Electrostatic Speakers - Janzsen ER139

Arrivals like this are truly what keeps me thrilled about Vintage Sound gear. I have been very interested in Electrostatic Speaker technology for as long as I can remember but had not had the opportunity to test them on my array of music. Acquired in a trade deal I came to own these Arthur A. Janszen designed ER139 Hybrid Speakers. Designed by this innovative ( i would dare to say revolutionary) sound engineer. In 1974 Electrostatic Research Corporation formed in Massachusetts and acquired Janszen for the sole purpose of developing an unprecedented omnidirectional Hybrid Electrostatic Speaker. As with most Estat speakers there is a somewhat small "sweet spot" for the listening plane due to the charge (notes+-) dropping of at the edges of the membranes of the speakers. The innovation here would be to offer the high end tweeter signals in a circular array thus eliminating the smaller listening plane then those of the traditional cone drivers. Well, these achieved that and more! The inverted cone you see mounted on the woofer magnet has an intricate array of ribbon wound tweeters. A true Janszen patent stroke of genius!
The cone extending from the woofer magnet was also designed to grab and project through a top port resonant mid-range signals although these were modified with the additional mid driver listener facing.
Here is a Popular Mechanics short review... The ERC139's
The Vintage Sound....
Come on! That's what I said when I heard them for the first run of Paul Desmond's "Take Ten" LP. (hugely recommended on vinyl - PL42045)

Said in the most excited way - not the disappointed verb age, These kicked my butt! Cymbals sooo pure I thought they moved into my listening room. Bass true and Musical. I mean these really hit an audiophile stratosphere I did not anticipate. Really up there with some recent Totem Storm's I demoed.
Really! That good. They are very thirsty and I would guess that they are 4 Ohm as it really took a lot of power to get them opened up and fully breathing!

With all electrostatics the membranes need a charge applied to them thus each speaker has an outlet plug to supply that charge. I noticed that it took a few minutes before they really opened up. Once they did it was a joy to hear. The reduced levels of (audible) distortion that electrostatics bring is really ear candy. Less distortion - less fatigue.

Here is the man himself with his electrostatic tweeter. One of 8 that would be fitted to the ER139's.
Although this design really was revolutionary A A. Janszen had to move on from ERC as they folded the company from under-capitalization. It is my understanding that only 50 sets were made and he had not even optimized a real production for them prior to closing. Timing is everything and had these been marketed as they should have they might well have taken on many large Estat companies of the day.
In the end the proof is always in the listener's hands (ears) and these are absolutely Dope!!!


  1. Amazing that any of those still exist. Nice find. Not a bad little article, either.
    The ER-139 was supposed to come out at $139/pair and compete with the Advent, but with higher fidelity -- finally, an electrostatic that even some college kids could afford.
    Indeed, aside from some free editorial, merchandising hardly went beyond a prototype pair loaded in Frank Dennesen's yellow Mercury Marquis for visits to local dealers. Probably it would have been better for ERC if Dennesen had rented a building and spent investor money on marketing, instead of surprising everyone by buying the building that he would continue to occupy after shaking off the other investors and reopening as Dennesen Electrostatic.

    David Janszen
    Janszen Loudspeaker, Ltd.

  2. For the last 30 yrs, I've had two 4-cell arrays of Janszen cells - identical to those pictured here - on top of my Dayton-Wright XG10 ESLs. I bought them in a kit sold by Dennesen which included a kit ladder power supply, dinky step-up transformers, etc. Guess I'm one of those people who think ESLs are in a class of their own.

    Thanks very much for write-up. Apr 2015.


  3. I bought several different speakers from Electrostatic Research and then from Dennesen over several decades and got to know Frank pretty well over the years. I agree with the assessment here on the ER139's. A good speaker that was able to produce a large sound. Not so great on imaging however, and as it turned out needed replacement parts to keep the jantzen tweeters going. I owned a pair myself and this is how I met Frank at ER. He graciously offered replacement parts for these speakers free of charge, wired the repaired speakers up into his amazing system and we enjoyed a glass of wine and some cheese together before he sent me off. Those were the days.... Anyhow, what I do not agree with is the off-color ill-informed comment by David Jantzen regarding how he ran the business. I knew Frank to be a passionate audiophile and well informed regarding his product line. I feel lucky to have a pair of the vertical alignment Dennesen speakers, along with the Soundtractor - a alignment device Frank had a patent on. Sounds like David has personal issues regarding this matter, and this reflects poorly upon his professionalism, or lack thereof.