Barry Wilkinson (March 2000):The financial difficulties referred to in the article below (by John Doe) took place in the early 80's . I can still remember the cover of the issue of Stereophile announcing that acoustat was returning from the dead (yes a Phoenix was on the cover) and that David Hafler had rescued them. Then later in the 80's, Hafler sold his Company (including acoustat) to Rockford-Fosgate, but it was not in financial difficulty, at the time of sale. Hafler became a division of R-F , but under Haflers Management and when he retired Jim Strickland took over as head of the Hafler division.

John Doe (April 2000): This company was originally based in Florida in the USA. My experience with them started in 1982 when I purchased a set of their Model 2+2 speakers. At the time, Acoustats were a rather tall speaker (almost 240 cm ! ) whose design consisted of an array of stacked electrostatic panels (one above the other) in multiple groupings. For example, the 1+1s were the smallest, then came the 2+2s, 3+3s, etc.. These speakers, in my opinion, were some the best sounding speakers available at the time. However, they had a few not-so-inconsequential problems : they required amplifiers with very high current delivery capability at very low impedance (down to less than 1 ohm in some cases). They were also very inefficient (82 to 84 dB with 1w @ 1m), and tended be a bit "beamy" sounding in the upper octaves (progressive narrowing of the radiation pattern with the increase of frequency). In the late 1980s, Acoustat was experiencing serious financial difficulties and was eventually absorbed by the Rockford Fosgate Corp. (the car audio people) who also happened to own the Hafler Company. By the way, David Hafler was also the brains behind the original Dynaco company, who are back in business building reasonably good solid state and tubed home components in the USA. Rockford relocated Acoustat to their own facilities in Arizona and invested a sizable pile of money into the research and development of an entire new line of hybrid and full-range speakers, which upon introduction, became known as the Acoustat Spectra Series. These speakers did not rely on physically placing the adjacent panels at an angel to each other to rectify the narrowing of radiation in the higher frequencies, but rather achieved this remedy electrically (hence, the name Spectra). There were initially three models available:

• Spectra 11 (1 panel)
• Spectra 22 (2 panels side-by-side ; I own a pair of these)
• Spectra 33 (3 panels)

• Spectra 44 (4 panels: 2 on top, 2 below)
• Spectra 66 (the "Ultimate" Acoustat) with 6 panels in the array.

Another interesting aspect of the Spectra line was that they were a Two way system, with half or more of the panels doing low frequency duty only, whereas the older Plus series was strictly full range. About a year before Rockford realized that there was no future for them in the high-end home audio field, a cosmetically updated series was made available, the 2200, 3300, 4400 and 6600, and the Spectra 11 was replaced with the Spectra 1100, which featured a built-in eight or ten inch dynamic woofer. This was not a subwoofer. Acoustat did have a line of two real subwoofer units which perfectly matched their ESL's, but were not entirely necessary. Acoustats can make bass on their own....REAL bass that you can Feel ! Rockford Fosgate also introduced a line of amplifiers under their Hafler name called the TransNova XL series. These amps were supposed to have simplified the choosing of amplification for the Acoustats because at that time, any amps which suitable to drive these speakers were extremely expensive. The TransNovas were more stable with the very low impedance found in the Ells, and had a large current output capability and huge heatsinks. Personally, I never liked the sound of these amps, and I have always used Classe electronics to drive my speakers. I have found them to be very musical and extremely durable and reliable. I have also used Sonic Frontiers amps with my Acoustats. My choice of amplification is also tempered by the fact that I live in Canada, and non-Canadian components such as Krell or Mark Levinson are much less affordable here. As far as I can ascertain, Rockford killed the Acoustat division in 1993. In 1995 (approximately) the Acoustat name resurfaced as a division of the Italian firm Audio Physic. They are building electrostatic speakers in Italy which are based on the Spectra design principals. However, when I contacted them, I was told in no uncertain terms that they had NO intentions of ever exporting these interesting speakers to North America. They were intended for sale in certain parts of Europe ONLY ! Audio Physic is selling only their dynamic speaker line outside of Europe.

Mike Savuto (July 2000): The first model manufactured by Acoustat was the Acoustat X, made from late 1976 until early 1980. The "X" designation was actually stylized from the electrical representation of an electrostatic speaker design as shown in the manuals. This is the floor standing speaker with the panels in a Walnut trimmed cabinet with the Servo-Charged amplifiers in the bottom of the cabinet and the removable "pegboard" back. They retailed for $1995.

The Monitor 4 came out in late 1978 or early 1979 at about $2995. Acoustat made it available as a DIY kit to upgrade Acoustat X's as well at a very reasonable price, $750. The original Monitor 4 was the "Wing" design with solid Mahogany (black grill cloth) or Oak (white grill cloth) top and bottom caps on a separate base as shown in the pictures on the ESL website.

In 1980 the Monitor 4 cosmetics were changed so that the "Wing" extended to the floor, doing away with the separate base. It was now a monolith design. This is the design shown in the Owners and Service Manual also made available during that time.

