Phonograph Stylus Wear Experiment

[ray_parkhurst]

You're asking me to design your experiment for you, which would take several days of effort just to outline and several more to verify. It's not like I know exactly what you need to do and can just type it up in a few minutes.

Actually, I'm asking you to design the next experiment. Then we can fix what we're doing wrong on the next go-around.

 

[JP]

Actually, I'm asking you to design the next experiment. Then we can fix what we're doing wrong on the next go-around.

Pointing out which rocks to look under and later on looking at some data is about it for this.

 

[morillon]

JP, why are you saying "complicated"? ;-)

so clearly the observation of the thd on high fixed frequencies is explicit .. quantifiable etc
a disc like the at-6605 (see the others offering it..) offers some, and adapted...

after rew or multitone , free, are perfect for these measurements..
the imd measurements that these software allow can also be essential.. and these tests are easily found on many test discs

and just to observe
high frequency harmonics requires high bandwidth in proportion
96k...bp 48khz max..
192k..bp 96khz max
that's all...

if the optics will allow pretty images, see explicit... the interest of the measurement via thd is quite obvious because it allows to have very easily quantified values..
this is a huge advantage...

the correlation aspect has a subjective approach seems surprising.. but it is essential.. otherwise what is the point..?

when do we subjectively estimate that ,
"There, now my cartdrige seems worn out"...
it becomes interesting to observe what it corresponds to on our measurements etc..
am I clearer?

the tests of 10.8k pulses like ttr103 are so brutal that they were quickly put aside..
that they could certainly be explicit.. they do not offer simple quantifications such as on 2 or 3 tone imds or on fixed frequencies such as 10k 15k 20khz
(in addition many serious cartdriges did not manage ttr-103 test them even new, we abandoned it for this reason)

(i going to see on my side when I have a little time if the tri tone of the shure ttr-117 200-2100-17k , (or the 16k-16k300hz of the srt14-a , multitone can easly use this one), is exploitable for this use.. can someone observe it if I take too much time?)

 

[ray_parkhurst]

Pointing out which rocks to look under and later on looking at some data is about it for this.

I think you're starting to understand. In your last response it sounded like you were thinking of a multivariable DOE or something!

 

[JP]

Wasn't aware that I wasn't understanding something.

 

[BendBound]

If you have the patience and are willing to wait a few days at certain points (ie pause your experiment), I can run your CBS test record recordings through the script. Other than that, I really don't understand the confusion. I have already gone through the steps you need to take with you--and recommended other measurements and test records--and it's a little frustrating reading your exasperated posts that can be read as implying you are not being helped or that people here haven't cared.

If you are only using the CBS test record, simply take an FR measurement of the cartridge at each step you decide upon and send them to me. I have already told you to get additional CBS test records, compare them, and to use a control cartridge to help differentiate between test record and stylus wear. Whether you choose to follow through with that is up to you. For us here at ASR, those results, if done properly, will matter most as anecdotes concerning listening tests are just that, anecdotes. I am going to assume most here are older gentlemen. No offense, but why should anyone trust your/our ears? Anecdotes are not evidence. Are you going to do professional A/B listening tests? As mentioned it may be likely that recordings near the inner groove may be the only useful ones. We've seen what a wide range of cartridge measurements look like. We know how bad distortion can get. We know frequency response is pretty much it for determining sound quality. JP has posted many professionally recorded AB tests and I have shown you the measurements of worn cartridges. It is brutally difficult to make any sort of determination through listening tests. And I'm glad you are taking measurements seriously because of this. But as that data will matter most, privilege it and get it right (heed JP's warnings).

Try sending me a recording of the test track so I can show you what it looks like and we can see if things look OK.

@USER, thank you and also @JP and @morillon, and others who have chimed in. You should know that several of your suggestions specifically have already changed and we want to acknowledge improved the trajectory of this experiment. Speaking for myself, I have a skill set I know and I am comfortable with. @Ray Parkhurst and @BMRR have theirs. Given that, I have read through this thread and at least one other long and detailed thread of measurements where the approach to decoding sonic attributes of different cartridges, even worn ones, and other equipment are discussed in considerable detail. This line of research is completely new to me. I have been a bit overwhelmed in the techniques, the software and add-ons, jargon, abbreviations, and interpretations of results are simply foreign to me. Thus you are correct to sense some exasperation in that I have yet to absorb all that is offered, in part to be honest, because of how it is provided in snippets.

