Big Sound 2015 Participant Report: Bob Katz
Day One: Blind Test and Headphone Shootout
I arrived at Tyll's on Saturday and was overwhelmed by the incredible assembly of gear that he assembled. Meeting the gentleman for the first time I know I have met a kindred spirit! Tyll has been dedicated to headphone technology officially for many years. While I'm way behind him on that score at least I can say that I have a collection of 25 or 30 cans and began my headphone adventures in 1972 with a set of Stax and a souped-up-by-me Stax headphone amplifier. So, let's say that Tyll and I went to different schools together!
Our first adventure was either a failure or a success depending on your opinion. It was comparing the best of delta-sigma DACs, the Antelope Audio Zodiac Platinum DAC, against a new version of the classic R2R technology, the unpronounceable Yggdrasil, aka the "Yggy" DAC from Schiit. My digital guru, Bruno Putseyz, has a number of disparaging things to say about the idea of resurrecting an R2R DAC, so I expected this comparison to be a piece of cakeI surmised the Yggy would sound colored and small. But this was not the case, and in fact, both Tyll and I failed the blind discrimination test, scoring no better than 50-50. We used a carefully-selected high-resolution reference recording from my collection that I know well, shortened it to about 20 seconds and looped it so we could compare one to the other blind in the fairest way. Still, sighted, Tyll and I both feel that perhaps the Yggy's got a little less depth than the Antelope. But maybe not, since we were unable to discriminate the two DACs blind and the Yggy is more than 4 times cheaper! I have an idea now for a listening test to proof the two DACs, but it's too late since I've already left Bozeman. If any of you readers gets an Yggy and has a good competing Delta-Sigma DAC, please contact me through Innerfidelity and I'll arrange to send you a special listening test signal that might reveal the sonic differences.
For the headphone shootout, I concentrated on tonal accuracy first, including bass and treble extension, followed by attributes like spatiality, depth, soundstage, and lack of distortion (purity of tone). I used my own reference recordings which I know very well and actually have mastered for commercial release using a reference corrected loudspeaker system which is flat to a target response from below 20 Hz to above 20 kHz. The target has a high frequency rolloff and was created by me by listening to about 50 different reference recordings and ensuring that the average high end falls right in the middle. It falls right in line with my Revel speakers native high frequency response but has been smoothed to remove crossover and tweeter response anomalies in Acourate, which I'll discuss later in this review. So it's a very accurate loudspeaker reference; it sounds very natural.
My headphone reference at home is a set of equalized LCD-X and Stax 007-Mk2. They are equalized by ear to match the loudspeaker playback as closely as my human brain can do. But as you will see later in this review, there are probably scientific ways to do even better and so we are still learning how to equalize headphones. Here's a summary review: I didn't think anything I heard flat came up to the standards that I have set for equalized cans. I would prefer an EQ'ed version of every can I listened toeven the lofty Stax 007 MkII can be improved with a hair of EQ. That said, there were clear winners in the headphone contest when auditioned flat, and in principle, any headphone which sounds good flat is a candidate for minimalist EQ.
My number one choice: The Stax SR-007 headphones. I did not like the 009's at all. They weren't even contenders. They sound way too bright and thin on the KGSS amplifier. Perhaps with a sweet sounding tube amp the 009's would come into their best, but why spend almost twice as much to get an inferior sound? I think Stax went the wrong way with those 009 phones. Some listeners have written that the 007 sounds rolled off, but that was not the case with the KGSS amp. Perhaps it is the case with a tube Stax amp. The 007's had the best and most accurate tonal balance from bottom to top in Tyll's collection without EQ, but for sure they are lacking bottom without EQ.
Another reaction that surprised Tyll was the Spritzer-modified 007's which I brought along. We shot them out against the stock 007's and it was no contest: The bass on the modified 007 is more solid, extended, accurate. This mod is a no brainer necessity. The hardest part of the modification is opening up the cans and you have to be very careful but once you open them up it's a minute to put a tiny amount of blue tack or Mortite in the port and then reassemble them. Tyll agreed with me that this modification is a must do.
