[Armaegis]

Yes, a V-shaped sound is good for low levels as that partially corrects for the natural loudness/hearing contours of the ear. At high volumes I find V-shaped headphones start to sound overbearing. 
 
And no, I do not believe the e5 would be sufficient. I used to have one years ago, and while I never paired it with the K272, I did try with various others and the e5 really is more suited for iems or easily driven cans. 

 

[Kukuk]

As far as volume goes, pretty much any MP3 player or phone will power the K271's to a listenable volume, unless you listen at really loud levels.
 
Even on the sound quality front, they only improve marginally with a good amp.

 

[NimbleTurtle]

Quote:

Yes, a V-shaped sound is good for low levels as that partially corrects for the natural loudness/hearing contours of the ear. At high volumes I find V-shaped headphones start to sound overbearing. 
 
And no, I do not believe the e5 would be sufficient. I used to have one years ago, and while I never paired it with the K272, I did try with various others and the e5 really is more suited for iems or easily driven cans. 

Yes I was referring to low impedance cans. I was too lazy to check what the impedance rating on the K272 was. 

 

[Armaegis]

The impedance of the K272 is 55, but that's only half the story. You also have to consider the sensitivity. They are rated at 104 db SPL/V, which is roughly  91 db/mW. This is very low for a headphone. Most consumer grade headphones are 100 or above. 

 

[talisman42]

Not sure if portability is a major factor or not, but some of the on-ears (opposed to over-ear) can give you fantastic results. Although I haven't owned the 25-1 - I'm confident that it will satisfy all of your criteria. As for full-sized cans,  I've owned the D1100 and they performed very well with portable sources - it's like instant full bass boost without having to fuss with EQ. For many songs, it was great - but I couldn't dial in on the sound I preferred for movies. Frankly, I don't think I gave them a fair chance. They are extremely comfy and light so I can see them being portable. M50 is another classic - but again, as an over ear design, they're bulkier along with their extra length cables. Most people love the sound they produce! I have to agree. Similar to the D1100, there is a mid-bass hump that makes songs lively at the expense of fatigue for some listeners and genres. I imagine the 1st gen vmoda have similar characteristics.
 
As others mentioned, you'll have to cross the open-back designs off your list.

 

[manxys]

Hm. Ok, so if I want (1) portable, (2) closed, (3) iphone powered (no amp) cans for 80 - 180$, what are the headphones I should consider?

 

[NimbleTurtle]

Quote:

Hm. Ok, so if I want (1) portable, (2) closed, (3) iphone powered (no amp) cans for 80 - 180$, what are the headphones I should consider?

V-Moda M80 is slightly over your price range but it comes with a sexy case, many cables, build quality of a tank, great sound quality, etc. 
 
This thread is perfect for you: http://www.head-fi.org/t/433318/shootout-102-portable-headphones-reviewed-panasonic-rp-htf600-added-04-29-12
 
Time for you to do some research! 

 

[manxys]

Quote:

V-Moda M80 is slightly over your price range but it comes with a sexy case, many cables, build quality of a tank, great sound quality, etc. 
 
This thread is perfect for you: http://www.head-fi.org/t/433318/shootout-102-portable-headphones-reviewed-panasonic-rp-htf600-added-04-29-12
 
Time for you to do some research! 

 
I wonder if there is a thread where someone compares how 'forgiving' the headphones are to source/ enough power.

 

[talisman42]

Quote:

Hm. Ok, so if I want (1) portable, (2) closed, (3) iphone powered (no amp) cans for 80 - 180$, what are the headphones I should consider?

Since the Senn HD25-1 go for around $199 new, those might be a stretch. You could consider buying them used-like new/refurbished for around $160 from a reputable source.

 

[Armaegis]

Quote:

 
I wonder if there is a thread where someone compares how 'forgiving' the headphones are to source/ enough power.

 
In a very general sense, headphones with poor or recessed treble can sound "forgiving". 

 

[lostmage]

Quote:

 
I wonder if there is a thread where someone compares how 'forgiving' the headphones are to source/ enough power.

V-moda m-80s are incredibly forgiving, and work just as well unamped as they do amped. They excel in anything involving vocals IMO, mids are amazing. The treble is still there, but it's a bit flatter than the mids and lows. 

 

[preferedu]

I have The KRK KNS 8400 it is a monitor headphone reasonably flat not perfect but reasonable can be driven with a computer headphone out but like most studio phones an amp or interface feeds them better and they sound better. Isolation is good .They are very revealing to the point of  being un forgiving of a crappy signal . Highs can get harsh when used with computer phone out  at higher volume on 128~ kb Mp** might be better on higher bit rate . I'm using the KRK's now on interface/ preamp  They got better  especially after about a week of use. 
They sound very balanced and  decent when fed with a clean robust  signal they can do 108 dB SPL  max .THD of 0.1% is good you won't hear it  if you feed it clean.   Good soundstage bass is clean and tight but not overemphasized  it is a little underwhelming if anything mids and highs are articulate detail is  very good but not spectacular. response is 15-25 k feed them  some good old school music you will hear    some low down clean balanced  bass good detail and horns excellent for Jazz I'm feeding them some old Ray Charles .flac rips right now have to say pretty good .
They tend to be more analytical/neutral  than musical but they are monitors by desighn oh  very good sound stage.  If you have heard KRK studio monitors then you get the idea they are voiced similarly . 
They might struggle with a portable  IMO although at 36 ohms and 97 dB @1mW sensitivity theoretically they could work well especially with a little Fios amp.  YMMV 
I've always thought studio phones and portables were an oxymoron but I could be wrong and Apple has that new  ALAC codec now.  I'm no expert there.
If you have a guitar center or any music store or even a worst buy near you take your device and take some phones for a listen  bought  these after test driving some others.  These KRK's  sounded better than some more expensive stuff. ~ within reason . The AKG 240s  is close they have a little more bass I might get a pair for variety I liked the AKG's  That being said .
plenty of folks here are in the know best regards and good luck  
 
EDIT a Review at Musicians  Friend Might be helpful one reviewer said he loves these on his iPod ?   there are some other reviews there 
Link :  http://www.musiciansfriend.com/pro-audio/krk-kns-8400-studio-headphones

 

[WhiteCrow]

Quote:

I've heard the HD25's, K271's, M50's, and DT770's Pro's, and I think of them, the AKG K271's would best suit your needs.
 
The HD25's and K271's have comparable isolation (both are excellent at isolating), but I prefer the K271's sound. They have a little less bass, but the mids and highs are smoother (while still retaining a great deal of detail and energy).
 
The DT770 Pro's and the M50's have weaker isolation, but both are still above average. They are both on the bassier side, but the DT770 Pro's are more well rounded, thanks to their more pronounced mids. They are also much more comfortable, and have a bigger soundstage.
 
Between the K271's and DT770 Pro's, I prefer the K271's for most music, though the DT770 Pro's might be better for movies, since they are more comfortable. Not to say the K271's aren't comfortable though, I've put plenty of hours on them without taking breaks.
 
The K271's are also a little easier to power, and come with extra pack-in stuff like extra ear pads and an extra cable.

I would say its a draw between the HD25, K271, and DT770. They all do different things so well and it really just depends on what you are willing to settle with. HD25 are better for on the go listening, but K271 are a more Involving sound so to speak. the DT770 are just giant fun bags that wont disapoint either. Keep in mind you can't go wrong with sound on any of them IMO.