He has 4 15" woofers in 4 sealed enclosures running a true 500 watts per enclosure.

Let us run the numbers:

The woofers are 93dB 1 W/1 M.

Using 4 of them, this would equate to over 100, but not much.

Givin the fact that He did hit 158dB, then it would take close to 500,000 watts to get to 158 dB.

The loudspeaker environment and loading does change the structure of the math.

Food for thought.

ref:

101 dB 1 W
111 dB 10 w
121 dB 100w
131 dB 1,000w
141 dB 10,000w
151 db 100,000w
161 db 1,000,000w