[bigshot]

No, they didn't sound muffled, although the upper mids were a little recessed. They were the closest I could find to something that sounded like speakers. A lot of headphones have accentuated upper mids and treble, and it was easier for me to adjust with EQ for the narrow range of recessed mids than it was to pull back a whole range of sound.
 
But with mid priced headphones the sample variation might be a lot. I think Sennheiser has a manufacturing tolerance of at least +/-3dB, so two identical pairs of cans might not sound the same at all.

 

[Music Alchemist]

  No, they didn't sound muffled, although the upper mids were a little recessed. They were the closest I could find to something that sounded like speakers. A lot of headphones have accentuated upper mids and treble, and it was easier for me to adjust with EQ for the narrow range of recessed mids than it was to pull back a whole range of sound.
 
But with mid priced headphones the sample variation might be a lot. I think Sennheiser has a manufacturing tolerance of at least +/-3dB, so two identical pairs of cans might not sound the same at all.

 
Hmm. I sent them back as defective, anyway.
 
A few other headphones that are said to sound similar to speakers in some respects are the Abyss AB-1266 (which the OP owns), Sennheiser HD 800, and AKG K1000.

 

[Music Alchemist]

@bigshot
 
Do you know the best way(s) to equalize headphones? The two links I provided a few posts ago involve doing it with precision, but it looks a little complex. If there's a simpler way to attain the same result, I'm all ears.

 

[bigshot]

I've got some reference recordings of acoustic music that I use for balancing by ear. I had my sound mixer friend come in and run tones on my current headphones. You can also look at response graphs on the internet and inverse them, but they usually don't relate to what human ears hear for some arcane reason.

 

[RRod]

 
Edit - BTW, I am also looking at getting a desktop amp to drive my HD 598s.  Do I really need an amp at all for moderate listening levels (instead of my iPhone 6)?  Do I get a O2, Magni, Asgard, Matrix-M, or start looking at tube amps / balanced designs?  The mind boggles ...

 
At moderate levels you should be ok with the iPhone. If you just have to have peaks at 120dB, then you will be want for juice. I can't even use my 598s with my Magni b/c it's too darn powerful for them; the Asgard works given the low-gain switch, but my iPod Classic handles them fine at about 75% volume or so. I haven't noticed any clipping or distortion yet.

 

[davidsh]

There's also the stax sigma

 

[jrbdmb]

   
At moderate levels you should be ok with the iPhone. If you just have to have peaks at 120dB, then you will be want for juice. I can't even use my 598s with my Magni b/c it's too darn powerful for them; the Asgard works given the low-gain switch, but my iPod Classic handles them fine at about 75% volume or so. I haven't noticed any clipping or distortion yet.

 
No, I don't notice clipping with the 598s and the iPhone, but I'm often got the volume set just a few steps below max, esp. on classical music which tends not be mastered as loudly overall as most recent rock / pop.  I also wondered about performance around 100 Hz or so, where the measured impedance (as per headphone.com) is just below 300 ohms, far above the 50 ohm nominal value.  Beginning to think if I do anything, it will be a smaller amp like the O2 or C5.

 

[RRod]

   
No, I don't notice clipping with the 598s and the iPhone, but I'm often got the volume set just a few steps below max, esp. on classical music which tends not be mastered as loudly overall as most recent rock / pop.  I also wondered about performance around 100 Hz or so, where the measured impedance (as per headphone.com) is just below 300 ohms, far above the 50 ohm nominal value.  Beginning to think if I do anything, it will be a smaller amp like the O2 or C5.

 
Pretty much all I listen to on it is classical, but you might like things louder than me. The impedance bump is there, but if you look at the frequency response plots you won't see a sudden dip due to the it. The bump has to do with the resonance of the headphone, and its effects are negated more by having a low enough output impedance of the amp (that is, low enough for the frequencies with lower impedance). If you want peace of mind get a small amp, but if the sound is loud enough and you hear no distortions or clipping (which should be obvious), why spend the moola?

 

[cel4145]

Pretty much all I listen to on it is classical, but you might like things louder than me. The impedance bump is there, but if you look at the frequency response plots you won't see a sudden dip due to the it. The bump has to do with the resonance of the headphone, and its effects are negated more by having a low enough output impedance of the amp (that is, low enough for the frequencies with lower impedance). If you want peace of mind get a small amp, but if the sound is loud enough and you hear no distortions or clipping (which should be obvious), why spend the moola?

Isn't the output impedance on iPhones low enough for the HD598s according to the 1/8 rule?

 

[Ruben123]

Yes.