That is likely quite a bit unfair, it is after all our experiment.

Simply stated, I could use more structure and I get that providing such involves perhaps too much time. In this way its a bit like if you knew I could tell you, but if you don't know, its too hard to explain. So excuse me for being on what I find to be a steep learning curve.

Its been discussed prior, but JICO uses a 3% THD benchmark to distinguish the approach to critical wear. I've stated it here as at least one other has in this thread, that I seriously doubt folks can hear that frequency or 3% THD at it. Moreover, and essentially repeating something you noted above, some users claim no, like zero, audible change in musical reproduction of their cartridge now worn for a 1,000 plus hours. How would they know, particularly if they are "older gentlemen"? I cannot recall how exactly a well-loved record sounds at the necessary detail even 10 hours later to make such a claim. But that is what we can read from someone on forum after forum as proof their stylus tip is as pristine as was the day they unboxed it thousands of hours of play later.

So thank you for your willingness to help. @Ray Parkhurst I know has addressed already some of the questions you posed. But I did not want more of the day to slide by without addressing your replies. Its appreciated as you work with this pilgrim.

PS: I figured out what "3.54cm/s from an at-6605" meant. A test record.

 

[JP]

Its been discussed prior, but JICO uses a 3% THD benchmark to distinguish the approach to critical wear. I've stated it here as at least one other has in this thread, that I seriously doubt folks can hear that frequency or 3% THD at it

Thanks to Paul, people can rather easily figure out their thresholds: https://www.audiosciencereview.com/...-audibility-of-distortions.10163/#post-277173

 

[USER]

Part of the problem, I think, is that there is, in effect, no good test record so we can't really give you step by step instructions on how to perform this experiment with the scrutiny it truly deserves. Each has its limits, and worse still, most are unusable and the decent ones are extremely difficult to purchase. One example that has been mentioned is that the CBS test record--even after JP maximized its use value with brilliant coding--cannot be relied upon for crosstalk measurements. That is but one example. So you're already extremely limited in your results already. I'll also now tell you that they are limited to about -40dB in terms of 2nd harmonic distortion at 1k. See these two measurements of the same cartridge using two different test records. Click to magnify.

Ignore the FR. You can see that crosstalk is more of a problem with the CBS. Note that -25dB at 1k is pretty much its limit. Also note that distortion is about 10dB lower at 1k on the clearaudio. These are some of the limits you will face. But the distortion you will be looking for is higher so it should still be useful. What's great about the clearaudio is that it tells you if your set-up is good to go with the channel balance measurement result. You'd still want to look at your set-up with the CBS nonetheless. It certainly functions as one indicator of a reliable measurement. EDIT: THINKING ABOUT IT RIGHT NOW, IT MAY BE THE CASE THAT THE 2ND HARMONIC DISTORTION LIMIT OF THE CBS RECORD WILL MASK EARLY WEAR.

We don't want to appear to be withholding information, but we are only now pushing these test records to their limits collectively on the script thread. The information there is recent, which is also another reason we don't want to regurgitate too much. Everything that we know is there. It is the result of years of experimentation and its fair to expect that you guys--as a group--take a few weeks to ingest it.

I currently use the CBS test record as well as the Clearaudio TRS-1007, which is superior but not without limits and, it seems, not as good as the JVC TRS-1007, which is the gold standard and which you will not get for this project. (If one is available be sure that I will do everything to snipe it!) More, it seems that we have purchased the last readily available copies of the now out of print Clearaudio record, so unless you are willing to wait a while and put up a good mount of money, it doesn't seem like it'll be available for this project. They are much more expensive than the CBS test record, and, frankly, if I only had one copy I sure as hell would not use it for this experiment. On top of everything, a test record is not guaranteed to be good! This is why I mentioned to try to see if you can get a good copy of the Tacet test record because it *might* be useful for channel balance if you get a good copy. Know that most copies are bad and all have centering issues. I've tried out nearly 2 dozen of them. If you want to go crazy, try to find a good test record for wow and flutter measurements!!!! Plenty of threads here on that. Regardless, it's not the end of the world.

I strongly encourage you to pare down the experiment for now and measure as few variables as you can with as much precision as possible. JP makes great points on this. Use a turntable with a robust tonearm that allows quick and easy cartridge replacement. Touch the latter as little as you can. Use a good direct drive. And just make the first run about distortion and FR measurements. If you temper your expectations you can see what happens and take off from there. More expensive and rare test records may not be worth it and aside from knowing how long the cartridges last we may already have the big picture info on wear effects (on the outer groove area at least).

