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On 7/18/2019 at 9:02 AM, flakmagnet said:

The one question that I have yet to see answered in a clear way is; what quality control is being adhered to with x-coil manufacturing? From what I gather they are hand made, which is fine I suppose, but how can one gauge the consistency of their quality? And, if that is not possible, then could there be variations in their capability? I have heard there have even been some rather remarkable variations in ML's GPZ coil quality, although I hasten to add I have no provable evidence this is actually true.

Does anyone have clarifying information about this?    

 

The dirty secret for a long time in metal detector land is the variance in coil performance.

I visited the Whites factory once. Basically all their coils and other manufacturer coils were hand built and most still are. Machines set up most of the components, but somebody has to lay the windings into the slots as seen in the photos above. There usually is a large amount of tuning via a few components in the coil to offset the inevitable variances in positioning, wire resistance... whatever. The coil can be perfect before the epoxy gets poured, then the epoxy hardens and shifts the winding slightly... coil out of tune again. The coil is assembled and tested multiple times and then one final check. If if falls within an acceptable range the coil ships. If the coil fails for some reason, it simply goes in a discard bin. The discard bin at Whites at that time had a lot of coils. Assembling them is as much art as science and the failure rate is/was pretty high though I have no statistics. And no way to fix economically after the fact, so rather than do that it was better to just make another one.

The problem then is the ones that ship. They do vary, and nobody knows by how much since no manufacturer wants to say. I do know that nearly all the out of box failures I saw as a dealer were new coils that were dead on arrival, so that means some do slip though that are completely dead. That also means many must slip though that work but are substandard.

To make it worse on a lot of older machines in particular each machine and coil are tuned to work as a matched set. How many people know that a Gold Bug 2 is tuned for the coil it ships with, and every time you change the coil you probably now have a slight mismatch? I have sent GB2 detectors back to Fisher just to have them tuned for a new coil. Fisher probably would prefer I did not post that!

I have always wondered how many people out there think Machine XYZ that everyone else likes sucks simply because they got a substandard coil on theirs.

I would think a major company like Minelab tries to make coils 100% by machine with almost no variance, but I honestly have no idea if that’s possible. Can a factory production line pop out coils with no human involved? I would love to know but I doubt it. No matter how you look at it, quality control standards must be all over the map, and most of us have no idea what those standards are, especially with aftermarket coil manufacturers.

Looking at the X Coil I would say that each one is an individual work of art, with no two exactly the same. I’m not saying that in a bad way... it’s been like that more than people realize since day one with coils. The case could be made that quality hand made coils manufactured by a person with very high standards is a good thing. Right now though probably more so with the X coil than most. Each one is basically a custom made coil. Variance is inevitable. How much? Well if you ever get a bad coil that’s the answer. A lot of variance between good and dead on arrival.

Check out this video around the 4:00 minute mark and notice how many times one coil gets tuned. All you need is a worker bee with a hangover or a fight with their spouse on their mind and....

And here is another, also start at 4:00 mark...

 

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21 minutes ago, flakmagnet said:

The one question that I have yet to see answered in a clear way is; what quality control is being adhered to with x-coil manufacturing?

Coming from many years of hand making a consumer product, that quality control is in the builders skill set and attitude towards making as good a product as possible. The customer will judge this and word of mouth will carry the pros and cons to other potential buyers. Personally I believe a hand made product by a craftsmen is as good in quality control or even better then mass produced, tis all in the hands of the craftsmen and his desire to sell his product. It is a juggling match as he has to make money from the venture.

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Thanks Steve, this tracks with the information I have been able to get - but coming from someone with your background certainly carries much more weight.

This line of questions is not to try to bag the x-coils. I am as interested in them being a step up as anyone but I also want to understand as much as possible about what I am getting before I put my GPZ on the line to eek out that next step in sensitivity - especially as I seem to have an extremely sensitive stock 7000.

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17 minutes ago, Norvic said:

Coming from many years of hand making a consumer product, that quality control is in the builders skill set and attitude towards making as good a product as possible. The customer will judge this and word of mouth will carry the pros and cons to other potential buyers. Personally I believe a hand made product by a craftsmen is as good in quality control or even better then mass produced, tis all in the hands of the craftsmen and his desire to sell his product. It is a juggling match as he has to make money from the venture.

That is very true Norvic. What is also true is we are all human and failures occur whenever humans are in the mix. Not targeting X coil. All coil manufacturing efforts... well, I’ve seen it all and I will leave it at that. People genuinely have no real idea how many substandard coils are in use no matter who makes them. And foam filled coils in particular can degrade with use.

Watching the two videos I posted above is enlightening.

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12 hours ago, flakmagnet said:

But why would someone with a GPZ want to pay  $3750 for essentially a smaller coil? I guess that's considered "good business" but I don't necessarily agree.

You have a good arguement, but I know multiple people who own both the SDC and the GPZ.  There are people paying for both.  I was almost one of those people. ?

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2 hours ago, Steve Herschbach said:

That is very true Norvic. What is also true is we are all human and failures occur whenever humans are in the mix. Not targeting X coil. All coil manufacturing efforts... well, I’ve seen it all and I will leave it at that. People genuinely have no real idea how many substandard coils are in use no matter who makes them. And foam filled coils in particular can degrade with use.

Watching the two videos I posted above is enlightening.

Yeah, I suspect we posted at the same time almost, because I have Satellite internet I have a wee more time delay and don`t always get a message that someone else has posted. Those vids are certainly enlightening, my perspective comes from building a consumer product for many years.

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Looking at those two videos you would think that one would see people out detecting as a common occurrence yet I hardly ever run into anyone and I live in a metropolitan area...yes hard to decide which is better factory or custom built....Humans create and program computers....just saying

strick

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To this day I have never, despite very heavy lobbying efforts, been able to get anyone to recreate the Jim Karbowski Bigfoot coil. 3” x 18” figure 8 winding, highly EMI resistant and perhaps the best park and field jewelry coil ever made when paired with a DFX or V3i. Used ones over a decade later sell for twice what they did new. I keep a V3i for no other reason than that it will run a Bigfoot. But despite the fact they often sell for over $500 used nobody will make them. Why? Tedious hand built coils, every one a work of art. Nothing wrong with hand made at all as long as the maker takes care and has pride in the work.

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5 hours ago, Andyy said:

You have a good arguement, but I know multiple people who own both the SDC and the GPZ.  There are people paying for both. 

Well Andyy, that may be true but it doesn't change the fact that, in essence, the SDC becomes a 3700 dollar smaller coil. That's an extravagance most of us cannot afford.

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