YES! A DD coil is MUCH better in highly conductive wet saltwater sand. I can't find anything from Whites that says they want you to use a concentric coil on a saltwater beach.
Here you go I hope this is helpful.
Posted by: deolslyfox Super Moderator
MX Sport Test Results - Continuous Update 4-23-16
My MX Sport, 950 and 6X10" coils, etc arrived today !! It is un-boxed and assembled. I'm going to give this unit a good field test inland and of course at the beach. All test results, tips, lessons learned, etc will be added to this thread, so check periodically if you want to see how things are progressing.
************* Beach Testing 4-23 -16 *************
Spent a few hours at Daytona Beach testing MX SPORT in the salt sand environment. I am happy to say that the unit performed flawlessly. I tried all modes but focused on Beach, C&J and All Metal. The beach was terribly sanded in following a couple weeks of bad weather, but I was able to glean a few targets from all three venues - dry sand, wet sand and shallow water. I also worked in front of a known high EMI spot.
Basic setup: 950 concentric coil, Sense = 9, Tracking = ON, 20 Tone ID.
Beach Mode: At the beach, so started with Beach Mode. After achieving a good ground balance I started working the dry sand. Operation was remarkably smooth. Dare say as smooth as the dual frequency DFX / BH 300 or the 3-freq V3i. I was pleasantly surprised at just HOW smooth the single freq MX Sport ran. Bumped the Sense up to 10 momentarily with no appreciable increase in "chattiness". I left the sense = 9 for the rest of the testing except as noted.
First target was a nickel at 2". VDI solid and pinpoint accurate. Next hit was a Zincoln at about 6". Again, good VDI and pinpointing.
Transition Dry to Wet: The transition from dry to wet was absolutely seamless. No additional ground balancing required, even though I checked. First pump = no change in audio. First hit was a zincoln at about 8". VDI a little bouncy but pinpointing good. With sense = 9 the unit was very stable, smooth threshold. Very little difference between dry and wet venues. Touching the wet sand causes a little "chirp" but that's it. Again = bumped sense up to 10. Smooth ops - no overload in wet salt sand venue.
Transition Wet to Shallow Water: As soon as the coil hit the shallow water the unit went into OVERLOAD. I dropped the sense to 8 then to 7. At sense = 7 the unit stabilized and ran smoothly. I could not get the unit to run with Sensitivity above 7 in any mode with the coil submerged in salt water.
C&J Mode: Changing to C&J mode required a new ground balance. After that the unit ran absolutely smoothly in the dry sand.
Transition Dry to Wet: Once getting to the wet salt sand, MX Sport was a little chatty at Sense = 9. Dropped to 7 and most of the "chat" went away. I bumped the sense back to 9, added Salt Tracking, rebalanced and the unit was absolutely stable again. Bagged a couple of zincs from the wet sand in the 6 - 8" range. Again, good VDI, good pinpointing.
Transition Wet to Shallow Water: Same as with Beach Mode. Had to drop Sensitivity to 7 to alleviate OVERLOAD condition. At Sense = 7, operation was smooth.
All Metal Mode: Here's the "payday" mode in my book. All Metal Depth with VDI. Add the Salt Tracking and you've got a detector with all the capabilities of a BH 300 with a VDI readout !! In dry sand the MX Sport will see an aluminum rivet from a beach chair at about 6". I know, I chased one around !! It will see a zincoln at 8" no problem and a clad dime just as deep. Dug both. Runs fine with Sense = 10.
Transition Dry to Wet: Just like other modes. No worries.
Transition Wet to Shallow Water: Again, just like Beach and C&J. Sense above 7 = OVERLOAD. Sense = 7 and below = smooth ops.
High EMI area: No worries. Even at Sense = 10 the Sport was more than usable in the known high EMI areas. I didn't even have to employ freq offset. Dropping sensitivity to 8 was enough restore absolutely smooth operations in motion mode. I could still detect a little chatter in pinpoint mode, but not enough to worry about.
End of the day: MX Sport is a top performer at the beach. With Salt Tracking activated, it can transition from dry to wet to shallow water seamlessly.
Recommendations: If you want to squeeze every last drop of depth out of your MX Sport at the beach, run in All METAL mode with Salt Tracking. Just keep in mind that you'll see the tinfoil bits, bobby pins, etc, but you'll also get the small gold chains and deeper targets.
Tips:
1.If you are working salt water, drop your sensitivity to avoid OVERLOAD.
2. Any time you change modes, especially if adding / removing SALT TRACKING, touch up your ground balance
3. Pinpointing over large iron gives you the threshold dropout just like the rest of the MXT line
4. In All Metal mode with Salt Tracking, the MX Sport can see a crushed aluminum can at about 20" in dry sand.
5. Run the 950 concentric at the beach if you have it. It is an excellent coil. Great depth, accurate pinpointing, very little falsing.
Hope this is helpful. If I have any other tips along the way, I'll add 'em to this post.
Good luck and good hunting !!
Just kidding. Whites make some fine machines. They are WAY overpriced, WAY too complicated to use and learn in many cases, and the dealers that sell them WAY over-hype them because they provide the highest profit margins allowed by the manufacturer. 
