Sony ES SS-M9ED loudspeaker
The playback system consisted of two new Sony speakers driven by Pass Labs monoblocks and preamplifier. The speaker was the SS-M9ED, part of Sony's ES series of high-performance components. Other than the addition of a ball-shaped supertweeter module and a high-gloss lacquer finish, it looked very similar to the SS-M9, which I had favorably reviewed in the September 1996 Stereophile.
I next heard the SS-M9ED at HI-FI '99 in Chicago, where Sony was again demoing the SCD-1. Again I was impressed, so I asked for a review pair. These actually arrived at Stereophile's Santa Fe offices at the end of 1999, but the relocation of the magazine's editorial department to New York and the inevitable delays in fashioning a dedicated listening room in my new Brooklyn home meant I couldn't start on the review until October 2000. Various things and other reviewing responsibilities then conspired to keep the review from being finished until Memorial Day. My apologies.
When Sony decided to launch their ES loudspeakers in 1995, they gave ex-Polk engineer Dan Anagnos a clean slate. Though the original ES SS-M9 was a three-way floorstanding design, conceptually it was a two-way minimonitor within whose enclosure twin woofers had been added. The goal was to combine the sonic advantages of a full-range design with those traditionally associated with a minimonitor: high loudness capability, excellent bass extension, midrange neutrality, and well-defined stereo imaging.
As I said above, the new M9ED speaker looks superficially similar to the M9. However, in Dan Anagnos' words, "it is really a completely new, ground-up design with entirely different goals and objectives. We began this design with an enclosure of the same approximate size and shape as the SS-M9 and a very similar drive-unit configuration (albeit with significantly different drive-units) because the SS-M9 was a successful and proven design platform."
Having access to high-resolution DSD-encoded recordings during the design process was apparently a major benefit. According to Sony's white paper, "By utilizing source material with much higher fidelity than CD, we were able to refine the M9ED's design to a point not possible in the past. Four basic tenets formed the foundation of our design philosophy for the M9ED:
"1. Exercising engineering as an equal combination of science and art—being creative and innovative by applying science in a constructive, imaginative, and artistic manner.
"2. Emphasizing 'Simplicity of Design' or a 'Less is More' philosophy throughout.
"3. Applying a fanatical attention to detail and never compromising; implementation of the design being equal to the direction or objective of the design.
"4. Utilizing a Balance of Design approach, with equal emphasis on all areas of design and their synergistic combination." [All italics Sony's.]
Powerful words. And despite the SS-M9ED's unassuming appearance, it appears that no stone has been left unturned in its design.
Although they look unprepossessing, the M9ED's drive-units are made in Europe to Sony's specifications and are impressively engineered. All feature careful shaping of the pole-pieces to give a symmetrical magnetic field gap—this, in conjunction with the overhung voice-coils, should result in low distortion. Aluminum flux-shunting rings are used on the midrange and woofer voice-coils to further improve linearity, and all the voice-coils are wound on large-diameter, vented aluminum formers to give high power handling. The twin midrange units and woofers all feature mineral-filled polypropylene cones with butyl-rubber surrounds, and the drivers are constructed on cast magnesium chassis.
The ferrofluid-cooled 1" tweeter uses a polymer-doped fabric dome shaped to give, in Sony's italics, "no resonance or ringing effects at all." A sealed rear chamber is used to absorb the tweeter dome's backwave, and the pole-piece behind the dome has been machined to minimize reflections.
The supertweeter, mounted in a rotatable aluminum pod atop the enclosure and operating above the audioband, is interesting in that it uses a stationary voice-coil. Had the coil and its former been attached to the diaphragm in the conventional manner, the ultrasonic output would have been curtailed both by the extra mass and by the usual voice-coil inductance. Instead, a single aluminum ring is attached midway along the length of a cylindrical extension of the ceramic/carbon dome, to give balanced drive. The diaphragm moves in response to the electrical current induced in this ring, and, because the main coil doesn't move and has a nearly saturated ferrous core, its inductance is said to be very low. A powerful but small neodymium magnet provides enough sensitivity for the unit to match the M9ED's other drive-units.
Biwiring terminals are provided, and the crossover uses audiophile-quality components, such as multiple polypropylene capacitors rather than single, large-value electrolytics, and, with one exception, air-cored inductors. The tweeter and supertweeter filters use what Sony terms the "Perfect Lay, Hexagonal Winding, Litz Wire Inductor." Seven separately insulated pure copper wires are twisted and wound in a computer-optimized manner, to eliminate proximity and skin effects. All the crossover components are damped, as is the printed circuit board that carries them, the board mounted with shear-loading thermoplastic grommets and aluminum ferrules to further reduce vibrational effects.