 

[morillon]

@USER, thank you and also @JP and @morillon, and others who have chimed in. You should know that several of your suggestions specifically have already changed and we want to acknowledge improved the trajectory of this experiment. Speaking for myself, I have a skill set I know and I am comfortable with. @Ray Parkhurst and @BMRR have theirs. Given that, I have read through this thread and at least one other long and detailed thread of measurements where the approach to decoding sonic attributes of different cartridges, even worn ones, and other equipment are discussed in considerable detail. This line of research is completely new to me. I have been a bit overwhelmed in the techniques, the software and add-ons, jargon, abbreviations, and interpretations of results are simply foreign to me. Thus you are correct to sense some exasperation in that I have yet to absorb all that is offered, in part to be honest, because of how it is provided in snippets.

That is likely quite a bit unfair, it is after all our experiment.

Simply stated, I could use more structure and I get that providing such involves perhaps too much time. In this way its a bit like if you knew I could tell you, but if you don't know, its too hard to explain. So excuse me for being on what I find to be a steep learning curve.

Its been discussed prior, but JICO uses a 3% THD benchmark to distinguish the approach to critical wear. I've stated it here as at least one other has in this thread, that I seriously doubt folks can hear that frequency or 3% THD at it. Moreover, and essentially repeating something you noted above, some users claim no, like zero, audible change in musical reproduction of their cartridge now worn for a 1,000 plus hours. How would they know, particularly if they are "older gentlemen"? I cannot recall how exactly a well-loved record sounds at the necessary detail even 10 hours later to make such a claim. But that is what we can read from someone on forum after forum as proof their stylus tip is as pristine as was the day they unboxed it thousands of hours of play later.

So thank you for your willingness to help. @Ray Parkhurst I know has addressed already some of the questions you posed. But I did not want more of the day to slide by without addressing your replies. Its appreciated as you work with this pilgrim.

PS: I figured out what "3.54cm/s from an at-6605" meant. A test record.

the use of frequency such as a 10 or 15k is critical with the wear and tear of their interest... much more than 1k..
this is also why we often use imd approaches with higher frequencies to test tracking
the idea of using such fixed frequencies allows for rapid acquisition.
* the idea is not to observe such fixed test frequencies such as 15k to subjectively apprehend the wear but when we estimate the wear and tear when listening to music, we observe the wear as measured..
(3% of jico remains to be discussed..corresponds to a given protocol...and joins the point *)



the dot * makes this all very debatable from the start...
wear is a gradual process from the first hours... when do you think the cell should be put away

that is the subject...
Sorry..

end for me
the auto translation is, I know, unbearable.. like the fact of repeating myself in the same way...
Sorry

 

[morillon]

Part of the problem, I think, is that there is, in effect, no good test record so we can't really give you step by step instructions on how to perform this experiment with the scrutiny it truly deserves. Each has its limits, and worse still, most are unusable and the decent ones are extremely difficult to purchase. One example that has been mentioned is that the CBS test record--even after JP maximized its use value with brilliant coding--cannot be relied upon for crosstalk measurements. That is but one example. So you're already extremely limited in your results already. I'll also now tell you that they are limited to about -40dB in terms of 2nd harmonic distortion at 1k. See these two measurements of the same cartridge using two different test records. Click to magnify.

View attachment 289851View attachment 289852
Ignore the FR. You can see that crosstalk is more of a problem with the CBS. Note that -25dB at 1k is pretty much its limit. Also note that distortion is about 10dB lower at 1k on the clearaudio. These are some of the limits you will face. But the distortion you will be looking for is higher so it should still be useful. What's great about the clearaudio is that it tells you if your set-up is good to go with the channel balance measurement result. You'd still want to look at your set-up with the CBS nonetheless. It certainly functions as one indicator of a reliable measurement. EDIT: THINKING ABOUT IT RIGHT NOW, IT MAY BE THE CASE THAT THE 2ND HARMONIC DISTORTION LIMIT OF THE CBS RECORD WILL MASK EARLY WEAR.

We don't want to appear to be withholding information, but we are only now pushing these test records to their limits collectively on the script thread. The information there is recent, which is also another reason we don't want to regurgitate too much. Everything that we know is there. It is the result of years of experimentation and its fair to expect that you guys--as a group--take a few weeks to ingest it.

