Janszen Z-600, Z-900, & Z-960 loudspeakers Janszen Z-900

JGH reviewed the Janszen Z-900 in September 1967 (Vol.2 No.4)

Every loudspeaker design must embody various compromises with absolute perfection, and while we have long felt that Janszen's Z-600 system was the most musically natural reproducer available for under about $500, we have also recognized the fact that some things about it could be improved. Its treble dispersion is not as wide nor as uniform as it could be, its low end (although better defined than that of most other low-efficiency systems) does not go quite as deep as, say, an Acoustic Research AR-3, and its low-frequency power-handling ability, while very good, could nonetheless be made better.

The new Z-900 sysem was intended to have all the advantages of the Z-600, but with fewer of its disadvantages. Instead of the two tweeter elements used in the Z-600, the Z-900 has four elements, so arranged that their treble beams span a wider angle and with more uniform coverage. And instead of the single woofer in the Z-600, the Z-900 uses two woofers, to extend the low-bass range and power-handling ability and to reduce bass distortion.

The four-element tweeter arrangement offers another advantage, too. With more total radiating area, the tweeter section's low-frequency limit is lowered, permitting the electrostatic elements to operate over a wider range of the audio spectrum, and the overall tweeter response is made flatter and smoother. A two-position tweeter-level switch is mounted at the rear of the speaker enclosure, to provide about 3dB of adjustment.

Z-900 Sound Quality
We tested two versions of the Z-900: an early model with what struck us as a rather unattractive grille comprised of dark-colored fabric with criss-crossed strips of wood veneer, and a later model with a choice of front grilles and a modified crossover network.

We were not very happy with the sound of the early model. It did have quite good treble distribution, along with the superb mid- and upper-range transparency and smoothness that we've come to expect from good electrostatic-tweeter systems, but the deep-bass improvement resulting from the two-woofer arrangement was somewhat offset by a noticeable mid-bass boominess, and the overall sound was strangely hollow and lifeless. Removing the grille panel (or replacing it with one of the later plain ones, without the criss-cross wooden strips) reduced the impression of hollowness, but did not entirely eliminate it.

The later model, with the modified crossover, had considerably better overall naturalness and sounded more alive, but we found there was still a slight tendency toward mid-bass heaviness and a certain subtle midrange coloration that imparted an "aw" quality to the sound.

The Z-900 has a superbly smooth, lucid high end—smoother and sweeter even than that of the Z-600—and an unusual degree of transparency throughout its entire range, and pickup tracking distortion, when it occurred, was noticeably less unpleasant-sounding from the Z-900. Yet there was no shortage of detail at its high end. It will put out a very strong 30Hz without audible distortion and at almost the same intensity as its 50Hz output, which allows it to rattle windows in a most satisfying way when the occasion calls for it, and the bass is very clean and tight. But some of the impact of this remarkable bottom is lost because of the slightly stronger mid-bass output, which the ear tends to latch onto as the "normal" low-end balance. Indeed, there were some locations in our listening rooms where a pair of Z-900s produced very oppressive mid-bass boom— something that is not easy to get from the smaller Z-600s—but careful choice of placement eliminated most of this.

Perhaps the best way we could describe our feeling about this would be to say that the Z-900s yielded the kind of bass fullness we are accustomed to hearing from most other systems of comparable size, whereas the Z-600s have the kind of unobtrusive low end that you're not aware of until a bass note comes along. To us, the latter is more like what one hears in the concert hall.

It is difficult to describe the midrange character of the Z-900, as this varies perceptibly depending on where you sit in front of it. Unlike most systems, which give maximum high-end output when you're on-axis, the Z-900 gives maximum midrange output when on axis. High-end distribution is subjectively uniform through an included angle of about 80°, but movement through this angle causes the midrange to vary from being quite forward-sounding on axis to fairly neutral at 40° off-axis. Consequently we found that best stereo imaging was obtained when seated midway between and symmetrical to the speakers. Under these conditions, imaging was quite good—better than that of the Z-600—and the midrange character of the sound could be adjusted to some extent by placing the systems flat against the wall or toeing them inwards as desired.

With most speakers we have tested, there was a marked change in sound when going from a good tube amplifier to an equally good transistor amp. The Z-900 showed the usual improvement in deep-bass output and detail, but otherwise there was less difference than usually noted. With a Dyna Stereo 70 tube-type amp, for instance, deep bass was quite adequate, with relation to the middle and upper ranges, but was slightly masked by the upper bass range. With the Dynaco Stereo 120 transistor amplifier, the deep-bass range from a pair of Z-900s was strengthened to the point where it was almost overly heavy, a not-at-all-unpleasant condition, but one that some listeners may not like, in which case some adjustment in room location is all that is necessary to rectify the situation.

The Z-900 is just a shade more efficient than the Z-600, which would make it around 2% efficient, on a rough guess. It is still a low-efficiency speaker, but since it will handle almost twice the power of the Z-600, it can produce plenty of output with a high-powered amplifier. If you want Row-A-type sound, this is not your ideal speaker—you'd do better with a good horn system—but it will easily put out Row-H-type levels with an adequate amplifier.

Summing up the Z-900
On the basis of objective criteria, then, the Z-900 should undoubtedly be judged superior to the Z-600, simply because of its smoother high end, higher power capability, and deeper, better-defined bass response. At almost twice the price, it should be better, and many listeners probably will prefer its fatter, more forward sound. After having lived with both systems for a while, though, we found that we derived more musical satisfaction, from a wider variety of program sources, from the Z-600 system. This is one case, however, where personal preference is clearly playing a major part in our decision, for whereas we are inclined to judge a system on overall musical naturalness first, and bass/treble performance afterward, listeners to whom full, rich bass and silky, extended highs are of primary importance will more than likely prefer the Z-900.

Janzen Z-900 Manufacturer's Comment
We emphasize that the Z-900 is a big speaker built primarily for use in big rooms. The variance in emphasis from bass to mid-bass and the occasional seeming boominess are, we believe, entirely a function of the characteristics of the listening room used for the tests.

The basic design principle of our speakers is to create individual components (electrostatic radiators and dynamic woofers] with the smoothest possible response, thus ensuring that combinations of these components will yield overall balance and smoothness. This will however be affected by the listening room and by the speaker's location in that room, just as would be the case if live musicians were performing in the room.

We agree that the changes made in the crossover network of later-model Z-900's have improved their performance. Only 60 units were produced with the original crossover network.—Frank Wetherill, Neshaminy Corp.

Neshaminy Electronic Corp. (1969)
JansZen Audio( 2022)
480 Trade Road
Columbus, OH 43204
(614) 448-1811

RichT's picture

I can’t judge the sound quality of course, but the build quality is incredibly primitive. How far we’ve come in only 55 years!

Anton's picture

Adjusted for inflation, the Z-600, which was 200 bucks in 1966, would be about 1600 bucks a pair now. You're dead right, that build quality nowadays would only be tolerated if the speakers cost much more than that. ;-D

You made me think of the recent review of the Mayfly Audio speaker at 5800 per pair, with stands. They seem kinda home brewed in their physiognomy, as well.

Then, you made me think of the look of the original Advents and the early AR speakers, especially the AR3. Speaker makers in those days really seemed to have a thing for hot glue!

We certainly have come a long way!

scottsol's picture

I believe the quoted price is for a single speaker. The pair price adjusted for inflation would be ~$3700.

MattJ's picture

I love reading the vintage reviews.