[kman1211]

  Thanks for all that! Good stuff. As I posted earlier, I'm going to get the 600 to compare to my long term 650 and hear for myself.

No problem. I owned both for a while, sold both, regret selling the HD 600 as I never got a real replacement/upgrade for it as I did with the HD 650. You should like the HD 600 quite a bit, curious which you will prefer long term. I also found the two to react a more differently on different amps and gear more than I expected.

 

[StanD]

  Thanks for all that! Good stuff. As I posted earlier, I'm going to get the 600 to compare to my long term 650 and hear for myself.

I A/B compared them (including the 700 and 800) on the same amp etc. using loops of the same pieces of music for over an hour before purchasing the HD600. I was expecting to purchase the HD650, possibly upping to the HD700.
I found the HD700's treble to be excessive at the point of being strident. Compared to the HD600, I found the treble of the HD650 a little bit subdued with no increase of presence. Although the 650 has a bit more sub bass, combined with the lesser treble I decided to go with the HD600 and keep some of my money in the wallet. In any case I did some careful listening and will say that the 650 is still an excellent headphone.

 

[rgs9200m]

Thanks. OK, now that I have both, I'm kind of amazed at how much I like the HD600 also. It has a more direct sound, with the vocals and central images just coming at me with great detail, force, and a wealth of texture, and even some shout, but all in a non-abusive way. It sort of leans to the Grado flavor that I also like.
It's very dramatic and compelling and fun, whereas the 650 is more ambient, with more hall-like overtones, where I am more aware of the atmosphere, reverb, and things in the very low sub-bass and the uppermost highs.
 
With the 650, I often keep turning up the volume to hear more presence, but the 600 is is just right there and present already, so I find that I listen at (slightly) lower levels and don't feel the need to pump up the volume.
Which of the 600 and 650 I like better will depend on my mood. I see what is meant by the 650 being more refined.
The 650 is more speakerlike, and the 600 is more in the traditional headphone mold, where it just grabs me and rivets my attention.
So these are different sounding headphones, more than I expected, and I'm keeping both.
 
I think I see the evolution of Sennheiser sound, where the 650 sounds like an effort to get a larger, room-filling sound with less central image emphasis than the original 600, and later the 800 went much further in that direction, with super-soundstaging and a kind of distant imaging approach (which I find to be not engaging enough and is why I sold my HD800 an reverted to my 650 and now both the 600 and 650).
 
It's amazing what the 6xx series can do and is a big favorite of mine among headphones of any cost. The 600 especially is extremely compelling. Both it and the 650 are absolutely great and I see why they are classics, the dean of high end headphones IMHO.

 

[ZoNtO]

  I A/B compared them (including the 700 and 800) on the same amp etc. using loops of the same pieces of music for over an hour before purchasing the HD600. I was expecting to purchase the HD650, possibly upping to the HD700.
I found the HD700's treble to be excessive at the point of being strident. Compared to the HD600, I found the treble of the HD650 a little bit subdued with no increase of presence. Although the 650 has a bit more sub bass, combined with the lesser treble I decided to go with the HD600 and keep some of my money in the wallet. In any case I did some careful listening and will say that the 650 is still an excellent headphone.

 
Congrats on the purchase! I'm sure you'll be happy with the HD600 for a long time. There's a reason it's still on InnerFidelity's Wall of Fame for open headphones.
 
What you described reflects the minor frequency response differences between the HD600 and HD650:
 

 
Frequency response isn't the only difference between the headphones though. From the link, with my comments:
 
Quote:

Let’s start with some quick facts: . . . 
 

1. The HD600 is more neutral, the HD650 more colored. [evident from the FR plots]
2. The HD600 is more forward, the HD650 is more laid back. [a function of the midrange peak around 3-4kHz; this can be fatiguing on some mixes]
3. The HD650 is darker, while the HD600 has more lower treble and upper midrange presence. [likely a function of the difference in response after 8-9kHz]
4. The HD600 has a more balanced frequency response (one of the best, in fact), the HD650 is more low-end heavy. [see above]
5. The HD600 can maintain a faster pace, the HD650 is generally slower. [I can see this as it's well-documented that the HD650 is better damped and has lower distortion measurements. The HD600 is less damped, so subjectively seems "faster" with its comparatively flabby bass.]

 
The main advantages of the HD650 are the lack of the midrange peak and lower distortion, in addition to whatever benefits can be attributed to the enclosure and/or cable. What you heard at the shop is the reason why many of us perform a few basic modifications to the HD650 (front foam "coin mod," removal of rear foam and spider, and mass loading in strategic portions of the enclosure and driver lollipop). These mods result in (1) much lower bass distortion and (2) an increase in clarity and treble response due to the foam removal between the driver and listener's ears. 
 
Pretty amazing that the HD600 are 20 years old this year. I started with the HD650, but purchased an HD600 this year to keep as a baseline and because I respect them so much for their age. (Same reason I keep my Etymotic ER4P.) However, I typically prefer the HD650 modded to the HD600 in most instances, simply due to the lack of the midrange peak. Love the 600's treble response though!

 

[kman1211]

  Thanks. OK, now that I have both, I'm kind of amazed at how much I like the HD600 also. It has a more direct sound, with the vocals and central images just coming at me with great detail, force, and a wealth of texture, and even some shout, but all in a non-abusive way. It sort of leans to the Grado flavor that I also like.
It's very dramatic and compelling and fun, whereas the 650 is more ambient, with more hall-like overtones, where I am more aware of the atmosphere, reverb, and things in the very low sub-bass and the uppermost highs.
 
