You're kidding aren't you 6.7mH vs 6.75mH less than 1%, shield leakage or twist rate could easily account for this and 1% is .1dB so what free field mic measurements were horribly screwed up? So just remember to cut a few feet off when it's used coiled up.
As for therory vs. measurement you must include the secondary variables (fringing field) or the theory is incomplete. For instance video over CAT5 has to account for the fact that the twist rates are different for different pairs.
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1K parallel mode. One end shorted. 6.7 ish uH result.
No you claimed there would be no difference. I know from practice there is as the twist cancellation is not perfect. It also goes up with number of turns squared. So for a full metal spool I expect results in the mH range, which will drop 10,000 hertz by more than 3 db. These are observed results.
This was just another quick demonstration that your knee jerk reactions to folks reporting observations is inappropriate and very frequently incorrect.
SY,
I make what I call Popcorn Diablo. You heat the oil with a few Chinese red peppers or equivalent. Once the oil is hot you remove the peppers and pop the corn with it. Properly salted the heat isn't noticed at first. However as it is in the oil it builds and lasts.
Also when the first kernel pops, I remove the pot from the heat and let it rest a minute, remove the popped kernels and then resume the heating. This gives a fluffier result.
For those not in the U.S. we do have special varieties of corn that pop much better than most.
ES
Um, no.
different beast, but not inductance.
Proximity effect. It alters the resistance.
It doesn't matter what frequency, the readings are off by about a factor of 3. (Just zoomed in, it does say mH...holy mackerel, he's out by over three orders of magnitude...sheesh.
Totally agreed.
S/B about 2.5 to 3 uH.
Lp/Rp?? no wonder, try Ls/Rs. Also, look in the manual to see what the manu states is the breakpoint for using one model vs another. You can easily be beyond the meter's resolution by selecting the wrong parametric model.
Don't forget, those meters cannot determine capacitive effects on the measurement. All it can do is toss a signal down the line and separate the in phase and out of phase current/voltage relationship. Current in phase is attributed to resistance, while 90 degree out is attributed to reactance (in this mode, inductance. The meter cannot remove capacitive reactance from an inductive measurement.
When I do tests like this, I will run the frequency measure from 20 hz out to about 200 KHz in steps of 2, 5, and 10 to make it easier to graph on a log scale. Once the Rs climbs into mud territory, like 2 orders of magnitude greater than dc, then the readings must be considered suspect.
Oh, and that meter? toss it. I stopped using one of those 20 years ago, they were unsuitable to the accuracies I needed.
Your meter is incorrect for the reasons cited.
The twist cancellation not perfect statement, while accurate, does not apply as you state. Only net current along the line will show a square law. Differential current with no net does not.
I personally did not knee jerk (you've not attributed that to me). I have pointed out how the inductance was not properly measured.
It is important to question erroneous data, lest it lead us further astray in conceptual understandings.
jn
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Reference Tracks
Am I the only one uncomfortable with discussing specific styles of music mixes in conjunction with fidelity in an engineering forum? Call me chicken s#!t, but the overwhelming subjectiveness of it all makes me gag. I understand that some are stating certain attributes of specific tracks in an attempt to be clear, but it doesn't help my nausea.
<caution - soapbox ahead>
Over the last twenty years I transferred hundreds of major label masters and engineered Telarc, DMP and Sheffield releases in multiple formats. I say this not to brag, but as a pretext to saying each label, producer and format has strong sonic variabilities and tendencies. Among the engineers in each of the projects I was involved, strong preferences were expressed for different sonic signatures, sometimes leading to arguments over the merits of each. In these pow-wows, who is right, who is wrong? After all is debated, it is usually the person who pays the bills who wins.
In the absence of actual flaws (distortions, response peakiness, high noise, etc.) a mix is A MATTER OF OPINION. Proper electronic fidelity is not. Let's try to stick to this topic, please. I applaud JC, PMA and SC and a few others for trying really hard in this respect.
<off soapbox>
OK, this being said, I am aware the whole point of our science and art is the reproduction of music, not test tones. For my own reference recordings to evaluate equipment, I use a mix of CDs and downloaded 192/96KHz 24bit tracks in FLAC format. I use several FLAC tracks for which I had the original label masters, and IN MY OPINION (no graphs, charts, etc to back this up) this last format sounds the closest to the originals.
