Acoustat Full Range Electrostatic Speakers

A group of us have owned Acoustat ESLs since the early 80's. We believe them to be vastly under-rated speakers that can compete on favourable terms with today's finest. In common with many ESLs competing in the reality of the marketplace compromises were made, however the parts that matter most were of very high quality namely the transformers and panels themselves.

My panels started off as Model 2s but after a few years, these were dismantled and new frames (very crude) were made in 1+1 configuration. Richard started of with Model 4s and then Model 3s. He then found two more panels and re-framed them as 2+2s. Others in our group have 1+1s and 2+2s most having started off in some other form.

For a description of what Acoustat electrostatics are all about, see James Strickland paper on The Technology of Full Range Element Electrostatic Loudspeakers.(1.2MB file)

The ESL Circuit is a great place to find out more about ESLs. For DIY types, The ESL Forum has a wealth of information on ESLs.

Frame

We believe the frame compromises a lot of commercial ESLs. For some reason, manufacturers build sleek stylish frames that are very flimsy. This must be for marketing/aesthetic reasons because most do not offer the rigidity required to do the job properly. An ESL may not have a large excursion but a full range ESL does have a large area and couples very well to the air in the room. It is our belief that the frame of a full range ESL must be rigid to resist movement.

Interface

The modifications described have been in use for approximately 15-20 years in a number of systems. We can therefore vouch for the reliability of the components we have used however due the the nature of the voltages in the interface we cannot comment on the use of other types. We welcome any input from the experience of others.

Hot Rod 1+1s

This is the current state of my 1+1s, the parts used and response measurements.

A Warning

Acoustat ESLs were no doubt designed to sound they way they do for a reason. We have taken that design and made it sound different and in our opinion, our designs/upgrades improve the speaker and bring the design up to date. In the process of doing that, the speaker can become a microscope and may highlight a problem elsewhere which the speaker could be blamed for. Many a time, we have thought about selling them on and getting something else easier to live with but each time, we find the speaker to be telling the truth.

If at some point in the future the speaker may be sold, ensure any modification can be removed and the speaker returned to standard. Check and double-check any wiring modifications as the transformers are virtually irreplaceable.