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In Reply to: RE: the late Al Sekela's choke tweak and True ribbon tweeter posted by Green Lantern on January 13, 2015 at 06:29:58
The choke tweak and series resistors are two different things.An attenuating resistor actually lowers the signal level in the tweeter range.....a 10uH inductor does not.
An inductor of this value simply raises the load impedance above the audio band and starts to disconnect your speaker from the amplifier. In some instances this may be a good thing, in others bad.This "tweak" was horribly conceived from the beginning with little understanding of the engineering by Al.
A much preferable way to approach this is with an RC Zobel across the speaker wire at the far (speaker) end. This terminates the speaker cable for frequencies above the audio band and minimizes the chance the speaker wire "antenna" will source signal back into the amplifier output to possibly interact with the feedback loop and cause problems.
Cheers,
Dave.
Edits: 01/13/15Follow Ups:
From what I recall, Al clearly understood the difference between a series choke and the use of a Zobel. He just tried the choke because it was cheap, readily available to him and simple to implement (just place it in the tweeter attenuator jacks instead of a resistor). I don't think it was "horribly" conceived, it just worked well for him. I also had success but I know there are others who were not overly enthused by this tweak.
Well, I disagree that he understood the difference, but it's water under the bridge now. I'm sure wherever he is he's happily listening without the choke tweak now.
Al was/is one of those who ventured into the audiophiledom bermuda triangle.......and it's very difficult to rescue somebody from there. :)
I made a few attempts but it was obvious I wasn't going to be successful, so I gave up.
Oh well.
Dave.
Thanks Dave; very interesting, do you have a source for the RC Zobel? Makes me wonder why such an added benefit isn't included in higher-end cables
They are sometimes. One of the reasons some cables sound different from others. :)
For a Zobel a capacitor of approximately 0.27uF and 10 ohm resistor should be fine.
Dave.
You should be careful about implementing a zobel network as some amplifiers already have one as part of the design. The Emotiva XPA-2 is an example.
Thank you Will. I will stay with the Bourne 5522....It does get me into the music, even if imperfectly....
This is a different usage of the Zobel with a much smaller capacitor value than typically used internal to amplifiers. It's application is only to terminate the far end of the speaker wires with a closer-to-nominal impedance.
Dave.
Looked at some graphs. Seems like you nailed it Davey.
Thank you Davey. . I am also eager to try it. Any more specifics would be useful. Thanks UT
I'm not sure what I nailed or what "specifics" you're asking about. You're going to have to be a lot more specific regarding specifics.
Dave.
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