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OTL Tube Amps and Full Range Electrostatic Speakers

I have Martin Logan CLX speakers which have a nasty impedance curve in the treble with a minimum of 0.7 ohms at  about 18 to 20 kHz - or so I have read.  The impedance of the CLX is, as many know, largely capacitive.  Over the years I have preferred tube amps and have heard OTL amps driving various Quad speakers with great results.  My own experience with the CLX's has been more positive with high quality solid state amps; I am currently using a Krell 402e which has no trouble driving this speaker well.  An ARC Ref 150 did not provide the control, particularly in the treble, which this speaker needs and did not provide the level of transparency which this speaker can provide.  I would appreciate hearing if anyone has experience with other tube amps with the CLX's or Sound Labs, particularly OTL's and whether autoformers provided a significant benefit.  Thanks for any insights.
soundhound

Showing 1 response by atmasphere

atmasphere's avatar
atmasphere
12,138 posts
 
Power increases into lower impedances!
@roberjerman

One thing about ESLs is their impedance curve is not also a map of its efficiency, like it is for most box speakers.
Instead, its impedance curve is a result of being largely a capacitor. For this reason, what is desired is the ability to put out constant power over the range of impedances presented by the speaker rather than constant voltage (which results in increased power into lower impedances per the quote above). Of course, no amplifier really does make constant power but they can come pretty close, especially if assisted by a set of ZEROs (www.zeroimpedance.com) since any tube amp that is designed to make constant power (like ours are) will tend to have a higher output impedance.
For more on this topic, seehttp://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

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