FD17: 1959 Fender Deluxe Tweed: Sound Sample on Bass 

A bass will not harm the speaker. The only thing that will harm a speaker is to feed a square wave into the speaker because 100% of the power from the amp is being driven to the speaker motor (coil). The speaker motor has no chance to cool down between cycles. Eventually, the speaker motor overheats due to the square wave. As the square wave output power to the speaker increases it raises the temperature of the speaker motor and the speaker burns out faster.