Do you know for a fact that much of the pop music is recorded into overload, or are you guessing here?
What they do in order for the music to sound louder is high compression, not overload.
This may be the case in some small studios.
Since I worked in recording studio and visited some others, I know that the majority of the recording studios are capable of very high quality recordings.
The level of some of the music is a different story.
One must consider what an eddy current is, what the current loop paths are, and what happens to the magfield energy stored and released by the eddy currents. For example, if I place a 1/2 inch thick aluminum plate in the flux path, the aluminum will cause a lowering of the inductance by exclusion..(Lenz's law). The eddies within the aluminum are bucking the field, and when the driving field collapses, the energy stored within the aluminum will be dissipated. That dissipation is 90 degrees out of phase with the forcing field. This is a typical problem encountered in my line of work.
As I stated in general. What I pointed out is the eddies are 90 degrees out of phase with the driving current, and that the two HP4284A's I have been using will attribute this loss mechanism to added series resistance of the primary windings. This effect is more pronounced in my litz wound magnets. The mech guys initially designed the magnets with 1/4-24 stainless capscrews down the center of the air core winding, and the losses popped up as a frequency dependent series resistance..
hmmm. I had to help some guys degauss a fridge size double walled mu-box for a mag monopole experiment..but I don't know how low they were able to go with the internal field..
Then you would be incorrect. (sorry)
When a conductive material is put into a time varying field, it will try to force exclusion of the field lines. That forcing is the eddy currents producing a magnetic field counter to the forcing field lines. Eddy currents within a conductor are still currents, and currents within a lossy conductor will produce noise. So your thinking that the currents do not couple back to the primary are seemingly good, but the noisy current does indeed produce a noisy bucking field.
As I initially stated, my HP4284A thinks the eddy losses are part of the series resistance of the coil. So, why would it believe that but yet audio signal circuitry wouldn't? I would think long and hard before accusing HP of being incorrect in a fundamental aspect of a piece of test equipment...
How long did it take to count the turns??? Note: the guys here have found that an even better application of rebar is to reinforce high density concrete...go figure..
As frequency increases, the current density within the functional cross section of wire will quickly rise, increasing losses. Again, how does one distinguish the "out of phase" noise of the effect from the straightforward loss noise of the pure resistance. The noise will not correlate directly to the forcing current, so the only thing left to look for is a phase shift of the noise power envelope. Measuring that to fractions of a degree at mid to hf audio? Most CVR's can't even hold that kind of phase lag, so measurement will be loaded with error components..
I agree with both statements..
I agree.
Agreed, it is not a given. However, the bucking field will be noisy as a result of the eddy current noise. How to measure, that's another story..My disagreement is a very fine point.(edit:you ol' nitpicker you...
I see eddy noise generated proportionally to the derivative of signal current, which of course is 90 degrees lagging.
Thank you for the cite John.
1 and 2 mil is a real "problem" shall we say? It has virtually no problem with slicing into skin, and that hurts. Even after the stabolite has been cured, the edges are very dangerous.
Luckily, my stuff is 1/2 to 1 mm in thickness.
Cheers, John
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I've encountered songs where the bass shows heavy waveform flattening..if I remember correctly, it was a song by No Doubt..
Cheers, John
Well, it looks like we will have to rely on Joachim to contact his colleague and report back. At least one manufacturer has 'done his homework' so to speak. I wish that I could get my boss to fork over $1000's of dollars and also pay for my time in testing every major transformer available, out there.
Yes it is: John G McKnight for those who has the AES preprints and Journals. Unfortunately, while I am pretty sure that I learned about this added noise from him, 43 years ago, as we often worked together on projects like this, his AES papers are rather complex and usually talk about other factors in tape head design, only mentioning the problems with 6mil or greater lams, in passing, even though it is actually 'Gorilla in the room' when it comes to high frequency noise and accuracy in high frequency response.
Looking through McKnight's papers, I can find no CLEAR graph that directly points to the magnitude of the problem, even though it implies it. Another MAJOR factor is that J. McKnight converted almost exclusively to 2 mil lams by the time he did the majority of his measurements, rather than suffer the added problems of the 6 mil lams. This moves the frequency where eddy current losses become important almost 10 times higher, and generally out of the way for audio reproduction. This requires a scaling of what graphs he presents, and in doing so, then reminds me of what I used to measure with a Q meter.
