First to the nonlinearities. As is common for most dual-concentric high-efficiency drivers, the 604 has excess energy in the second octave above middle C. On two recordings I played, one with vocals, one with violin, the soloists kept riding that very spot to have certain notes flash like sunlight refracting off watery ripples. The emphasized notes thus also seemed to physically move forward. The bandwidth or window of this aberration was significantly narrower than it is on untreated Lowthers, the extent of the rise clearly lower. It thus took specific recordings which unwittingly focused on these spots to make them stand out. On most material, these upper midrange squigglies were surprisingly well hidden.

Because Hiraga hadn't brought the direct radiator tweeters, triangles decayed prematurely and top-end air was subdued. Of the amps tried, Nelson Pass' FirstWatt F5 had the best top-end extension under those conditions while the MiniWatt surprised all in our party with its treble refinement and effulgence.

Because we sat in closer proximity than ideal -- ditto the sidewalls -- hard-panned events to the left and right didn't disconnect from the big boxes as well as they had minutes earlier with the narrow Albedo HL2.2s and their small 5-inch ceramic mid/woofers.

Now to the interesting stuff. As you'd expect, image outline sharpness with the big 15-inchers was less acute than over the Albedos (which I had Hiraga listen to for a few tracks to help him acquire a baseline impression of the room and system; and which is why the big 130-watt German tube monos on the Albedos remained in place for the first Altec session even though they didn't remotely require such power). As such, image specificity leading to soundstage holography wasn't of the heightened kind that's so popular with modern listeners.

This included the handling of bass transients which lacked the cyborg brutality lovers of overdamped alignments mistake for realism. Yet bass output and extension were surprisingly capable and clearly abetted by the bass reflex loading considering that contemporaries of this vintage driver considered 50Hz to 15kHz fully exploded bandwidth. As a brief descent into ethno ambiance by way of Mercan Dede's Nefes proved -- Taiko drums too would have done the business -- Hiraga's implementation of the 604 does profound pressurized bass to accommodate the kind of modern music the original designers of the 604 couldn't have predicted in their wildest dreams.

What they couldn't have predicted either is just how anemic a presentation by comparison many a 21st century listener would gladly settle down with while parting with very serious coin for the dubious privilege. If there's one core quality Hiraga's speakers celebrate, it's got to be Flesh & Blood. Fanciers of vintage Tannoy dual-concentrics will instantly relate as would those familiar with Bernard Salabert's 12-inch PHY with central piezo. These are the abandoned mines of Solomon folks like Zu and WLM work in again to recapture qualities that were lost when hifi pursued small diameter drivers of low sensitivities and when the audio press began to celebrate the predominantly visual aspects of the playback experience.

Our forefathers went after a bigger bolder sound whose spatial presentation far closer tracks the ambient-rich farfield experience wherein images don't stack one next to the other with laser-cut edges but transition more gently. The qualities they went after were tone mass and dynamic reflexes. One could -- rightly -- protest that true timbres require the full participation of all harmonics; that without the assist of super tweeters, the 604 clearly doesn't invite to the party all the overs in tone. Touché. Still, how to explain that instrumental and vocal timbres sound more realistic over this type of vintage driver than many modern variants? I would have loved to hear the front-firing super tweeters for that precise reason. They're crossed in lower (12kHz) than the rears (14kHz), Hiraga opted to set up the pair he did bring to fire backwards and I wasn't going to argue with a legend.

'Bold' in modern parlance could connote shock-jock values but the way Hiraga's speakers handled that aspect was gentler. There wasn't the kind of focus on shattering transient demolition impact modern hifi deems important. To borrow from boxing, there was enhanced follow-through right past the initial contact. Where contemporary small drivers might dazzle with their speed of attack, the 604 impressed with the amount of connection its fist made with the shoulder, then hip and heel of the body behind the attack. This segues directly back into the earlier tone mass. Vintage aficionados would cite paper and Alnico and perhaps even solid wood for the enclosure. I'm not suitably familiar with this sector to feel competent assigning causes to specific observations. I merely report on observable effects and tone mass captures the chief one most adequately.

In this context, it's quite interesting that the earlier mentioned Zu and WLM designers rely on Eminence driver platforms. Eminence after all specializes in supplying transducers to musicians who must amplify their instruments. Why don't musicians favor aluminum, Titanium, Beryllium, Kevlar, Carbon fiber and plastic membranes over paper?

It would be fallacious to assume from the above that the JH-MS15 is so vintage-y of mien as to require pipes and slippers to appreciate. I don't know how this driver sounds in other implementations to understand how much or little Hiraga has done to bend it to his will. From what I heard, the speaker did not celebrate bygone times in bad SET fashion (no bottom, no top, deep triode colorations). Particularly in bass power and extension, it is thoroughly modern. I'll assume much the same on top once the two missing super tweeters are added.

With those concessions to modernity in place -- and this isn't vacuous as modern music is very bandwidth extended -- the special allure of the JH-MS15 is its majesty of tone whose impact is centered on the rise portion between transient and decay; its dynamic wallop; and the color richness and density of its presentation which is less holographically separated and more organically integral than contemporary values.

It's perfectly fitting that Hiraga as the self-styled champion and first born-again Western apostle of SETs, horns and other high-efficiency speakers would issue the JH-MS15 as an ongoing demonstrator and reminder that long-dead engineers at Altec, JBL and Western Electric had gotten far more right than we in general give them credit for. Newer isn't always better, the past rarely as golden as we remember it.

Where exactly one's own proclivities fall depends on the usual subjects of taste, exposure and priorities. Regardless, it's vital to not forget past accomplishments to insure that modern advances build upon them rather than trade in specialized aspects to lose sight of the bigger picture. Hiraga's labor of love will only sell 10 pairs. The perhaps even more interesting second chapter of this story will be if his planned reissue of the 604 driver itself comes to pass. To make available again one of the most legendary of vintage transducers -- perhaps even improve its linearity with applied hindsight wisdom or more modern manufacturing capabilities -- is quite the tantalizing proposition. Anyone with an opportunity to hear Hiraga's MS15 should do so as a matter of education. To earn a well-rounded audiophile diploma relies on being exposed to a wide range of approaches and solutions. To be on familiar terms with the Altec 604 certainly belongs on that curriculum.

Jean Hiraga website