Review: Green Mountain Audio EOS HD Monitor

Category: Speakers

GREEN MOUNTAIN AUDIO EOS HD REVIEW

Choosing the EOS HD

Even after my system had evolved to include high performing components from sources to cables, something still seemed to be interfering with the music. Of course, I was aware of the usual suspects and had taken steps to eliminate or minimize “noise” by using robust power supplies, quality parts, power conditioning and anti-vibration devices. Then, one day, I happened to read “Loudspeaker Phase Accuracy and Musical Timing”, by Roy Johnson, originally published in the Winter, 1997 issue of Audio Ideas Guide. Even after reading it numerous times, there are parts I still do not fully understand. However, what I learned led me to Green Mountain Audio and my first truly time and phase coherent speaker, the GMA Europa.

When I listened to the Europa for the first time, the music it reproduced was a revelation, in fact so involving and real, I didn’t want to turn it off. On every kind of music from classical and jazz to pop and rock, I hadn’t heard any pair of monitors that did so many things right regardless of price. When listening to recorded music through the Europa, the “something” that “always seemed to be interfering with the music…” was gone! I was hooked and knew then I would never buy another pair of speakers unless they were fully time and phase aligned.

When reviewing the GMA Callisto in the April 2005 edition of Sixmoons.com, Paul Candy validated my own listening experiences to the extent that he actually described a pair of Europas on steroids. He concluded by stating: “They were truly mesmerizing loudspeakers and easily one of the most convincing and emotionally satisfying designs I have heard to date.” I had felt the same way about the Europas. But Candy’s review suggested to me that music played through the Callisto was more captivating, and even more satisfying than what I had experienced with the Europa.

Without the least bit of skepticism and my credit card in hand, I called Green Mt. Audio only to discover that it had been discontinued. EOS Designer, Roy Johnson explained that he replaced the Callisto with a new speaker promising ‘breakthrough’ features and refinements that surpassed the Callisto’s performance. These included: an entirely new 45 lb. Q-Stone cabinet touted to effectively control interior vibrations as well as surface/edge diffraction with an advanced dual port for even more defined bass response; a newly-designed, fabric dome tweeter said to give a stunning presentation of voices and small details with less inter-transient noise; an improved crossover circuit and Zobel circuits as well as significant improvements in tweeter and woofer performance with ultra-premium quality capacitors and cryogenically-treated Litz wires. According to Roy, this new speaker’s performance was beyond even his own expectations. And so, the EOS HD was born.

With this information and some experience to fall back on, I did the unthinkable and ordered the HDs without ever hearing them. I rationalized as follows: First, I already had listened to the Europa for a year in my own system. Its design was very similar, some important components, identical (especially the woofer), and its time and phase alignment spoke volumes. Second, the Callisto had received Sixmoons’ “Blue Moon Award” for “Exceptional Size-Defying Performance In the Monitor Speaker Category”. (I had found Srajan Ebaen’s and other Sixmoons reviewers’ opinions to be quite reliable.) Third, Roy Johnson was so confident about the EOS HD’s performance he discontinued the Callisto despite its great success as arguably one of the best monitors available at any price. He told me that the EOS’ midrange and treble revealed even more clarity, detail, and sparkle, and that its bass response was tighter, fuller and had more impact than the Callisto’s. He also knew from his own listening experience that the benefits of its time/phase coherent design would be audible in virtually every important category of performance. Fourth, and finally, in today’s world of automated customer service, Roy is one of very few company owners and speaker designers I know of who will actually take a customer phone call to answer questions. He responds to emails personally. He will even call a customer himself if there is something to communicate about the status of an order. Always friendly, professional and with a passion for his work, Roy is not a ‘hard sell’ kind of guy. He is honest and will stand behind his products. After registering the EOS HDs within 30 days, GMA will absorb the costs for all parts and labor for as long as the purchaser owns them provided there is a defect that is the company’s fault.

Review Summary

The EOS HD has been in my system for 34 days and approximately 125 hrs of playing time.

