Those who own milling machines (no time for jealousy now, but I'll hate you in my next life) might enjoy This Old Tony:
YouTube
where he shows how to make stool steel and how to cut left-handed threads with a normal right-hand tap. YouTube videos rock and roll.
All good fortune,
Chris
So, measuring actual rise time at the speaker end of a cable should show the effects of different speakers on a cable and vice versa. However it won't untangle the "modulation effects" of changing impedance handling complex signals.
At least it should be possible to take several speaker cables of different construction and see the differences in rise times with different loads. What to drive with? I have a Tek 109 but I don't want to abuse it this way. I don't think you need sub nS rise times for this to be relevant.
Possibly a reasonably fast amp, a fast square wave and slow sine wave and look at the modulation on the rise time as the voltage changes? I have an HP 467 that has a bandpass to several MHz (no output network and a modest Zobel) that may be a candidate. But is this going to show the issue?
Actually, a Wheatstone bridge made from 49R9 resistors is enough.
That's how the DG8SAQ VNA works. In the end, it's only the calibration kit
that makes the difference.
< https://www.google.de/url?sa=t&rct=...m_dg8saq.pdf&usg=AOvVaw2ioqNKiX9oWap_BjhVQFM7 >
(first answer)
< https://www.sdr-kits.net/documents/VNWA_W10_W8_W7_Installation.pdf >
< http://literature.cdn.keysight.com/litweb/pdf/5965-7709E.pdf >
The DG8SAQ VNWA is quite good; I've got one from generation 2
when it still was available as a kit. There is not much hardware: 2 DDS,
2 Gilbert mixers, a CODEC and some Atmel single chip controller.
It delivers the same results as my R&S ZVB, with some restrictions on frequency
and amplitude range. The lower frequency corner is only 1 KHz.
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Demian, anyone with instrumentation can do this. Actually, Nelson made such measurements more than 30 years ago and shown it yesterday. What it says to possible audio issues? Nothing. Audio signal at the output of audio systems is strongly bandwidth limited. There are no fast edges, short rise times. There are no 10kHz square waves with ns rise time. The square would have rise time no shorter than 10us, equivalent of 35kHz sine. Cable analysis with short rise time or high frequency (I hope at least someone understand the equivalence of both) is nice, however irrelevant for audio. Measurements with BW limited signals clearly shown there is nothing happening in the speaker cable of several m length. I resign to further discussion on this topic. Everything has been already said and shown, without any effect.
Many like to think that speaker is the weakest link but the true concept of this is that anything from input to output can be the weakest link. And often system improvement can be easily done (not too complex or labor intensive) but requires money. Speaker drivers are expensive but cable is cheap.
And amp can often be the weakest link too. Actually it should be part of an integrated amp-speaker system design. If money is not an issue, i will probably buffer my amps with current buffers (hint: 'turbo F4') to match my amps to my speaker.
The biggest improvement of my system during the last decade came from my understanding about how amp and speaker should be designed (to sound good), not from budget increase. But i pay attention to everything including capacitors and cables. Not to find the best ones but to avoid using bad ones (which may become a weak link).
Is there a reason not to test for audibility without trying to measure (the unmeasurable??) first.
If two loudspeakers sound differently, there always is a difference that can be measured. If two loudspeakers measure differently, they still may sound identical. In short, measurements can discriminate beyond human hearing capabilities. This should be no surprise.
Of course, tid bits of knowledge like this have been derived from blind listening tests, an ex ante disqualifier to hard core subjectivists.
Planet 10 can hear his (in)famous DDR whilst he's looking at the fairies footprints 😉🙂
BTW, he can also hear it whilst using 24awg cat cable (single solid pair!) all the way from amp to speaker, imaging integrity is a speciality of his, take note JN, you are wasting your time 😀
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Yes, a Wheatstone bridge can be used in principle to measure impedances down down to DC. The problem, as you very well know, is the differential to single ended circuit required to measure the imbalance. This is usually a transformer, which is required to have the same differential impedance as the measurement port, hence the difficulty to scale down the lower frequency limit.
Such a transformer can be replaced with any type of differential mixer, in particular a Gilbert cell. This would provide down to DC measurement capabilities, and a reasonable upper frequency limit. I found this article some time ago https://www.jstage.jst.go.jp/article/elex/8/11/8_11_814/_pdf but never attempted to build such and evaluate its performance, I simply can’t find the time for this, I’m not a professional in such, so I’m constrained to use mostly over the shelf components.
