Classical Music Shootout: AD2000, HD650/600, K701/K501 (sorry, longwinded)
Sep 10, 2006 at 10:23 PM Thread Starter Post #1 of 91


500+ Head-Fier
Apr 12, 2004
Classical Music Shootout: AD2000, HD650/600, K701/K501
(sorry, this is a very longwinded read)

I’ve thought about doing something like this for a while, and now that I’ve accumulated a nice stable of highly regarded cans to play with, it’s fun to listen to them all and compare how they deliver different types of classical music. I picked some cuts from a few of my favorite CDs. All are great musical renditions captured on clear and ambient recordings. I thought about mixing in other genres as well, but maybe that can be another thread sometime. I don’t care for the vast majority of studio recordings through headphones, so I’m not going to venture too deeply into those waters.

Three of the headphones are TOTL for their type, and the HD600’s and K501’s were top dogs not long ago. In order to help level the playing field with the flagships, I used a Headphile V2 cable on the 600’s – would then put them in the price range of the both the 650’s and 701’s, still below the AD2000's. The K501’s are stock, but see how they certainly showed up on most of the events!

Anyhow, maybe some Headfiers might enjoy reading of my little journey here. It is specific to classical music that would resemble the below pieces, although some aspects will translate to other genres. As with all reviews, it is subjective – YMMV because MMDV!! If people like my approach, I can do a scaled back jazz shootout sometime with a group of cans.

The Recordings used:

E. Elgar, Symphony #1, esp. the 1st movment.
London Symphony, André Previn, cond.
Large orchestral texture, esp. shows soundstage, dynamics and detail in a large texture.

F. Chopin, Etude in C Minor, Op. 25, #12, and other cuts
Louis Lortie, piano
Shows midrange and depth of the stereo image.

M. Tournier: Sonatine for Harp.
Erica Goodman, harp
Shows a great deal of delicate detail and lifelike delivery of very intimate music

R. Vaughan Williams, from Songs of Travel:
The Roadside Fire, Whither Must I Wander & Bright Is the Ring of Words
Bryn Terfel, baritone; Malcom Martineau, piano
Male vocals with piano, shows detail and lifelike delivery in a small setting

J. Brahms: Phänomen, and various other cuts.
Judith Blegen, Soprano; Frederica von Stade, Mezzo-Soprano; Charles Wadsworth, piano
Female vocal duets with piano, shows placement of two voices in simple musical textures.

The Engish Concert, Trevor Pinnock, cond
Small orchestral texture, solo vocals and chorus, shows both soundstage and detail

Wagner: Prelude to Die Meistesinger (transcription), & other cuts
Mark Laubach, organ
Huge musical texture, with demanding sustained tones, from the deepest bass to the upper limits of audibility.

The Source Gear used:

Denon DN-600F CD player (used as transport), ART DI/O DAC with upgrades by Bolder Cable Co., Fisher X1000 and 500C tube amplifiers, both restored by Terry DeWick of Knoxville, TN.

The Denon is just an ok CDP, but functions very well as a sturdy and reliable transport with good operational features. The ART DI/O DAC is incredibly detailed, and the Bolder mods make it even cleaner and more dynamic than stock. For the listening tests, I used two vintage tube amps with fed from a splitter off the DAC, this so I could do quick comparisons of the headphones. I switched amp/can combinations during the tests to make sure that one amp wasn’t favored. The restored 1962 Fisher X-1000 is one of the Holy Grail units of vintage audiodom. The most powerful integrated amp that Fisher made, the preamp section develops incredible depth with great detail, and the EL34 amp delivers effortless dynamic power. The restored 1968 Fisher 500C 7591 amplifier was Fisher’s most popular unit and actually gives up very little to the X-1000, the differences between the two being very difficult to impossible to detect even with a blind A/B tester. The Fisher pieces are worthy of this challenge, no little toy amps here. Two or three cans going at once allowed me to switch between them quickly.


Here we go: Shootout at the Bach Chorale!

Test # 1: Large Orchestra - Elgar Symphony

AD2000 Very large and dynamic sound with a very tall and wide soundstage.. The brass have a nicely controlled brilliance. The strings are a bit dull sounding in the middle registers, with no “rosin on the bow”, although the violins can be pretty lively when they are high and loud. These aren’t the most lifelike cans of the bunch by any means with this CD, but still there is something quite pleasant about them. They are both spacious and smooth.

