ESL crossover or not.

[dstockwell]

What you all think, is no x/o feasible in the DIY arena.

From Audiostatic web site http://www.audiostatic.com/product.html

The audio signal is direct coupled. It has been routed from the amplifier into the four step-up audio transformers and to the electrostatic element without passing any crossover components.

[MJ Dijkstra]

Hi

The claim of audiostatic of using no crossover is very tricky.
They are electrically segmented. 6 to 8 wires are driven full range.
The remaining (stator) wires produce bass + mid upto a freq. of around 3 kHz. The limited freq. range of these parts is achieved with the aid of resistors. The resistors in combination with the capacity of the element create a low-pass crossover. Wheter this is crossoverless or not depends on your definition. Only the 6-8 wires in the middle are non-crossoverless.
To my opinion the audiostatic is a full range electrostatic loudspeaker, but it is not crossoverless. Some call it semi-crossoverless (Sheldon Stokes) and this seems very appropiate.

Cheers, MartinJan

[dstockwell]

Thanks for the explanation., Guess if they do not have capacitors thats how they call it crossover less.

[MJ Dijkstra]

Hi,

Exactly!
Old types of audiostatic had a large capacitor in the primairy section. This large capacitor blocks any DC from the amplifiers output and this helps to protect the transformers from getting into core-saturation. However some people blaim the capacitor for reducing low-bass response.
This capaicitor is absent in the new types of audiostatic like the DCI and that's what they are probably advertising for.

Martinjan

[Capaciti]

Hi,

the capacitor prior to the stepup has a differnet task than to block DC.

In combination with the primary inductance of the stepup it creates a bandpass filter. In interaction with the specific impedance at e.g. 100-150 hz the peak is positiv, means sound pressure is increased between said frequency range, since amp will deliver more voltage in that range. At the same time this special circuitry damps the heavy peak at fundamental resonance, since the capacitor acts as a 6db Filter lower than 100 Hz.

This compensates for the dip between 100 and 300 Hz, which is typical for ESL with small baffles due to pahse cancellation. People remove this capacitor since they think a capacitor is worse for quality, but i think they like it for the deeper and warmer bass at 35-40 Hz and accept the dip at 100-300 Hz. It makes the ESL sound cleaner and more crisp, but objectively it suffers from upper bass response which sounds a little bit thin for specific instruments like cello , toms ......

The only way to go around that capacitor is to avoid phase cancellation. But you need a significant baffle width of more than 25". Small baffle fullrange ESL find their master in large baffle ESLs, since the smaller ones will never offer the mighty, pressure and completness in sound of the wider ones.

capaciti

[MJ Dijkstra]

Hi Capaciti,

I don't understand your statement 'amp will deliver more voltage in that range', I think it doesn't. Do you mean that efficiency in low bass is decreased to match the level of the cancellation dip?
This means lowering the efficiency of the total speaker to the level of the dip, which must be pretty low!
Except from the DC-block, the capacitor limits extreme low frequence from getting into the transformers. This improves ultra-low bass power handling. People who removed the capacitor had more bass but complained about the saturation effect. The DCI has four transformers in stead of two. Maybe the improved power handling made it possible to omit the capacitor??!!
Have you measured the response with and without the capacitor?

[Capaciti]

Hi martin,

my explanation was wrong. I mean the amp can deliver more current in that frequency band and as a result more voltage will be induced in the seondary winding.

The effect of the capacitor is clearly visible in the impedance plot by a reduced impedance between 100 and 300 Hz. Thats why the amp will deliver more current. As a result the sound pressure increases proportionally by about 2 - 3db.

if you remove the capacitor, saturation is obvious, since the capacitor cuts off frequencies lower than 100 Hz by about 6 dB/octave. This means that the esl stepup without the capacitor must handle double power at 50 Hz, which is significant.

Audiostatic removed the capacitor at the DCI models and compensated to phase cancellation by additional transformers. They patented this circuitry as "mirror drive" in the 80's.


capaciti

[MJ Dijkstra]

Hi Capacity,

The mirror drive is used in the 200RS and 300RS. These models conatined an extra 1:2 transformer in addition to the two identical full range step-up transformers. As far as I know the DCI contains 4 identical transformers, no mirrordrive.