Can you use a 8 ohm 400 watt speaker on a 4 ohm 350 watt amp to play bass?

Yes, you can use an 8-ohm 400-watt speaker with a 4-ohm 350-watt amplifier to play bass. The speaker will receive less power from the amp, resulting in lower volume, but it won't damage the speaker or the amplifier. Just ensure that the overall impedance of your setup matches the amplifier's specifications to prevent any potential issues.