HD600 Very good balance top to bottom. Huge, yet still lively sound. The strings just seem to be a warm presence suspended in midair. The percussion timbrels are plenty dramatic enough, although less so than the K501

HD650 Sounds like overly restrained 600’s. My gosh, these things are smoooooth. The trombones and cellos sound like they are in front of the band, with everyone else back a bit. A setting of -1 on the bass and a +1 on the treble helps some. These are so refined and seem to be without any harshness anywhere, but I’d like just a little more definition and a bit less weight.

K701 Decent enough balance, refined, nice detail, but something is missing here. Difficult to nail down, but something in (or not in) the midrange is giving me a two dimensional feel here. The brass do have lots of fire, the strings have detail but do not have the sensuous wraparound of the 600’s or the vibrancy of the 501’s. Although they sound very good, these cans just don’t present this large texture with as much breadth as the others.

K501 OMG! Very lively. Sounds a bit like its big AKG sister, but with a much more open and free presentation, if a little less deep. The strings sound more vibrant than the 701’s, and all of the other instruments have a great deal more energy. The percussion really jumps out, simply fantastic!

Prizes: Oh so tough to call a winner between 1 & 2
1st - HD600 the appropriate big, full sound top to botom
2nd- K501 (with a +1 bass) very special, a little more fullness and this little feller might well have pulled the upset
3rd - HD650 gosh these sound nice, but with an overabundance of girth.
4th (tie) - K701 & AD2000 701’s marked down for recessed mids, esp. in the most massive passages. AT’s avoid the cellar due to a very proper huge presentation of the huge orchestral textures.

Test # 2: Piano - Chopin Etudes

AD2000 Airy presentation with an ok balance. A bit distant, a few rows back from the Senns, and many rows back from the AKG’s. The big Steinway doesn’t “bloom” in the tenor range like it ought to, the upper mids are not as clear as the other ‘phones, and the stronger treble passages sometimes have a slight harshness with the percussive attack. The actual soundstage is narrower than the Senns, but there is a distinct ambient spaciousness about them.

HD600 Seems very nicely balanced. Lush and luxurious sounding. The stage is wide and the sound seems to be reflected all around in a concert hall. The Steinway has lots of body, and the detail is good, maybe I want just a little more of the detail sometimes? The music sounds like it is being played in a warm, acoustically sympathetic space.

HD650 Quite similar to the 600s, not quite as clear on top, maybe even more lush. Not quite as wide of a stage, with a little deeper sound. Borders on slightly muddy at times, even with the bass set at -1.

K701 Very detailed and lively sound, at times perhaps a little too crispy on the very top end. The mids and lower mids are not there in the quantity that I would like from a big piano. More transparent than the Senn sisters, not as full sounding. The detail reminds me a little bit of my departed DT 880’s, but more controlled. I can hear some things that I wouldn’t hear in real life, and some minor flaws in the instrument and the performance can be detected at times. After setting the Fisher bass up +1 and the treble –1, now the tonal balance falls a little better into place to my ears. I soon noticed that the K701’s do sound their best with the softer pieces on this CD.

K501 This is really nice, somewhat similar to the K701’s. Even more transparent, but less ambient than the 701’s.

Prizes: Tough call here in the first three places
1st - HD600 by a nose, best balance and ambience.
2nd (tie) - HD650 & K701 different from each other, but a toss up.
4th - K501 really nice, just a little dry and light weight.
5th - AD2000 not clear enough, mostly very smooth but with occasional harshness

Test # 3: Solo Harp - Tournier

This is pretty good, but the clarity and fine detail in the mids is less present than with the other ‘phones. However, the higher treble is acceptably clear and delicate. The overall musical setting sounds quite large, maybe appropriately so as this recording was made in a church.

HD600 Good presentation really, maybe slightly fuller than I would expect to hear from a solo harp. Detail is all there. The ambience is that of a larger overall setting than the AKG sisters.

HD650 Quite a good presentation with nice detail. The light touch of the softer passages comes across very well. Alas though, again, the “big hips” sound of these cans fill in more lower mid/upper bass body than might be realistic. With a bass setting of -3, this bulbous effect is partly alleviated.

