Point is that audioband risetime is always obviously far slower than response time here......
You need to rerun your work with correct audioband risetimes, then you'll see the lack of latency. Simulate it, but you owe us an answer on your own prediction for a 25uS audioband risetime into 8R if you disagree with classic prediction of c 0.13uS latency attributable to cable inductance.
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You are completely uneducated with respect to this topic. Please inform yourself. Alas, I didn't recall that Cyril's actual construction of a low impedance bridge is in the same article part 2. I assumed you knew the material, my bad. He goes in depth into reflection stuff at audio, with lots of scope photo's from reflection bridges. I'm afraid that I've tried to locate the link online and come up empty. I do have a paper copy, and if you wish, I'll look for the electronic one as well. Unfortunately, the PM system here cannot send a file that size.
Who said 25 uSec audioband risetime into 8 ohms" Do you think that making up garbage is going to fly here?
My work involves running 50 to 75 meter long parallel pair cables to loads running in the 1 to 3 ohm range and 5 mH to 100 uH depending on frequency. The built in latency (delay) caused by a long line terminated at both ends with very low impedances rises into the 20 to 50 uSec range. The feedback system this is included within cannot handle the latency caused by waiting for the line to charge to the currents the load requires.
So come again? Why make things up? So far, you've been better than that.
Go ahead, re-do your simulation using the lumped values for a real cable..don't think for one moment that making up arbitrary numbers is "proof" of anything.
YOU have demonstrated the latency I speak of, and did so with the cable parametrics I recommend. So why are you afraid to use a real cable, and show us the 5 uSec latency with the waveform of your choice, the 25 uS ramp.??
I've learned long ago, that even if I post content, people like you will not believe it. YOU have to prove it to yourself.
jn
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Hmmm, that's not even particularly representative of a washing line. An AM radio antenna, maybe.........? 😉 Very funny, that's made my day. But yes, these are the lengths one needs to go to obtain sufficient LP filter values to obtain a notable audioband delay..............
What do you expect ? If you post technical stuff it's always open to review and challenge. The truth will out. When it's shown to be flawed it shouldn't be believed. You should re-run with audioband risetimes, then even you might not believe it..........jneutron said:
So where did your incorrect assertion go?? You know, what you made up..
That is precisely why we are having this discussion.
As I said, you will not believe it anyway. That is why I told you to re-run your own simu, but this time don't make up fictional numbers to try to support your belief.. Use a REAL cable.
BTW, the 50 ohm impedance of the 8721 does not change the result he displayed. The only problem with it is it absorbs.
He goes into quite a bit of detail in part 2, provides a schematic as well as discussion on the use of a two transformer directional coupler, which has very little insertion loss as opposed to the hp unit.
So what's the story, why are you afraid to show everbody you simulation using a 25 usec rise and a real model of a zip wire, instead of made up values.
Go on, we all know the results...don't be afraid. You say "when showed to be flawed", yet you used bogus numbers in your "proof".
jn
ps..let me know if you'd like a copy of part two, we can work something out if nobody else chips in.
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Thanks for admitting that you have nothing to offer as far as audible aspect of speaker cable lifters go.
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Diversion is coming from you. That is unless you posted something about the audible aspect of speaker cable lifters. Please point it out if I missed and I'll thank you for it.
Er, I already did. And I used params taken from tables in Davis 1991. It's valid. It's definitely your turn to post any content, modelled or measured, based on real audio risetimes.......
You cannot be serious.........jneutron said:
If you're planning to write this nonsense up, I won't be the only one..... ;-)
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Isn't it always bound to happen, though. Sometimes, I think there's a formula to figuring out how much poo slinging will happen, it's a factorial of the combined years of education vs how little research is available to read outside of the discussion. 🙂
I'm just teasing, I find all of this fascinating to read and try to follow.
I've learned that when a set of parameters for a cable is published, to be wary of the values. Inductance by far is the parameter which is measured incorrectly. The standard error is the erroneous use of the inductance meter. Many users will set it for Lp/Rp and try to measure a cable. Those who choose the correct setting, Ls/Rs, split into two groups.. The first group fails to exercise the auto-zero function of the meter, so swamps the inductance measurement with test setup error. The second performs the test properly.
Capacitance, by nature, is trivially easy by comparison.
For typical cables, L time C (both in nano per foot), the product of the two is 1.043 times the effective dielectric factor, ranging from 3 to worst case 6 or 8 depending on the conductor spacing.
For typical parallel conductor cables such as zip, the value sqr(L/C) is in the 120 to 150 range. This is length independent by design.
Your lumped inductance and capacitance value fails the second test. This means that the cable is not zip construction, but is either multiple twisted pairs, stripline construction, or coaxial. Again, a strawman cable for the discussion.