The Model X was superceded during that same time by a Monitor 3 with the monolith cosmetics similar to that of the revised Monitor 4. Also in 1980 the first Magnetic-Kinetic (MK-121) interface was introduced. For a time the Monitor 3 and 4 were available with the Servo-Charged amplifiers and the same panel configuration with the MK-121 interface designated as "Model 3 or 4".

In December of 1981 the last Servo-Charged amplifiers were built. All subsequent models utilized the MK-121, and later the Spectra, interface and amplifiers of the owners choice. One source of confusion is that every Servo-Charged amplifier, until very close to the end of production, had "Acoustat Model X" on the serial number sticker. The amplifiers were all the same basic design for each model. The model designation of the speaker array itself was never indicated on the speaker "cabinet" or the Servo-Charged amplifiers. During the time when the MK-121 was being introduced, and the Servo-Charged Amplifiers were being phased out, an excellent article was produced by a short lived audiophile publication, whose name escapes me, that tested and compared the sonics of two designs and officially announced the passing of the Servo-Charged amplifiers. The King was dead.

Hafler home page (January 2001): James C. Strickland, Vice President - Engineering, received his degree in 1963 from the University of Miami. Jim taught physics and mathematics from 1963-1969, while also pursuing development of electrostatic loudspeakers. Jim started his electronic design career with MCI-Sony in 1969. Shortly after becoming Vice President of Engineering there, he developed both analog and digital circuitry for professional multi-track tape recording machines. His work on the digital Automatic Locator and the digital and analog controls of the JH-100 tape decks allowed this series to become the most widely used multi-track machine in the world. In 1984, Acoustat was merged into Hafler, with Jim remaining as Chief Engineer for Acoustat. He developed the SPECTRA drive principle for electrostatic loudspeakers and the IRIS system of digital-analog remote control - ultimately yielding another patent for Rockford, which acquired Hafler in 1987.

Phil Porcari (Februari 2002): As an owner of Acoustat speakers I can tell you that they are sadly no longer being manufactured. The last company I know of who made them was the Rockford Corp. in Tucson.

A Historical Overview (Andy Szabo, march 2002)

The Robot Underground (November 5, 2004): I worked for a summer for Lightning Audio. At that time the accessories brand was being absorbed by Rockford Corp and I got a tour of the RF facilities. One thing that was mentioned was that when RF bought Acoustat, the guy that wrote the contract forgot to place reponsibility for repair on Acoutat speakers to the Italian company that had bought the brand. When I called for info on my Specra 11 power supplies, the tech confirmed what I had heard. That contract guy was so fired. RF is still responible for build on speakers that had a lifetime warranty. RF tech support: 800-669-9899.

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Andy Szabo's Technical Bulletins

Acoustat owners are among the most lucky hifi enthusiast in the world. Who else can rely on having a former Acoustat engineer, designer and general manager like Andy Szabo and an Acoustat refurbishing expert like Mike Savuto to keep their beloved speakers alive? Andy has been answering questions of Acoustat owners for over four years now and since a year and a half Mike has joined forces to answer the questions for the oldest models.

Andy Szabo was an engineer and general manager for Acoustat, from 1985 (when acquired by Hafler), to the end of US production. He is available to answer questions, both technical and historical. His product knowledge is most complete for models produced after 1985, but he knows a good amount about older models, too. Mike Savuto's will answer the questions regarding the Model X, Monitor 3 and Monitor 4. His company Analogue Associates can refurbish and/or upgrade them.

All questions will be answered as promptly as possible. Before posting a new question, please check the section corresponding to your speaker model number. Your question may have already been answered. Also check the sections for similar models under the same main heading (for example, if you have a Model 2+2, check all the sections that use the same interface. You can ask your questions directly on the concerning models pages and we will t ry to answer them within a reasonable time.

Rather than answering frequently asked questions directly, Andy has chosen to write some general documents that will hopefully answer these questions, and provide much needed information to others. Many commonly asked questions are answered there..

General Model Information
Grille cloth removal, cleaning and replacement
Medallion transformer Modification
MK-121 Interface Versions
MK-121-X Low Frequency Transformer Tap
Popping Panels
Spectra Sectoring and Color Codes
Spectra series, Bass Equalization - transformer taps
Ultrasonic Bias Power Supply - When, Why & How, Wall transformers and Adjustment
Ultrasonic Bias Power Supply -Update Acoustat Spectra series

Modifications

General Notes (by Bear, March 2002)
Notes on Acoustat (by Sean Bowes)
Tweak for electrostatic speaker owners (by Bob Blase)
The Medallion modification (by Kevin Ferry)
C-Modification, MK-121 Series (by Andy Szabo)
MK-121-2(A) Medallion "C" Modification Parts and upgrade wiring from the older to the newer medallion upgrade.It does not contain the schematic of the older 121-2A transformers.

Bill Armstrong (May 11, 2009): Good day gentleman,
Would you be good enough to furbish with the frequency range of the spectra series speakers.
The Spectra 2200 Hz - Khz?
3300 Hz - Khz?
4400 Hz - Khz?
6600 Hz - Khz? As well as the physical dimensions of each speaker?
Thanks guys,
Y/t,
Bill

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