[Daygloworange]

Nah...it's too funny as it is...

Cheers 

[Kevin Haskins]

There is some type of FR irregularity at around 1900. This is without a doubt certain. And the proof is there on the page on a different graph.

Since this type of windowed FFT has some resolution limitations, one may argue about the exact nature of the FR irregularity, but it is not a nearfield artifact.

You can either seek the truth or not.

Can you see it measured @ 1.0M?   I don't have any interest in defending Danny's product (he is my competitor) but if you measure it in the near field and not in the far-field then what is it?   

[Mark K]

There is some type of FR irregularity at around 1900. This is without a doubt certain. And the proof is there on the page on a different graph.

I have seen similar effects with other drivers as well. You are too close and getting a cancellation at that wavelength.

Dan, thanks for your incite.

Too late

[Mark K]

Aw, shoot, it deleted the following. Obviously a conspiracy. What I tried to post out was--

"Oh, I think we don't need anymore incite...a little insight would be nice though.   "



Anyway, more detailed explanation with additional measurements will take some time to generate. Still, there are more answers self evident on my page. You can consider those while I investigate further. If I am wrong, I will certainly eat my crow.

[Danny Richie]

Yea, I guarantee you that if you want to give me a good poke or two just watch of my misspellings and typo's. I am horrible at both.

[DanWiggins]

Just for an example, here's a set of measurements I made of an Extremis at multiple positions from the cone:



All responses are normalized at 500 Hz.  The white trace is at the standard 1m distance; all others have their listed distance from the center of the cone.

Of interest to note, the frequency of the peaks and dips, as well as the amplitude of the peaks and dips changes with distance from the cone!  In the near-field, things are weird; you get linear effects like amplitude differences, and non-linear effects like frequency shifts of the peaks and dips.

Near-field measurements may be instructive in some situations, but should be, IMHO, avoided as much as possible for measurements.  If you have to use near-field because of noise issues (common for THD measurements), then take the THD measurements with a huge grain of salt.  See if you can borrow a quiet place to do your measurements; many churches and small theaters will let you do some measurements in their auditorium in exchange for a few measurements of their sound systems.

[Watson]

Just for an example, here's a set of measurements I made of an Extremis at multiple positions from the cone:

Dan, are you sure that you have the legend (labelling) correct on that graph?  As is, the measurements are getting progressively "worse" the further away the microphone moves from the cone.  I don't see how the trend would converge to the 1 meter white curve.

[DanWiggins]

Let me clarify a few things...

The white trace is an Extremis mounted in a cabinet.

The other traces are a raw Extremis, no baffle, no cabinet.  Essentially a free-air driver being measured.

The response is actually as expected; close-in, there isn't a discernable dipole roll-off; as we move further out, we start to get more of a roll-off (approaching the 6 dB/octave slope of a dipole).

And many of the dips actually get better - 1.8 kHz, 2.2 kHz, 3.2 kHz, and 4.5 kHz.  Some get worse - 1 kHz.

But that's really not the issue; the issue here is that the response CHANGES as you move straight out from on-axis.  The on-axis response measurement is dependent upon the distance from the cone.  And it won't really converge to a normal response until you're a good half meter or so out.

Near-field measurements are highly fraught with problems.  Here's another graph that is highly informative about the issues of near-field measurements:



White trace is as before.  Red trace is on-axis at 1 inch from the center of the cone.

The other traces are made 1" from the cone surface, but at different distances from the edge of the cone.  The green trace is 1" from the peak of the surround.  Yellow is 1" from the cone, 1" in from the center of the surround.  Orange is 1" from the cone, 2" in from the center of the surround (moving in radially).

In this case, the differences are not due to distance out from the cone - the colored traces are all at the same distance from the cone.  The differences are from measurements at different locations AROUND the cone, but the same distance out.

Again, this is indicative of issues with near-field measurements.  Taking near-field measurements at different locations - even at the same distance - will not provide repeatable measurements.  And issues with frequency response will affect THD as well - significantly.

[RAW]

Dan the man.
Is this part of the data you were going ahead with which involved testing on axis for I believe it was DIYmobileaudio awhile ago about measurments and the time frame window you were making with longer on axis measurments.

[jacket_fan]

I have no dog in this fight, but am intrigued in this discussion.  I tried to take an unbiased evaluation of the three sets of data compared between 3-6 kHz.

