Radical Mods/Hacks for Koss ESL
Since the KOSS "Model 2" ESL had some seemingly well made panels, I wondered if I could make them run full range electrostatic instead of only up to the 2.5khz limit on the factory originals.
I found the HF E/S modules were a four-layer sandwich using dual-polar HV biasing. This limited HF response to about 4khz tops (were they trying to make a high powered E/S panel ?)
By separating the diaphragm/stator layers (by removing external binding silk packaging tape, I came up with six individual panels). These six panels, running single diaphragm would perform full range I discovered with no high frequency loss (no need for dome tweeter in factory original).
Run them in a surround system with a SW below 80hz. Tapered side baffles extend LF performance < 100hz
I have never repaired, or built electrostatics, but have read a little here.
This looks like an interesting project :) From what you said no point in keeping these museum style, like I feel a Quad ESL 57 should be.
I suggest you search this site, about using to modern power supply transformers, and see if options popular on this site such as 8V/240V step up transformers are as good as people say. Could you measure the turns ratio on driving transformer?
Hoping you can make a Hifi dream on a budget.
( a great source of panels & audio transformers that can sound good when liberated from Koss's disastrous over-engineering.)
For power supply, I use a 5-inch TV w/ tube removed & resistor divider to obtain 2.5 KV from 5 KV.
The resistive measurements of the Transformers in Koss are on the schematic in other thread
Looks like a fun project. The factory original dome tweeter was likely to provide wide angle coverage of some top end as your panels will be very directional. That is an interesting idea to make the speaker have a wider angle of dispersion at high frequencies. Personally I prefer a more directional speaker. Hope you have good success with the project. Best regards Moray James.
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