Infinity Servo-Statik 1 loudspeaker J. Gordon Holt Summer 1975

J. Gordon Holt returned to the Servo-Statik in the Summer of 1975 (Vol.3 No.9):

We have our own corollary to Murphy's law, which we read off like the Rights of the Accused to every manufacturer who sends us equipment for testing. It goes: "If one sample out of 50 off the production line is to become defective immediately after passing final inspection, that will be the one sent to Stereophile for testing.

In April 1975, Murphy moved in to stay. Our preproduction prototypes of the Infinity Servo-Statik 1A speaker system arrived, having been previously tested for only three months. It wasn't enough. Within the first three days, the electronic crossover started cutting off the tweeter in one channel. Obviously a simple case of a defective part on a plug-in circuit board, right? Right.

Except that when the new, production-type board arrived, it kept popping fuses on the crossover. Seems it was not quite like the pre-production one, and was shorting to a mounting bracket which, in the production crossover, had been moved so as not to short out the new board. We fixed that with insulating tape, but by then the rectifier had been so over-taxed that it let go.

Then the electrostatic speaker power supplies started popping. And so did two replacement circuit boards. Next, we lost two of the Infinity midrange panels, and somewhere in between our first sample of the switching amplifier pooped out.

The full report on the Infinity SS-1A scheduled for this issue has therefore been postponed...For the nonce, though, we can report the following:

Unquestionably, the SS-1A's weakest point is its stereo imaging. This is very good, but is not outstanding. Nonetheless, the system is one of the two most accurate reproducers that it has been our good fortune to hear. Like other dipole radiators, it is very critical of room placement. Improper positioning can cause midrange colorations (nasality, honkiness, etc.) and imperfect "meshing" of the lower-range response of the panels with the upper range of the single-box woofer. Similarly, improper positioning of the woofer can cause excessive, inadequate, or irregular bass response. But the advantage of having the woofer separate from the upper-range speakers is that all of them can be located for optimal, no-compromise performance if you have the patience (and know-how) to do so.

Balance settings on the electronic crossover are critical, too. The tendency is for most dealers to set both the bass and treble too high, causing heaviness and hardness. Finally, these speakers absolutely must be driven by the best available electronics, and that implies either top-notch tube stuff or Infinity's switching amplifier. The preamp should be an Audio Research SP3A-1, but a good Dyna PAT-5 does a very passable job.

More particulars in the next issue. Meanwhile, this has become our standard by which other reproducers (and the original tapes that we make) will be judged for the foreseeable future.

Infinity's first Servo-Statik system, the SS-1, gained a reputation (justified or not) for undependability, and our experience with our pre-production SS-1A did little to undermine that reputation. One tweeter channel in the crossover was intermittent, then the crossover started popping fuses and had to be replaced. The other has worked fine ever since. Two power supply supply boards in one electrostatic unit broke down, due to a set of filter capacitors that were inadequate for the task despite conservative voltage ratings. The replacements, with twice the rating, are working fine. One power transformer in the other electrostatic developed a short through its output wire insulation to the end bell. The replacement transformer—current production—had a grommet in the end bell to prevent that from happening again. Finally, two of the midrange electrostatic panels split, and these had to be replaced.

Our SS-1A now seems to be doing fine—nothing has failed for over 2 months—but only time will tell how other samples fare in the field. (Electrostatics have to be less dependable than dynamic speakers, by virtue of their powering circuitry. But that's a risk we will gladly swap for the quality of sound that can come from electrostatics.)

Addendum: Several weeks after our SS-1A arrived, we received our finalized FMI J-Modular speakers, and a1though we are still very much impressed with the SS-1A, we must now report that the FMI is in the same league as the Infinity. The Infinity is rather more versatile, in that it can be made to operate optimally in a wider variety of acoustical environments, and it has noticeably better middle-range focus and "snap," but it no longer has the Class-A group to itself. This must now be shared with the FMI, which is reported on elsewhere in this issue.

There is, incidentally, a way you can determine whether your listening room is bright, soft, or neutral. Read our "Recommended Components" Notes for some of the loudspeakers you have owned, and compare the description of their sound with your own reaction to them. If you have found that the speakers in question sound brighter or shriller than our notes would indicate, yours is probably a bright room. If the opposite is the case, you probably have an acoustically dull room, and will thus probably prefer the Infinity to the J-Mods. In a middle-of-the-road case, the Js tend to be a little polite, the SS-1A a little more forward and alive.—J. Gordon Holt