Take a look at the curve for 0 ms.  In the first figure, the curve appears to be about 1 dB lower in magnitude for number 1, but the area under the curve is greater than figure 2.  In the third figure the magnitude is slightly higher and the area under the curve looks to be the same or a bit greater than figure 2.

For .1 ms.  For figure 1 the peak is higher and the area under the curve greater than figure 2.  Comparing 3 to 2, again the max amplitude and area under the curve are greater than figure 2. So for the first .1 ms, it appears the 130 is slightly better.

I won’t try to do all 30 curves, but that is the way I read the data.  Especially since I cannot see the curves that are blocked by the curve in front in many cases.

The third driver has peaks closer to 6 kHz and lower magnitudes out past .3 ms.

On a more subjective view, the 130 has a smother roll of and the amplitude stops sooner than driver 1 or 3.  If you totaled the area under all of the curves, I believe the third would have the lowest total area. 

So what is more important, a smooth transition from 0 to 1 ms, the total area under the curve, a peak in frequency response or amplitude?

[Kevin Haskins]

The low frequency data looks like it should.   

The only trouble you would get into doing distortion measurements down there would be with the harmonics.    You could take those with a grain of salt.   


Another question for you Mr. Big Brain Wiggins.   What is the best way to set levels for distortion testing?   Obviously if your working with a 6.5" driver and trying to normalize it somewhere for unit to unit distortion test you have to calibrate it to a level.   If you pick an individual frequency you may end up on a peak or dip of an individual driver.   If you pick an average over a range you have to choose the range & that might be fraught with peril if your unit has a large dip or peak in that range.   

How do you set levels for driver to driver distortion comparison?   I'm seeing a scenario whereby one driver or another could be put at an advantage/disadvantage based upon the non-linear frequency response of the driver.   You could pick an input level and ignore the output level.   Then adjust based upon the calculated sensitivity to bring all of the drivers into parity.     

The tweeter comparisons have the same issue but it has more to do with bandwidth.   When your looking at the distortion curves for tweeters with more bandwidth (down low) they are put at a disadvantage compared with the tweeters with less bandwidth.    If your interested in the true distortion figures down low, you have to look at both the FR curve along with the distortion curve and adjust accordingly.

[Danny Richie]

It's kind of a crap shoot, huh Kevin?

[ShinOBIWAN]

Just for an example, here's a set of measurements I made of an Extremis at multiple positions from the cone:

All responses are normalized at 500 Hz.  The white trace is at the standard 1m distance; all others have their listed distance from the center of the cone.

Of interest to note, the frequency of the peaks and dips, as well as the amplitude of the peaks and dips changes with distance from the cone!  In the near-field, things are weird; you get linear effects like amplitude differences, and non-linear effects like frequency shifts of the peaks and dips.

Near-field measurements may be instructive in some situations, but should be, IMHO, avoided as much as possible for measurements.  If you have to use near-field because of noise issues (common for THD measurements), then take the THD measurements with a huge grain of salt.  See if you can borrow a quiet place to do your measurements; many churches and small theaters will let you do some measurements in their auditorium in exchange for a few measurements of their sound systems.

Probably the most useful purpose for nearfield is bass response below 200-300hz if your messing around with measurements in an unsuitable room(that's most listening rooms) and can't use large gated measurements at listening position etc.. Kevin also mentioned that the higher frequencies from gleamed from nearfield measurements aren't really indicative of performance and I can pretty much agree with both Dan and Kevin there. However much depends on the baffle size when doing nearfield and whilst I don't know what size John uses exactly I can say that its good enough for his measurements to be accurate enough to be considered valid but certainly not a reference and John would agree. So whilst this is a valid observation from folks, it isn't wholly applicable to Zaphs data sets.

I'm going to avoid technical dissections as there's been enough attempts at that and instead just look at this as a DIY'er who has his head screwed on.

I'm not sure what Danny's beef is really. Your making a mountain out of a mole hill given the context of Johns measurements and the fact that he himself actually has disclaimers plastered all over the place regarding the accuracy. When someone says take his measurements with a pinch of salt they aren't being revelatory because John himself has said the same thing. This situation and thread has come about because of idiots who don't deserve such a resource because, for them, everything has to be an absolute and they have too little knowledge to understand without make sweeping conclusions, almost as if John's work is gospel which isn't what he set out to do at all. The more level minded can look at what he posts, use common sense, bear in mind Johns own words about accuracy and finally the provided data sets can only really be compared directly to others in that particular group because each has had the same testing methodology applied. All things John has pointed out already. Johns work is useful because it save me going out buying a load of drivers and coming to similar conclusion, what John gives are indicators. Having said that there's nothing that compares to doing your own measurements with your own cabinets, sensible folks realise this.