Of course, when measuring tape head Q with frequency, AND when you add a transformer to the measurement, if the transformer is virtually perfect, only the DC resistance of the wires will lower the Q a little. However, in actual measurement I noted when the transformer eddy current losses kicked in, lowering the Q even faster that what would be expected from an 'eddy current lossless' transformer. This is what I am concerned about with moving coil transformers. They could present the same problem, if their laminations are 6 mil or thicker. Sowter mentioned 4 mil in his literature, but I don't know about anyone else. This converts to about 150um for 6 mils, and 50um for 2 mils. If anyone has any info on the lamination thickness of these transformers, I would be interested.
Yes it is: John G McKnight for those who has the AES preprints and Journals. Unfortunately, while I am pretty sure that I learned about this added noise from him, 43 years ago, as we often worked together on projects like this, his AES papers are rather complex and usually talk about other factors in tape head design, only mentioning the problems with 6mil or greater lams, in passing, even though it is actually 'Gorilla in the room' when it comes to high frequency noise and accuracy in high frequency response.
Looking through McKnight's papers, I can find no CLEAR graph that directly points to the magnitude of the problem, even though it implies it. Another MAJOR factor is that J. McKnight converted almost exclusively to 2 mil lams by the time he did the majority of his measurements, rather than suffer the added problems of the 6 mil lams. This moves the frequency where eddy current losses become important almost 10 times higher, and generally out of the way for audio reproduction. This requires a scaling of what graphs he presents, and in doing so, then reminds me of what I used to measure with a Q meter.
Of course, when measuring tape head Q with frequency, AND when you add a transformer to the measurement, if the transformer is virtually perfect, only the DC resistance of the wires will lower the Q a little. However, in actual measurement I noted when the transformer eddy current losses kicked in, lowering the Q even faster that what would be expected from an 'eddy current lossless' transformer. This is what I am concerned about with moving coil transformers. They could present the same problem, if their laminations are 6 mil or thicker. Sowter mentioned 4 mil in his literature, but I don't know about anyone else. This converts to about 150um for 6 mils, and 50um for 2 mils. If anyone has any info on the lamination thickness of these transformers, I would be interested.
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In McKnight's paper: 'Magnet Design Theory for Tape Recorder Heads' JAES Mar 1979, where he publishes research that he originally did in 1971, he acknowledges: Wm. Pottberg for making the 2 mil lam heads. This brought up the old memory of Pottberg in 1968, bringing 2 heads into my office, and daring me to tell him which was 2 mil lams and which was 6 mil lams. I got out my trusty GR Q meter and showed him. Was he ticked! Of course, a few years later, 2 mil was introduced into ALL Ampex audio products and 6 mil was quietly forgotten, as it should have been fazed out, 10 years before. And so it goes!
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Jan presented some slides once and I have seen them on the web, data right off of CD's of HARD clipping on many pop recordings.
Then you would be incorrect. (sorry)
When a conductive material is put into a time varying field, it will try to force exclusion of the field lines. That forcing is the eddy currents producing a magnetic field counter to the forcing field lines. Eddy currents within a conductor are still currents, and currents within a lossy conductor will produce noise. So your thinking that the currents do not couple back to the primary are seemingly good, but the noisy current does indeed produce a noisy bucking field.
OK you win
As I tried to mention I use the term excess noise specificly the way EE's use it (at least those in the semiconductor industry). Maybe there's one of those physicist vs engineer terminology things here? I would look at the sqrt(4KT/R) or sqrt(2qI) type noises as having a flat spectrum and excess noise as I use it as having a 1/f spectrum. It is fair for me to assume a resonabley pure sample of metal would have very little excess noise making mechanisms. So we actually agree, I think.It is a good question as to how measure this directly. Maybe a superconducting coil force/sense where only the eddy current makes noise? How about the noise of a single electron in a SQUID. Yes, I will remember not to make my superconducting coil out of copper.
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This is different from the remark I referred to.
No doubt there are many lousy recordings. Actually, my impression is that really good recordings are rare, but that is not because of the majority of the recording studios aren't equipped to enable good recordings. Anyhow I seldom listen to pop music of the last 30 years or so.
