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August 2007
Enjoy the Music.com Review Magazine

The Micropure Kotaro (Cz302ES) Minimonitor Loudspeaker
A cut above the competition.
Review By Dick Olsher
Click here to e-mail reviewer


Micropure Kotaro (CZ302ES) Minimonitor Loudspeaker  A newcomer to the United States, Micropure is apparently quite popular in the Japanese home market, at least so I'm told by folks who should know. The Kotaro (meaning 'small child' in Japanese) sits comfortably in the minimonitor category, being tiny enough to practically fit inside a shoebox. And yet, the adage that good things do come in small packages (think diamonds) holds true for the Kotaro. It is in my estimation a cut above the competition in its genre. Here's a product that is both remarkable and unusual in several respects.

Designer Sakuji Fukuda evolved his acoustic sensibility during his tenure with Nobuyuki Sato, a well established concert sound engineer at N & N Sound Freaks, a company specializing in customizing Japanese concert venues. He says that working with a wide range of musicians (which included Bruce Cockburn, Milt Jackson, Maynard Ferguson, Jessie Colin Young, Elvis Costello, Concord Jazz Orchestra, and Mercedes Sosa) gave him an intuitive feel for sound quality and musical authenticity. Years later, when he took on the mantle of speaker designer, he sought as a sonic priority to reproduce the "organic" aspect of a live performance. Is there a connection between the Japanese culinary art of sushi preparation and the design philosophy of the Kotaro? Apparently, yes, according to Sakuji-san, as in both cases a simple but perfect form defines the quality of the final product.


Technical Details

For starters, the cabinets are constructed by Fujiken Inc., a company said to be a world-leader in the manufacturing of music boxes and instruments. They are undeniably beautiful with a level of finish that is quite remarkable relative to the veneered cabinets that attempt to pass for a piece of furniture these days. Handcrafted from solid woods, mahogany sidewalls and a maple front baffle, the cabinet design flies in the face of conventional wisdom. Instead of using higher density MDF and various damping treatments, Micorpure has chosen instead to minimize cabinet mass. Solid wood is much less dense relative to MDF, which accounts for the featherweight of the Kotaro. At 5.5 pounds each, these speakers can easily be carried under one's arm. Rather than sealing the drivers into the cabinets, which is standard practice, the Kotaro's drivers are mounted with point contacts, not unlike the way the strings of a violin or a guitar are mounted to the instrument's body with a bridge. The microscopic air gap that isolates the driver from the cabinet is said to facilitate a natural harmonic decay analogous to the sound of a stringed instrument.

Presumably, as a result of both low mass and significant lack of damping, the cabinet's resonant time signature features rapid energy decay. Some cabinets continue to release energy for several hundred milliseconds after the initial excitation and thus manage to obscure the music's detail and rhythmic drive. The opposite is true with the Kotaro; cabinet resonances do not linger. The music is consistently allowed to ebb and flow with supreme clarity.

Micropure Kotaro (CZ302ES-XP) Minimonitor LoudspeakerThink of the Kotaro as a full-range design augmented by a super tweeter. A 4-inch coated paper cone essentially reproduces the entire musical spectrum, with frequency extension to about 15kHz. There are no crossover networks in the critical midband. The Murata spherical piezoelectric super tweeter fills in the extreme treble and extends the response into the ultrasonic range. As I've said before, while ultrasonics can't be heard in the conventional sense, such energy can couple directly to the brain and be perceived. There is in fact scientific evidence (including PET scans) that demonstrates cerebral blood flow activity in response to ultrasonic energy. Of course, these findings are irrelevant to music reproduction in the home since the program material is severely bandwidth limited. For example, the standard CD format is constrained by a 20kHz hard limit. Yet despite the program bandwidth limitations, in my experience, the higher the tweeter's upper frequency limit, the faster and more alive a speaker typically sounds.