The directivity constraint for measuring very low VSWRs remains in this case as well. 60dB directivity is tough, whatever way one approaches it.
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There is where all the question lies in my book.
For the audio salad, it is better to turn wine in vinegar (because there is nothing good to be expected from the miracle you pretend) and make vinyls sound like digital.
Reading-you, i think you are a fanatic.
A pure objectivist, half wrong in his religion, that means wrong.
Because you believe we are able to measure all the phenomena in action.
Because you believe the recordings are perfect and made by GOD.
I give-it up: there is no way to bring a pure objectivist to reason as well as a pure subjectivist that is half wrong as well.
Again and again, hifi is a "make believe" game. An illusion. A representation in 2D of a 3D reality.
Measurements, yes, "can discriminate beyond human hearing capabilities".
But we measure only what we know *what and how* to measure.
When you measure a response curve of a speaker with a mic, you measure (in a flawed way, because the mic is not transparent), only whats happens at the point where is the mic, missing what happens 10cm ahead. And this mono mic has nothing in common with our stereo ears and they very complex directivity in all directions. This is an example
We don't really know how human hearing compute those 2D sounds, once projected in our 3D listening rooms that are all different. No model. or very approximative ones.
Subjective listening impression are flawed ? Yes. We measure only a part of the reality, yes. Think twice and make your conclusion with a minimum of balance, please.
You cannot pretend that a black hole do not exists because you do not see-it with your telescope, as well as you cannot pretend it exists because you 'feel' it".
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If the sound difference is perceived by those who does not have good ears, the difference must be huge such that it is easy to find the variable to be measured. Consequently, if it is perceived by those with good ears, you may have trouble to find the variable to measure.
Yes, even TAD ME-1 will sound identical to P3ESR for reason stated above.
No difference at all whether it is about speakers, amps, DACs or cables. What i can see is that there is a poor common knowledge about audibility of things. Most if not all of those with good ears will agree but not with most of those with not so good ears. The latter will think that the job is done and if you don't think so it is because you don't understand Physics or cannot do measurements.
And it is just an imaginary fence between subjectivist and objectivist. A subjectivist can appear to be an objectivist when debating with someone with much less knowledge.
In speaker design, i would be in trouble defending my opinions and decisions to leave high order crossover slope behind. No, it is not because it is difficult to do it right. I left it when i think i could do it right.
IMHO, it has nothing to do with 0.25dB response curve. The other argument is irrelevant too. But that's just my opinion 🙂
Thanks syn08 for responding.
Can you please say a few words about why a resistor bridge like the one in my last link is so hard to work at LF (high audio frequencies or a bit above) ?
And a brief description -principle of operation- of your build here?
George
The only requirements are that the amp support the output node reasonably well through the reflections, and that rise time be sufficiently fast to not affect the time region of interest. Standard test thinking. Trying to measure roughly 1 uSec, I would go 500 nS to maybe 250 nS as the fastest required.
I really loved the 109, but yes I abused it. It would really worry me now how to find a new reed relay as I don't know if a replacement can be found.
Jn
Agree on everything. (despite I prefer high slope (48dB/oct) crossovers ;-)
I only know one way to make a good work of design. To use what we know by the science, in the most rigorous way as possible, to measure the results in order to look more objectively, thinly and deeply, then to ... listen, because I don't know, reading some measurement number what I can hear or not of what I read.
Lying on pure numbers is stupid: If an amp with 0.5% of distortion sound more natural TO ME in a system than a 0.00001% one, which one to chose ?
Everything you understand may have been done, but not everybody is willing to remain stuck in the past, hindered by your beliefs.
Nelson did good measurements, but did not look for what I discuss. You can try to see rise time and settling on those scope photos, but it is obvious to all that it was not the intention of the test. A speaker is a current fed beast, terminal voltage is a part of the story, but just a start. Note I am sticking to coil based beasts.
Again, you are stuck as you are saying there are no nS rise times in audio. Well, duh. It's a test signal, the rise time is just to excel the speed of the entity being tested. If I use a 100 uSec rise time, the entity is hidden by the poor choice of test signal. I would have thought that you would understand proper test technique, and am not happy that you do not in this regard.
Jn
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That was just my opinion as well. I can justify with words why, and how (relative phases, relative levels, time alignment:group delay etc.). But it will not help.
The only way for you to figure out if it was so "irrelevant" would be... to listen to the result ;-)
It is not perfect, I did the best that i could do. But listening to my recent awful Kef LS50, I think I was not so wrong;-)
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