After many hours of listening to some of our favorite recordings, both my wife and I agreed: The EOS HD conveys the richness of the music in a way that just sounds right and feels right. Instruments and voices are abundantly real, natural, and musical. The distinct timbre of each instrument can be heard and felt. The music is vividly clear, palpable, and has an immediacy that is pleasing in every musically meaningful way.*

(*I first heard the expression “in every musically meaningful way” from Kevin Carter (KandK Audio) when he used it to compare two DACs. In my opinion it is a cogent and telling phrase that accurately describes how pleasing I found the EOS HD to be.)

Sonic Elements

Articulation: On good recordings, voices were especially clear and intelligible. I could hear inner details missing through other speakers. Even recordings of lesser quality sounded better through the EOS HD than through other speakers I have owned.

Accuracy/Fidelity: The tonal quality/harmonics of recorded instruments and voices closely resembled the timbres of real voices and instruments as one would experience from a live performance.

Frequency Response:
Overall- Tone was remarkably cohesive from top to bottom. No one range dominated another and the music blended seamlessly.

Treble – The upper range was transparent, extended, smooth, airy and open.

Midrange – Mids had excellent pace with a live quality. Voices and instruments had pinpoint clarity with surprising definition and inner details, not previously audible to me, were revealed. The music flowed and was airy and open.

Bass – Was tight, full, natural and provided a convincing foundation for the music. This is exceptional for a two-way design requiring, at times, a bit of cognitive dissonance to reconcile the diminutive EOS with the ‘Hulk-like’ bass notes it produced.

Transient Response: Attacks were sharp and not merged or squeezed with decays; notes sounded full; musical pace, rhythm and timing were natural and realistic.

Soundstage: On all recordings, performances were behind the speakers, deep enough when necessary to create the illusion of space occupied by a symphonic orchestra. From side to side, performances were between the speakers with excellent center fill and layering, sometimes extending to the side walls. Overall, the EOS soundstage created a presentation that tended to place the listener in the same room with the performers more often than bringing the performers into the listening room. I experienced the latter on a number of solo instrumentals and on individual vocals where performances were most lifelike. At times, I thought locating instruments and performers was not consistent in that their location seemed to change somewhat from left to right or vice versa. I discovered this was due to room reflections especially coming off the side walls and was able to lessen them with readily available objects grouped somewhat randomly. This seemed to minimize the problem. However, I plan to add diffusion panels that will undoubtedly be an improvement.

Imaging: When positioned well enough according to the size and acoustics of the listening room, the EOS’ ability to disappear while creating the illusion that music is not coming from the speakers themselves was simply stunning. As with most monitors, positioning is important to get these results.

Other Characteristics: The Eos HD’s dispersion and off-axis performance was impressive. The sound was wide and uniform. While best within the sweet zone, its sound was impressive from any seat in front of the speakers.

A very good listening test for judging a speaker’s ability to reproduce music accurately and convincingly is to listen to it from another room. From our dining room table, two rooms away from the listening room, my wife and I were incredulous at how clear and dynamic the music sounded. We were hearing all of the sound, including on and off axis, plus the room reflections. For the music to sound that good from two rooms away, the speaker drivers, crossover, and cabinet must combine to reproduce it on time and in phase.

Fit and Finish: I couldn’t find one flaw in the fit and finish of either speaker cabinet. Much care and attention to detail were evident and quality control was outstanding.

Value: Considering its design, advanced features, quality of parts, Q-Stone cabinet, unique ‘form follows function’ good looks and most importantly, the EOS HD’s high performance, it offers very high value for a fair price.

Distinctive and Most Outstanding Strength

Its overall design is the EOS HD’s strength and allows it to reproduce nearly all information crucial for the realistic portrayal of the spatial, tonal, and timbral characteristics of music. Although there are many important contributing factors including the other high performing components in my system, this ability is the major reason why the EOS sounds so right, so natural and musical. The choice of drivers, shape of the cabinet, and crossover design, are all critical for establishing its ability to reproduce music on time and in phase. The design explains why music sounds so pleasing in every musically meaningful way. Were it not the case, the contributions other high performing components bring could not be fully realized. Its seems clear that this is why a loudspeaker that does not carry a design through sufficiently to reproduce all of the music is at risk for being the weak link in an otherwise high performing audio system.

Listening to the Recordings

I selected a variety of music for this review. The selections chosen would provide a thorough test for any speaker. Jazz, Classical, Rock, Pop, both vocal and instrumental, were included. Also, the selected recordings are, for the most part, sonically superior.

