I’ve had some Martin Logan’s that had no treble fresh out of the box; perhaps the panel needed to be fully charged? I confirmed it with in room measurement.
The panel does, of course, need a charge. I've read 2500V, but that's from a dim memory, and may not be accurate.
Mine are 22 years old now. They turn of their charging circuit after a while when no signal is applied, and the charge on the panel leaks down over time (more than a few minutes, maybe hours). If you play them unplugged, eventually you will notice dulling. totally discharged, the panel might be silent.
I could perform a fresh experiment for that.
I use them less now, having JBL LSR 308 for daily casual TV and HDRadio use.
I have not noticed a problem when, on Beer Saturday, after maybe a week of being "off", they are hit again with signal.
I would estimate the charge time at maybe a second (probably less).
I don't know which model or vintage speaker is referred to above, there could be differences, but I find it doubtful.
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Limited experiment:
They've been off for at least 12 hours, maybe 36... Don't remember. They probably didn't play last evening, but did recently late at night.
I unplugged them after verifying their "charging" LED was off, and applied TV signal:
I expected worse, they sound almost normal.
The bass is exaggerated a bit
Let's look closer...
No recharge power yet. Pink noise applied.
Crossover from woofer to panel is 180Hz.
Panel frequencies look pretty flat, It;s not like any particular frequency range is affected more than another.
Upon plugging them in, I hear the change occur over one to two seconds.
Approximately 10dB gain seen on the panel, bringing it more in line with the woofage.
So, with 12 and probably 36 hours of idle discharge, about 10dB was lost on the panels.
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Unplugged again. No change. It
will change, as the panel leaks down. over time