K701 Nicely delicate and detailed, a little more distant sounding than I had expected. Very tall soundstage, but not as wide as the Senn siblings or the AT’s.

K501 OK, this might be about as good as it gets here. Even clearer and more delicate than it’s big sister, with a wider image. These have a most remarkable ability to carry the sustained tones very clearly after the pluck of the string, where all of the others tend to bury the light, already played notes with the new sounds being produced. The ambience is good with a soundstage appropriate to the music.

Prizes: There is no shame here, all sounded very good to excellent
1st - K501 Just so clear and lifelike, as if she’s playing music on the cobwebs inside my head!
2nd - K701 Can’t quite match its little sister, but a very sweet presentation indeed
3rd – HD600 Nothing wrong here at all, just can’t quite match the delicate detail of the AKG’s
4th – HD650 Would have jumped a place or two with a lighter presentation
5th – AD2000 Not as clear in the mids as the others, still very nice.

Test # 4: Male Vocals and piano - Songs of Travel

AD2000 Wonderfully open and full presentation, very dynamic. Maybe the best voice placement of the group, but also the most distant. The piano sound seems to be reflected from everywhere, as if in a fairly large hall. The piano blooms hugely in the mids – where was that big Steinway tenor/mid blossom in the Chopin with these cans??

HD600 The piano accompaniment sounds like a luxurious velvet backdrop to the voice. Better balance than the 650’s, but this is one where the 650’s refinement edges out it’s often prettier sister.

HD650 Well, this might be the just about most elegant thing that I’ve heard in some time. A little darker than real life, but this is something special to my ears. Terfel sounds like he’s got b@lls the size of church bells, and the 650’s and the Fisher X1000 are up to the task!

K701 Very lively, yet refined. A bit narrower presentation than the AT’s. The huge baritone voice does not quite bloom as well as it might,

K501 The piano accompaniment shimmers beautifully, different than the 600’s, but equally sweet. Very lifelike and real, if perhaps just a slightly light presentation,esp. the big baritone voice. A worthy contender, however.

Prizes: Wow, these cans all sound really great with this CD
1st HD650
2nd (tie) HD600 & AD2000 600’s strong, but AT’s could have won if they were clearer.
4th K701 Could use more weight in the mids, but good sound here nonetheless.
5th –K501 sounds good enough, but just can’t match the fullness of the big guys.

Test # 5: Female vocals and piano - Brahms

AD2000 These two wonderful voices blossom and blend so well on the AD2000’s. So seductive these two. (Oh gosh, not impure thoughts again!?) The piano sounds so full and vibrant here, but lacks some resonance in the tenor register. The overall effect is just slightly more distant than I expected, but excellent nonetheless. Nice job, AT!

HD600 Yup, these are really getting it done here. The two voices are nicely full and resonant, and are placed further apart than with any of the other ‘phones – an advantage to my ears. The piano is just about perfect. The best sonic image of the group.

HD650 The two voices are slightly closer together and darker than the 600’s, but oh such a full and effortless sound the divas are making here! At times, the HD650’s can get fine detail across cleaner and more gently than any other can I’ve heard – but this only happens when there isn’t a lot of bass tone to make them “overbloom” down low. Well, here is a place where the Senn flagship cans really shines, outresolving their pretty little sister by a fine blonde hair with the vocals. The piano has nicer presence on the 600’s though.

K701 This is really nice too. The vocals are much fuller and with nicer presence than with the 501’s, not quite as rich as the Senn sisters, with just a bit more presence than the AT’s. Also, the piano is more forward than with the AT’s, nicely done. All in all, a very lifelike rendering of the music with these cans, lighter and brighter than the Senns – not a bad thing.

K501 The gals sound like they are standing back from the piano quite a bit. Judith is clear on top, if a little thin, and Frederica’s full mezzo sound is missing something, and her sonic image is almost in mono with these cans. The overall effect of the vocals is distant and thin. The piano is light, but resonant and nicely placed in the sonic image.

1st (virtual tie) HD650, HD 600 & K701 Different from each other, but all excellent in their own right. This music doesn’t have a lot of bass, so the superior resolution of the 650’s lifts it to the top.
4th AD2000 Absolutely no dishonor with 4th place here, these sound absolutely wonderful with this CD.
5th K501 OK, but can’t compete with the imaging and nicely rounded presentations of the others.

