Hi
I have been thinking about building ESLs on and off for many years now. The output of this has been zero so far, sorry to say.
One thing that bothers me is that I still don't really understand how they work... If you bear with me I will explain what the "problem" is. I will use the following ESL scenario, just the standard way to do it:
We have a cell with two stators (A and B) of perforated metal or whatever with a coated mylar membrane placed between them using plastic spacers. That is, a standard cell.
To drive the cell we use a transformer delivering a high voltage audio signal to the stators from its secondary winding.
The midpoint of the secondary winding is attached to the positive node of the bias supply. The negative node goes via a high value resistor to the membrane giving this a negative charge relative to the stators.
This is the way almost all ESL speakers are made.
If we look at this cell before we try to play music thru them (statically), the membrane is attracted to both stators by the fact that objects of different charge, i.e. positive and negative, are attracted to each other. To prevent the membrane to get stuck to one of the stators we stretch the membrane tight when we put the cell together.
Now we start to play music on the cell.
For the sake of argument, the mid point of the secondary winding is our reference point at zero volts.
Let’s say that the transformer delivers a balanced signal of 1kV p-p on the stators A and B.
Let’s say that the bias voltage at the stator is at 4kV negative.
At one point stator A will be at 1kV positive and stator B at 1kV negative.
The relative voltages, stator - membrane will be:
Stator A - membrane = 5kV
Stator B - membrane = 3kV
The membrane will thus still be attracted to both stators but as the voltage between stator A and the membrane is the highest the membrane will move towards stator A. After ½ a period the reverse will be true, and stator B will attract the membrane the most.
Questions:
1.
Is this really a push-pull speaker?
2.
We usually have a reference when talking about voltages, most often “ground” or GND. If we in the example above lift the midpoint of the secondary winding using a DC voltage of say 5kV positive (everything else being the same), then the membrane would be at 1kV positive relative to ground and the stators at 5kV positive. Will the field force, stator-membrane be one of repulsion instead of attraction?
A long mail. I’m missing out of something both crucial and basic. If you se my “problem” and can be of assistance please comment.
/Urban
I have been thinking about building ESLs on and off for many years now. The output of this has been zero so far, sorry to say.
One thing that bothers me is that I still don't really understand how they work... If you bear with me I will explain what the "problem" is. I will use the following ESL scenario, just the standard way to do it:
We have a cell with two stators (A and B) of perforated metal or whatever with a coated mylar membrane placed between them using plastic spacers. That is, a standard cell.
To drive the cell we use a transformer delivering a high voltage audio signal to the stators from its secondary winding.
The midpoint of the secondary winding is attached to the positive node of the bias supply. The negative node goes via a high value resistor to the membrane giving this a negative charge relative to the stators.
This is the way almost all ESL speakers are made.
If we look at this cell before we try to play music thru them (statically), the membrane is attracted to both stators by the fact that objects of different charge, i.e. positive and negative, are attracted to each other. To prevent the membrane to get stuck to one of the stators we stretch the membrane tight when we put the cell together.
Now we start to play music on the cell.
For the sake of argument, the mid point of the secondary winding is our reference point at zero volts.
Let’s say that the transformer delivers a balanced signal of 1kV p-p on the stators A and B.
Let’s say that the bias voltage at the stator is at 4kV negative.
At one point stator A will be at 1kV positive and stator B at 1kV negative.
The relative voltages, stator - membrane will be:
Stator A - membrane = 5kV
Stator B - membrane = 3kV
The membrane will thus still be attracted to both stators but as the voltage between stator A and the membrane is the highest the membrane will move towards stator A. After ½ a period the reverse will be true, and stator B will attract the membrane the most.
Questions:
1.
Is this really a push-pull speaker?
2.
We usually have a reference when talking about voltages, most often “ground” or GND. If we in the example above lift the midpoint of the secondary winding using a DC voltage of say 5kV positive (everything else being the same), then the membrane would be at 1kV positive relative to ground and the stators at 5kV positive. Will the field force, stator-membrane be one of repulsion instead of attraction?
A long mail. I’m missing out of something both crucial and basic. If you se my “problem” and can be of assistance please comment.
/Urban