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In Reply to: RE: the late Al Sekela's choke tweak and True ribbon tweeter posted by neolith on January 14, 2015 at 07:21:39
LOL! Neo, I may take a leave from the "leave" at times like this. If I turn on the Android tablet while waiting in a doctor's office, I may discover compelling items -- such as this one -- in the forum.I see that you remembered the reason why adding chokes on my MMG's mid/bass driver may make sense (the bi-amp). I should add that limited testing with a regular xover and chokes on all drivers also delivered some SQ goodies. They were less palpable, though still appealing to me. Line-level multi-amping paints the SQ gains (from the chokes) on a better canvas. The differences are more clearly perceived.
Your effort to moderate our reactions here are much appreciated, as always. I got more, far more, from Al Sekela than from Davey. The fact is that well beyond the chokes, Al's suggestions are very key to the additive gains that made my MMG's what I like so much versus other speakers, even some pricier Maggies. Being a trained musician, I may know a thing or two about good music sound. As I evaluated, tested and measured some of his ideas, it was clear that Al Sekela knew a thing or two also.
Speaking of measurements, I found it intriguing that the ribbon tweeters in your IIIA seem to have reacted less sharply attenuated by the chokes than what I've seen QR tweeters do. Here is something that I posted a few centuries ago. At the time, I was evaluating and measuring various types of chokes. Please note that these two sweeps below are quite different. However, the impact on frequency response from two kinds of chokes can be clearly seen inside the hearing range (1st chart). Aside from their lack of sufficient improvement on 3D imaging, the toroidal chokes attenuation at the top was always annoyingly dull to my ears. Of course, some engineers would have said that 10uH is always 10uH and sounds the same no matter what choke design. Neither my ears nor the microphone would agree.
LEFT MMG Speaker Standing Straight, bi-amped
Blue=no choke, Green= 5502 choke, Red=Toroidal choke.
Chart at 1db scale
(chokes at negative tweeter terminal plus a 5502 choke at negative of low panel)
Calibrated microphone at speaker 78" away, vertical & horizontal center----------------------------------
Both speakers, MMG reverted to stock xover: Red=no choke, Green= 5502 choke. 8db scale.
(choke at negative speaker terminal NOT at tweeter jumper)
Microphone at center from seating position
Edits: 01/15/15Follow Ups:
The attenuation I reported (0.4 db at 20 Khz, 0.1 db at 10 Khz) is calculated not measured which is why I said that the affect you are getting from the chokes is not due to simple attenuation. I am not a subjective v. objective purist when it comes to things audio but I do get nervous trying to argue against the math. The difference that you got with toroidal and standard chokes is another example of reality screwing with our heads. Perhaps we should study string theory to see if there is another construct which will explain things audio.
You should be more than nervous when arguing against the math. :) (And that's not to say everything we hear is measurable or not measurable.) But if you measure something that simply shouldn't be there it warrants a raised eyebrow and further investigation. It's been my experience that a culprit can usually be found.
At this point, JBen is so hard over in his defensive posture that he appears incapable of even considering alternative explanations.
Oh well.
Dave.
Davey, in your first post in this thread you said:
"An attenuating resistor actually lowers the signal level in the tweeter range..... a 10uH inductor does not. " (my italics)
Then, I just showed that a calibrated MICROPHONE, not just my head or my ears, can sense the changes by the 10uH choke, within the audible range. I also showed that even chokes of the same value but different design may yield different results. So, I already presented some real-world data to partly account -- again, for PART OF -- what may affect perception. I took these measurement in 2009, not now. They were not the only ones I made, just what I posted then. You just said to Neo: "But if you measure something that simply shouldn't be there it warrants a raised eyebrow and further investigation." Well, I agree. I did some due diligence and conducted other tests. I no longer have the measurements of real-world phase response and group delay that I once made but they suggested ways in which perceived benefits could be real. I even had several chokes matched for true value because they DO vary from nominal value.
Who, then, is "so hard over in his defensive posture that he appears incapable of even considering alternative explanations"?
(coming soon, a reply to what you just posted while I wrote this one)
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