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Impact & Kruzer NBPT ... 4X7½ DD vs 7" Concentric.

February 10, 2018 07:36AM avatar
Eric, I apologize. Somehow I missed your post on Jan. 30th and I think I will blame it on our unseasonably warm weather and an illness with the 'bug.' sad smiley

The detecting bug that is. smiling smiley I was doing a little detecting and taking care of some in-the-field evaluation of the new Multi-Kruzer and another device, and that included swapping coils from my Impact to my Multi-Kruzer and, coincidently, checking out their performance on my Nail Board Performance Test. To do a broad comparison of performance I also used comparable search coils and my CoRe, Relic, Racer 2 and Impact.

Hello all I am wondering which 7" Impact coil does best on the nail board test the dd or the concentric?
Eric, you asked 'which 7" coil' which is one way to look at them, but don't forget that the small elliptical coil measures only 4" the other direction and maybe ought to be compared against something like the 5" DD.

Therefore, having spent time with my NBPT using ALL of the Detectors that make up my 'Team,' along with all of the search coils I usually keep mounted and ready or swap to when hunting the densely iron infested old sites we enjoy, I made use of the 4X7½DD, 5" DD and 7" Concentric. I compared these three coils I have for my Impact on the Multi-Kruzer 'test sample' device I have. That was prior to Dilek announcing the 5 available search coils for the new Kruzer and Multi-Kruzer models, so I wasn't sure what would be offered.

I knew what I HOPED would be made for the Kruzer series, but that's when we let our biases take control of out decision making. I go by experience afield and by performance, and try not to consider a search coil's appearance or what I might guess it could do. Looking at the Kruzer coil offerings, I have my three favorite search coil choices that just happen to match my 3-coil preferences for the Impact.

You also asked: "... the DD or the Concentric?" We need to take into consideration several things when making any comparison on performance in any test scenario:

Search coil size, in all directions.

Search coil shape, be it Round, 'Out-Of-Round, or a more pronounced Elliptical shape.

Search coil 'type', such as a Double-D or Concentric.

The particular metal detector being used and how it was engineered to process target responses.

The detector settings that are used, especially the Discrimination's rejection break point.

I apologize if this has already been discussed. I'm going to get the multi frequency Kruzer and it looks like the coils for it and the Impact are very similar.
I haven't seen it asked yet about the Kruzer series because only those with a 'test sample' Kruzer or Multi-Kruzer have not had the opportunity to compare search coils other than the stock 7X11 DD, and not all testers were aware that the Impact coils can interchange. They have much shorter coil cables and that can make it difficult for some testers if they are taller, but now we know what will be offered and I can share my experiences.

There were tests done with the Impact and the Pro Pack supplied with the 4X7½ DD elliptical search coil. Matter of fact, YES, there wads a test done that compared Impact search coils when the only available smaller coil was the 4X7½ DD. I put my 'test' Impact to work on the NBPT and using the 4X7½ DD it passed the NB test ... when I was using an Indian head or modern Zinc 1¢ (USA coins).

I set the Discrimination low enough to just barely accept the four iron nails, and then I tested that coil with the Disc. set to just barely reject iron nails. It passed the test, but not all of the 8 passes gave a really great audio response in 3-Tone with 2-Tone being a little better on the tougher sweep routes, but it passed. I require any detector/coil combination to get at least 6-out-of-8 hits in order to 'pass' the NBPT, and personally prefer 7 or 8 responses with a smaller coil to be in my personal detector arsenal for those really dense iron nail plagued sites we hunt.

Then, in March of 2017, I invited Oregon Gregg over to my place with his White's M6 w/6½" Concentric coil, Makro Racer and Racer 2 w/'OOR' and 5" DD coils plus his NEL Snake and Shooter DD coils, and I had an original Tesoro Silver Sabre w/7" Concentric and Bandido II µMAX w/6" Concentric, my favorite Nokta CoRe and Relic devices, with the 'OOR' and 5" DD's, in that order, plus the then newly released Impact w/4X7½ DD.

It was an invite to check out what I called a 'Tough Challenge' because we used a much more difficult coin in the test. You can discern a bit of performance difference when you switch from a Penny coin to a slightly narrower Dime, but I made it more of a challenge. Back in February of '91 if I recall, Rich(UT) and I were out at my all-time favorite ghost town of 'Twin Flats' (a name I assigned it on May 4th of 1969) Utah. My last coin for the day before we headed for home was an 1836 Capped Bust Half-Dime.

I used that Half-Dime in the #1 spot on the NB and that one change made a lot of detectors and coils 'flunk' the NBPT. The coin is narrower in diameter, and as you know they are a very thin and that makes these dinky-sized coins difficult to get a decent signal on when surrounded by the four different-sized iron nails.