Why won't I discuss the actual titles I use? Because the whole point of music is person-to-person communication at an emotional level. If an artist's music gets to you it transcends the medium. If they speak in a way or in a milieu that you do not connect with, the recording, no matter how gorgeous, will not do s#!t for you emotionally. IMHO, we open our senses to that music which connects with us, and close off from the others. There is no level playing field across all genres. Isn't this why we use test equipment to quantify performance? If a certain musical selection causes a piece of equipment to change the sound, then we should be trying to find a piece of equipment to quantify the change. I think this is what JC is doing with his discussion of PIM and TIM. He hears something and is trying to quantify it using a piece of equipment, not opinion. In the absence of proper specifications and equipment to measure them the discussion becomes mired in unsupportable opinion with no hope of consensus.
To close this post I will agree with both Bonsai and Frank that REM's Monster is a compressed pop recording. It has both limited dynamic range and decent imaging, with (on my Staxs) a bunch of IMD in the more congested passages.
Specifically regarding the track "What's The Frequency Kenneth?", the engineer left a lot of clipping on kick peaks and an assortment of other sins, including a strange mastering flaw on my CD copy: at 3:30 it looks like the mastering engineer finally realized the transfer level was too hot and they knocked back the level in both channels by 0.6dB. All of these warts and more are all par for the course on many if not most commercial releases. It is directly analogous to designing equipment: you take care of the biggest design issues first, and tweak till the budget runs out. The result is almost never perfect...whatever that means.
This all being beaten to death, I like that R.E.M. album, so I listen to it uncritically and smile. It is not a treatise on world peace, test tones or brain music. It is a dance record...body music. But that's the last I'll contribute on that subject, I thought this was an audio engineering forum, not a place to critique recordings, or is it?
My $0.02 worth.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
Am I the only one uncomfortable with discussing specific styles of music mixes in conjunction with fidelity in an engineering forum? Call me chicken s#!t, but the overwhelming subjectiveness of it all makes me gag. I understand that some are stating certain attributes of specific tracks in an attempt to be clear, but it doesn't help my nausea.
<caution - soapbox ahead>
Over the last twenty years I transferred hundreds of major label masters and engineered Telarc, DMP and Sheffield releases in multiple formats. I say this not to brag, but as a pretext to saying each label, producer and format has strong sonic variabilities and tendencies. Among the engineers in each of the projects I was involved, strong preferences were expressed for different sonic signatures, sometimes leading to arguments over the merits of each. In these pow-wows, who is right, who is wrong? After all is debated, it is usually the person who pays the bills who wins.
In the absence of actual flaws (distortions, response peakiness, high noise, etc.) a mix is A MATTER OF OPINION. Proper electronic fidelity is not. Let's try to stick to this topic, please. I applaud JC, PMA and SC and a few others for trying really hard in this respect.
<off soapbox>
OK, this being said, I am aware the whole point of our science and art is the reproduction of music, not test tones. For my own reference recordings to evaluate equipment, I use a mix of CDs and downloaded 192/96KHz 24bit tracks in FLAC format. I use several FLAC tracks for which I had the original label masters, and IN MY OPINION (no graphs, charts, etc to back this up) this last format sounds the closest to the originals.
Why won't I discuss the actual titles I use? Because the whole point of music is person-to-person communication at an emotional level. If an artist's music gets to you it transcends the medium. If they speak in a way or in a milieu that you do not connect with, the recording, no matter how gorgeous, will not do s#!t for you emotionally. IMHO, we open our senses to that music which connects with us, and close off from the others. There is no level playing field across all genres. Isn't this why we use test equipment to quantify performance? If a certain musical selection causes a piece of equipment to change the sound, then we should be trying to find a piece of equipment to quantify the change. I think this is what JC is doing with his discussion of PIM and TIM. He hears something and is trying to quantify it using a piece of equipment, not opinion. In the absence of proper specifications and equipment to measure them the discussion becomes mired in unsupportable opinion with no hope of consensus.
To close this post I will agree with both Bonsai and Frank that REM's Monster is a compressed pop recording. It has both limited dynamic range and decent imaging, with (on my Staxs) a bunch of IMD in the more congested passages.
Specifically regarding the track "What's The Frequency Kenneth?", the engineer left a lot of clipping on kick peaks and an assortment of other sins, including a strange mastering flaw on my CD copy: at 3:30 it looks like the mastering engineer finally realized the transfer level was too hot and they knocked back the level in both channels by 0.6dB. All of these warts and more are all par for the course on many if not most commercial releases. It is directly analogous to designing equipment: you take care of the biggest design issues first, and tweak till the budget runs out. The result is almost never perfect...whatever that means.
This all being beaten to death, I like that R.E.M. album, so I listen to it uncritically and smile. It is not a treatise on world peace, test tones or brain music. It is a dance record...body music. But that's the last I'll contribute on that subject, I thought this was an audio engineering forum, not a place to critique recordings, or is it?