I believe what John originally started was doing measurements for his own curiosity and to better what he builds. He decided at some point to share this data and, because of popular demand plus the lack of independant testing, has now grown the website for the benefit of level headed enthusiasts. Unfortunately you can't keep all the idiots out of such a place and you get misinformation spreading. The keyword here is context.

John's stuck between a rock and hard place, on one hand he enjoys sharing his work and on the other, because his website has become well known, he attracts many questions from people. I can see why he is absolutely fed up of the idiots who email him everyday asking the same stupid questions especially considering he doesn't make anything from this unlike Danny who makes a living out of it so its in his interest to make himself accessible to any prospective customer - its really two sides of the coin and in more than one way. People would do well to remember that. Why doesn't he want to chat to Danny? Who cares? People are confusing the data and the context of that data with the characters and their opinions, that is just BS in my opinion and the reason why this whole thing has a bad smell.

I'm not sure what Danny expected from all this. Whilst I've learnt something about characters, I've learned absolutely nothing audio related from reading this thread that I didn't already know, no truths have out and Johns measurements are still useful in their context. Judging by the opinion over on other forums this seems to be the case for the majority of seasoned DIY'ers.

I don't think Danny has done his business any good nor harm from this and the value of John's work hasn't changed either. For many this was just a silly showcase that made a few folks look like ass's.

[Kevin Haskins]

It's kind of a crap shoot, huh Kevin?

It is certainly something to ponder.   I'm mainly interested for making my own comparisons.

[Daygloworange]

I'm not sure what Danny's beef is really. Your making a mountain out of a mole hill given the context of Johns measurements and the fact that he himself actually has disclaimers plastered all over the place regarding the accuracy.

ShinOBIWAN,

There are a lot of budding enthusiasts who don't have a lot of knowledge as it pertains to the technical side of audio. If there is conflicting data out there, it becomes all that more overwhelming. Regardless of any disclaimers John might acknowledge, people will still look at the data. If he's leaving the door open to the possibilty his data is not reliable, then it might as well not be there for the potential to cause grief to other parties. That's negligance on his part.

I don't think you are taking into account the business aspect here. Danny probably gets innundated with quite a few calls and emails in order to answer questions regarding any discrepancies. You have to factor that in this equation, and I'm afraid you're not. You seem to think that only John is the one who is overwhelmed by people wanting to talk to him.

John doesn't stand to lose anything in the form of a lost sale, Danny does. It's not hard to see the ramifications to a business. Please think about that.

In simplest terms, Danny is confident of his driver, and it's performance. An enthusiastic hobbyist posts critical data that may be erroneous. Danny feels it misrepresents his driver. It's his right to defend it. Period. It would be foolish of him not to. A business manager would make it a first priority.

So by virtue of John Krutke's analysis, Danny was put in a position where he had to. Pure and simple. I would as well. Even if it was just for the principal. Any business owner would. Period.

If John doesn't want to deal with the grief, then don't put info out there that could threaten someone's bottom line. Even if he posted his results with no harmful intent, there still could be harmful implications. He is more than intelligent enough to expect backlash of sorts.

I believe what John originally started was doing measurements for his own curiosity and to better what he builds. He decided at some point to share this data and, because of popular demand plus the lack of independant testing, has now grown the website for the benefit of level headed enthusiasts. Unfortunately you can't keep all the idiots out of such a place and you get misinformation spreading. The keyword here is context.

Agreed. But as you pointed out, he has no control of who does what with the info. If the byproduct is that Danny gets overwhelmed with requests for him to defend the performance of his drivers, then it's a burden to his business, and takes valuable time and resources away from him ( and a potentially lost sale) . Time is MONEY. Period.

John's stuck between a rock and hard place, on one hand he enjoys sharing his work and on the other, because his website has become well known, he attracts many questions from people. I can see why he is absolutely fed up of the idiots who email him everyday asking the same stupid questions especially considering he doesn't make anything from this, it actually costs him to host that webpage. People would do well to remember that. Why doesn't he want to chat to Danny?

Really? And Danny isn't? You don't seem to understand that Danny has to field questions regarding the conflicting data? Again, time is MONEY. Why do you only see the grief and costs as they affect John and not Danny?