This 'Tough Challenge' was posted by Oregon Gregg in the Relic/Old Site Forum back then and it got a lot of attention ... especially from Dilek at Nokta/Makro. I got an immediate e-mail with a follow-up phone call and we discussed the performance of the Impact, as well as the small elliptical 4X7½ DD coil. As I explained to her, I felt the Impact was performing very well in general, but part of the performance issues was the physical size and shape and type of search coil.

For example, and refer to the marked comments I made above, we can be surprised at times over what we would anticipate a result to be. I really like the Makro Racer 2 a lot, and I guess it is due to the appearance I also have favored the 'OOR' DD over the round 5" DD on the racer series. The Racer and Racer 2 share search coils so you have a choice, and my choice is to use the 'OOR' coil in the nastiest iron debris sites.

But using THAT 'OOR' DD search coil in THAT specific test using THAT very thin, small coil ... we only got 6-out-of-8 hits. Both Gregg & I were surprised because I have enjoyed excellent in-the-field performance with the Racer 2 & 'OOR' DD coil, but this is a tough challenge.

Then we compared the 'OOR' DD (that Makro says measures 4.7X5.2 inches) against the round-shaped 5" DD (that measurers closer to 5¼" diameter), and the 5" DD gave us 7-out-of-8 hits with the same Racer 2.

I used my Nokta FORS Relic with comparable settings and the same-sized round 5" DD coil and it, also, gave 7-out-of-8 hits. But the surprise of the bunch of detectors using their factory-produced search coils was my Nokta FORS CoRe w/'OOR' DD coil. It was the exact same-size Out-Of-Round search coil shape as that used on the Makro Racer 2, and the settings were as close as you could match them, but the CoRe w/'OOR' was the ONLY detector with a factory-supplied search coil to give us 8-out-of-8 responses on that Half-Dime.

I will insert here that Gregg really likes his NEL Snake coil, and after that first test he got the NEL Sharp or whatever they call their round 5" DD, and both of those coils, on a Racer 2, hit 8-out-of-8.

Personally, I very seldom like an aftermarket search coil if there is something comparable made my the detector manufacturer, and with the Racer 2 I am just fine with the 'OOR' DD coil and 7" Concentric coil as my primary-use search coils, now keeping the 7" Concentric mounted full-time. I also like the 7" Concentric mounted on my Nokta Impact for day-to-day hunting, but I do have the smaller 5" DD at-the-ready on a spare lower rod when conditions call for it.

As I mentioned, I got a quick e-mail and call from Dilek and we discussed detectors and coils and I shared my thoughts with her. I told her, again as I have when I first got my CoRe and then Relic and then Racer 2, that I really wished there was a round-shaped Concentric coil in the 6" to 7" diameter for them. I also expressed a desire to have either an 'OOR' or 5" DD smaller coil for the Impact. Let me just say here what we already know, and that is the Nokta and Makro engineering team can do, and will do if necessary, everything they can to being consumers the detectors, and search coils, that are called for. And it's the commendable performance of Dilek who keeps up on Forum activity and consumer comments and discussion to share what she reads and hears.

In very quick time I was informed that they were still working on a Concentric coil that could operate on all three frequencies, but they had two 5" DD coils and would like me to evaluate one on the same 'Tough Challenge.' I got that 5" DD and had Gregg over to also witness the performance, and it brought the Impact right up there to match what I got with a 5" DD on the FORS Relic and Racer 2. thumbs up I was sold on the performance on the 5" DD on the Impact in very dense iron littered sites and that's now my preferred coil on the Impact, and will be on the Multi-Kruzer, for really dense ferrous challenged sites.

A we know they then finished work with the Concentric coil efforts and brought out a 7" Concentric for the Impact as well as a 7" Concentric for the Racer/Racer 2 devices. I have switched the Impact's 7" Concentric to the Multi-Kruzer to finish some evaluation work and it goes back onto the Impact later today.

Of all the three coils I compared, adding the 5" DD Impact coil in the comparison with the Multi-Kruzer, could handle the 1¢ coin, as normally used on the NBPT, okay. For day-to-day hunting in most average trashier sites, I prefer the 7" Concentric on my Impact and Racer 2, and most likely will on the Multi-Kruzer. When debris conditions get really terrible, then my favorite go-to coil is the 5" DD. I have those two coils ready for my Impact and Racer 2, will get them for the Multi-Kruzer, and therefore have no real want or need for the 4X7½ DD coil.

Just my thoughts.


"Your EYES ... the only 100% accurate form of Discrimination!"

Stinkwater Wells Trading Post
Metal Detector Evaluations and Product Reviews
monte@ahrps.org ... or ... monte@stinkwaterwells.com
Fisher:(1), Nokta-Makro:(3), Tesoro:(4), White's:(2), XP: (1)
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Edited 2 time(s). Last edit at 02/10/2018 11:02AM by Monte.
Subject Author Views Posted

Impact 4X7.5 coil or 7"

Utah1971 492 February 10, 2018 07:28AM

Impact & Kruzer NBPT ... 4X7½ DD vs 7" Concentric.

Monte 559 February 10, 2018 07:36AM

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