Test # 6: Small Orchestra, etc. - Messiah

AD2000 Now this is a big, airy, yet laid back sound. The strings and harpschord sound pleasant enough, with less treble intensity than with any of the others, even the 650’s. The double basses are reserved, yet have a remarkable bloom to them, best in show, I think. We are hearing music in a large space with these cans. Wow, there is a reverberation in the hall that falls in the sweet spot of the AD2000’s. I didn’t notice this with any of the other headphones, although I can hear it on them all now that the AD2000's pointed it out to me.

HD600 The strings sound so fresh – gentle, but yet incisive and with authority. The overall presentation is somewhat airier than I expected. The solo vocals are presented in a nice image. In all, a very convincing rendition of the performance.

HD650 The overall texture of the period instrument orchestra is wonderfully light and airy, but with the authority of good tone throughout. The harpsichord continuo is convincingly light, and the strings just seem to wrap around the entire hall, although not quite as sweetly as with the 600’s. Takes a seat a row or two back I the hall from the 600’s. The double basses sound nicely deep, but maybe a little heavier than I would like, but that’s just me being very anal for picky here.

K701 This is exciting! We’re sitting close to the violins and away from the basses. The harpsichord is so clear, and the double basses have just enough authority. The solo vocals and chorus sound as if they are standing on a platform above the orchestra. The fine polish of this superb ensemble comes through. There had better not be any wrong notes when listening though the K701’s, because you’ll hear every one of them loud and clear! These cans can really show their stuff here, since there isn’t a rich, strong midrange to deal with.

K501 This is like Handel on horseback! Totally fresh and incluttered, - like a lighter, more agile rendition of the K701’s effort, the sport version!. Everything sounds closer to where I am, like a front row seat in a smaller hall. The string ensemble has a nice spacial aura about it. As with Bryn Terfel’s voice, John Tomlinson’s big bass voice could use some depth, but this isn’t bad at all. The music feels quicker on the K501’s as if the group is playing at a faster tempo – an aural illusion to be sure.

Prizes: Oh crap, do I have to choose? There are NO losers here, so this is going to be tough! How about we rate them two different ways – once for excitement and once for just being pleasant?? Since this is my review, that’s just what we’re going to do!

Excitement ratings
1st K501 The Porsche 911, with perf. mods - what a ride, but would eventually wear me out!
2nd K701 The Porsche 911, stock with touring tires
3rd HD600 The BMW sedan
4th HD 650 The Mercedes sedan
5th AD2000 the Lexus sedan

Comfort ratings:
1st HD 650 The Mercedes sedan
2nd HD600 The BMW sedan
3rd AD2000 the Lexus sedan
4th K701 The Porsche 911, stock with touring tires
5th K501 The Porsche 911, with high performance mods

Test # 7: Pipe Organ – Wagner

AD2000 Now here is a good contender. These have the deepest and most natural low bass of the bunch. The upper detail is clear enough, although somewhat reserved. The midrange gets a little congested as the musical texture thickens and the power of the instrument is exerted, almost like some sonic “glare” that rises into the music when there is a huge amount of sonic information to contend with. The mid bass could use more presence, and the treble lacks brilliance. All of this being said, these cans do show an airiness that is rather fresh in approach to this, at times, rather heavy music. There is nothing meek or fussy about this presentation, but I’d expect to hear a little more harmonic intensity in general.

HD600 The winner of this event will be the one that can most faithfully render all of the different elements that make up the massive wall of tone that is the full sound of a large Romatic pipe organ. The 600’s have thrown down the gauntlet! They go deep and can stay deep. I’m really pumping it to them and there is no strain at all. Upper detail is all there, nicely laid out, and the intense harmonics of the organ are in full play. The large space is portrayed nicely in an ambient presentation.

HD650 These resemble their sister’s work here, just a little fuller in the mid bass and slightly reserved in the treble. It feels sort of like the 650’s are trying to counteract the natural bass rolloff of the organ. The ambience is quite good, but not quite up to the 600’s spaciousness.

K701 Well now, this is an exciting ride. The bass goes very low, actually below the Senn sisters, although it is not very loud down there. There is an overall brilliance that comes across with the 701’s that is immediately engaging, but would eventually wear me out, I predict. There is more upper harmonic intensity than with the 600’s, not good or bad, just an AKG thing. They do lack some of the midrange bloom that develops in the large space.