The Sound

Let me start with the bass, an area that minimonitors are notoriously weak in. There's no cheating Mother Nature. With a four-inch woofer pushing air, bass efficiency and dynamic range are limited. Forget about deep bass, in my room bass extension was flat to about 60Hz. In addition, the tonal balance was on the lean side of reality, with the upper and mid bass range, below about 200Hz, shelved about 3dB relative to the lower midrange. I've been partial to a full-bodied tonal balance for many years, and planar speakers such as the Magnepan MG-3.6/R and Sound Lab A-1 that have made it into to my personal pantheon, are naturally exceptional in this regard. But the good news is that the Kotaro's midbass reproduction was not only consistently quick and tight, a minimonitor trademark, but surprisingly dynamic and rhythmically engaging to a level that transcended the ordinary. Thus, despite its limitations, bass lines retained a bit of concussive punch, quite remarkable for a bass reflex tuning.

The purity of the midrange was electrostatic in character with squeaky clean harmonic textures, and exceptional retrieval of low-level detail. When matched with the deHavilland GM70 monoblocks and Audio by Van Alstine's Transcendence 8 line stage, it was tough to argue with what upon first impression felt Mozart-like in its pedigree of perfection. Harmonic colors retained a satisfying warmth and natural vividness. Transients were quick to unfold and the soundstage exhibited minimal veiling. I see that I'm being entire too analytical with respect to the sonic character of this speaker. Above all else the sound was superbly cohesive, alive and engaging, and I'm sure that the presence of the Murata super tweeter played a significant role in the heightened perception of the music's drive and verve. This is not the sort of speaker you can ignore. It demands attention and gives the music's emotional content satisfying scope for expression.

I recommend that you setup this speaker using a minimal toe-in with respect to the listening seat, as the lower treble range is emphasized by 5 to 8 dB on the tweeter axis. I realize from personal experience that a bright balance may be highly addictive (at least in the short term), and that there may be a cultural preference for bright sound in some markets, but do me a favor: do not listen to this speaker on axis. If you do, its tractor beam of high-intensity treble will latch on to you and abduct you to another dimension. A 10 to 20 degree toe-in relative to the woofer axis provided the most natural presentation, though you should experiment with toe-in angle to match your own tastes.

Orchestral crescendos did give the Kotaro a case of congestion at anything above moderate playback levels, generating excessive distortion levels. So be careful with playback levels and pick your music carefully - please, no hard rock! And in case you're wondering, imaging specificity was pin-point in its focus, in keeping with the fine reputation established by minimonitors in this regard. Soundstage depth perspective was nicely delineated and stage width with natural recordings was also commendable.



The Kotaro redefined my expectations of what minimonitor sound is all about. It is without a doubt the most engaging, enjoyable minimonitor I've had the pleasure of auditioning in a lifetime of musical pursuit. It is said that in cooking the proof is in the tasting. In audio the proof obviously is in the listening, and the Kotaro made a believer out of me. Bottom line: when deployed as described above the Kotaro is capable of ascending to sonic heaven and singing like a little angel.



Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High-frequencies (3,000Hz on up)



Inner Resolution

Soundscape width front

Soundscape width rear  
Soundscape depth behind speakers

Soundscape extension into the room



Fit And Finish


Value for the Money



Type: Two-way monitor / bookshelf loudspeaker

Tweeter: Murata Super Tweeter

Full-range driver: 10cm coated paper cone

Frequency Response: 70Hz to 105kHz

Nominal Impedance: 4 Ohm

Power Handling: 60 watt RMS, 100 watt peak

Sensitivity: 86dB/W/m

Dimensions: 163 x 247 x 192 (WxHxD in mm)

Weight (per speaker) 2.5 Kg.

Cabinet Material: Baffle = Solid Maple, Body = Solid Mahogany

Price: $2800 per pair


Company Information

Micropure High Performance Speakers

Voice: (81) 42-581-7825
Fax: (81) 42-581-7825
E-mail: info@micropure.jp
Website: www.micropure.jp













































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