Diana Krall’s recording, The Girl in the Other Room (Verve), includes 6 original songs co-written with husband Elvis Costello. Each song combines intricate, personal lyrics with beautiful and, at times, haunting melodies. On nearly every track, the sounds of piano, bass, guitar and percussion were alive in an acoustical space that created the intimate ambience of a jazz nightclub so revealing I kept repeating to my wife, “I never heard that before”. Whenever Krall’s voice and piano, or Christian McBride’s acoustic bass and Anthony Wilson’s intricate finger work on guitar surprised me with inner details, natural timbres and dramatic attacks, I realized how much more deeply into the music I was able to hear than ever before. Krall’s subtle phrasings and delicate shadings were highly resolved. Any sibilance was inaudible against a black, silent background. The texture of her voice, with its hoarse, and at times raspy tone, and sweet, velvety softness came through vividly and was palpable to a degree I hadn’t heard through most other monitors and floor standers I had listened to before. The lyrics of the original songs together with the music are vital for receiving the full emotional impact of the music. Here, the EOS proved to be especially transparent, revealing enough inner detail to make the lyrics intelligible and easy to follow. No speaker from another manufacturer I had heard before reproduced voices to this level of articulation, although a few have come very close.

A description of the music on The Girl in the Other Room would not be complete without mention of Krall’s stunning piano. A loudspeaker’s ability to reproduce the tonal balance, transients, dynamics and harmonics of a piano is a very good test of its clarity, articulation, speed, treble, mid-range and bass quality, as well as the degree of emotional involvement it can evoke from the listener. The EOS HD excelled in all of these areas reproducing Krall’s piano with pinpoint accuracy, revealing fidelity, soft trebles, and convincing bass. The piano had an immediacy so compelling, that I easily was lost in the music.

Both the music and sonics on K.D. Lang’ s recording, Drag (Warner Bros. Label) combined sumptuous arrangements and Lang’s masterful rendering of familiar songs that brought the topic of smoking and cigarettes to a whole new level that is certainly not hazardous to your health. Lang’s soaring voice was given air and plenty of space through the HDs. My Old Addiction opens with a sustained bowing of the cello. I could almost feel the vibrating strings, energized by the bow, as they resonated from the body of the cello. The richness and warmth of the sound was billowy but not bloated. The special characteristics of the cello’s remarkable timbre, with its familiar warm and mellow quality also proved to be capable of a larger, more dramatic sound especially on attacks. In contrast to the smearing I have heard before through other speakers, music from cello and voice arrived to my ears distinctly and simultaneously on time. On ‘Til the Heart Caves In, Lang’s voice conveyed both power and an elegant quality as befit the lyrics and music. The HDs convincingly produced a soundstage on which, voice, bass, electric and steel guitars, occupied their separate spaces just behind the speakers.

Canon in D by Pachelbel is one of many sonically outstanding recordings included on First Impressions Music (FIM) Super HDCD Audiophile Reference IV album. The assortment of percussive instruments is a true test of any speaker’s ability in many important areas including: imaging, definition, soundstaging, transience, musical nuance, micro and macro dynamics. What struck me most about this version of the Canon was how highly resolved each instrument sounded. Faint details, such as the low level sounds of bells and other delicately struck percussives could be heard up to the final reverberation of their decay. The various percussive instruments used in place of bass and violins to play the simple and repetitive contrapuntal structure of the Canon sounded crisp without being etched, delicate but not faint. Likewise, the floating tones of bells and triangles seemed to take shape in air with a convincing presence.

