As far as putting a coaxial speaker, like a 4", wouldnt be a good idea. The glovebox lid wouldnt be a good (sealed or sturdy) enclosure. On a RG at the Dragonfly Concepts booth, they did have a tweeter pod on each glovebox lid, firing towards the rider. It looked like ABS plastic pipe, cut at an angle, and molded into the glovebox lids. It looked nice, but I think anyone with some crafty skills could replicate 'em.
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