You can swing faster in AM. I think the manual might even say that in disc you can pick up your speed a bit in silent search mode. That's useful for say clad hunting or scouting the woods looking for any signal to indicate an area of activity to then work slow.
I'd like to change my advice a tad here. Yes, probably about 2 seconds per sweep for me. That might sound fast, but I don't sweep wide like other people do. I mainly keep the coil right in front of my feet, so I'm still sweeping pretty slow. That might be the difference in what Bryce says about 4 seconds per sweep on his Explorer. He might have a bit wider sweep than I use. I've found that it's more important to be concerned about the ground right in front of your feet and work that slow and overlap your sweeps, and not worry about reaching out far left and right. If you're not careful that can hurt your technique because you might tend to pick up the coil at an angle at the ends of those wider sweeps if you don't keep good control over it. Now, for beach hunting I'll swing a bit wider so cover more ground as I grid, as I drag my sand scoop to mark off the row I am doing so I can then "mow the lawn" with the next row without missing anything. But when I'm old coin hunting on land I keep the coil right in front of my feet. At the most it may go about a half a foot to the side of either foot, so even though I'm saying 2 seconds per sweep is the norm for me it's still rather slow.
One guy posted on here a while back that he has very mineralized (I think he said red iron rich clay) soil, and that if he doesn't crawl really slow he'll lose the threshold. I think he even said that the threshold still drops out and nulls a lot in that soil, but that if he keeps the coil to an absolute crawl his GT will still sound off the targets through the null. I've read others say this as well...That the Sovereign will sound off through nulls at least some times, and probably not at the depths it would if it wasn't nulling.
As said, if your threshold is dropping out sweep over that same spot several times. If it keeps nulling it's iron, but if it doesn't every time then you either are swinging too fast or you have your sensitivity too high. Before you lower your sensitivity, see if a slower sweep will stop the threshold from nulling out. If it won't then lower sensitivity. Me? I mostly these days run sensitivity a bit high and unstable. As long as I keep my sweep speed slow the threshold doesn't really null out unless I hit iron. You'll know when you are riding the edge of unstability sensitivity because the threshold will "reset" or "fade" and change here and there. With practice you can tell if that's being caused by the unstable sensitivity level or an actual hit from a deep target. When in doubt just do short fast wiggles or sweeps over that spot and see if it's a deep target or not.
Most importantly, when you do it on a deep and soft target try normal sweeps like you are hunting over it at different speeds. See which speed gives the hardest initial hit on the target, then use that speed while hunting. This can change from site to site depending on the ground and sensitivity level, but it usually doesn't really change that much if at all. If you are going slow then you'll probably be right in that zone you need to hit best on the deep stuff.
If you are just clad hunting or searching for that first hit in the woods then lower sensitivity to say 3PM or so and you can sweep faster. Throw it into silent search and you can probably sweep even faster while doing that, but when you want to search an area good you need to use threshold mode and slow down for sure.
