Autocad figure

Figure 1: Cabinet drawings, all dimensions in cm.


ESL specifications

Parameter Value
Panel height 90 cm
Panel width 25 cm
Wire size (Cu) 0.5 mm2
Wire-wire distance 3 mm (note 1)
Wire diameter including insulation 1.5 mm.
Openness (physical) 50% (note 2)
Openness for C-calculations 25% (note 3)
Diaphragm-stator distance 3.0 mm (note 4)
Spacer distance 10 cm
Polarization voltage 5,730 V
Polarization resistor 30 MOhm
Audio trafo step up ratio 200 (note 5)
# Wires 82
Segment # wires, ladder resistor
Segment 1 6 wires, 20 kOhm + 20 k (note 6)
Segment 2 6 wires, 360 kOhm
Segment 3 12 wires, 540 kOhm
Segment 4 20 wires, 2.0 MOhm

Note 1. The wire to wire distance is measured from center to center.

Note 2. The physical openness between wires is the area that alow the sound to come out. It is specified at 50%.

Note 3. Compared to a solid plate condensator we estimate that the openness of the wire stators reduce the stator to stator capacity by 25% which is used in the capacitor calculations.

Note 4. The diaphragm to stator distance is 3.2 mm measured to the middle of the Cu wire and 2.825 mm measured to the edge of the Cu wire.
We use an average of 3.0 mm for all calculations.

Note 5. We use a step up ratio of 200 in all calculations. The ratio is defined as the ratio from input (primary) to output (secondary) from stator to stator.
In real life Steen uses a salvaged step up trafo from a Martin Logan CLS II. It has a number of taps with step up ratios up til 120 per trafo and with two trafos (one per stator) this result in a step up ratio of max. 240.
John uses 4 toroid line trafos (230 V : 6 V) giving a total step up ratio = 4*(230/6)  = 153. These trafos function very well because they don’t have to handle low frequencies.
A step up ratio around 150 is a good compromise between high efficiency and not too low impedance.

Note 6. The first ladder resistor is 20 kOhm. To this we add the 1 Ohm resistor on primary side which is equivant to 40 kOhm on secondary side, devided between two stators giving an extra 20 kOhm per stator.

Bass specifications

Parameter Value
Loudspeaker 10 ” subwoofer
Scan speak Discovery 26W/4558T00
Link to speaker specifications Scan speak 26W4558T99
External cabinet dimensions (H*W*D) 34.3 cm * 34.2 cm * 33.8 cm
Wall thikness 1.8 cm
Net internal volume 30 l

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