True, to the extent the system is time invariant. However, no physical system is perfectly time-invariant. So it depends on the needs of a particular project.
Maybe because at least some amplifiers can drive the load, and because the amplifier and speaker taken together as one overall system outperforms other approaches.
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Hallo Gerhard,
Good to hear again from you.
It would be nice if you read a bit more the previous traffic before a specific snapshot. I did have said that VNA (with proper equations, the ones you mention in Rhea's book, or from other books if you fancy) is possible too. Likewise with impedance analyzers and direct measurements. For my taste, the later fits the bill nicer. Contradict me, please
If my understanding was correct, Andrea told me that impedance analyzer is not the proper tool, being current source and hence a la 70s. That, I did not understood and I tried to correct. The calibration for VNA would be more sensitive, compared to direct readings of impedance analyzer plus its simpler calibration. For what is worth, this is my opinion.Anyways, good that you are healthy, beautiful day in St. Wendel today, and have more time to be back online with us. Thanks for sending me straight to beginners books
P.S. do not forget here is audio range, not our GHz daily stuff where only VNA exists. For audio, and up to MHz (where Qz-oscillators are measured), the impedance analyzers were more expensive than VNAs, if I remember correctly.
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Hi Mark,
I think there is a market for it that has little to do with how it sounds. There are systems where the cost is more modest that sound amazing too. I suspect it may come down to some people who buy the most expensive stuff and declare it the best (because it is more expensive).
I can't tell you how much equipment I have worked on that were horribly expensive, but didn't really perform that well. I don't want to bash brands beyond illustrating my point, so I will name as few names as possible. But I am thinking of an amplifier that will drive them that runs so hot that it needs complete "recaps", including main supply caps every so often. In order to do this, every output transistor and driver must come out as well. The cost of doing this is several thousand dollars and is considered normal maintenance. I think that is a tad extreme, don't you? Never mind the power costs and people are told to leave them on all the time! Very poor advice.
-Chris
I think there is a market for it that has little to do with how it sounds. There are systems where the cost is more modest that sound amazing too. I suspect it may come down to some people who buy the most expensive stuff and declare it the best (because it is more expensive).
I can't tell you how much equipment I have worked on that were horribly expensive, but didn't really perform that well. I don't want to bash brands beyond illustrating my point, so I will name as few names as possible. But I am thinking of an amplifier that will drive them that runs so hot that it needs complete "recaps", including main supply caps every so often. In order to do this, every output transistor and driver must come out as well. The cost of doing this is several thousand dollars and is considered normal maintenance. I think that is a tad extreme, don't you? Never mind the power costs and people are told to leave them on all the time! Very poor advice.
-Chris
It's ok Andrea, don't bother. Better let it dropped as is.
I was probably a bit nostalgic and too sensitive, leading to misunderstanding. From where I come, the modern replacements of 70&80s instrumentation preamps, which were made back then by Ortec using custom designed&manufactured discretes, are a shame. Not audio and not the only example, when our today's best specialists cannot believe how something could be made so good, and have absolutely no clue how to make it identical again. Lost know-how...
I was probably a bit nostalgic and too sensitive, leading to misunderstanding. From where I come, the modern replacements of 70&80s instrumentation preamps, which were made back then by Ortec using custom designed&manufactured discretes, are a shame. Not audio and not the only example, when our today's best specialists cannot believe how something could be made so good, and have absolutely no clue how to make it identical again. Lost know-how...
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Inquiring minds need to know, how did you use a VNA "to analyze the oscillator circuit"?
Tools are available today that were either non-existent or really rare in the 1970's. I just went through some calibrations of '70s era instruments and the tools referenced for frequency adjustment seem really quaint (e.g. using a time mark generator + scope to adjust frequency accuracy on a Tek 191 constant amplitude generator, frequency counters were really rare then).
For example a speaker analysis system using a chirp was a fantasy in the '70s and now a common hobbyist tool. Same for a $100 VNA.
One time variation in typical drivers that can relate well to different amplifiers- voice coil heating. It essentially captures the broader envelope of the audio signal and modulates the sensitivity of the driver. The time constant is not that fast. An amplifier with a higher output Z may actually slightly compensate for that effect seeming more dynamic than a zero output Z amp. TI has a platform for measuring the change in voice coil resistance with audio and applying that to DSP in their amps to prevent burnout on microspeakers. I asked them about applying it to linearize the sensitivity of the drivers. They sounded interested but silence since. There may be some similar things in some prosound speakers. This is only useable in a combined amp-speaker system.
For example a speaker analysis system using a chirp was a fantasy in the '70s and now a common hobbyist tool. Same for a $100 VNA.
One time variation in typical drivers that can relate well to different amplifiers- voice coil heating. It essentially captures the broader envelope of the audio signal and modulates the sensitivity of the driver. The time constant is not that fast. An amplifier with a higher output Z may actually slightly compensate for that effect seeming more dynamic than a zero output Z amp. TI has a platform for measuring the change in voice coil resistance with audio and applying that to DSP in their amps to prevent burnout on microspeakers. I asked them about applying it to linearize the sensitivity of the drivers. They sounded interested but silence since. There may be some similar things in some prosound speakers. This is only useable in a combined amp-speaker system.
'Amazing' might be taken to mean the best someone has heard so far, or maybe a system very close to that level. Once a better system is heard then the previous standard may not sound as amazing anymore. One never knows until one hears better.
Agreed. Some is expensive junk, especially some of the very expensive cables. Then again, some of it is very good.
The point has been made by various people that we can't share how something sounds in text, which is indeed a problem.
Its can be worse than that actually. Some people happened to be lucky enough to find someone who is expert in putting together a great system for them, and do so at a fair price. But then some of those people will start reading magazine reviews and start redesigning the system themselves, believing they are smart enough to do better than the expert they used. They buy the expensive junk cables, some other awful stuff, and sell off the good stuff they had. Then when their friends tell them they ruined the system, they get mad because that's not what they wanted hear. I am told doctors and lawyers are the worst
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You could be right Mark, but in my experience, high current levels for normal SPL levels typically doesn't work out well.
As far as your reference is concerned about sound quality, of course. You can only judge by the best you have heard. I have heard some extremely good systems, and a lot of live sound (acoustic and amplified).
-Chris
As far as your reference is concerned about sound quality, of course. You can only judge by the best you have heard. I have heard some extremely good systems, and a lot of live sound (acoustic and amplified).
-Chris
How you would evaluate if the system needs pre-distortion?
I try to imagine. First, feed in the amplifier a pure sinus then measure the acoustical spectrum and see presence of H2 generated somehow by the drivers. Ok. Then try to pre-distort with proper H2 generated in anti-phase, to cancel the acoustic response of driver?
But would this not be against most audio reviews tell, it is better to have a decent presence (to hear it) of H2? This is the Valve superiority mantra, and we try to cancel it.
Or, maybe you mean, that not a total cancellation is the goal?
And that would be optimized for a small volume range and track?
Would be then nice and useful to have a variable H2 dial... right?
Sorry if I did not understand or see how else to understand your answer. If you see here more than I do, could you detail a bit more please?
Pre-distortion is just another way of linearisation of an amplifier instead of, or as a complement, to NFB. Its absolutely not a way to give it a sound...
But you are on the rigth thinking - the sum is the result - thats why testing a single component like an amp is a bit strange really...
//
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