My number two choice: The Audeze LCD-3. I've now auditioned two samples of the LCD-3 and they are as different as can be. This sample sounds a lot more like my preferred LCD-X. I wager that unit-to-unit variations are greater than the differences between the two models. That makes it hard for someone to make a decision unheard and I advise you to go to a dealer that has both and audition two for-sale models if possible. This sample of the LCD-3 has the classic Audeze issue: missing a bit of the air frequencies, but like all of these great Audeze phones, it has a very pleasant tonal balance and is a great candidate for touchup EQ. The bass was as usual, Audeze-excellent. My number 1 and 2 choices are nearly tied, depending on whether you like high end more than bottom. Each one has its compromises and its strengths.
Number three snuck up on me. My first listen to the Enigma Acoustics Dharma was too quick. I dismissed it initially because after hearing the LCD-3's I got hit by accomodation and I felt the Dharma had a bit of an artificial hi-fi zing above 12 kHz, but on a second listen at Tyll's urging, after a bit of an ear rest, the Dharmas were very impressive from bottom to top with a little excess sibilance to tame circa 10 kHz. I definitely want to have a swing at these at home if I can get a loaner. Maybe with EQ the Dharma can beat the Audeze. It remains to be seen.
Number four is, surprisingly, the modified Sennheiser HD 800. To be honest, I think these phones are overpriced. When you open up a pair of these you wonder about the construction and the components. While a can like the Dharma have a specially made crossover and use separate custom-made low frequency and electrostatic drivers go for $400 less than the much-simpler Sennheisers! The modified HD800's, though, have a decent lower midrange, a reasonably tamed treble except for certain resonances excited by trumpets, for example, and a weak bottom that could easily be remedied with careful EQ, provided that your amplifier has the headroom. Bass frequencies require a lot more power than higher frequencies because of our ear's equal-loudness curve. People claim the unmodified HD800s have a lot of "resolution" but I think this is a result of a rising high frequency response. Not fair. If you like to "detail" at the expense of accurate tonality, then buy the HD800s and don't modify them.
Take a look at the video that Tyll shot to get my reactions to the rest of the phones, but the summary is that I didn't like the rest. It was either feast or famine folks, sorry.
Day Two: Amplifier Shootout
My new reference amplifier is my do-it-yourself build of the AMB M3 which I've written about in my column. I have been very interested in seeing how the M3 compares to the delectable commercial amps available for tasting at Big Sound so I brought it along in my carry-on. A suitcase loaded with a Prism DAC, a headphone amp and power supply and two premium phones. You should have seen the crazy time I had with TSA at the airport! In the time available I was not able to level match all the amps with Tyll's Fluke meter so most of these comparisons were matched by ear. Frankly, I was underwhelmed by the sound of the majority of the amps on display: Most of them sounded veiled, with a loss of definition usually in the treble but often in the bass as well. I'm a big fan of tight, responsive, low impedance voltage regulation which I believe translates to a speedy yet pure sound and I wonder if voltage regulation is the issue with some of these amps. My electronics guru, John Chester, says that when a manufacturer advertises he uses four stages of regulation for low noise, it's nonsense if you can't get it right with just two.
Perhaps these manufacturers aimed for use with some of the overbright headphones on the market, or to make "beautiful sounding" amps that complement some of the harsh-sounding loudness-war casualties in pop music. I can't blame them for trying. I love Coldplay's music but I can't bear to listen to their fatiguing recordings for long on my reference loudspeaker system. My friend, mastering engineer Bob Ludwig, who has made some of the finest-sounding recordings on earth, basically told me, "We can't tell Coldplay we would like to make a master that's lower in level than their mix!" So probably the source of the grunge goes back to their mixing, not the mastering. Bottom line: Some audiophiles want to listen to current pop and the only solution is a euphonic playback system. It's the only explanation that makes sense why a $4300 headphone amp sounds overly soft and fake-tubey, the Simaudio MOON Neo. It looks very impressive and has great features, but I'm afraid its sound does not come up to its looks. When Tyll listened during my comparison, he asked me, "are you sure you level matched them?" And I replied, "yes, to less than a tenth of a dB". And there's the rub: If an amplifier sounds "soft and warm", matching the voltage will not match the perceived loudness. Tyll and I agreed that we should manually turn up the Moon a few tenths in order to match the subjective loudness of the M3. Even then, on a level playing field, it did not come up to the sonics of the custom-built amplifier.
