Electrostatic speakers


I picked up a pair of Electrostatic Research Vista by Sunrise Audio;. Hooked them up to test them and both work. One sounds significantly louder them the other with balance set evenly. Does anyone have any ideas as to why? I am running them with a pioneer receiver just to test them. They are at my office have not brought them home yet. I plan the run them with two NAD 2200 amps, biamped. 
thanks

lester350

Vacuum the panels. Dust accumulation on the panels can do that. If it won’t help, the panel is most worn out. 

There are no places to adjust anything externally 
Thanks I’ll give the vac  a try. 

Use a brush attachment and make shure it’s clean. But first disconnect the speakers for 5-6hrs, preferably overnight 

It looks like it is the panel. i tried to vacuum them. no difference. i did switch out the panels with the bases/woofers and the problem moved with the panel. Can anyone recommend a company who rebuilds panels?