I currently use the CBS test record as well as the Clearaudio TRS-1007, which is superior but not without limits and, it seems, not as good as the JVC TRS-1007, which is the gold standard and which you will not get for this project. (If one is available be sure that I will do everything to snipe it!) More, it seems that we have purchased the last readily available copies of the now out of print Clearaudio record, so unless you are willing to wait a while and put up a good mount of money, it doesn't seem like it'll be available for this project. They are much more expensive than the CBS test record, and, frankly, if I only had one copy I sure as hell would not use it for this experiment. On top of everything, a test record is not guaranteed to be good! This is why I mentioned to try to see if you can get a good copy of the Tacet test record because it *might* be useful for channel balance if you get a good copy. Know that most copies are bad and all have centering issues. I've tried out nearly 2 dozen of them. If you want to go crazy, try to find a good test record for wow and flutter measurements!!!! Plenty of threads here on that. Regardless, it's not the end of the world.

I strongly encourage you to pare down the experiment for now and measure as few variables as you can with as much precision as possible. JP makes great points on this. Use a turntable with a robust tonearm that allows quick and easy cartridge replacement. Touch the latter as little as you can. Use a good direct drive. And just make the first run about distortion and FR measurements. If you temper your expectations you can see what happens and take off from there. More expensive and rare test records may not be worth it and aside from knowing how long the cartridges last we may already have the big picture info on wear effects (on the outer groove area at least).

the beaches of sweep have been dedicated to fr observations and ""not to do everything""..
the experience of observing crosstalk was quite explicit, it seems to me...
must be used for what they are intended
and look for more specific tests for other uses (and there is no shortage..)( and the use of large free software offers great prospects..)
if you want to observe thd seriously .. it will be better to use very qualitative fixed frequency ranges "references" or imd
(not in principle, but due to the quality and the efforts made or not in the realization of the test tracks of our discs)

end for me

ps
we are already observing the greater or lesser rigor, wondering about the fr according to the different test discs.. in sweep and fr...
so rigorous?
uhhhhhh
;-)

(
I just invite you to find out which discs offer fixed frequencies clean at more than 10k.. not overmodulated... for these thd measurements..

the a-t was just the first that came to mind..
but can there be better?
same for imd
"à creuser"
for me, it's just small thoughts "aloud" or warnings - precautions to take
)

 

[ray_parkhurst]

I like the idea of using IMD instead of THD or individual harmonics to measure HF distortion, but unfortunately the STR100 does not have IMD tracks (correct?). I also don't see IMD shown on the various plots. Is it not common to do this? Do the scripts you guys are writing cover IMD? I assume so, but am not sure the dynamic range and resolution of the various test records, or the capabilities of the analysis. What is the limitation for IMD? For now we have Harmonics as our measure, and as long as we use the same system to do the measurements, we can at least see degradation if not absolute numbers. But perhaps a future experiment can utilize an IMD-capable measurement and analysis.

 

[morillon]

why focus on cbs?
many other test discs offer imd... see fixed frequencies "hf"
and as I told you...
rew or multitone, free software offers the processing of one or the other in realtime with a correct sound card output from your prephono

 

[ray_parkhurst]

Because that is what we purchased for this experiment.

 

[JP]

Or take a breath and figure it out for this one.

”The script“ is for measuring FR only. Crosstalk comes along for the ride and we show 2H and 3H, which is of course not THD.

I’m not aware of any threads here covering the various tracking or “wear” tests. Around a decade ago I did some tracking tests with TTR-103 and other test records that I can’t recall to compare Shure styli to Jico replacements. The punchline is that these are extreme tests and mapping outcomes to audibility with typical program material is fuzzy. My primary interest has been FR as that‘s the one factor humans are most sensitive to, assuming nothing pathological.

Unless there’s something relevant to riff off of, and likely regardless of that, there’s going to need to be validation of methods and calibration of outcomes. I’m thinking it’d take a test cycle or two to flesh that out - I don’t think you’re going to hit the ground running on the next one.

That said, if limitations are going to be imposed by what test records are on-hand these discussions are just mental masturbation.

