Captain Brownlie has been the form player for the Knights and he looked in good touch until he charged spinner Anaru Kitchen and was stumped for 14 to leave the Knights 42-2 in the seventh over.
Power hitter Corey Anderson suffered from long periods without the strike and was just getting going when Wagner removed him for 39 off 30 balls.
Seifert hit the majority of the 19 runs scored off the ninth over to lift the run rate over seven but his boundary-laden innings came to a close at 41 in the 12th over thanks to a superb catch taken by Kitchen on the boundary rope.
Santner started sweetly with well-struck blows to and over the boundary before holing out for 19.
Needing 7.9 runs per over to win, the Volts' openers Kitchen and Hamish Rutherford hit the opening over from local boy Boult for 16 and the next from Southey for eight.
Rutherford then treatedSantner with scant respect as the Volts raced to 40 off three overs. Scott Kuggeleijn knocked over Kitchen at 51 in the fifth over which brought Neil Broom in, recalled to the Black Caps last week after six years in the international wilderness.
Boult came back to get rid of Rutherford for 39 off 24 balls with the Volts 67/2 in the ninth over. Michael Bracewell, son of Mark Bracewell who is one of four brothers to attend Tauranga Boys' College and play first class cricket, came in next with the Volts under no pressure.
Tauranga's Jono Boult, vastly underrated at this form of the game, bowled his off spinners tidily and younger brother Trent came back well to slow the Volts' momentum.
But crucially they had wickets in hand, the key to any successful run chase, and were helped by Southee dropping a sitter with 45 to win.
Broom ended the match with a six to finish 54 not out, with Bracewell 41 not, in a match winning partnership of 91.
The Knights return to Bay Oval for two matches over the holiday period against Auckland Aces on December 27 and Canterbury Kings on December 29.
Knights 157-5 (T Seifert 41, C Anderson 39; N Wagner 3-22) lost to Volts 158-2 (N Broom 54*, M Bracewell 41*; S Kuggeleijn 1-17)