It’s Magic (2008, JFD Productions & Dreyfus Jazz) is Ahmad Jamal’s latest recording and the sound of his piano is in full force. Jamal is known for the subtlety of his playing. On It’s Magic, he brings subtlety along with an all out assault that uses nearly all 88 keys and 7 octaves that would challenge any speaker’s ability to faithfully convey the tones, overtones, harmonics, dynamics, and timbre of a Steinway Grand. On every track, the EOS HD was able to reproduce these distinctive piano traits with ease. On Arabesque, Jamal’s own composition, his piano was like an orchestra unto itself. It ran the gamut from delicate to fierce, with intricate patterns and riffs, lightly struck trebles, breathtaking glissandos, tremolos and non-stop harmonics. The tones were rich, vibrant and had a huge presence in my listening room. Drums, percussion and bass provided just the right mix to support Jamal’s virtuoso performance by adding to the foundation of the music with tight bass notes, dynamic rhythms, percussive attacks and even subtle inner details. While listening to this incredibly imaginative and mesmerizing music, with eyes closed, I came as close as ever to believing the musicians were in the room. I got so far into the music that I stopped taking notes, just sat back, and held on for the ride. Of course, later when the ride was over, I realized how the EOS had created the illusion of the performance by bringing it into the room itself so convincingly.

Rachmaninoff’s Symphonic Dances (HDCD), performed by the Minnesota Symphony conducted by Eiji Oue, is an award winning recording considered by some reviewers as the best ever Reference Recording and the best for real concert hall reproduction. The sumptuous dynamics and huge climaxes of this work will challenge even the very best audio systems, especially the speakers. This is one of a select group of recordings I have heard that convincingly conveys the “being there” experience. I had listened to it many times through other monitors long before purchasing the EOS HDs. My expectations were therefore modest. When I first heard it through the Europas, those expectations changed, but not nearly so much as after hearing Symphonic Dances through the EOS. It is the first two-way monitor I have heard that can reproduce this recording convincingly enough to convey full symphonic sound played in a large hall with enough realism to surpass more than a few speakers with larger drivers. I especially enjoyed the roof-raising dynamics, driving energy, and excitement created by the stunning performances of the individual instruments. The treble sounds were liquid and massed strings sounded sweet. The soundstage was dimensional, with ample depth and width that conveyed the ambience of Symphony Hall with the slightest inner details as well as enormous bass impact. This is one recording that sounds best with plenty of power. The EOS HDs can play very loud and I kicked-up the volume past my normal listening level. They could easily have exceeded the 95dB that charged my listening room.

“Stimela” from the album, Hope, performed by Hugh Masekela includes one of my favorite horn solos. Masakela is a master of the horn and arguably of the best two or three horn players I’ve heard, including Miles Davis, live. His playing is fueled by his emotional connection to the South African coal miners whose plight inspired this composition. Through his horn, Masekela conveyed both anger and hope. The EOS did a superb job of reproducing the sound of the flugelhorn authentically conveying subtle breath notes as well as its rapid, staccoto-like bursts and powerful dynamics as played by Masekela. Goose bumps can be expected.

On "Someday Baby" from Bob Dylan’s most recent album, Modern Cool, the lyrics are vintage Dylan and the band is, according to Dylan himself, the best he has ever assembled. My wife and I heard them live at a Dylan/Willie Nelson concert a few years ago. She has heard every band with whom Dylan ever recorded and agrees. On this track the EOS was very revealing of lyrics and instruments, especially in the upper base and mid range. The driving beat and repetitive rock n’ roll rhythm provided by bass, drums, percussion and guitars was augmented by how clearly each one’s distinctive sound stood out in the mix. Together they provided the power behind Dylan’s somewhat laid back baritone voice as he kept repeating after every verse, “Someday baby, you ain’t gonna worry po’ me any more.” The music made me want to boogie and drew me in a little more than did the lyrics, although Dylan’s phrasing and interpretation were masterful. Inner details on all vocals revealed the emotion in his voice.

EOS HD Design Summary

Roy Johnson has thoroughly described his design concept for the EOS HD and its critical features in “New technologies plus design refinements equals Eos”. [Note: The article, originally available on the website, was removed in anticipation of the debut of a new GMA website. At the time of this review, Janet Lynn, GMA’s CEO confirmed that Roy’s Design Concepts for all active GMA speakers will be available on the new website.] He suggests that the relationships between the drivers, cabinet, crossover circuit and room are highly interdependent. I’ll try to paraphrase and quote from this article to summarize these relationships.

