This all started when I got a HD600 loaner from Jay. I told him I haven’t listened to the HD600 for a while, and asked him if I can borrow his HD600. Being the generous guy that Jay is, the HD600 arrived at my desk without much delay. The HD600 is similar to the HD650, but in a way it’s also different enough as it offers some things that you can’t seem to get with the HD650. I really enjoyed the HD600 that I decided to buy a new-old-stock HD580, which was discontinued a while ago. Now that I have all three members of the Trio in my hand, I decided to write a brief comparison between them.

The Trio apparently started life back in the Spring of 1993, with the release of the HD580 (there was also a wireless digital infra red HDi850 released in August 1993). Thanks to Tyll’s wonderful article at HeadRoom, I can get a sense of what it was like back then to have a HD580. To quote Tyll:

“The dynamic cans available in those days just wouldn’t hold a candle to the speed of the Mylar diaphragms and dedicated electronics of the e-stats. Then Sennheiser introduced the HD 580 and everybody that cared about headphones (there were like twelve of us back then) were stunned.”

“The HD 580 had punch and warmth, most headphones of the day were thinner sounding. There was speed and coherence up top, not the confusion and congestion that characterized the under-engineered “accessories” as they were thought of at the time. Sennheiser had really put some thought into these new cans and it was easy to hear.”

It seemed clear that the HD580 was quite a successful product, and on Sennheiser’s 50th Anniversary in 1995, the HD580 Jubilee Edition was released. The Jubilee is a limited edition version of the HD580 with a glossy carbon fiber look finish, a special box and special certificates. After the limited edition release is finished, Sennheiser continued the Jubilee into a regular production in 1996 as the HD600 (though without the certificate and the carbon fiber finishing). The HD600 supposedly have better acoustics and tighter driver matching than the HD580, although I can’t seem to differentiate the sound between the two (when you’ve changed the grills on the HD580, more on that later below).

In 2003, 10 years after the HD580, Sennheiser released the HD650. It seemed that they went around consulting almost everyone who cares about headphones, from high end audio people, engineers, journalists, and even internet forum members. From the HD650 Press Release:

“In their quest to develop even better dynamic headphones, Sennheiser consulted high-end specialists, sound engineers and trade journalists. They even consulted internet forums to complete the picture. This intensive research revealed an interesting fact: that listening habits have changed. Today, people prefer to “feel” the music rather than to analyze it. The result was the HD 650 – headphones that captivate the listener with the ultimate in lifelike reproduction, while still maintaining absolute precision.”

Indeed the research very accurately captured the kind of sound that people want to hear in a headphone. So accurate in fact, that even today many people still prefer the HD650 over the HD800′s sound. The HD650 become a headphone synonymous with its coloration, albeit a very pleasing coloration. While other headphones come and go, the HD580/600/650 continues to be respected among the enthusiasts circles, even by people who don’t enjoy them. At one point, the HD580, which is essentially a marked down HD600 is available for as low as $120. Never before has reference quality been so affordable. In the midst of the current race of $1,000 flagship headphones, I started to look back to the years when you can get the “best” headphone for merely $300.

HD650 disassembled.

Digging up further, I found an article by Wes Phillips that outlined even more of the changes on the HD650:

Sennheiser has actually used a tougher metal mesh for the earcups that shouldn’t dent as easily as the old stuff. (I welcomed this news — my 600s, which have traveled to many a recording session, are quite banged up.) The whole structure of the HD 650 seems far more solid and less resonant than that of its predecessors, possibly as a result of a stronger spring in the headband. Sennheiser states that it has beefed up the 650′s “baffling damper” — a membrane that controls the chamber resonances of and within the earcups themselves — for “tighter acoustic control.” If that means the headphones feel dead-quiet and free from any structural vibration, then: mission accomplished.

But the biggest changes in the HD 650 are the aluminum voice-coils, the new diaphragm material, and a Kevlar-shielded OFC cable that sports a dedicated 1/4″ phono plug (a phono-to-miniplug “cable reducer” is also provided). In addition to being made of a different material, the 650′s diaphragms are constructed differently — it’s a membrane of variable thickness that has been tuned by ear. Not only by ear — Sennheiser has comprehensive test and measurement facilities — but engineer Axel Grell found that when the ‘phones measured flat, they sounded harsh. So he very carefully tuned the response to have notches at 5kHz and 16kHz. These notches, speculates headphone maker-designer Tyll Hertsens, of HeadRoom, mimic the ridge notches of the concha — the largest and deepest concavity of the external ear, or pinna — which help you determine the azimuth and elevation of sounds.

So, from Wes Philips’ article, we learn of some additional differences between the HD650 to the predecessors. The HD650 has a more solid structure — this I can confirm. Not sure about the metal mesh, as I don’t want to damage my headphone to test it out, but that’s also possible. The beefier baffling damper is possible, seeing that the color for the HD650 assembly may indicate slightly different plastic material. All these changes would most probably contribute to a better acoustics, something that is definitely heard on the HD650. Then there is also the aluminum voice-coil, new diaphragm material, and a new cable. Interesting indeed. I won’t talk too much about the cables, but the aluminum voice coil and the new diaphragm with variable thickness may contribute very strongly to the superior HD650 soundstage (as we will discuss more thoroughly later).

With the right set up, the HD600 and the HD650 proved to be just as enjoyable to my ears as any of the thousand dollars offerings. Take the HD800 for instance, it has gobs of technicality superiorities over the HD650, and yet it didn’t win as many converts as the HD650 did. At a certain level, any additional technical superiority becomes irrelevant. And even if the HD650 may be inferior to new $1,000 flagships, it has enough technicalities to please just almost everyone outside the Electrostats-addicts. Perhaps the Sennheiser engineers were right when they opted for musicality rather than accuracy in developing the HD650.