K501 These little troopers are pumping as hard as they can, but they just don’t have the muscle of the big guys for this huge task. The deepest bass notes are but a figment here. These are not at all unpleasant and do present a clear and brilliant version of the performance, albeit a bit light (see subwoofer comments in closing remarks). If I were to scrutinize the instrument or performance, these would be my cans of choice, along with the Beyer DT880’s.

1st HD600 Overall the most ambient and convincing, surpisingly not the deepest bass
2nd K701 Surprised the heck out of me, but they did hold their own. 2nd best deep bass
3rd HD650 Mostly a darker version of the 600’s, really good, could be clearer though
4th AD2000 Good, would have placed higher with clearer mids. Best deep bass.
5th K501 Out of their league in the bass department, but still an engaging presentation.


If I had to live with one pair, it would have to be the HD600’s. They were very strong in every test. The K701’s have not been my favorite from the time I got them, even made a deal to sell them once that didn’t work out. I’m surprised at how well they sounded to me in the head-on situations. The HD650’s – I’ve had these the longest and I do prefer the 600’s in most situations. They could have been better than the 600’s – maybe they are, but I prefer the music that comes out of the 600’s. I’ll be very eager to hear Sennheiser’s next top model, whenever that will be. The K501’s are special little cans that pulled some surprise finishes in my tests. I’d like to think of what they would be like working in concert with a small but deep-reaching subwoofer and a carefully tweaked crossover. Maybe I’ll mess with that – could be fun. The AD2000’s are my newest cans, and I’m still trying to get my head around them. I do like the spaciousness of them, and their bass is the deepest of all. There is a colored sound to them that I don’t mind - until I compare them to other cans. They showed themselves esp. strong with vocals. I will branch out and listen to some other genres with them soon. Maybe I should sell everything else and listen to them exclusively. I would be happy then? Yea right.
Sep 11, 2006 at 1:41 AM Post #4 of 91


1000+ Head-Fier
Jan 18, 2006
Very interesting, thanks! I dont listen to classical but i think your tube amps are doing something very strange to your cans
By what i read from your impressions the AD2000 seems to have a distant and laid back sound, but in my experience its the most upfront can right after grados.
Sep 11, 2006 at 2:35 AM Post #5 of 91


500+ Head-Fier
Apr 12, 2004

Originally Posted by bizkid
Very interesting, thanks! I dont listen to classical but i think your tube amps are doing something very strange to your cans
By what i read from your impressions the AD2000 seems to have a distant and laid back sound, but in my experience its the most upfront can right after grados.

Hey thanks. I don't think the tube amps are adversely affecting the AD2000's, since they don't sound much different straight out of three different CDP's, or an SS amp that I have. The tubes do allow them to develop an incredibly huge soundstage. I put a Sting CD on through them to hear what they do, and yes they are indeed pretty upfront in the mids, sound better than the 600's to me on this recording. In my tests though, the AT's do lose their midrange edge with carefully balanced acoustical recordings made in the large settings which most of my cuts were done in - not a bad thing, just a different delivery. Maybe they are optimized for vocals in studio recordings? If you consider the demands of different kinds of music, most non-classical vocals have a much smaller and lower range.

The results of a RnB, Jazz, or Rock shootout with the above cans would have been quite different, I'm sure.
Sep 11, 2006 at 6:58 AM Post #6 of 91


100+ Head-Fier
Mar 19, 2006
Nice read, thanks!

Don`t listen to classic, but still comparing the HD650 with the AD2000, for several months now, without coming to a definite conclusion.

It might be stating the obvious, but it depends very much on the electronics (source/amp) as for how a headphone performs. That doesn`t go that much for the AD2000, but certainly for the HD650.

Anyway, while voices (esp. female) with the AT are very beautiful, the heights do sound a bit harsh every once in a while. Bass is very controlled and nice (I had best results with using Amperex white label tubes for the AT).

In all other aspects I tend to prefer the Senn more and more.
(Source: Cayin CDP, amp: Rudistor RP5.1, tubes: NOS Philips JAN 6922).

Now what does "in all other aspects" mean?
See, that`s my problem, I can`t tell.
Other than "more fun to listen", that is.

