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final Sonorous X Closed Back Headphones

09-10-2018 | By Robert H. Levi | Issue 99

final Sonorous X Closed Back Headphones

The final Sonorous X Closed Back Dynamic Headphones are the unmatched audiophile enigma of the decade. This cost-no-object luxury model of S'Next Co. Ltd. of Japan is both:

1) The most scientifically advanced, meticulously-complex, exquisitely-designed, delivering superior imaging and soundstaging, with the ne plus ultra definition I have ever heard; and,

2) have received a Rodney-Dangerfield-styled series of respect-less reviews in minor publications utilizing DACs, headamps, and sources way below those needed to truly evaluate them.

It may not have mattered anyway as these cans demonstrate year 2020+ futuristic technology being reviewed in 2017 upon their introduction.

The first time I recall acquiring a piece of high-end gear so far advanced and beyond the rest of my system was when I obtained the ARC SP-3 preamplifier. It took two years of hard work and big money to bring out the real benefits of this great preamp. The next time was when I bought a Decca Grey Mark 5 Cartridge, renowned for its lack of a cantilever. The stylus was directly connected to the cartridge coils. I tried a prairie-wide selection of tonearms, and only the London International Tonearm worked—sort of. I never did find out how great it was until 30 years later, when a current model appeared. The E.A.R. 890 Amplifier came in for review and embarrassed a pair of PASS X600 Monoblocks which I sold a week later. I bought a second one a year later and have used them since 2005, finding nothing that I liked better, and no limit to their musical goodness as my sources mature. 

In the world of headphones, I have found the Stax 009, Grado PS2000e, Audeze LCDX, MrSpeaker Ether Flow, Focal Utopias, AKG 1000, Ultrasone Edition 8, Sennheiser HD 800 and the LA&OC Audio Society 25th Anniversary Custom Grado Headphones made of a unique California wood to be at the top of the heap. (And that's a big heap!) My go-to headamps include the E.A.R. HP4 Tube headamp by Tim de Paravicini, loaded with NOS GE and RCA matched tubes, David Berning's MicroZotl all-tube output transformerless headamp with Bugle Boy and GE NOS tubes, the Grado AC Powered headamp designed by Sid Smith, and the headphone output of my vintage fully restored McIntosh MR80 FM Tuner by George Meyer TV, Culver City, California. I tried the Fios and the Pioneer $600 Music Players, but found the Astell & Kern A&ultima SP1000 Series High-End Music Player (copper) was both superior and advanced in ways analogous to the Sonorous X.

Astell & Kern A&ultima SP1000 (image courtesy of Astell & Kern)

final Sonorous X

With a large 3D metal chamber, their unique BAM technology, extremely special titanium voice coil, and more ingenious craftsmanship than I have seen, the X rivals the renowned NAGRA Professional Analog Tape Decks for fit and finish. The Sonorous X does Warp 10 performance if the sources are up to the challenge! Take a look at how the X is designed and the outstanding high-tech construction:  HERE  and  HERE.

I  used my best reference CDs, hybrids, Tidal Master, and three reference turntables featuring the Grado Epoch, Grado Aeon, The Stein Music Aventurin with Benz LPS motor, and the EAT Jo No.5 phono cartridges with all E.A.R. phono and Zesto Audio Andros Allasso amplification. Where all of the reference cans performed at-and-beyond the expected (no surprise here), the X was unpredictable. With the X, some recordings were just alive, simply alive. Some, not so much.

On female vocals from expensive XRCDs, the reference cans were fun and alive sounding. On the X, you were drowned in added sweetener and misdirected ambiance that was so dense, your only salvation was to hit stop. 

The Yuko Mabuchi Trio LP

On the new Yuko Mabuchi Trio all-analog, all-tube LP from Yarlung Records, with the Grado Epoch cartridge as source for both the E.A.R. HP4/X and Stax 009, the Stax was delicious and musical, as well as very, very smooth. With the X, you sat next to the piano. There was no recording chain. It is really a shock to hear (this with the DSD download on an A&K A&ultima SP1000 DAP). I wish I had more LPs like this. Maybe 10% of my collection deserves the X. This is 3D sound from headphones is an experience likely to rock your headphone and audiophile world.

The Acoustic Sounds LP re-issues, Classic Records re-issues, Impex Masterpieces, most Direct to Disc, Yarlung Records, Reference Recordings, and Chesky Records were all tape-like and reborn musically with the X. Other cans were more forgiving and just covered up more shortcomings. 