 

[morillon]

the use of measurements, moreover now totally democratized with our sound cards costing almost nothing and overpowering software..free, allowing assistance with settings, in particular in low or high frequency thd, in imd...etc tends to show that orders of magnitude are easily significant in vinyl...
by reconciling the approach in relative values of course
;-)
on the other hand for each subject it is necessary to do well to try to find the most serious disc on this given test, because indeed sometimes disappointing...
a small collective effort can be
;-)

 

[morillon]

I like the idea of using IMD instead of THD or individual harmonics to measure HF distortion, but unfortunately the STR100 does not have IMD tracks (correct?). I also don't see IMD shown on the various plots. Is it not common to do this? Do the scripts you guys are writing cover IMD? I assume so, but am not sure the dynamic range and resolution of the various test records, or the capabilities of the analysis. What is the limitation for IMD? For now we have Harmonics as our measure, and as long as we use the same system to do the measurements, we can at least see degradation if not absolute numbers. But perhaps a future experiment can utilize an IMD-capable measurement and analysis.

just to shed some light on the subject.
only resume the forgotten approaches of the 70s early 80s.. but now within everyone's reach

really nothing revolutionary but to shed some light on these topics
(on the other hand I have never tested vinyl test "redone " of them... the essential in the end)

AnalogMagik Turntable Setup Cartridge Alignment Tutorials

AnalogMagik Turntable Setup Cartridge Alignment Free Tutorials. Azimuth, VTF, VTA, Antiskating, SRA, Vibration, Resonance, Loading, Gain, Wow & Flutter

www.analogmagik.com

ps
if the wear and tear "is understood quite easily in circumstances a little "demanding difficult delicate" ... it is hardly difficult to measure it in our field ...
;-)
I maintain that the two essential subjects are
when and how I think it's worn out listening .. what matters?
And
because it's a delicate subject.. which bias of anti-skating adjustment....with a precisely significant impact on wear "over time"

 

[ray_parkhurst]

Or take a breath and figure it out for this one.

”The script“ is for measuring FR only. Crosstalk comes along for the ride and we show 2H and 3H, which is of course not THD.

I’m not aware of any threads here covering the various tracking or “wear” tests. Around a decade ago I did some tracking tests with TTR-103 and other test records that I can’t recall to compare Shure styli to Jico replacements. The punchline is that these are extreme tests and mapping outcomes to audibility with typical program material is fuzzy. My primary interest has been FR as that‘s the one factor humans are most sensitive to, assuming nothing pathological.

Unless there’s something relevant to riff off of, and likely regardless of that, there’s going to need to be validation of methods and calibration of outcomes. I’m thinking it’d take a test cycle or two to flesh that out - I don’t think you’re going to hit the ground running on the next one.

That said, if limitations are going to be imposed by what test records are on-hand...

We've already taken several breaths on this experiment. It is time to start and get some data, which will help inform next steps. We could plan this out for the next 6 months, and someone would still find fault with the outcome.

I am not sure how relevant or useful the "wear" tests are. We decided early on, based on input from you and others, to use harmonics as the method of correlation between visual wear and audio impact. Tracking is also not relevant IMO, unless someone can tell me that worn styli track worse. It may be true. Swept vs single tone harmonics are still being debated I think.

Regarding calibration, we'll be focusing on comparative data, so it is self-calibrating.

For this first experiment the test records have been chosen, but discussion for next experiment is still relevant. Not sure how many times I need to say this but I'll keep trying.

 

[ray_parkhurst]

when and how I think it's worn out listening .. what matters?
And
because it's a delicate subject.. which bias of anti-skating adjustment....with a precisely significant impact on wear "over time"

I'm fairly confident we are addressing both of these items. Not sure how "precisely significant" any study like this can be though. For sure we'll see if there is an AS bias by comparing L/R wear. We've seen many examples of poor adjustment of AS that resulted in asymmetric wear, and if we begin to see this we'll make appropriate changes to the settings.

 

[BendBound]

Okay, officially my head is spinning.

As the trio of @JP, @USER and @morillon provide the necessary and unvarnished glimpse of "uncontrolled variables that make this (approach, or test) non-conclusive" for getting at THD or IMD for our experiment. Much of this appears from my read to reside in the test medium itself, a vinyl record designed by CBS, Audio Technica, Clearaudio, JVC, or others. Those press initially in likely a 1,000 disc run will not be identical to the last 100, or they are warped as @JP noted of the CBS test records available on the popular auction site. Calibration is required. Or they are as rare as hen's teeth for which a bidding war will make using one somewhat untenable for such an experiment. Or they don't contain the requisite tracks to do these types of evaluations. To summarize, quoting @USER, "...there is, in effect, no good test record..." Message received.

