TeensySaber V3 and Proffieboards uses a digital amplifier that works best with 4 ohm speakers. Higher ohm values are ok, but lower are not. The amplifier can put out 3 watts, which can overload or destroy small speakers, which is why the default volume is set fairly low. (1000) Assuming your speaker can handle it, volume values up to 2200, or possibly even 2500 can be used. (There is no actual upper limit, higher volumes just increase the chance of distortion from clipping.)
One potential workaround for the limits of small speakers would be to use two 8-ohm speakers in parallel. It is currently not known if that will actually make the sound better or not. It probably depends a lot on how they are mounted. If they face one another, it is recommended to wire one of them 180 degrees out-of-phase by reversing the + and - leads. This will allow the air waves from each speaker to work with one another, not fight against each other, especially in a mostly closed tube that is a saber hilt.