Kodawari Chronicles: A Touch More on Top

Fostex T900A (Alnico Super Tweeter)

Seasoning. A pinch of salt, a grind of pepper, a dash of umami. Miniscule additions in the grand scheme of any dish. And yet they make all the difference between average and amazing results. Overdo it however and disaster awaits, as single tastes overwhelm any subtlety and depth.

Such is the delicate balance act when attempting to augment a classic like the Altec 604E. For this edition of the 604 Altec’s published measurements (and my own in-room sweeps) show a fairly steep drop after 10K. This lack extension was remedied in later models. Some may even consider it a plus. In everyday listening I never felt I was missing significant high frequencies — the top end never seemed compromised. But perhaps things could be even better…

Browse enough images of Japanese 604 set ups and you’ll frequently see tweeters mounted topside. Ditto one of the last serious 604 implementations, the Jean Hiraga JH-MS 15 Reference. It was, I believe, an aperiodically bottom vented, narrow baffled floorstander (narrow being a relative term in the world of 604 cabinets). It featured two topside tweeters on each speaker. The forward facing a Fostex(?) crossed over at 12K, the rear a JBL 2402 bullet adding its voice above 14K.

Hiraga JH-MS 15, Munich 2008

Those that heard this combination at the Munich Hi-End Show praised it as impactful and lifelike, giving little ground to more modern speakers but exhibiting a raw palpability and stunning dynamics. Sadly not much more has been written of that first outing as the battery powered components driving the exhibit self-immolated on the evening of the first day, reducing the entire setup into a pile of charred what-might-have- been. The only other widely circulated look at the speaker was a brief demo for 6Moons.

But anytime I see both the Japanese audio cognoscenti and Mssr. Hiraga exploring similar avenues I am intrigued. To scratch the itch I tracked down some 2402’s, a pair of Fostex T900a and some PIO caps and began to experiment.

First up was a duplicate of the Hiraga setup. This led to an increase in air but something was a little confused and disjointed, the benefit coming at a cost of slighty reduced clarity. This very well could be the result of the (unfortunely necessary) placement of my speakers on the wall boundary. Given the room to breath that Hiraga utilized behind his units this may still be the way to go for those blessed with more accomodating rooms. Out went the JBL units.

Next I tried the Fostex crossed over at 9K and forward firing. Too heavy a slathering of the treble sauce. I tried dialing down the the overall impact via a pair of Fostex autoformers (beautiful and handy pieces of kit BTW) but still no bueno. Not only was there too much overlap at the crossover point, the system had taken on some of the characteristics of the etched treble present in many of today’s modern highend speakers. Not a bad thing in all cases but not what I was going for in my build. Stringing together some 3uf capacitors in series enabled me to up the crossover point to 13K. Much better. But still not there.

Moving the tweeters to fire at a 45 degree angle relative to the front of the speaker was a leaps and bounds improvement in air, with a significantly greater sense of space and presence. A final move rearward to a position that was approximately in a vertical line with the 604’s compression driver locked in the benefits.

Angling for air

This addition has given the 604 an added dose of palpability, something this driver already possesses in spades. One could liken it to casting just a bit more beautiful light on a subject at the golden hour, or breathing a little more deeply in a mountain meadow — burnishing an already great experience to yield a subtle but important improvement. As always your mileage may vary, but I strongly encourage giving it a shot as another interesting step on the journey. Onward.

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