Sorry to tout two articles both published in The Vinyl Press, but I do so for context. The first was published in September 2018, entitled, "The Curious Case Of Record Cleaning In The Quest For Sonic Perfection", and the second was published in May 2019, entitled, "The Finish Line for Your Phonograph Stylus…" These articles are survey pieces that in essence collect prior research and put that historic work together with contemporary anecdotes into a narrative of personal discovery. In the included historic work are two fundamental themes: reality of stylus wear, and record cleaning to minimize stylus wear. The former is supported by imaging of progressively worn styli tips. In the course of examining those, degradation in sonic qualities is mentioned, but rarely is it the focus or shown with the type of frequency charts shown by @USER. Yet these two aspects of vinyl record playing go hand-in-glove.

The aforementioned JICO 3% THD claim opened the door to the possibility for verifiable measurements. In many ways I now better appreciate, the benchmark is a rabbit hole, sorry @morillon, fraught with issues. In January 2016, I met Hans Weedon, who holds crucial patents for logarithmic analog-to-digital conversion, from when he was at Analogic Corporation. We spent 10 days together and have communicated since. He regaled me with many stories about these AD devices, the pros and cons, the flaws, and about audio in general. He knew of my passion for vinyl records and my hobby of converting the music from them to digital formats. Because he tested such things, he shared with me that he took new and pristine vinyl records and measured their frequency response on the first play and subsequent plays. He noted that after one single play, a vinyl record loses forever its highest frequencies – likely inaudible to humans. Subsequent plays further degrade records, but to an increasingly lower degree. AC had the necessary equipment to make these measurements. I though we could measure those trends with some work, especially after seeing the skills developed herein. That, perhaps naively, is why we captured 96/24 dubs of three sides of vinyl.

As stated (sorry to be redundant), we are hoping to couple evidence of progressive physical wear on a stylus tip with evidence of increased distortion from the worn stylus, regardless of how one measures it. And as a bonus, measure increased degradation of the signal from a worn record. @Ray Parkhurst absolutely has developed the skills, techniques, and equipment to properly evaluate this physical wear. He has found the pitfalls, as one poster noted at the beginning of this thread, and he has the experience to avoid these. But as mentioned in prior historic research, we want to close the loop, to be complete. We wanted to couple actual physical stylus wear with audible changes from the cartridge as a consequence of that wear, and even attempt to see both physical degradation within a vinyl groove and increased distortion.

My read from @JP, @USER, and @morillon is that task is much, much easier said than done.

Edit: just noticed that Ray has addressed some of this. Yeah, I'm wordy, because I want to be clear and complete.

 

[JP]

We've already taken several breaths on this experiment. It is time to start and get some data, which will help inform next steps. We could plan this out for the next 6 months, and someone would still find fault with the outcome.

I am not sure how relevant or useful the "wear" tests are. We decided early on, based on input from you and others, to use harmonics as the method of correlation between visual wear and audio impact. Tracking is also not relevant IMO, unless someone can tell me that worn styli track worse. It may be true. Swept vs single tone harmonics are still being debated I think.

Regarding calibration, we'll be focusing on comparative data, so it is self-calibrating.

To be clear my earlier input was to correct the misconception that harmonics couldn't be measured with sweeps and that my opinion is that THD as a percentage is a very broad brush that's not that insightful beyond that. I doubt the increased distortion with wear will be readily audible short of the stylus reaching a pathological state, and maybe not even then. FR is where we're sensitive, which is why I'd advocate for that but also why I'm advocating that FR for both outer and inner grooves is important. Most FR tracks are on the outer grooves, but it's the inner grooves where the wear will present first.

I don't mean calibration in the sense of absolute values, rather is the test/measurement doing what we thought it should, is the test record track sufficient for the purpose, etc.

For this first experiment the test records have been chosen, but discussion for next experiment is still relevant. Not sure how many times I need to say this but I'll keep trying.

I don't believe there's a comprehension problem. As I've said I think there's a lot to learn/define for this and I think some trial runs are a necessity, so not taking advantage of that now, to me, is a significant waste of time and resources as there's no substitute for collecting real data during an actual run. Crystal clear that we don't agree and that's fine - it's your experiment.