[Music Alchemist]

I don't really find the HD 650 too dark personally, but rather it's a bit too warm with some slight extra energy in the 9-10k that shouldn't really be there, it is a bit more refined than the HD 600 though. Honestly some sort of mixture of the HD 600 and HD 650 would be about perfect tonality wise, I'm honestly likely not going to get anything more expensive than an LCD-2 personally. I'm about to stop spending anymore in this hobby for a long period of time honestly.

 
To me, dark and warm are the same thing. What's the difference, in your opinion?

 

[SodaBoy]

HD600 response in blue, HD650 response in green, both new pads (Credit to Solderdude).
 
The HD650 is not a dark headphone compared to the HD600, the two headphones sound very similar. This has been discussed before by various people, including me, who have listened to both headphones extensively. This can also be confirmed by measurements from Tyll Hertsens. That's all, anyone is free to disagree but I would like to see objective data.

 

[Sefelt103]

This differs a bit from your curves, which one is correct. I always thought the HD650 was darker than the HD600, hence its much greater popularity with the masses compared to the HD580/600

 

[kman1211]

To me, dark and warm are the same thing. What's the difference, in your opinion?

Accurate warmth is generally has to do with the upper bass and lower mids having proper presence. Too much warmth is essentially too much emphasis in this area causing almost a suffocating effect to the sound. Too little can cause the headphone to sound somewhat thin and lacking in proper body. Darkness has to do with the treble region having a bit too little energy. Most extra warm headphones do tend to be dark.

 

[kman1211]

HD600 response in blue, HD650 response in green, both new pads (Credit to Solderdude).

The HD650 is not a dark headphone compared to the HD600, the two headphones sound very similar. This has been discussed before by various people, including me, who have listened to both headphones extensively. This can also be confirmed by measurements from Tyll Hertsens. That's all, anyone is free to disagree but I would like to see objective data.

That is a bit different than some graphs I've seen but I agree, I don't really find the HD 650 dark compared to the HD 600 personally, if anything it's a bit brighter in the upper treble than the HD 600.

I have owned both headphones for a while now and don't really find them all that alike. Similar yes, but distinctly different at the same time.

 

[Music Alchemist]

  HD600 response in blue, HD650 response in green, both new pads (Credit to Solderdude).
 
The HD650 is not a dark headphone compared to the HD600, the two headphones sound very similar. This has been discussed before by various people, including me, who have listened to both headphones extensively. This can also be confirmed by measurements from Tyll Hertsens. That's all, anyone is free to disagree but I would like to see objective data.

 
Some people think the HD 600 is dark/warm too.

 
The HD 800 is definitely more neutral than the HD 600. Just look at the measurements.
 
http://cdn.head-fi.org/a/a9/a9650bb7_Sennheiser_HD800_Frequency_Response_HRTF.png
http://www.innerfidelity.com/images/SennheiserHD800.pdf
http://www.innerfidelity.com/images/SennheiserHD600.pdf
 
The green line in the first graph is the flat speaker HRTF. The black line is the Harman-Olive HRTF, which is an average of the sound people prefer. Ignore the latter and the mislabeling. Look how closely the raw grey measurements follow that green line, then compare the HD 800 InnerFidelity measurements to that of the HD 600.

 

[TMRaven]

For me, the most accurate/close to overall neutrality I've heard given the frequency balance as a whole:
 
1. HD-800 with mods/shelved treble via eq -3db 6khz up
2. HE-560 with eq +3db 2khz, -3db 4khz and Focus Pads-A
3. HD650 (silver damping) 
4. LCD3 (pre fazor)
5. HD600 (silver damping)
6. PM-3
7. Focal Spirit Professional
8. LCD-X
9. T1

 

[Music Alchemist]

My best friend told me this privately, in response to some of the info in this thread. (He does not post here much.) I hope it's okay that I quote him:
 

I have no idea why Audezes ever show up in natural or neutral lists. They sound amazing but every single Audeze I've heard is so faaaaaaaaaaaaaaaar from natural and neutral it's ridiculous. This is by no means negative I need to keep emphasising, it's just that they simply aren't natural sounding.
 
One thing I'm surprised with is that people think that the HD800 particularly and the SR-009 to some extent is treble focused. Most people into head-fi (especially the ones who own $1000+ headphones) are 30/40 years+ unlike myself, and if anything their hearing should have deteriorated such that they don't hear the high end nearly as well. Whereas someone young like me often hears really high pitched noises that really annoy me that none of my older colleagues can hear. You'd think they'd be less likely to notice the treble in the HD800 and SR-009 but it's the other way around. I suspect there must be something going on. Like say they lose the highest notes but that in turn amplifies the usual musical treble to them or something. Cos you know that I think the HD800 is as neutral as it gets. Weird.  

 

  For me, the most accurate/close to overall neutrality I've heard given the frequency balance as a whole:
 
1. HD-800 with mods/shelved treble via eq -3db 6khz up
2. HE-560 with eq +3db 2khz, -3db 4khz and Focus Pads-A
3. HD650 (silver damping) 
4. LCD3 (pre fazor)
5. HD600 (silver damping)
6. PM-3
7. Focal Spirit Professional
8. LCD-X
9. T1

 
Interesting that the LCD-3 ranks higher for you. I always hear about how the LCD-3 (especially the old version) is so dark, warm, lush, etc.
 
And the measurements support this: http://cdn.head-fi.org/0/0e/0ef3958e_Audeze_LCD-3Rev2SN2613375_Frequency_Response_HRTF.png (Note the mislabeling mentioned in my above post.)
 
So I'm wondering...what makes it sound so neutral/accurate to you despite the mids and treble being far below neutral?