With the 650, I often keep turning up the volume to hear more presence, but the 600 is is just right there and present already, so I find that I listen at (slightly) lower levels and don't feel the need to pump up the volume.
Which of the 600 and 650 I like better will depend on my mood. I see what is meant by the 650 being more refined.
The 650 is more speakerlike, and the 600 is more in the traditional headphone mold, where it just grabs me and rivets my attention.
So these are different sounding headphones, more than I expected, and I'm keeping both.
 
I think I see the evolution of Sennheiser sound, where the 650 sounds like an effort to get a larger, room-filling sound with less central image emphasis than the original 600, and later the 800 went much further in that direction, with super-soundstaging and a kind of distant imaging approach (which I find to be not engaging enough and is why I sold my HD800 an reverted to my 650 and now both the 600 and 650).
 
It's amazing what the 6xx series can do and is a big favorite of mine among headphones of any cost. The 600 especially is extremely compelling. Both it and the 650 are absolutely great and I see why they are classics, the dean of high end headphones IMHO.

Glad you are enjoying them so much. Seems you find the HD 600 and HD 650 as different as I did. You did explain the differences better than I did, but that's how I view the two as well. 

 

[rgs9200m]

Thanks. I've always liked Wes Phillips' Stereophile review of the HD600 from when they were new. If you never read it, it's a good read and still feels right today:
http://www.stereophile.com/headphones/408/#BDfJyj6YuWljxKKo.97
[and the Sam Tellig sidebar]
http://www.stereophile.com/content/sennheiser-hd-600-headphones-sam-tellig-hd600s#6pTe2EEydU6LHEhS.97

 

[StanD]

   
Congrats on the purchase! I'm sure you'll be happy with the HD600 for a long time. There's a reason it's still on InnerFidelity's Wall of Fame for open headphones.
 

I bought mine years ago, so it's been a long time already. It actually holds its own with my Orthos/Planars that I paid much more for.

 

[kman1211]

  Thanks. I've always liked Wes Phillips' Stereophile review of the HD600 from when they were new. If you never read it, it's a good read and still feels right today:
http://www.stereophile.com/headphones/408/#BDfJyj6YuWljxKKo.97
[and the Sam Tellig sidebar]
http://www.stereophile.com/content/sennheiser-hd-600-headphones-sam-tellig-hd600s#6pTe2EEydU6LHEhS.97

Thank you for the review. It was a nice read. I should be getting the HD 600 again in a month or two. Looking forward to having a pair again. I let go of the HD 650 because imho the Nighthawks do the darker lush speaker-emulated sound better than the HD 650. I did find the K712 quite similar to the HD 600 but while faster and tighter sounding wasn't as transparent in the upper mids and treble as the HD 600 and I felt the HD 600 was better overall on most gear, on summit-fi gear the two traded blows though. I agree with you about the HD 800 overdoing the soundstage, I did like the HD 800S a lot better as it didn't go as overboard with the soundstaging. Something I realized over time is I like center focused and intimate headphones more than the spacious ones, there are some exceptions to this but as a general rule I just have more fun with headphones with a more direct sound like the HD 600.

 

[ETanner]

For those of you who've used the HD600s both SE and Balanced on the same amp, are the benefits significant? I'm pleased enough with mine that I'll be upgrading other equipment before buying new phones. Currently I'm running Valhalla 2 in front of my Bimby. With the new Schiit Jot I'm thinking about running it with the phono add-in and using the phones with it some. Since I've got a Schiit Sys I might split the Bimby to that new amp also.

 

[rgs9200m]

I always run my 650s and 600s balanced. Several yrs ago, I decided balanced was best on the 6xx with some experimentation back and forth. The bass is more transparent it seemed, along with other things.

 

[ubs28]

Whats the benefit of low output impedence?

I find i cannot drive my low impedence earbuds or headphones without hiss on my amp unless i set it to high output impedence

That means your amplifier is of low quality rather than a problem caused by the low impedance.

My Auralic Taurus MKII has no hiss with my Shure SE846 and Shure SE535.

My opinion is that amplifiers should always have a low impedance because it can screw up the frequency response of a headphone if the impedance is too high.

 

[Audioholic123]

I was a massive fan of the HD600 until I heard the AKG K712 Pro's. I have sold the HD600's now as I feel that the K712's scale better with more expensive equipment. I think the K712's are seriously underrated.

 

[FLTWS]

That means your amplifier is of low quality rather than a problem caused by the low impedance.

My Auralic Taurus MKII has no hiss with my Shure SE846 and Shure SE535.

My opinion is that amplifiers should always have a low impedance because it can screw up the frequency response of a headphone if the impedance is too high.

 
Out of curiosity is there a point in impedance where your experience tells you it's too high? or is it load dependent?

 

[RickB]

   
Out of curiosity is there a point in impedance where your experience tells you it's too high? or is it load dependent?

A rule of thumb I've read is that ideal output impedance should be 1/8 of the headphone's impedance. 

 

[audiojun]

For me damping ratio (impedance load/impedance source) is a matter of preference. High damping ratio makes the sound tighter and thin sounding. Low damping makes the sound softer and thicker. Higher damping is generally better for most people, it allows for better control of drivers, it also improves transients and dynamics.