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The YS-500 did defy a number of assumptions. In no particular order, here were a few. #1, which of my valve amps would rein supreme? From Emission Labs solid-plate direct-heated 45 power triodes to EML 300B-XLS to MIG fighter 6C33Cs in single-ended zero-feedback mode to Russian EL84s and 6N14Ps in push/pull with NFB, I tried everything I had on hand.

Surprisingly, I favored the 6BQ5 push/pull amps from Luxman and WLM. Of those two, the Austrian/Serbian Minueta in pentode was best. The Yamamoto A-08S was too lean and not controlled enough in the bass. The A-09S and Ancient Audio Single Six monos were too soft and not grippy enough. Those in the know will lift an eyebrow. Upon consideration, they'd apply the implied counter balancing action to reliably predict certain things about the speakers. Obvious differences between amps were output power, feedback/output Ω and 2nd vs. 3rd order THD dominance.

By favoring feedback amps of—relatively—higher power connected in push/pull pentode, it would be correct to think that I found the YS-500's ultra laid-back personality happily responsive to an injection of sharpness, edge definition, spunk and speed. Those who'd equate all horn speakers, even 'half horns' like this one, with an incisive upfront edge-of-seat personality would have already misjudged the Yamamoto speaker by a lumbering country mile - at least relative to how it performed for me without a de facto rear wall (more on that in the conclusion).

What surely played into this—anti—equation was the hybrid nature of the dispersion. Being partly dipole in bands where the conventional 4pi pattern of direct radiators no longer reaches, the YS-500 energized more of the subjective sound field behind the speaker. Sounding admittedly truer to life in gestalt because of it, it also introduced diffusiveness, blurring and very soft transitions. When coming from the usual uni-directional radiators, this took serious acclimatization.

Assumptions #2 and #3 would predict either mondo bass by just looking at the buffo woofer; or very curtailed lumpy bass when envisioning dipole cancellation from the open back. With my office desk at the end of the L-shape behind the kitchen island facing the windows, I'm intimately familiar with room resonance nodes outside the listening area. I discovered right quick that the YS-500 did not trigger them (whereas my usual ASI Tango R rides them fiercely at that end of the long space).

My room treatment of absorber columns behind the listening seat and Franck Tchang-installed tuning devices throughout have arrived at respectably even response in the seat considering how the thrice-woofer'd Tangos really do plumb the depths. Even so, unnatural bass fare of Mercan Dede caliber and at high volumes can approach overload at certain frequencies. The YS-500 triggered no such resonances to suggest that at least in my setup, dipole bass (which involves the room more) causes less audible problems. However, neither did bass extend as low nor did it hit as hard. The Zu Essence in my inventory for example goes lower and is decidedly ballsier and feistier all around. True, the YS bass had more swing and nonchalance and for that sounded more real in that band. That's a qualitative or fundamental difference even though undeniably there was also less quantity. But the latter registered less. I'd often read advocates of dipole bass preaching their gospel of superiority but never before enjoyed personal experience in a room I knew well. After the fact, I'd cautiously sign my name on their side of the ledger while admitting—in parallel or series—that as with most things hifi, it's another one of those tradeoffs. Here it was between more natural but rather lighter and less extended bass vs. more 'audiophile-impressive' impact bass with true reach.

Assumption #4 states with conviction that broad baffles don't image. Better ride a different horse. That one's so lame, it barely walks. Soundstage depth and width with the YS-500 were no worse or better than the usual quality artillery. Image focus or outline sharpness were quite softer, arguably closer to real life but far from as holographically visual as modern hifi can aim for.

Assumption #5 knows that because 2-watt amplifiers are plenty sufficient for such speakers, they're superior by definition. From my options, that clearly wasn't the case. Whether the Minueta in pentode "won" due to power (14 Ultralinear watts), superior definition, a more developed top end, a specific THD profile, other factors or a particular combination thereof can't be answered. Still, it's a useful reminder. Just because high-sensitivity speakers don't need more than a handful of watts doesn't disqualify more powerful amps on principle. It's important to try anything and keep an open mind.

Assumption #6 might be the most prevalent, namely that horns correlate with a fierce, super-direct kind of honing or bore action whereby the sound transmits through the air. And there are horns that fit the description. Not Yamamoto's however. Again, the overall sound of this speaker—without benefit of rear-wall loading perhaps—was big, billowy, relaxed, surprisingly even and tacitly soft, nearly bordering on the indistinct. Dynamics scaled with vigor but transients never sliced. The YS-500 far from acted as though it were dialed for speed and jump. It seemed about warmth, richness and laissez-faire but unduly so. Because of the soft top verified with triangles and their decays and general leading-edge ease all around, resolution did not match more conventional modern speakers.

Assumption #7 correlates high voltage efficiency with superior low-level listening satisfaction. This is one belief I tend to subscribe to myself but in the case of the YS-500, I found the 91dB ASI Tango R to be clearly more persuasive at whisper levels. It's far more resolved in the traditional sense of the term. Ditto for the Zu Essence. The YS-500 wanted a few extra clicks on the volume before it awoke and even then its innately soft character rendered rhythmically complex material too loosely structured and not sufficiently vigorous while the general impression was of a broadband suck-out or dip. Describing this sound in terms of farfield effects where the ambient field dominates, where separation blurs and transients lose their power is probably the most apt.

Assumption #8 coincides with the conclusion but is the most important. That's because I'm highly suspicious that the YS-500 performed far from its best within the setup geometry my space enforced. Given my unabashed admiration for Yamamoto amplifiers and DACs and extensive experience with them, I expected rather more from the speaker. I found it too polite, distanced, bordering on the amorphous and neutered. That's decidedly not how Shigeki-San's amplifiers sound. Hence I refuse to believe that he'd author a reference speaker that does. In fact, in Asia the YS-500 has already garnered an Audio Excellence Award for 2010. My gut instinct tells me that my own experience was far from representational. I believe this speaker probably wants a solid wall behind itself within 1 or 2 meters. That's in fact how Yamamoto himself set it up at this year's Japan audio show [above]. Readers interested in this speakers are strongly advised to consult other opinions to gain a more balanced notion on what the Yamamoto YS-500 is really on about!

Quality of packing:
Cardboard with cardboard/foam inserts and plastic sleeve is quite light in construction but was obviously sufficient to deliver the speaker from Japan to Switzerland in perfect condition and without trashing the boxes.
Reusability of packing: At least once.
Quality of owner's manual: No manual required or supplied.
Condition of component received: Flawless.
Completeness of delivery: Perfect.
Website comments: Limited by software-generated translations from Japanese to English but informative if you can make sense of the often garbled English.
Human interactions: Professional and very friendly.
Pricing: At ca. €7.500/pr when based on its performance as described, the Zu Essence even at its European €5,000/pr price would be the wildly more attractive proposition.
Application conditions: Appears to want a back wall within reasonable proximity.
Final comments or suggestions: Recommendation to remove the grill coincides with either leaving screw holes in the baffle or remounting the screws with their standoffs for a not entirely stylish look. The open back isn't cosmetically attractive if the speaker must be placed such as to present it to the eye.
Yamamoto SoundCraft website