Big Coil vs Small Coil: Which One Should You Actually Buy Second?

A search coil generates an electromagnetic field, and a larger coil produces a larger, deeper field that also spreads wider at the edges. That wider field is what lets a big coil cover more ground per sweep and reach a little further down on a large object in clean soil. It is also what causes two separate targets sitting close together, a coin and a nail a few inches apart, to fall inside the same field at the same time and produce one combined signal instead of two clean ones. A smaller coil's tighter field does the opposite: less ground covered per sweep, but a much better chance of reading two close targets as two targets.

This is why Minelab describes Minelab EQX 06 Coil (6 inch) as ideal for "difficult terrain" and high trash areas, and Minelab EQX 15 Coil (15 inch) as built for "wide open spaces." Neither description is marketing fluff, it is a direct statement of the physical tradeoff.

Both figures below come from Minelab's own coil listings.

Your site is genuinely open and comparatively clean: a large field, a quiet beach, pasture with light trash. Here a bigger coil's wider coverage means you search more ground in the same afternoon, and its stronger field on a large or deep target, older large silver coins or bigger relics, gives you a real edge Minelab's own listing credits it for. Run the coil coverage calculator before you buy one, since the ground-covered difference is larger than most people expect, and read the beach detecting guide if that is your typical site.

Your site has any meaningful trash: an old home site with nails, a city park with decades of pull tabs and foil, ground near a fence line or other buried metal. A small coil is also lighter, which matters on a long day, and it is the right tool for working tight spots a big coil physically cannot reach. The metal detecting in parks guide and the Equinox coil compatibility chart cover the rest of what to expect from this size.

No, not the ordering. Target ID is a conductivity reading: iron sits at the bottom of the scale, foil and small gold read low, nickels and pull tabs sit in the middle, and copper and silver read near the top, and that physics does not change with coil size. What changes is signal clarity. A small coil gives you a cleaner, more isolated read on a target sitting close to junk; a big coil is more likely to average two nearby targets into one confusing number. Either way, the exact number your machine shows is conditional on soil, depth and orientation, so bury a few known items in your own ground and check what your machine actually reads, which the test garden guide walks through, and the target ID chart explains the general ordering in more depth.

$225.00 for the small coil against $290.00 for the large one, so the small coil is also the cheaper of the two in this pairing, on top of being the more broadly useful second purchase for most sites. Add it to the intermediate setup before you add a second detector entirely, since a coil swap solves more real problems per dollar than a second machine usually does.