Drivers, Cabinet, Crossover

First, the drivers have been specially selected for their ability to carry enough of the shared band of frequencies to keep the sound seamless and in phase. Only drivers of the highest quality are cable of such performance. The woofer and tweeter are positioned in their separate cabinets so that they are in step and their signals don’t arrive ahead of or behind one another. Second, the shape of EOS itself was designed to vary in order to control the reflections around the cabinet and off the walls in each tone range. Also, its asymmetric, six-sided profile was designed to reduce interior reverberations and to provide “the variable wall thicknesses that reduce what is called ‘shear-wave’ transmission of sound in the Q-Stone marble.” Third, the first-order crossover follows the golden rule that says “Keep the signal path simple and uncluttered”. It has but one capacitor and one resistor that work together to hand off the signal at the appropriate frequency.

Johnson’s training and background in Physics has added an important dimension to his understanding of the relationships between the electronic, mechanical and psychoacoustical elements of speaker design. Also, his understanding of the math behind the two-way design, especially in the time domain, has resulted in more refined relationships between the drivers, cabinet and crossover.

Again, referring to “New technologies plus design refinements equals Eos”, it is clear that the EOS HD’s Balanced Phase first-order crossover allows the woofer and tweeter to move as one unit and deliver their signals with no delays. The crossover network includes a “finely-tuned” Zobel network connected in parallel with the EOS tweeter. Simply stated, Zobel networks are a type of filter. According to Roy Johnson, “A properly tuned Zobel circuit makes the woofer appear to be a simple resistor to the inductor; it makes the tweeter appear as a simple resistor to the capacitors, thus controlling the resistance (impedance) at each frequency.” He has further explained that, “ the woofer’s inductor and the tweeter’s capacitor can be chosen to have opposite impedance curves, or ‘mirror-images’, exactly as if they formed a ‘Y’ adapter for the incoming signals.” This Balanced-Phase circuit design is said to be “a good thing for the amplifier, because it cannot then know that a capacitor or inductor exists.” The “…EOS appears to the amplifier like a 4- to 5 – ohm resistor at almost every frequency, which allows the amplifier to deliver its power with the least distortion.”

Concluding Remarks

As is evident, I consider the EOS HD to be a very special speaker and the best monitor I have ever heard. It no doubt can compete with more expensive speakers. It is deserving of consideration by anyone who is looking for a speaker that is truly capable of conveying the realistic and natural sounds of music. While writing this review, I was aware of my enthusiasm for the EOS but had no fear of going out on a limb by not finding any faults with its performance. It isn’t that I think the EOS HD is perfect. No speaker is perfect. Of course, how its strengths and weaknesses are judged will vary depending on the listener and other variables mentioned elsewhere in this review. Each person who listens to the EOS will have to judge and decide for himself.

Finding the right speakers was the most challenging part of building my system. While my budget wasn’t limitless, I could have afforded more expensive speakers, although the EOS is not a budget, entry level choice by any means. I chose it because it is so musically satisfying and emotionally involving. I can now enjoy the music and stop listening to the equipment.

No attempt was made to compare the EOS HD directly with other speakers simply because to do so fairly would require listening to them in the same listening environment, i.e. same room with the same system components. Since I don’t have access to speakers I would likely choose for comparison, this could not be done. I have only mentioned monitors I have owned and listened to by name as required by Audiogon and not compared them directly with the EOS. Because judging speakers, as well as any other audio component, is matter of personal listening experience, taste, psychoacoustic factors, and the nature of individual audio systems, such reviews cannot be conducted scientifically. They are neither subject to experimental design and control of variables nor capable of irrefutable conclusions. As far as the use of measurements and derived specifications are concerned, the numbers simply won’t tell you how a component sounds.