Sep 11, 2006 at 7:06 AM Post #7 of 91


Headphoneus Supremus
Jun 3, 2006
very nice work here, bill! i'd love to hear more if you do this comparo with other genres such as rock and jazz. i'd also be quite interested in how a good sand amp would affect this. perhaps the senns would be better controlled under those circumstances. maybe the ad2k would benefit too.
Sep 11, 2006 at 10:15 AM Post #9 of 91


Headphoneus Supremus
Feb 18, 2006
Really good review. Thanks a lot for your time & effort.
Just one remark: I think it is good to realise that with the slight differences you perceived a different amplifier would probably have given a totally different appreciation & ranking. It is (IMO) the combination with the amp that will make or break phones especially in the sort of details we are talking about in this review. With the right (matching) amp, any of these phones could have "won" I think.
Nevertheless, this review gives a very nice picture of the different natures of these phones.
Thanks again, much appreciated.
Sep 11, 2006 at 1:51 PM Post #10 of 91


HeadFest '07 Graphic Designer
Supplier of fine logos! His visions of Head-Fi
Mar 27, 2003
Great read Bill. It's interesting to hear the kinda forgotten K501 placement in this lineup. Also the HD600 v. HD650 strengths/weaknesses.
Sep 11, 2006 at 2:53 PM Post #13 of 91


Headphoneus Supremus
Aug 15, 2003
Nice review! Very well thought out, and well written. It's nice for a change to have headphone reviews that are classical music oriented. So often we poor classical listeners are left to interpret headphone reviews that are based on pop, or rock music, which doesn't tell us much about how the cans will perform on the music we are addicted to.

- augustwest
Sep 11, 2006 at 10:55 PM Post #15 of 91


500+ Head-Fier
Apr 12, 2004
Thanks for all of the nice comments. I enjoyed the process of discerning my impressions of the different cans.


Originally Posted by fjf
Nice review...Pity you don't have a DT880, I would have liked to know how good/bad this one does...

I had some DT880's that I bought new, listened to them daily for about 16 months. Nice enough cans, but I eventually found myself distracted by the incredible detail. It would've been fun to have included them in my shootout. They were incredible with the harp CD and did well with deep pipe organ bass, better than the Senns. However, I did not like them very well with piano music. Sold them last winter.

Here's an update on my review from the weekend:

I've been trying to get used to the AD2000's but they are a different animal. I', convinced that it isn't the tube amps messing them up because they have about the same tonal balance out of anything else that I have. I've seen a few comments here and there on HFi that describe the typical AT sound as having a "honky midrange". I had the AD700's and I heard that effect with them, although I did like them ok. I'm scratching my head - I really do want to like these cans, so what is going on?

So, just for kicks, got out my Rane ME15 EQ and put it in ahead of one of my amps with the AD2000's, The other was amp fed straight from the DAC with the 600's. Started messing with the EQ to see if it would be possible to get the tonal balance of the AT's anywhere near the Senns. Well, after a few minutes, I realized that the mids were really elevated on the AD2000's, and the top and bottom rolled off a bit. I EQ'd down the mids and brought up the low bass and the upper treble. Then I ran some of the CD tracks that the AT's didn't do as well on.


The result is a "tricked" AD2000 with a sound that falls somewhere between the HD600 and the K701, with warm mids, great detail, and a soundstage that is much larger than either of the others. Wow! After listening a bit like this, I hit the EQ bypass buttons back and forth to see where I had started with them. Yup, indeed the elevated mids were what was clouding everything up for me. Thinking back to my listening tests, these cans with the EQ might well have ruled the day. FWIW, the Rane EQ is a very good professional unit and is very quiet - but do I want to listen to EQ'ed cans? I'll need to decide that.

Here's what I worked out:

BinK’s Rane ME15 EQ settings for the Audio Technica AD2000: (still tweaking)
25 hz. +2db
40 hz. +1.5db
63 hz. +.5db
100 hz. +0db
160 hz. -.5db
250 hz. -1.25db
400 hz. -1.75db
630 hz. -1.5db
1k hz. -1.5db
1.6 k hz. -.5db
2.5k hz.+.25db
4k hz.+.5db
6.3k hz.+1.db
10k hz.+1.5db
16k hz.+1.75db

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