Surprise! The A&K A&ultima1000 utilizing the 3.5mm outputs is better than you know! With 24/96 up to 4x DSD, these musical files from top distributors who deal in these things are better than you're imagining with the X. I liked the DAP; now I love, love, love this DAP. What a chip set! It is another ARC SP3! It does not perform to that exalted standard with any of my reference cans until you plug in the X. When you do, welcome to the show! This is the combination of the audio gods. The Ultima SP-1000/Sonorous X combo convey the most portable audiophile experience on the planet!

Keep in mind we are dealing with space-age technology and a 105dB efficient/16 ohm headphone that plumbs the lowest lows to the highest highs with intense, mellifluous definition, and a neutrality with bullet timbres which are for the extreme musical connoisseur. That is me in a nutshell. I have a collection of rare LP lacquers which are masterpieces and last only 100 plays. Yes, these Sonorous X cans are for me. 

Another surprise! The under-$500 Grado AC Powered headamp is extremely fine with the X. Designed for LOW Z use, they are an inexpensive out-performer on the Sonorous X. I was very pleased with the overall performance of my tube references. Really good sources are required...forget many large solid-state headamps. Forget most CD players that are solid-state. Use only the finest cables you can afford. UITaudio Cables are terrific with the X. Love Kubala-Sosna, WyWires, Kimber Kable, and Jorma to get the maximum connectivity and fidelity.

How sensitive is the X? Every time I plugged them into my E.A.R. HP4 I heard a bell ring. With the unit on, but no signal, and volume set at zero, each plug-in or out rang a bell! I was hearing a filament in one of my NOS tubes greeting me. The same thing happened when I tapped the chassis just so. I have never had cans so out-of-this-world-sensitive where voltage so low was detected in stereo! 

Though the headamps and the DAPS used here were not perfect or totally neutral, their shortcomings were detectable with the X. I listened through them as well as to them to truly hear these outstanding headphones. A collection of SD chips forming the Maria Callas Opera Recordings in 96kHz/24-bit, produced in cost-is-no-object fashion by Astell&Kern, are a learning experience. Nothing is fake, compressed, expanded, or screwed with. On the Astell & Kern A&ultima SP1000, or fed into my E.A.R. DAC 4 to the E.A.R. HP4 headphone amp, the final Sonorous X was unabashedly a window on the performance, i.e., utter perfection. Callas was the authentic Callas, singing from the first act of Carmen, as real and breathtaking as ever heard. The symphony played just behind her, filling the soundstage. The chorus was behind and above the orchestra.

Though perhaps the phrase is overused by me, it still must be said:  With the very best material and playback devices, the final Sonorous X is the state-of-the-art. This will become even more apparent as DAPs, headamps, and software/sources increase in definition and decrease in artifacts in the future. 


The final Sonorous X closed-back headphones have been available for about two years in the U.S. My take is that they are generally misunderstood, and have been more or less ignored in this country. Their ultra-beauty led some to believe they were BEATS competitors. Others saw them as a closed-in design, and not really competitive with top open-back headphones. Others heard excellent performance, occasionally outstanding performance, but usually with playback equipment that was generally not up to the task. And finally, others just could not get past the $5000 price! 

The Sonorous X is beautiful because it is exquisitely designed and requires special elegant 3D printed metals. BEATS sound like cotton in your ears compared to the X. No open design can better the X, not even electrostatics—when the stars align for the X with the very best amplification equipment and source material. That's absolutely essential in my experience with them.

And yes, they are expensive—no getting around that.

Time will tell. Their low key approach to the marketplace may doom their success. Other less expensive Sonorous models may be more accepted and be close enough to the Sonorous X's overall performance to satisfy the marketplace.

All I can say is that the glimpse the final Sonorous X closed-back headphones give of musical perfection is real and thrilling if that kind of audiophile thrill ride is your thing. It sure is mine! Positively recommended – if only the cutting edge ultimate headphones of tomorrow suit your needs today!

final Sonorous X Headphones

Retail:  USD $5000

S'NEXT Co., Ltd.

3-12-7 Kitakase, Saiwai-ku, Kawasaki-shi,

Kanagawa 212-0057, JAPAN


Distributor In U.S.

Michael Brown


[email protected]

Review pair graciously loaned by:

The Source AV Custom High End Audio

All images courtesy of final, except as noted.