I will give it a go. Im trying to get my head around why your circuit has a voltage divider for div low instead of that being connected to 36v gnd.
Yep, you could produce Vref Low from the 36V supply. But producing both Vref Low
and the Sig_In from the same place(through their same proportion potential dividers) should mean that if the mid 18V is off a bit, it effects both of them - so the
Vref Low voltage level should still run right through the very middle of the
signal's waveform even at low volume levels. That was the idea anyway.
If you're looking at the last circuit I posted, R7 28K represents the
internal resistor string inside the LM3915, I added it because of the small effects it has on the 2 potential dividers.
Changed speaker to 6R
Had to change the potential dividers R2 from 3K9 to 4K7, and R6 from 390R to 470R.
Plot looks good to me!
Blue is the 500Hz (peak 31V) reaching
Vref High,
Yellow shows the peak Watts in the 6R = 112W = 79 W RMS.
Shirley that's close enough!
I've not worked out the 3dB representations, I'm leaving that to you.
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