A while ago I had a discussion with the owner of large and respected local recording studio. He said that recordings are deliberately mixed so that they will sound "good" on mediocre sound gear, because of the majority of the potential consumers have such gear. This is a demand posed by the music companies and producers.
This may happen during the mastering, not necessarily during the recording.
I don't have many positive comments on the quality of recording and mixing in recent decades, however some comments made here sound to me purely imagined. The "loudness war" is made by compression, not by clipping. The same goes for many radio and TV commercials, which are highly compressed in order to sound louder.
What are you referring to? Recording quality? I'm not sure it's off topic, because of it may reflect on the quality demands of audio reproduction gear.
Hi John,
I know that the Nortronics hyperbolic heads that I used in the mid-Sixties had a good reputation, but I'm guessing from the time frame that they must have used 6 mil lams. Is that correct?
Cheers,
Bob
Studio Sound
Absolutely my experience as well Joshua. I hate to admit it but the potential fidelity difference between semi-pro and fully pro studios has dropped into the pop music noise floor. The biggest difference in sound quality (not performances) in most releases now is the skill of the engineer and producer. This being said, I go back to a subject previously covered here: the superiority of direct-to-cutter LPs. The very best fully pro studios still have much more fidelity 'headroom', if you will, whether or not is is utilized.
(insert segue to blatant plug here) Then maybe you would enjoy listening to a show I am doing on WXYC this evening at 9PM EST. It is a 70s Underground Special, the music of the then-new FM band in the late 60s and early 70s in the US. Yep, I'm old. I plan to even play some of JC's guys!
Thus the aforementioned "Horrortones" (in reality Auratones) to emulate what someone in a car with poor speakers would hear.
The same logic applied to using Yamaha NS-10s. I hated them, but a mix without audible distress on them would work well on an average home or car stereo. And of course 30+ years ago everyone had a single Auratone at console center to make sure the mix was monoing without problems.
p.s. I had the honor of working with Jay McKnight on a NAB/ITA cassette standards committee, and he was freakin brilliant!
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
Absolutely my experience as well Joshua. I hate to admit it but the potential fidelity difference between semi-pro and fully pro studios has dropped into the pop music noise floor. The biggest difference in sound quality (not performances) in most releases now is the skill of the engineer and producer. This being said, I go back to a subject previously covered here: the superiority of direct-to-cutter LPs. The very best fully pro studios still have much more fidelity 'headroom', if you will, whether or not is is utilized.
(insert segue to blatant plug here) Then maybe you would enjoy listening to a show I am doing on WXYC this evening at 9PM EST. It is a 70s Underground Special, the music of the then-new FM band in the late 60s and early 70s in the US. Yep, I'm old.
I plan to even play some of JC's guys! Thus the aforementioned "Horrortones" (in reality Auratones) to emulate what someone in a car with poor speakers would hear.
The same logic applied to using Yamaha NS-10s. I hated them, but a mix without audible distress on them would work well on an average home or car stereo. And of course 30+ years ago everyone had a single Auratone at console center to make sure the mix was monoing without problems. p.s. I had the honor of working with Jay McKnight on a NAB/ITA cassette standards committee, and he was freakin brilliant!
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
The Auratone was a very popular speaker to check the mix. First it was recorded often on many tracks (16 typical) and mixed down onto two tracks using a pair of "Studio Monitors" which very often had been equalized to present as flat a frequency response at the mix position as the knowledge and equipment allowed.
Once this mix tape was made it would be reviewed over speakers intended to be of the quality of car audio speakers to be sure it still carried the same intent of the producers mix.
One side effect of this was that some recording engineers found they heard stuff on the single driver check speakers that they had not noticed on the multiway equalized "Studio Monitors." This resulted in higher quality single driver "Full Range" monitor speakers to become more popular. The next change was now that such small speakers were being used as a reference the engineer could take their own personal pair with them to different studios. That way the engineer could reduce variations due to each studio having different models of monitor speakers or even different sounding versions of what were supposed to be the same model.
Of course once Bose started selling auto makers on improving car stereo systems, there was much less need to mix to really bad speakers. As annoying as it may be to some Bose did raise the standard.
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