how to design a power amplifier for electrostatic speaker

hello

i have no idea about electrostatic loudspeaker ESL
and just searched and knowing it could be a capacitive load which require different design compare to conventional amplifier. but cannot find how to.

question is,

what is the problem when conventional amp uses with ESL?
impedance or phase or any reasons?

and what is the different of amplifier for ESL?
can i convert a conventional amp to ESL amp, or probably can drive both without sound degrading?

Thank you very much.
 
hello

i have no idea about electrostatic loudspeaker ESL
and just searched and knowing it could be a capacitive load which require different design compare to conventional amplifier. but cannot find how to.

question is,

what is the problem when conventional amp uses with ESL?
impedance or phase or any reasons?

and what is the different of amplifier for ESL?
can i convert a conventional amp to ESL amp, or probably can drive both without sound degrading?

Thank you very much.

ESLs are normally driven through step-up (often 1:100 or more) xformers. I'm surprised you can't find anything - there's tons about it here and through Google.

Your amp must be stable for capacitive and/or low impedance loads, but other than that there's no special need.

Jan
 

hahfran

Member
2007-12-19 8:53 pm
a very old design is quite interesting : direct coupling of the electrostatic speaker to a high voltage tube push pull. All you need is these high voltage tubes and a power supply 5,000 Volts at 50 mA . I tried that once with a Quad Esl and FM transmitter triodes made in Russia. Was absolutely excellent sonic quality until the triodes begun to glow bluish... that was it.
 

Ketje

Member
2012-12-19 7:24 pm
Flanders
Long time ago Elektor has published an amp for high voltage output.
Perhaps you can find the description and prints still there.
Mona
 

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ESLs are normally driven through step-up (often 1:100 or more) xformers. I'm surprised you can't find anything - there's tons about it here and through Google.

Your amp must be stable for capacitive and/or low impedance loads, but other than that there's no special need.

Jan

Thank you for reply.

as i did some research, ESL requires voltage rather than current.
So it may not good to design for both conventional speaker and ESL.
they seems require different design.
 

hahfran

Member
2007-12-19 8:53 pm
The membrane moves between the two electrodes which have the signal , since capacity is reversely proportional distance between membrane and electrode, the capacity changes with the signal amplitude , as capacity is Asec/Volt , current is required for charging and decharging. The force that drives the motion is in first approximation a Coulomb force which is proportional to charge. If charge were constant then the membrane could not perform sinusoidal motion.
If the speaker electrodes are directly coupled to a push pull amp, then this is basically a voltage amplifier.
 
Thank you for reply.

as i did some research, ESL requires voltage rather than current.
So it may not good to design for both conventional speaker and ESL.
they seems require different design.

They are quite different designs, but that doesn't mean they cannot be driven from the same amp - with the step-up xformer. ESLs require high voltage across a cap, so they STILL need current - to charge the cap.

In fact, the tend to draw more current from your amp than a 'normal' driver; the cap is transformed back to the amp output as a quite large cap that requires quite large currents. How would a 1nF cap at a secondary of a 1:100 look at the primary??

Jan
 

hahfran

Member
2007-12-19 8:53 pm
They are quite different designs, but that doesn't mean they cannot be driven from the same amp - with the step-up xformer. ESLs require high voltage across a cap, so they STILL need current - to charge the cap.

In fact, the tend to draw more current from your amp than a 'normal' driver; the cap is transformed back to the amp output as a quite large cap that requires quite large currents. How would a 1nF cap at a secondary of a 1:100 look at the primary??

Jan

Electrostatic and electrodynamic speakers behave differently the latter becomes inductive at frequencies above resonant, the first capacitive. That is the reason that ESL perform poorly in bass range which must be compensated by large membrane area. But once they have some 2 m² they will have a bass performance which is the best of all way outperforming speakers that rely on resonance effects such as vented box.