(regarding the equivalence of the 50 ohm bridge)
Most certainly. The insertion loss of the device has no significance to the reflection coefficient down the line.
In addition, the paper part 2, which you do not have, details far more in terms of both building a proper low impedance device to satisfy you, and also provides quite a few actual scope waveforms detailing exactly what he did.
So in essence, you don't have a problem with me. You have a problem with Cyril Bateman.
Why don't you give him a call or send him an e-mail? You can argue with him all you want.
I've already begun the process. In discussion with you (edit: and others of course) (thank you,by the way for your time and effort), I learn what the people who have no direct experience with T-lines, reflections and reflection bridges do not know. For me, that is a good thing for me. The people I've had to teach this to have sufficient background as to quickly understand what I've been talking about, how to model it, and how to work around it. Most of the physicists don't initially get the engineering aspect, but when I explain why zero delay (also, single transit delay) is a violation of lightspeed given the line to load ratio, they quickly understand. So I really do not have much experience trying to explain the heavy technical aspects with those who do not do it for a living.
The first part of my article, as is evident, is a primer on T-line theory. I find that most engineers glossed that over in school. Honestly, I cannot blame them. If it weren't for our back and forth, most viewers would already be asleep.. I don't even know if Jan would consider publishing it..
I find a dilemma with respect to test instrumentation however. I can easily re-built my sources, my loads, and even cables of various characteristic impedances.. But I cannot publish results using the equipment at my disposal, and do not have any at home. It is a serious COI for me.
It would be most interesting to see if anything comes of the picnic.
I'd be happy to discuss it with whomever you are speaking of....but no belly rubs, sorry..
jn
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No one has offered anything but the most tenuous explanations for how they could possibly work, as its basically another Audiophile myth we might as well discuss signals, unless you have some evidence/explanation regarding cable lifters...
The audible benefit? None that I found from listening without knowing when they are in use or not.
How do you offer an explanation for something that dosnt exist. I guess there's magic. What kind of plausible explanation did you offer?
if jn is running 50 - 75M cable driving 1-3 Ohm loads, I can see where the cable may impact the sq at the load.
This sounds more like commercial equipment (concert sound system?) than a typical home installation /diy operation.
I think the longest run I will have will be the rear speaker which is about 7M, and I'm driving nominally 8 Ohm speakers that dip to around 6ohms at low power levels. My primary speakers only have about 2.5 M of wire. With 12 AWG twin-lead, I don't think I'll see any of the effects being discussed.
That said, I can simulate cable lifters to my front speakers by simply cutting the length to disallow them touching the floor. ;^}
This sounds more like commercial equipment (concert sound system?) than a typical home installation /diy operation.
I think the longest run I will have will be the rear speaker which is about 7M, and I'm driving nominally 8 Ohm speakers that dip to around 6ohms at low power levels. My primary speakers only have about 2.5 M of wire. With 12 AWG twin-lead, I don't think I'll see any of the effects being discussed.
That said, I can simulate cable lifters to my front speakers by simply cutting the length to disallow them touching the floor. ;^}
That is not what I am doing. The loads are part of a big machine. The loads have a 10 Khz bandwidth. The cables can easily drive the load at 10K. The problem is, the delay caused by the cable's length coupled to the horrible impedance match to the cables in concert with the upper limit of the speed of light (EM waves) in a media (cable). Since the loads for the most part, are constant impedance, the delay is consistent. Too long, but consistent.
It is not possible to compensate for the latency caused by the cable to load mismatch. Instead, by dropping the cable impedance, it is easy to reduce this latency, or following error, or whatever we wish to call it.
With cables and audio, the consideration is what is the sometimes wildly varying load impedance doing with respect to the built in delay caused by the mismatch. Since it is impossible to match the cable with the load, the best one can hope for is to put the cable impedance smack in the middle (or close) of the impedance range.
It really costs nothing if one simply parallels 3 or 4 medium awg zips. No need for fancy, incredibly expensive yahoo type wire. And as Lucky posted a while ago, as long as one uses 3 or 4 zips in parallel to reduce the impedance down to the 40 to 50 ohm range, even 1 ohm loads in a rudimentary simulation show 1 uSec level delays which are of no concern.
A good sim of real zip runs the delay up to about 5 uSec, which begins to enter audibility for ITD effects..so best to stay away from normal wire if your load swings wildly down to 1 ohm and you need more than 15 or 20 feet.
I run 90 foot #12/2 for my PA stuff, and simply do not care if there are delays across the band..the application certainly does not warrant it.
Nor, in my backyard, nor in my living room.
But that's just me.
jn
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