Question: what is 4 ohm bridged?
Answer: Bridging at 4 ohms is the same as running both channels at 8 ohms. The Mo'Bass is most likely 450 watts a side at 8 ohms, hence the 900 watts bridged at 4. The amp would be 1200 watts at 1 ohm bridged, not recommended. 4ohm bridge is equivalent to each channel at 2ohms, not 8.