Although subjective, my remarks represent my honest impressions, based on hours of listening. I haven’t pointed out areas of weakness in the EOS’ performance for the simple reason that I found none that indisputably could be attributed to the EOS alone and just as easily could have been a weakness in another component, including room acoustics. This was exactly the case mentioned in the paragraph describing Soundstage above. It also applies regarding amplifiers. To the extent that I was quite familiar with the sonic signature of each tube amp that was used, I could tell when it was the amp that was contributing its own sonic signature more so than the speakers. To me, this was not necessarily a bad thing since I prefer the sound of a well-designed tube amp. I considered the EOS to be quite revealing of each one’s unique flavor. This suggests to me that the EOS is quite transparent. I used four different amps during the review. My reason for this was primarily to hear how the EOS would perform with different vacuum tube amps that included: a Class A, 8W/channel 300B; Class A, 15W/channel (in triode) push-pull; Class A 35W/channel (ultralinear) push-pull; Class A/B 50W/channel monoblocks (in triode); and a solid state Class D, 300w (at 4ohms). The EOS acquitted itself quite well when matched with the low output 300B. It actually sounded more efficient than its rated 90dB. Each of the other vacuum tube amps was a good match with more than enough power on the most demanding music such as Symphonic Dances. I used the Class D amp (on loan) mainly for comparison on Symphonic Dances. While the power advantage was obvious, to my ears the quality of the harmonics, degree of bloom and shear musicality were neither as pleasing nor as natural as with the tube amps. However, I thought it sounded better on some recordings than on others.

Associated gear
Related System Components

Sources:
Digital: Raysonic CD 128 with NOS 6922 tubes;
Analogue: VPI Scout Turntable, upgraded JMW 9 tonearm with Nordost wires in special tapered and damped armtube; VPI anti-skate device, VPI stainless steel record clamp; Dynavector 20XL MC cartridge.

Amplification:
Preamplifier:
Custom Class A Preamplifier:
This preamp was custom-designed for me by Kevin Carter of K and K Audio. I assembled and soldered the electronic components and constructed the case with all control features. It includes the K and K Audio Class A Single Ended Triode phono stage (maxxed-out version). The circuit topology is the same design as the Art Audio Vinyl Reference from the same designer, and is sold only in kit form to DIY enthusiasts. Kevin is also the designer of the Art Audio Vivo 300B amplifier. The Class A Differential Line Stage was designed by Dave Davenport (Raleigh Audio) with modifications by Kevin Carter. It includes an active output stage and is fully balanced from input to output.
Amplifiers:
Custom Class A Stereo Tube Amplifier:
This is a prototype that uses the original transformers (output and power) from a vintage Dynaco ST-70 and the original, but highly modified chassis. Designed by Kevin Carter and constructed by me, the circuit topology is entirely new, uses tubes, solid state devices and interstage Lundahl transformers. It bears some physical, but no sonic resemblance to the ST-70. The amp is configured to run in either triode (12-15 W output/channel) or ultralinear mode (35 W output/channel). The sound is open, airy, with stunning clarity, dynamics and bass response. I’ve listened to various amps and continue to prefer this one for its tonal balance and a midrange that sounds quite similar but not identical to that of a very good SET.

Cary/AES Sixpac monoblocks ( Upgraded)

Assemblage 300B (with upgrades): This amp is a work in progress that I am modifying to improve its sonic performance. Kevin Carter, again, is my design resource and has already suggested some changes that I’m working on.
Speakers:
GMA EOS HD monitors on two-post Skylan stands, each filled with 40 lbs. of sand/lead shot.
Power Conditioning:
Shunyata Research Hydra 8 Power Conditioner with
Shunyata Research Python Alpha Helix Power Cable
Cables: Custom made interconnects, speaker and power cables.
Vibration Control Devices:
Herbies Audio Labs anti-resonance devices (Tenderfeet, Iso Cups with Acrylic balls, Tube dampeners)
Component Storage: Solidsteel 3.5 rack; hardwood cabinet/credenza.

Listening Room: Dimensions: 11’ 4” W X 15’ 2” L X 8’H.
The room’s cubic volume makes filling the space with sound an easy job for almost any amplifier and for most monitors. Room dimensions will easily accommodate one fourth of a 20Hz wavelength which is all that is needed to achieve adequate bass response. The room has no audible flutter echoes, a common problem in many small rooms. The tonal characteristics of the music sound natural and are not distorted to a degree that is audible except, perhaps, to the most observant listener. There is ample control of reflections provided by carpeting, furniture, shades, bookcases and other decorative objects sufficient to allow a spatially pleasing and articulate sound that is open and airy. However, all sound characteristics most likely can be improved and I plan to treat the room with Schroeder-type diffusion panels.

Similar products
Monitors only: GMA Europa; Proac One SC; Proac Tablette Reference 8; EPOS-ELS-3; AR 3A; Advent; Energy ESM 1; Paradigm Point 1E.