X, ES speakers

Read more on the Acoustat X in our home audio section

Mike Smeed2006-09-18 01:19

I recently acquired a pair of Acoustat model X speakers with servo amps. They appear to have been sitting unused for quite some time. One of the amps definitely has damage. I can see burnt marks where one of the resistors was and underneath the circuit board. This one I plan on repairing. The other amp does not show any signs of failure, but I have not applied power to it yet. I would like to check and see if the panels are good and if it is worth repairing the amp. My plan is to use the amp that appears good to check the panels. I am somewhat familiar with tube amps and have an electronic background. Since I have no experience with ES speakers I have a few questions: 1. Can the ES panels be tested before power is applied? 2. Is there a life expectancy on the panel…how long are the panels expected to last? 3. Is the thin wiring to the panel susceptible to shorts? 4. How do you connect to the servo amps? Are they connected to a basic pre-amp out put through the RCA jack? 5. Any precautions before plugging these in?

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Andy Szabo2006-11-03 14:19

1. Unless you have some sort of transformer interface/bias supply or servocharge amp to provide the stepped-up audio and high-voltage bias, there is no way to test the ESL panels. 2. Acoustat panels will last a very long time. Many of the original panels are still working after 30 some years, so true life expectancy is unknown. If the panels have been kept reasonably clean, and suffered no physical damage, they should still work fine. (Note this is almost certainly NOT true for other brands of ESL\'s when they get that old.) 3. The \'thin\' wire has special high voltage insulation rated at 10,000 volts. The gauge of the wire is very small due to the very low currents involved. 4. The servocharge amp has an RCA input jack that is intended to be connected directly to the output of the preamp. 5. Precautions before plugging them in? Yes, lots of them. If they have been sitting idle for some time, they likely require service. The arcing on the board is a common problem on these units due to the high voltages involved (5000 volt B+). Contact Mike Savuto for service and parts - he does work that both rejuvenates and improves the reliability of the circuit. (See contact info elsewhere on this site.)

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