Ped,
I have an Infinium LS with the 10x14 mono coil. It is a great salt water beach unit once you learn how to set it up for your area.
If you are going to use the LS as a salt water beach unit, there are a few things you need to do.
First, make sure you go through the Frequency check process. There may be beaches you are hunting that have towers or other EMI sources, so making sure you get the optimal frequency with the least chatter and best stable threshold is paramount.
Second, ground balance the unit with the discrimination knob at 0, threshold in the 4-5 range...first in Slow mode for about a minute, then in Fast for the same time frame, prior to putting in Lock. If your beach has a lot of mineralization and you feel the conditions change frequently, then run it in either Slow or Fast mode. The beaches I hunt are pretty tame, so I go through that process and then hunt in Lock mode. When doing this procedure, make sure the coil is just barely off of the sand, and slowly move it side to side ( not up and down) for the 45-60 seconds.
Lastly, the discrimination knob CAN be used to eliminate small foil and small bits of aluminum...but why do that ? You will only also eliminate small gold. The only thing I use the discrimination knob for is to tune the unit to the conditions.
Bear in mind the LS is a GOLD prospecting unit, and it does NOT have the internals tuned to cancel out the salt water conductivity. That is what the discrimination knob is to be used for when salt water beach hunting. Just up the discrimination BARELY, until the unit is stable. I almost always run mine at 0 if I can, and will hunt with it a tad on the unstable side ( ie, some chatter/falsing). I have learned the sound of the solid hi/lo or lo/hi signals, as most falses will not signal hi/lo or lo/hi when sweeping from different angles. The LS will hit on small gold that a lot of other units will not hit on in the 0 discrimination setting.
Sweeping a target from different angles is key, because if you get hi/lo or lo/hi signals from all angles, there is a target down there.
Most gold, nickles, tabs, aluminum will signal hi/lo. Clad, silver and iron will signal lo/hi. Notice I stated iron will signal regardless...there is no way to eliminate it. The iron discrimination on the unit is to actually alert you that it IS iron, and not something else. What I mean is, if you get a solid hi/lo and then turn the discrimination all the way up to the Iron Discrim setting and still get a hi/lo...it's probably iron and NOT gold. The discrimination knob is like the Pulse Delay on other PI units, and can be used as such.
The above is basically for hunting salt water beaches. If you want to use the LS on land, I suggest getting the 8 inch mono coil, and if you want to clad and silver hunt, only dig the lo/hi signals. I have used the stock DD coil once and sold it...I did not like it and it's too heavy for me. But since I use the LS only for beach hunting, the 10x14 mono is all I use.
One last thing.....when you save enough money, get a straight shaft for it. It makes the unit much better balanced and way easier to swing.
Hope this helped.
JC