This situation repeated itself until I arrived at the beautiful red-faced HeadAmp GS-X Mk2. The photo of the Mk1 on Headamp's site does not do the Mk2 justice. It is now finished in a gorgeous "audiophile-grade" red finish as well as having sonic improvements. The GS-X has a pure tone, excellent transient clarity without any high end exaggeration, sweet midrange and good, solid bass. I felt that the GS-X Mk2 is in the same neck of the woods as my M3. I definitely wouldn't kick the GS-X out of bed, even though I felt the M3's bass definition a little bit better, we're picking nits here.
The only amp on display that I felt equaled the M3 in sonic quality was the custom-built KGSSSRE (Kevin Gilmore Solid State Special Reviewer's Edition E-Stat Amp), which you can't buy. I wonder if the original KGSS is still available. If it is, grab it, it's probably the best solid-state electrostatic headphone amp that's been made. Even though I could not audition the M3 and the Electrostatic amp with the same headphones, clearly all aspects of the two amps are in sync: transparency, impact, depth, purity of tone, soundstage... When you reach this league, the differences between Electrostatic and Dynamic melt away and you can just immerse yourself in the music.
Does this mean that you have to custom-build to get an accurate-sounding headphone amp? Not really. As I said, I really liked the GX-X Mk2. I haven't heard all the amps out there and I'm sure that some others are built with equal care and skill. Let's start to look for some more uncolored commercial models, ones with neutral, transparent sonics, since most people do not have the expertise to custom-build. Keep in mind that there are builders out there who will build an M3 for you. Builders are listed on the AMB website in the section on the M3 amplifier.
Day Two: Headphone Equalization: Seeking An Ideal Target Curve
I have began my EQ'ing adventures solely by ear, but at least I use reference recordings and compare them with the standard of a calibrated loudspeaker system and room: my own calibrated and flattened loudspeaker system that's been adjusted using a psychoacoustic measurement approach pioneered by Jim Johnston and interpreted by Dr. Uli Brueggemann. Brueggemann's loudspeaker/room measurement system is called "Acourate" and implements a variable measurement window according to psychoacoustic principles. Using 50 reference recordings that I know intimately, which I have recorded and/or mastered over the years, I have produced my own preferred loudspeaker target curve. Flat bass in the loudspeakers is my preference and a high frequency target with a gradual rolloff at the high end. It seems that many trained and professional listeners prefer this type of curve, while many untrained listeners like a greater bass boost and a bit less treble. This could be for entertainment (people love big bass), but keep in mind that I tend to listen to forte passages at an SPL around 83-85 dB, while many listeners use a lower level, so the equal loudness curves would dictate that listeners who play things softer need more bass boost.
But there's much more: Harman's curve contributes science to the art. If not for Tyll, his visit to the Harman facility, and his subsequent generous tutorial on the subject at Big Sound 2015, I would have been ignorant on this development. Since then I've read Sean Olive's seminal paper* and studied the research which has inspired Tyll and now me. Now I'm undertaking a systematic approach to quantify and evaluate these new curves from the perspective of a professional recording and mastering engineer. I hope that these observations take you all closer to your goal of headphone nirvana and I'll talk about them in upcoming episodes of Katz's Corner.
The principle of Olive's paper is that listeners prefer a similar response in their headphones to that produced by a flat-response loudspeaker in a listening room as measured at the eardrum position of a head and torso simulator. Olive's research also shows that untrained listeners prefer a curve with more bass boost than trained listeners and less treble than the loudspeakers measure themselves. In the next few months I hope to quantify and confirm those conclusions using my own reference recordings with my ears and visitors'.
Harman's listeners used recordings which they are not necessarily familiar with, while I have intimate experience as the creator of my reference recordings, which is a distinct advantage. The Harman testers liked a curve which sounds the most pleasing to them, while my goal will be to produce a curve which I think is most accurate because it most resembles the impression of the loudspeakers in my room and ultimately, natural, accurate sound. However, the closer a transducer is to the ears, the greater the perceived high frequencies and transients, and so it is logical that all of us will prefer a slightly more rolled off curve in the highs than what we hear from the loudspeakers.
Despite these variances, I think it will be possible to come up with a headphone target curve between two limits that you, the readers, will be able to take advantage of. We are living in interesting times, and I look forward to adventures with the Harman curve.
