Now, I've owned some interesting speakers before but, these have to be one of the most interesting speakers I've come across in quite some time. Why? Well, probably because the mid drivers and woofers are made out of aluminum.
By today's production, aluminum may not seem so uncommon. However, back in the 70s/80s, there were probably only a small handful of manufacturers using aluminum cone drivers. Other than Hitachi, I can only think of Bozak using aluminum cones. I am sure they are more, I just can't think of any other manufacturers at this time. The woofers also uses an aluminum voice coil, think vintage JBL.
Another shocking aspect is the weight of these speakers. You would assume they look somewhat substantial, but they are fairly light weight. Makes one wonder why? I won't speculate as I'm not a speaker designer/engineer.
However, I can tell you that they sound really good. You wouldn't expect that a light weight speaker can produce such a nice sound. The bass has real good pace, depth and speed. Probably, faster than most paper cones I've heard. The mids are also quite nice and the treble is also shocking.
Despite using a titanium diaphragm in the tweeters, they are not harsh at all. They are very pleasant and non-fatiguing to my ears. I know they are not as harsh as some horns I've heard or other metal diaphragm tweeters I've heard too. The Magnat All-Ribbon-4 were much "harsher" in comparison.
They do have this particular Japanese sound signature to them and they remind me of the HPM-60 we've had. They kind of have this flat or balanced sound signature with a average soundstage. Hard to describe it. And, it's probably wrong for me to generalize. But, from the Japanese speakers (mostly bookshelves) I've heard, they tend to be quite controlled in SQ. Almost makes you think they could be pushed harder but, they've been tailored back a little bit.
I have owned my fair share of odd Hitachi speakers like the HS-55. Driver longevity is pretty good, there is no foam, so no need to replace surrounds. The mids have a treated fabric surrounds and the woofer has that "gather edge" surround.
Overall, they are an unique sounding pair of speakers, that's in great shape. Too bad it's vinyl wrapped but it's wrapped in a simulated paduk vinyl.