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My thoughts on a Double-D Vs Concentric in a sort of mid-size range.

August 22, 2018 12:40AM avatar
Gee those early days of detecting were simpler to understand when it came to search coils. Most search coils were round shaped while some of the Double-D's in the '70s were Round or just barely Out-Of-Round (my original use of the term an 'OOR' coil). For example, my Garrett Master Hunter TR-Disc. model's larger DD coil (the Master Hunter versions were 2-coil packages) is an 'OOR' shape, while the normal-size DD is round and about 8¼" in diameter. Compass, who is credited with starting the use of a DD coil with their Yukon TR series, also used round-shaped coil housings.

Most 'average' standard search coils measured 8" to 8½". Then the smaller-size search coils were generally in the 4½" to 7" size range, and larger-size coils, designed to provide deeper detection of larger-size targets for Relic Hunters, were commonly 10", 11", 12" and on up to the 14", 15" and 16" diameters, and most of the time they were round shaped. Also, the majority of them were a Concentric design and we didn't see very many Double-D offerings until the latter '90s.

I'll credit Minelab as the major manufacturer who brought top and, and top dollar, detectors to the market featuring Double-D search coils. Those in the 10+ to 11" size. In '88 White's changed most of their models to have a 950 Concentric coil in place of the 8" coils they used to use as a 'standard' coil size. In 2000 Tesoro started offering many of their models with an 8X9 'OOR' coil instead of the round 8" 'donut' shaped coil, and other makers introduced more 'standard' coils of 9", 10" 11" in round shapes of Concentric or Double-D, or the 7X11, 8X11 and similar elliptical-shaped coils as standard.

The main reason so many manufacturers increased the size of their standard coil is, or so they claimed, because the consumer wants more depth. Back in '88 I listened to White's then marketing manager tell an audience at the Texas Council of Treasure Clubs get-together that he felt they made a mistake. That was when they moved from the 8" standard coil to the 950. He explained why he felt that way and I totally agreed with him. Alan & I discussed that topic for several years to come on some of our visits at the factory.

Anyway, we have seen that trend continue to this very day even on some lower to mid-priced models. Look at the current Garrett model line-up and see the 'standard' search coils used:

The Ace 200 and Ace 250 come with a 6½X10 Concentric coil.
The Ace 300 comes with a 7X11 Concentric coil.
The Ace 400 comes with an 8½X11 Double-D coil.

Having owned a mix of 5 of the 250 and 400 models, I felt all of the coils were a bit over-sized for the detector and how they performed in the real world. The smaller size Concentric coils felt better, but I wished they would have offered something smaller and more round-shaped, like maybe in the 6" to 8" diameter.

White's also offers 9" and 10" round coils on their lower-cost Treasure Master or Treasure Pro units, and we see this with the F4, F5, F22 and F44 from Fisher, and Teknetics Patriot, Liberator, Minuteman and Euro-Tek Pro models .... all having a standard-size coil larger than the old common round 8" coils.

Today, I very seldom use any of the 'standard' size search coils because, in my opinion, they are oversize for the majority of everyday places most average Coin Hunters search, and are definitely over-sized for the very trashy sites I hunt 95% of the time. Every detector I have hanging on my den wall just waiting to be grabbed for a day of adventure is fitted with a smaller-size search coil with the exception of one model.

Current search coils used routinely range from a 5" Double-D to a 5½" Concentric, a 6" Concentric and up to a 6½" concentric size. The one exception is one of my Nokta FORS CoRe units of which I have two. My most-used device has the small 'OOR' 4.7X5.2 DD and the 2nd CoRe has a mid-sized elliptical 5X9½ Double-D open-frame coil mounted. I keep all the 'standard' coils for these nine detectors on my 'Team' in an Accessory Coil Tote for the only periodic times I might need them.

There is a lot more discarded non-ferrous trash out there in public areas today than we used to encounter from the mid-'60s and on thru the mid-to-late '80s, and because of that the smaller-size coils will give the detector operator a better chance of working desired targets out of discarded debris. In the sparse-target to moderately littered places, I have found a good mid-sized search coil to work better for me than what is considered a 'standard' coil on most models today.

Yes the digital readout is pretty small. I always try to keep my coil about an inch off the ground, I noticed that in their video also.I had to go back and check Garretts brochure, they list the 6.5"x9" coil as a DD. I think they made a typoconfused smiley, their only concentric listed in it is a 9"x12".
The Garrett website lists a 6½X9 as a Concentric coil for the AT series. I don't have their brochure at hand to check it out, so I just double checked on their website.

What are your thoughts on the 5"x8" DD for open areas like ball fields or dry sandy areas or do you think the concentric would be a better performer there?
My thoughts are simple. I like it out of the coils they offer, and preferred using the 5X8 DD on the AT Pro and AT Gold, but as a 2nd pick I liked the 4½" in the trashier and more iron debris filled sites I hunted. Those models didn't handle the iron trash as well as some of the competitive units in my arsenal with a comparable mid-sized search coil to unmask desired 'keepers.' I had to use the benefits of the 4½" Super Sniper.

Just my opinions from ample experience afield with many detectors for over five decades, and based upon the types of sites I hunt. Others might like the bigger-size search coils but they seldom work well for my wants and needs. Just smaller-size to a few medium-size coils are all I need to get me by so my biases show.


"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
Detectors: Vanquish 540 / CoRe, Relic & Simplex + / Bandido II µMAX & Silver Sabre µMAX / XLT / ORX
Pinpointers: Pulse-Dive .. Headphones: Killer B's 'Hornet' & 'Wasp' ... Garrett MS-3 Z-Lynk
Note: Detectors are listed alphabetically by Brand. Models are chosen based on search site conditions.
*** All working well today to make memories for tomorrow. ***
Subject Author Views Posted

I don't see many Garrett Metal Detector users in my area, but ....

Monte 1011 July 15, 2018 04:48AM

Re: I don't see many Garrett Metal Detector users in my area, but ....

Timbertodd 378 August 18, 2018 06:48PM

Todd, my thoughts on your AT Pro.

Monte 500 August 20, 2018 04:42PM

Re: Todd, my thoughts on your AT Pro.

Timbertodd 386 August 21, 2018 03:33PM

My thoughts on a Double-D Vs Concentric in a sort of mid-size range.

Monte 463 August 22, 2018 12:40AM

Re: My thoughts on a Double-D Vs Concentric in a sort of mid-size range.

Timbertodd 352 August 22, 2018 03:46PM

Well, half of my goal is achieved to get an American S2 TR back in my detector group.

Monte 434 August 03, 2018 12:13AM

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