Adding a series resistor to loudspeakers

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I've just finished reading an old HiFi world where Noel Keywood added a small value resistor for the HF unit of a Martin Logan electrostatic / hybrid speaker.

He then discovered the 20khz response was down 10db :confused:

However.. on another well known technical hi-fi forum, it has been suggested / recommended that to drop the HF level by 1db, you need only insert 0.5R

I'm racking my brains... but I see that the only major effect of adding R in series with the HF circuit is to reduce all of it's output - i.e. adding a shelf in the response

Have I got this right ? If not, why not ?

Thanks
 
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No, you don't have it right, sorry. :(
You are trying to apply what is done to a conventional speaker, to a very unconventional one.
Electrostatic speakers are basically capacitive, so a series resistor attenuates *much* more at higher frequencies than at lower ones.
From the Quad ESL literature:
The second downside is that they are a difficult load for the amplifier to drive. They are highly reactive loads (primarily capacitive). Their impedance drops as the frequency increases.
Which, by the way, is to be expected from two metallized sheets separated by a dielectric.
 
I should have mentioned... The speakers in question where the 0,5r is being added, are not electrostatics but moving coil designs.

I have probably mixed the 2 issues up. 1) I didn't realise that the characteristics of electrostatics were wildly different to normal designs... Thks for the clarification and 2) wanted to check the theoretical effect of adding 0.5 to a normal HF section
 
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I should have mentioned... The speakers in question where the 0,5r is being added, are not electrostatics but moving coil designs.
Yes, I already knew that ... but your doubt was about the
Martin Logan electrostatic / hybrid speaker.
and that's what I answered.

EDIT: just read your addendum.
Fine, in that case don't worry, if you work with conventional, moving coil speakers, you'll get the shelf you want.
Good luck :)
 
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