 

[TMRaven]

I wouldn't be so quick to generalize about the majority of people into head-fi being old.  Seems as though there's a lot of younger asians into the hobby too.  Literally most everybody I've known from the hobby or shipped stuff to/received from has been Asian.  Maybe they like their brightly mastered k-pop and can't stand HD800 treble, who knows.  I jest of course.
 
Frequency response charts aren't everything there is to determining accuracy.  The PM3 follows the harman target response the closest of all the headphones on my list, yet it ranks only 6th, because its closed-back nature and... Oppo driver nature, makes it so that it sounds cramped and not as articulate as a more realistic sounding headphone like the Hifiman or the Sennheisers.
 
Conversely, if you compare apples to apples and look at Headroom's direct comparison of LCD-X vs LCD3 frequency charts, you will see that LCD3 isn't as dark as the LCD-X, which my subjective impressions confirm.  I rank the LCD3 so high because it is very even-handed from bass midrange all the way up to say 4khz, while only showing some deviation in the lower-mid treble, and being slightly elevated in upper-treble.  What it lacks in is articulation, favoring a syrupy, smoothed over sound rather than a snappy one.  Things in real life aren't that syrupy sounding.  And no, this has nothing to do with a lack of treble, it's just the Audeze house sound (for LCD series anyways.) 

 

[goropeza]

+1 I never thought Audezes sounded natural either.

 

[Aizura]

From most natural to least natural sounding:
 
1: DT48
2: ER4S
3: HD600
4: HD800
5: RS1i
6: HD25-1
7: iPhone loudspeakers
8: random $5 battery powered Bluetooth speaker
9: Ultrasone Pro 900

 

[SodaBoy]

I've been looking at these measurements from Innerfidelity:
 
http://www.innerfidelity.com/images/SennheiserHD600.pdf
http://www.innerfidelity.com/images/SennheiserHD650.pdf
 
Very similar FR graphs, like twins in the headphone world. Key differences seem to be better driver matching for the HD650s, and lower levels of higher-order distortion. The HD6XX headphones are still reference grade, and you would have to move up to the HE-560 to surpass that duo.
 
On the Audezes...
 
I heard the LCD-2 when it was first released, and I was shocked at how dark it was compared the HD650s I a/b'ed them with. I'm sure the subsequent revisions have fixed some of the issues, but the treble remains shelved. This is a shame because the LCD series have extremely low distortion and excellent impulse response, matching even the SR009. The HE-560 on the other hand, is less damped with slightly higher distortion, but is much more linear in its FR, pretty excellent overall.

 

[Music Alchemist]

  I've been looking at these measurements from Innerfidelity:
 
http://www.innerfidelity.com/images/SennheiserHD600.pdf
http://www.innerfidelity.com/images/SennheiserHD650.pdf
 
Very similar FR graphs, like twins in the headphone world. Key differences seem to be better driver matching for the HD650s, and lower levels of higher-order distortion. The HD6XX headphones are still reference grade, and you would have to move up to the HE-560 to surpass that duo.
 
On the Audezes...
 
I heard the LCD-2 when it was first released, and I was shocked at how dark it was compared the HD650s I a/b'ed them with. I'm sure the subsequent revisions have fixed some of the issues, but the treble remains shelved. This is a shame because the LCD series have extremely low distortion and excellent impulse response, matching even the SR009. The HE-560 on the other hand, is less damped with slightly higher distortion, but is much more linear in its FR, pretty excellent overall.

 
I've only owned and heard the HD 650. I liked it a lot. Sounded very nice, but still way too dark -- darker than certain studio monitor headphones that are still too dark to be neutral -- for my purposes. Smoothed over some detail too. I think the most common thing I hear from people who want to buy it is that they want something warm and smooth, so that could be a good thing for them, but I'm looking for the most accurate headphones out there. Kinda get the feeling that I'll have to get an SR-009 or similar system to be satisfied.

 

[kman1211]

Some people think the HD 600 is dark/warm too.

The HD 800 is definitely more neutral than the HD 600. Just look at the measurements.

http://cdn.head-fi.org/a/a9/a9650bb7_Sennheiser_HD800_Frequency_Response_HRTF.png
http://www.innerfidelity.com/images/SennheiserHD800.pdf
http://www.innerfidelity.com/images/SennheiserHD600.pdf

The green line in the first graph is the flat speaker HRTF. The black line is the Harman-Olive HRTF, which is an average of the sound people prefer. Ignore the latter and the 0mislabeling. Look how closely the raw grey measurements follow that green line, then compare the HD 800 InnerFidelity measurements to that of the HD 600.

You should watch Tyll's explanation video of frequency response and the target curve, he explains why the HD 800 is too bright for neutral and why it doesn't properly fit the harmen curve for headphones. The treble doesn't slope down quick enough after the slope up, a similar problem with the AKG K701 treble. What makes the HD 800 great is low distortion and how good it's square waves but measurements show its too bright. The HD 800 is more neutral than the HD 600 until you get to the treble. The PM-3, HP50, focal spirit pro/classic, and DT 150 follow the harmen curve better than the HD 800 or HD 600/650.

 

[metal571]

You should watch Tyll's explanation video of frequency response and the target curve, he explains why the HD 800 is too bright for neutral and why it doesn't properly fit the harmen curve for headphones. The treble doesn't slope down quick enough after the slope up, a similar problem with the AKG K701 treble. What makes the HD 800 great is low distortion and how good it's square waves but measurements show its too bright. The HD 800 is more neutral than the HD 600 until you get to the treble. The PM-3, HP50, focal spirit pro/classic, and DT 150 follow the harmen curve better than the HD 800 or HD 600/650.

This is simply correct. There is a prominent 6k spike but everything else before is very accurate.