[Dobrescu George]

I tested k550 today. i lost all interest in them. they are the best detailed, best treble, best bass, best just BEST at 300$ price point. Period. But i am going to get something around 1000$ or more price point, and k550 is not in the same league. anyways, if anyone needs the best headphone under 300$, and it has to be neutral, this is the safest bet.
my ultrasone dj one pro sound much much better for me, but they are not neutral, they are sweet and fun. k550 was much more pointing towards neutral. 
depending on my mood, if i were blocked on a 300$ budget i would either get k550, ultrasone dj one pro, or sennheiser urbanite xl, but k550 was the  most neutral, out of all. the timbre was nice. out of fiio x5 was a little under-powered. adding fiio e12 added so much more exactity to the sound. 

 

[toolio]

I tested k550 today. i lost all interest in them. they are the best detailed, best treble, best bass, best just BEST at 300$ price point. Period. But i am going to get something around 1000$ or more price point, and k550 is not in the same league. anyways, if anyone needs the best headphone under 300$, and it has to be neutral, this is the safest bet.
my ultrasone dj one pro sound much much better for me, but they are not neutral, they are sweet and fun. k550 was much more pointing towards neutral. 
depending on my mood, if i were blocked on a 300$ budget i would either get k550, ultrasone dj one pro, or sennheiser urbanite xl, but k550 was the  most neutral, out of all. the timbre was nice. out of fiio x5 was a little under-powered. adding fiio e12 added so much more exactity to the sound. 

Odd. I don't find them the least bit underpowered with my Fiio X5. I think the K550 and X5 are a nice pair. The K550 is easy to drive.

 

[nw130d]

Just throwing it out there... K550 has a pretty flat frequency response any sound difference is probably due to colouration of the amp, not how well they are driven. They are pretty easy to drive.
 
And yah if one is looking for flat freq response, with articulation throughout the freq range along with a wide sound stage... there is no better. Only other in the same price range is the K7XX Massdrop?

 

[TheGiantHogweed]

I have the K550s and the FiiO X3. They pair very well and the X3 easily has enough power to drive them. I don't know much about the X5 but since it is quite a lot more expensive than the X3, I would have thought that it would have even more power. I could be wrong though. But I do fine that almost anything will drive the K550s easily.

 

[Dobrescu George]

the sound was much better when i introduced fiio e12 into the mix. i am not bragging about how x3 or x5 cannot drive, but about how much better k550 were when added an amp, not even expensive one.

 

[vaibhavp]

  the sound was much better when i introduced fiio e12 into the mix. i am not bragging about how x3 or x5 cannot drive, but about how much better k550 were when added an amp, not even expensive one.

 
is x5 amp not even as good as e12?
 
e12 is quiet a bit cheaper.

 

[Dobrescu George]

   
is x5 amp not even as good as e12?
 
e12 is quiet a bit cheaper.

e12 e12a and x5's amps op-amps and more details are different. they are going to give out different sounds. it is only normal. i liked x5+e12 more than x5 standalone with k550, when i tested.

 

[TheGiantHogweed]

The E12 will only be cheaper than the X5 because all it is is an amplfier. The X5 is a DAP and it has a decent amplifier in it. The E12 will probably quite easily improve the sound of the X5.
Sorry for going a bit off topic from the K550s.

 

[vaibhavp]

The E12 will only be cheaper than the X5 because all it is is an amplfier. The X5 is a DAP and it has a decent amplifier in it. The E12 will probably quite easily improve the sound of the X5.
Sorry for going a bit off topic from the K550s.

 
then it is possible e12 will improve sound of k550. they are quiet sensitive to quality of amplification and improve noticeably when changing from direct streaming to kernal streaming of foobar.

 

[x RELIC x]

The e12 is a fairly transparent amp and allows the signature of the source to come through. It is also twice as powerful as the X3 which is a little more powerful than the X5. I find that there is not much difference in sound going from the X5/X3 to the e12 when everything is volume matched. With the K550 there is very very little difference in SQ from the e12 until the bass boost is used. Then it's just an awesome pairing.

 

[sludgeogre]

The e12 is a fairly transparent amp and allows the signature of the source to come through. It is also twice as powerful as the X3 which is a little more powerful than the X5. I find that there is not much difference in sound going from the X5/X3 to the e12 when everything is volume matched. With the K550 there is very very little difference in SQ from the e12 until the bass boost is used. Then it's just an awesome pairing.

 
I have an E18 that I use with my K550, usually with the bass boost on and I can say that is really is an awesome pairing. Giving the K550 a lot more power usually tightens up the bass a lot and makes that awesome sound stage even more apparent, but the bass boost on Fiio products really warm the bass up and gives the music a much more pleasant feel with the K550. I don't use the bass boost with anything else I've tried that amp/dac with, just the K550. Something about it is just incredibly pleasing.

 

[Shaffer]

FWIW, I use no EQ/bass boost with mine. Just good amplifiers, a high quality CD player/DAC, and good source material (zero MP3). I feel no need to alter anything. YMMV

 

[TheGiantHogweed]

I think that mp3s sound very good through the K550s so long as they are about 320kbps. I have mainly mp3s on my FiiO X3 andI have just a few 24bit flacs. They are noticeably better but not by a huge amount. I can tell the difference in sound quality much more easily with my AT ATH-AD700s. Mp3s also take up quite a lot less space than the other formats too so that is another reason why Ilike them. I have over 3600 tracks on my X3 and it is only taking up about 40gb of space.
I still think that my K550s go really well with my X3 and they don't need any extra amplifier added. They my sound better though if I use one that is better than my E11.

 

[lawrecedent]

I have an E18 that I use with my K550, usually with the bass boost on and I can say that is really is an awesome pairing. Giving the K550 a lot more power usually tightens up the bass a lot and makes that awesome sound stage even more apparent, but the bass boost on Fiio products really warm the bass up and gives the music a much more pleasant feel with the K550. I don't use the bass boost with anything else I've tried that amp/dac with, just the K550. Something about it is just incredibly pleasing.

I used to find the same thing with the e11 with bass boost on 2

 

[TheGiantHogweed]

I used to find the same thing with the e11 with bass boost on 2

Even though I have other FiiO devices, the E10 and X3, I still use my E11 very often. It seems to have the deepest bass boost of them all. It goes quite well with my K550s but better with my Audio Technica ATH-AD700s. They are open back and in my opinion, they are really good at everything other than the weight to the deep bass notes.
 
One thing the E11 helps the K550s with is the midrange. I think the midrange on the K550s without any bass added sounds clear but extremely thin. This seems strange because they have quite a lot more bass than my AD700s. The midrange on my AD700s sounds a little warmer. Using the E11 with my K550s though adds even more bass, too much at times but it makes the midrange sound a little better to me.
 
Even though I think the E11 is quite a basic amplifier, I still think it improves a lot of the sound. Even the treble stands out more, especially when it is on high gain.