Forty cubic feet? Wow.
Without knowing the parameters of your woofers, I'll just toss out the possibility that your box is too big. Can you tell us what the woofers are, and perhaps even what the port tuning is (or what the port dimensions are)?
If those are high-efficiency woofers that don't have a lot of excursion, at low frequencies you can exceed linear x-max with less than ten watts input. If your woofers are going into over-excursion, additional damping material won't help.
By the way, you used the correct term - "damping" instead of "dampening". The latter is what happens when you spill your drink on the sub.
Duke
dealer/manufacturer
Without knowing the parameters of your woofers, I'll just toss out the possibility that your box is too big. Can you tell us what the woofers are, and perhaps even what the port tuning is (or what the port dimensions are)?
If those are high-efficiency woofers that don't have a lot of excursion, at low frequencies you can exceed linear x-max with less than ten watts input. If your woofers are going into over-excursion, additional damping material won't help.
By the way, you used the correct term - "damping" instead of "dampening". The latter is what happens when you spill your drink on the sub.
Duke
dealer/manufacturer