffled, devoid of the clarity that it deserves.  In the SP330 and moreso in the HP100s, Meiko’s voice is completely revived and sounds vivid and lively. However, the Beyers do good job of creating a warm instrumental to complement the lively tune of the song.

1. Snarky Puppy – Sleeper

I’ve recently gotten into Snarky Puppy, a New York based jazz band whose combination of keyboard, percussion, brass and guitar always keep me coming back for more. I can truly say that while a little veiled with the brass instruments, the t51i’s played this tune wonderfully. Perhaps it may not have sounded as expansive as my bigger headphones, but the warmth and intimate soundstage of this headphone made this song a wonderful treat to enjoy.

1. Dystopia – Acid Smile

Hungarian Rock band Dystopia’s first release in 7 years, Acid Smile is the first single off of their 2014 album Way to Unfold and the Beyers, save a few caveats perform this song well.  The Beyers have a trick relationship with Rock music; the bass guitar, drums and cymbals are usually emphasized while the vocals and guitar are left slightly veiled and less encompassing.  This leaves a very interesting mixture which, depending on the song can be enjoyable or overbearing.

1. Jamiroquai – Two Completely Different Things

My favorite track off of 2009’s Rock Dust Light Star, Jay Kay’s voice falls a bit short along with the saxophones and percussion. While the warmth of the T51i does create a lush atmosphere and the piano rings in clear, the bass somewhat clutters the rest of the elements of the song. In this instance, the intimate soundstage of the t51i is more of a hindrance than an aid.

1. Little Dragon – Cat Rider

Little Dragon’s singer Yukimo Nagano’s vocals ring in loud and clear in of the instances the Beyers can reproduce vocals flawlessly. Here, the beats reverberate, the cymbals sound and the warmth combined with Yukimo’s crystal clear vocals create a hot and cold combo that everyone must hear.
 
So for those who perhaps don’t exactly have my tastes in music, what does this all mean? Well, to be blunt, in most musical genres in which bass and treble are the emphasis of the music (electronic, rap/hip-hop, dubstep, R&B etc,) and mids are not much of a concern, the Beyers excel. However, in musical genres with a mix of frequencies across the spectrum or vocal talents are there as the main element rather than supplementing the music, the Beyers tend to not do as well. This is not to say that these genres sound bad on the Beyers; quite the opposite. Most of them still sound quite enjoyable. However, compared to headphones with more neutral sound signatures and better clarity, the t51s will simply not perform as well.
 
Final Thoughts/Conclusion
                While these headphones provided me with a very interesting listening experience to a sound signature I wasn’t previously introduced to, I think I will be returning them.  That being said, I should state that I am very partial to a neutral sound signature in which all frequencies in the spectrum are emphasized equally.  Also, I found that using equalization on my Fiio E17k provided a more pleasing sound signature with which to listen to. These are pretty nice sounding headphones for what they are; a warm, intimate sounding headphone with recessed and laid back mids and clear highs. However, I believe the price for these headphones is quite steep at an MSRP of $300. Even at the $275 that I paid, I cannot justify the purchase, considering most portable headphones in the $100-200 range provide competitive sound at a much cheaper price.  I think that if Beyerdynamic reduced the price to $199.99, they would have a real killer of a headphone that I’m sure a lot of people would enjoy having.
 
P.S.
Woot! Second review! Hopefully, I’m getting better at this….Well, to all who read this review, I give you massive thanks and feel free to leave feedback on how I should improve. If you have any questions, feel free to ask!

Hi my name is Adam I have been into hi-res audio since I was in high school, and am now 38 years old. I have been doing reviews for some months now, bear with me since I am not the greatest writer actually I am pretty bad at it. Audiophile that I am not love quality music and sound that I am, my journey into the Head-Fi Forum started by doing a search online for some new cans and just about every search landed me here.  So I like to keep my reviews simple for the average Joe or Jane can get a review that they can understand and not filled with terms that they can't make sense of.
 
This review is for the Beyerdynamic T51i the little brother of the T51p, Beyerdynamic has been around since 1924 and was started by an electrical engineer named Eugen Beyer in Berlin. Based in Germany most of there products are made by hand by skilled craftsman. I have been a Machinist and a certified Tool & Die Maker for more then 20 years, if anyone knows anything about this trade you will know the best Tool makers are out of Germany and are highly regarded. I would like to say thank you to Peter from Beyerdynamic for sending me a sample to review, I am not an employee or I am being compensated for reviewing the T51i. I guess I will start with specifications then work my way down, you can purchase them for $299 right from Beyerdynamics web page.
http://north-america.beyerdynamic.com/shop/hah/headphones-and-headsets/at-home/music-pleasure/t-51-i.html
 
 
Technical Specifications
 
Transducer Type                        dynamic
Operating Principle                    closed back
Nominal Frequency                   10-23,000 Hz
Nominal Impedance                  32 ohms
Nominal SPL                             111 dB
Sound Coupling  to Ear             supraaural
Power Handling Capacity          100 mW
Max. SPL                                   131 dB
Weight with out cable                174 g
Cable                                         1.2m/double sided straight cable
Connection                                mini stereo jack plug (3.5 mm)
 
 

 
 
Packaging
 
So the Beyerdynamics came in a plain box with a nice hi-res photo, the headphones were packed in there carrying case. I am not sure how they come from a store or if you buy them directly , these were a pair of demo units. But it serves the purpose and gets them from point A to B. There isn't much more to say then that I would assume that if they were brand new they would be rapped in a plastic bag or something.
 