I don't think Danny has done his business any good nor harm from this and the value of John's work hasn't changed either. For many this was just a silly showcase that made a few folks look like ass's.

It could have been avoided, yes, I agree. I don't think either of them desired this. I have no problem whatsoever with Danny's efforts to defend his position to defend his product anyway he sees fit. I do with my own work. I think a lot of people don't really weigh the factors and implications of business on Danny's side of the equation.

Cheers

[ShinOBIWAN]

I've put across the points that I believe are correct.

John's measurements by his own admission aren't infallible nor are they a reference. If idiots wish to quote them as such then whilst I feel for Danny, I just have to say that idiots go with the territory. He makes the money and also has to put up with the hassle that entails. What does get me a little is that Danny makes out that these issues are Johns responsibility, which is laughable given the context of his website. People need to get a grip and realise what ZaphAudio is aiming to do.

Discussing the fine points is really the preserve of committee who have time to devote to such trivial matters. Much like John I don't get paid to come here and chat, I'm here because I enjoy this hobby and frankly this part isn't enjoyable. This really is a case of something for the sake of nothing or in otherwords, talk for the sake of talk. At the end of it all Danny will still get the idiots anyway regardless of whether John deletes his site, changes testing methodology or whatever. Stupidity always finds another route such is human nature.

BTW I think GR is the only company to actually take serious issue with the data on John's website. Not a trivial thing given that GR is small fry compared to the Skanning, Scanspeak, Seas, Peerless, Dayton etc.

[Daygloworange]

What does get me a little is that Danny makes out that these issues are Johns responsibility, which is laughable given the context of his website. People need to get a grip and realise what ZaphAudio is aiming to do.

You're just not getting it. Please re-read my last post. It is entirely upon John not to potentially harm someone's business in the pursuit of his hobby.

At the end of it all Danny will still get the idiots anyway regardless of whether John deletes his site,

As far as the types of people out there. There is the bell curve, and the fallout from that. Danny doesn't need anything that is going to make his life (needlessly) anymore difficult.

BTW I think GR is the only company to actually take serious issue with the data on John's website. Not a trivial thing given that GR is small fry compared to the Skanning, Scanspeak, Seas, Peerless, Dayton etc.

GR is a company geared toward the hobbyist/ DIY'er. Implications could be huge. You're not factoring the scale properly here at all. It's small business 101, you're still not looking at that aspect at all.

Cheers

[Danny Richie]

Probably the most useful purpose for nearfield is bass response below 200-300hz

Yes, but even that too varies depending on if it is taken in free air of mounted in a box. It also doesn't take into account the output of PR, ports, horn loading, or transmission line loading.

I'm not sure what Danny's beef is really. Your making a mountain out of a mole hill given the context of Johns measurements and the fact that he himself actually has disclaimers plastered all over the place regarding the accuracy.

Just read through this thread some more to get a better understanding. My "beef" isn't so much with the measurements which I agree has to be taken with a grain a salt. Some have good or reasonable accuracy and some don't. It is bad that many people give heavy weight to those that are less accurate and not telling of how anything will really sound.

What's bad is people believing that John is providing some type of unbiased service. Considering the relationship with one of the companies he provides feedback for... how can he be unbiased? More so is that he has a hostile and aggressive attitude towards me and my company. He looks at me as the enemy. I claim audible differences in areas that the objective camp claims there are none. Objective verse subjective, listeners verses measurers, etc. His person vendetta has clouded his judgement and it is even so noted by my competitors here in this thread. Just have another look at the unfounded commentary on my M-130 woofer, and tell me there is no intent to demean. It almost looks like a "I'll get even with him smear campaign". How can I not have a "beef" with that? How can I not have a "beef" with the nasty e-mail? How can I not have a "beef" with what he said in his blog calling me a snake oil salesman? Now how unbiased is his data?

[ctviggen]

Exactly what is the purpose of John's website?  I can't quite figure that out.  Apparently, he's not related to any of these companies, doesn't use any of the these products, doesn't really understand what his results indicate, and yet publishes results under the guise of knowing more than he really knows.  If his measurements aren't to be used as a reference, then what are they to be used for?  

So, what the heck is the purpose of John's website?  

[ShinOBIWAN]

Yes, but even that too varies depending on if it is taken in free air of mounted in a box. It also doesn't take into account the output of PR, ports, horn loading, or transmission line loading.

Yes but we're talking about testing the driver not the driver in an alignment.