Spakers instead of kick panel vents

[forestb]

I am planning on installing spakers where the kick panel vents are. I love having the vents but when installing a vintage air ac you can no longer keep the passenger side vent. Sense I will be installing an ac I figured I will not need the vents. So my question is if I install the spakers instead of the vents how do I keep the back of the speakers from getting wet when it rains? The truck has already been painted so I don’t want to weld the cal vents shut. I am going to put phome cups on the back of the speakers and was thinking of using thick plastic and liquid gasket to keep the water off.