 
 
Accessories
1/4 jack adapter
Flight Adapter
Black Nylon Carry Case
 
 


 
 
 
 
 
 
The T51i comes with your basic accessories a 1/4 jack, flight adapter, and a nice carrying case. The case is very nice and has a carrying handle with a Velcro strap to keep them secured, the headphones lay flat inside the case with a molded cut out.  Also included is a short adapter for non-apple products, there are other accessories that can be bought from there direct website. Beyerdynamic pretty much covers all your basic needs, the case is one of the nicer cases that I have seen for portable headphones.
 
 
Build and Comfort
 
For portable audio this is one of the main factors besides the sound, everyone from teens to old people use there portable devices now for music or even to answer calls. The T51i sports brushed metal ear cups with there logo on it, the fully adjustable headband is made of metal also. The ear cups swivel 90 degrees to insure comfort and slide up and down with notches on the band for a positive lock,  the under side of the band looks like it has the same material the ear cups are made off. The ear pads are made from synthetic leather with memory foam underneath to form to your ear. The outer part is some kind of durable plastic with a satin black finish, all edges are smooth and sleek looking. It kind of looks like a retro modern look mixed into one, that works really well. Wearing these over a long train ride I found to be probably the most comfortable portable cans that I have worn. Compared to the V-Moda XS the T51i have less clamping force were the V-Moda's can be uncomfortable over long periods of time.  The ear pads have got to be the plushest pads that I have ever felt and mold around your ear very well. Considering how much metal these headphones are made of they are pretty light in weight.
 


 
 
The cable is fixed and can't be removed but has really good strain relief, at this price point I would have like to seen a removable cable especially for being portable. The cable is rubber coated and it was very comfortable even ran down my shirt. I run the cable down my shirt with just about all headphones so it doesn't catch on anything and it just looks cleaner. The plug is gold coated and is a 90 degree angle with a very low profile and fit just about every phone I had with a case on it. The Y splitter is very nicely done with a plastic housing with a metal face strain relief was way above average.The volume control is a 3 button apple certified control in a metal housing for music and phone calls, I also used it on a Samsung Alpha the pause button work and I could also change tracks with a double click. Using it with an IPhone 6 and Mini IPad it work flawless, making phone calls the mic worked better then most other portable headphones that I have used. I had my daughter call me wearing the T51i's and couldn't tell she was on a headset and it sounded crystal clear.  Isolation was very good considering it is an on ear headphone, it surprised me on how well they isolated even on a train.
 

 

 
 
Sound
 
 
The most important factor of the headphone to most people, headphones have become a fashion accessory like woman's hand bags. I have seen teens wear them around there necks and not even connected to anything. It reminds me of people wearing glasses with lenses in them that are not prescription and only for looks. I mainly used my Fiio X1 with WAV formatted files from CD's. These are very easy to drive from any source, I also tried a Fiio E07K amp that gave the T51i even deeper and tighter bass. They also use Beyerdynamics Tesla Technology for there drivers with high efficiency and low distortion.  The T51i has a warm sound signature with the bass extended very well. The bass doesn't  take over all the other frequencies though, the midrange is smooth and detailed especially with Pop and New Age music. When I say smooth I don't mean it's veiled or laid back compared to V-Moda's XS the XS mids are more forward and brighter sounding to my ears and  the XS lacking the T51i's bass extension. The high frequencies have great clarity and smooth transitions. Considering they are closed back you wouldn't expect a good soundstage with the T51i. Soundstage is very hard to achieve with headphones since there right on your ear, a lot of people have different takes on it. I think it's more of imaging and placement that you mentally visualize I don't even know why you would call it soundstage for headphones. But call it what ever you want the T51i's give you a great image or soundstage and it is very easy to mentally picture the size of the venue with good placement of instruments. It also has good instrument separation with great layering of details. Using them to watch movies was no different they just sound awesome. During explosions in movies you can feel the deep bass rumble in your head. These are the type of headphones that you could enjoy all day, without having high frequencies or to much bass that would lead to be annoying and fatiguing  they just sound well balanced with a natural warm sound. All vocal parts just sound so clear and life like you just have to hear them to see how good they sound. If anyone has a chance to audition these don't pass up the chance you wont be disappointed.
 

 
 
Conclusion
 
For the price you won't find anything better then the T51i's for on the go listening. I was honestly amazed at how well these performed for being so small, they sound better then a lot of full sized headphones that I have heard. The build quality is outstanding and will last for years and can probably take some abuse. The only thing I would have liked to seen is a removable cable, especially for portable headphones that are going to see a lot of use. I have spent a good amount of time listening to these in a very short amount of time that I have them for, they will definitely be on my list of things to buy. With technology advancing every day I am sure we will see more products shrink in size and the quality of sound go up, Beyerdynamic just does it does it better then every one else at this point in time in my opinion. I will recommend these to anyone that's looking for a fashionable headphone that has top notch sound for on the go or for people that just want a small sized headphone for at home. Thanks for reading I hope I helped anyone interested in buying these.