I second, third and even fourth Rons input about adjusting the helmet speaker positions.ronbien said:You can add an amplifier. Electrical Connection sells some.
A cheaper fix might be to make sure the speakers are positioned exactly in front of the ears and pointed correctly as well. Think of it as fine tuning them. You would not believe the difference it makes. I am not saying you have not done this already, but if not, it is worth the effort.