Our first attempt at EQ was very promising. At Big Sound, working with Tyll, I took my pair of LCD-X's and manually applied an EQ that is the difference between that of a measured LCD-X and the brighter of the Harman Curves, modified with Tyll's suggested 2.5 dB bass boost instead of the "typical" listener's 5 dB bass boost. Tyll was very gratified to find that we both think this curve sounds very good. I then began to modify the curve as auditioned on my own headphones. I found I had to brighten the 5 to 10 k range compared to the prediction. But that prediction was based on a different sample of LCD-X phones than my own. It was rewarding to discover after Tyll measured my personal phones, that they measures a lot more linear than the previous sample and so it was logical that I would need to push those frequencies. Clearly this procedure brings science into the art! In future episodes of Katz's corner I will start with Tyll's measured curve of my personal cans and algebraically subtract it from the Harman curve to derive a scientific EQ which I will begin with.
Another point is that bass and treble are yin and yang frequencies. If you boost bass you will perceive less treble and vice versa. This is why Quad invented the "tilt EQ". It's also how the smiley curve came into being! "More treble, Charlie. Now give me more bass. More treble. More bass." My brother's car inevitably had a graphic equalizer shaped like: A smile. But when you have boosted the bass, and suddenly think you need more treble, the first thing to do is not to fall into that trap, to reduce the bass a bit rather than add more treble. So it's going to take some time for me to evaluate this LCD-X EQ at home, decide whether the 2.5 dB bass boost is right and evaluate the treble in the context of the bass.
As of this writing, I haven't yet made a new EQ curve based on the exact scientific difference between my own LCD-X and the Harman target, but that is definitely in the near future. Here's a screenshot of the work in progress:
This eq resembles the shape that I had previously created, but the turnover points are quite different. Remember, this is a difference EQ, the amount of correction needed to be applied to a headphone's response to yield the Harman target curve. It is also a hand-tweaked curve because it was originally based on a different pair of LCD-X. To see the actual response of the headphones, we would need to display the resulting response of the headphones with this EQ. In future episodes of Katz's Corner I'll be sure to do this, using actual measurements.
Just before I left Sunday, Tyll showed me a pair of inexpensive Chinese phones that I think cost about $69.00 and reside in his wall of fame. Tyll, what model was that? I want to get a pair. These are perhaps the best cans I've heard under $300! They'd go great with my iphone. My previous "inexpensive" winners are the Sennheiser HD280 Pro: I own three pairs! Perhaps these Chinese cans beat the $95.00 280s. What a wonderful visit and what a wonderful discovery.
Ed Note: Those were the Noontech Zoro II HD, Bob. On the Wall of Fame currently; great little headphone/headset.
* Audio Engineering Society Convention Paper 8994, "Listener Preferences for In-Room Loudspeaker and Headphone Target Responses", by Sean Olive, Todd Welti and Elisabeth McMullin.
AURALiC Vega DAC ($3499)
Simaudio MOON Neo 430 HA ($4300 w/DAC).
HeadAmp GS-X Mk2 ($2800)
Schiit Ragnarok ($1699) and Yggdrasil ($2299)
Burson Audio Conductor Virtuoso ($1495 w/PCM1793; $1995 w/ESS1908)
Woo Audio WA-234 ($15,900)
Antelope Audio Zodiac Platinum DSD DAC, Voltikus Power Supply, and 10M Rubidium Atomic Clock. ($13,045)
Apex High Fi Audio (TTVJ) Teton ($5000)
Eddie Current Black Widow ($1248)
Violectric V281 ($2299)
Bakoon HPA-21 ($2995) current output headphone amplifier.
KGSSSRE (Kevin Gilmore Solid State Special Reviewer's Edition E-Stat Amp ($Unobtanium)
Sennheiser HD 800 ($1599)
Audeze LCD-3 ($1945) and LCD-X ($1699)
JPS Labs Abyss AB-1266 ($5495)
Stax SR-009 ($4450) and SR-007 ($2350)
HIFIMAN HE-1000 ($3000)
Mr. Speakers Ether ($1499)
Enigmacoustics Dharma (~$1200)
Audio Zenith PMx2 ($1398)
Headphone stands by Klutz Designs