From the factory, Trigger Bank 1 is selected in the TD-50, which is appropriate for the TD-50K set. If you have the TD-50KVX, you'll want to choose "Trigger Bank 3" in the TD-50 which will optimize the sensitivity for each of the TD-50KVX's pads.
Here's how to select Trigger Bank 3 in the TD-50:
1. Press the TRIGGER button.
2. Press the PAGE UP button to access Page 1.
3. Press F1(BANK).
4. Use the cursor buttons to highlight the Bank number (i.e. Bank No. 1), and the press the [+] button to choose "Bank No. 3 TD-50KVX + KD-220."
5. Press EXIT when you're finished. The new setting is saved automatically.