 

[RRod]

Isn't the output impedance on iPhones low enough for the HD598s according to the 1/8 rule?

 
Yes exactly. With that taken care of it's all about driving power, and I've never found even my old iPod classic wanting with the 598s. If I wanted my peaks higher, maybe I'd need an amp, so that's my point to jrbdmb: decide what you need and assess if you have it already or not.

 

[PDVJAM]

   
That's the problem with online ABX results; you either trust em or you don't. More and more I feel like I should tell people "do an ABX for yourself and take from it what you will, but don't expect me to believe the outcome online." I do doubt in this case that the tester bothered to rig logs with 80+ trials, but it's not exactly hard or time-consuming to do with a PC in front of you. But I'm willing to believe these and recommend people just test for themselves the audibility of various lossy algorithms and bit rates. Besides, people like me with ears blown out from playing actual music live shouldn't exactly be the torch-bearers of lossy audibility ^_^

 
Sorry for necroposting, but foobar2000 ABX tester has some signature that somehow should tell you is this test was valid or not.
BTW, I can't hear any difference between flac and mp3 320 (latest lame, cbr) for, for example, Tomorrow's Eve - The Years Ahead. Or Wintesrun - Starchild. I got something like 1/10 in foobar abx test.
But I've found a music track where the difference is easily audible: Schola Cantorum / Hymn to the Virgin, catalog number 2L-095-SABD. I did 2 testes, one with HD650, one with AM10SE (from headphone output of lenovo y500).
 
There are the results:

Spoiler: Warning: Spoiler!

foo_abx 2.0 report
foobar2000 v1.3.3
2015-03-17 20:45:53

File A: 05. Morten Lauridsen - O nata lux.flac
SHA1: 1de929dca9d214d1670a4af2cbcd3d83e2c1bb75
File B: Schola Cantorum - Hymn to the Virgin - 05 - Morten Lauridsen- O nata lux.mp3
SHA1: f5e0ee6b8f8bce963982c83d342597714877d7db

Output:
DS : Primary Sound Driver
Crossfading: NO

20:45:53 : Test started.
20:47:07 : 01/01
20:47:21 : 02/02
20:47:31 : 03/03
20:47:41 : 04/04
20:47:52 : 05/05
20:48:03 : 06/06
20:48:19 : 07/07
20:48:30 : 08/08
20:48:47 : 09/09
20:49:04 : 09/10
20:49:04 : Test finished.

 ----------
Total: 9/10
Probability that you were guessing: 1.1%

 -- signature --
aa66adbda906cc18f40dc0d4cb3701fccfaf462a

 

Spoiler: Warning: Spoiler!

foo_abx 2.0 report
foobar2000 v1.3.3
2015-03-18 10:40:38

File A: Schola Cantorum - Hymn to the Virgin - 05 - Morten Lauridsen- O nata lux.mp3
SHA1: f5e0ee6b8f8bce963982c83d342597714877d7db
File B: 05. Morten Lauridsen - O nata lux.flac
SHA1: 1de929dca9d214d1670a4af2cbcd3d83e2c1bb75

Output:
DS : Primary Sound Driver
Crossfading: NO

10:40:38 : Test started.
10:40:54 : 01/01
10:41:15 : 02/02
10:41:34 : 03/03
10:41:58 : 04/04
10:42:09 : 05/05
10:42:21 : 06/06
10:42:42 : 07/07
10:42:49 : 08/08
10:43:00 : 09/09
10:43:07 : 10/10
10:43:07 : Test finished.

 ----------
Total: 10/10
Probability that you were guessing: 0.1%

 -- signature --
98b8f0adbb0be46abfb6e533fb7f2921d906f09f

 
First one was with AM10SE, the second one - HD650.
I did a mp3 rip myself (320 cbr, LAME3.99r) from 24/96 original.

 

[RRod]

Seeing as how choral music is that last place I'd think 24 bits or 96kHz are useful, what exactly were you hearing? This is why I don't trust online results or foobar's black box, nothing ever adds up to a cohesive story about what difference people can hear.

 

[PDVJAM]

I would say something with voices, like reverberation. It is very obvious.
You can try it yourself, this archive contains both files: https://www.dropbox.com/s/4rtglqc2mlanftj/HTTV.zip?dl=0

 

[RRod]

  I would say something with voices, like reverberation. It is very obvious.
You can try it yourself, this archive contains both files: https://www.dropbox.com/s/4rtglqc2mlanftj/HTTV.zip?dl=0

 
The differences between 320 and Redbook, at least, are not supposed to be obvious. Whenever that word is dropped I am automatically suspicious 

 I'll check out the files, thanks!