My $0.02 worth.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
Not as good as the 535Kcmil I use. And, we twisted the cable pair. The wire pullers were NOT happy about that.
That's because your speaker fell over backwards from the weight.Been there done that , horrible mid/top , made everyone sound short and fat..
It's not about defense or offense. It's about accuracy.
The only way uncoiling would make a difference is if both ends had the shield connect to ground. Then ya needs a DI box.
jn
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Ed,
Back in 2011 when I was making a valhalla clone, I took measurements of variations on a theme.
Using half inch wide copper strip, I measured L and C when the conductors were 1.5 mils apart via insulation film, and 1.5 inches apart. Here's the data plotted to show the characteristic impedance of the pair.
I started at 500 hz and ran it out to 500 khz. Note that the tight stripline maintained it's 8 ohm impedance out to 200 Khz, while the split pair went off at 200Khz and 500 khz. For the wide spacing, I can trust the data out to about 100Khz, but above that the data is suspect. It was the inductance that went nuts, btw. The meter started getting confused by t-line effects.
That is why I graph the measured parameter vs frequency, and take the freq well outside the range of interest just to make sure the equipment is telling me the truth.
jn
Back in 2011 when I was making a valhalla clone, I took measurements of variations on a theme.
Using half inch wide copper strip, I measured L and C when the conductors were 1.5 mils apart via insulation film, and 1.5 inches apart. Here's the data plotted to show the characteristic impedance of the pair.
I started at 500 hz and ran it out to 500 khz. Note that the tight stripline maintained it's 8 ohm impedance out to 200 Khz, while the split pair went off at 200Khz and 500 khz. For the wide spacing, I can trust the data out to about 100Khz, but above that the data is suspect. It was the inductance that went nuts, btw. The meter started getting confused by t-line effects.
That is why I graph the measured parameter vs frequency, and take the freq well outside the range of interest just to make sure the equipment is telling me the truth.
jn
Attachments
While I find that many 'subjective' opinions stated here are not very well grounded, I must say that WITHOUT subjective opinions, we would get almost nowhere. It takes both objective measurements and understanding, as well as subjective feedback to get it right. (Now, I am in trouble!) '-)
You bet you are
All we need now is an Sfb amplifier design to complement the Vfb and Cfb threads...
The issue was does coiling a microphone cable of 250' affect the sound. The answer is it may.
You may not trust the absolute reading of my measurements, but they show there is a difference between coiled or not on only 25 feet of cable.
The point is that there are lots of issues that affect sound reproduction quality and if you don't acknowledge them, you are missing something.
Now if I want to measure inductance more accurately I have a better bridge, but it is older and requires manual nulling. Since it doesn't make as nice a photo essay I didn't use it. I actually bought it because there was a fellow who claimed he had measured all of the loudspeakers in a stadium and found errors. He claimed to have used that version of a bridge. It never made it to court, but the idea was to see if he could even operate the unit. (Based on his claims the answer was clearly not.)
ES
It doesn't affect the lower bandwidth, that was evident from the graph. I believe the problem with the high impedance one was the fact that to measure inductance you short the far end, and a 150 ohm cable is far more mismatched w/r to a short than the 8 ohm cable.
So far, you stated that inductance is proportional to the number of turns squared, which is correct. But then you show a test of 45 feet of cable on and off the spool, and the difference is pretty much within the error band of the instrument. If the number of turns did in fact matter, then why were your readings almost identical?
May not trust the absolute reading? Ed, your readings were three and a half orders of magnitude out. It is akin to reading a AAA battery with a voltmeter and getting 3,500 volts!!
Your measurement is not just out of the ballpark, it's not on the same continent.
And yet you are sticking to a fractional percentage change of a HUGELY erroneous reading as proof?
And how did we get there? You just went from a measurement that was two thousand times larger, tried to explain it (erroneously), and now it's this? I cannot acknowledge misconceptions and bad measurements as "issues" that affect sound reproduction.
Fix your meter.
It is important to understand what is being measured, and how to do the measurement accurately. Inductance is not easy to measure correctly, you got bit.
btw, I kinda know what this inductance stuff is...
jn
You bet you are
All we need now is an Sfb amplifier design to complement the Vfb and Cfb threads...
There is the answer (patent applied for?): an amp that listens to the grumblings of its owner and tunes to a minimum. Changing to meet the current subjective mood. With things like voice recognition and the Kinect visual monitoring it would only require a little learning to determine what to do. . .
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