If Possible Don't Permanently Mount Speakers
If you ever need to use the compass it will work better without stray magnetic fields around. Perhaps the OEM compass isn't that sensitive but if it was ever upgraded you'd be stuck if the original was used as a sensitivity test.The Northwest is prone to fog and low visibility and a sensitive compass is still something good to have. I have had electrical circuit failure, along with the GPS, radar, and autopilot failure (all at the same time), so having an accurate compass was really handy. It's a C.Plath "Venus" which is a good one. As a test to find a safe distance to install the "talk-back" speaker for the loudhailer I found it had to be more than 6 feet away before the card wouldn't move, and this was before the little speaker was energized! We're only talking about a 2" speaker here!!!Since I couldn't find a safe distance for installation in the cockpit the talk-back speaker still hasn't been permanently installed and I have no stereo speakers in the cockpit for the same reason.Besides the compass issue I've seen many boaters cut large holes in the cockpit to mount their speakers. I hope they never have a knockdown because that speaker cone isn't going to stop the flood of water from going down below and possibly sinking the boat.Consider creative ideas like, say, a Velcro attachment. Run the speaker wires to the cockpit and have pig tails on the speakers for connecting. The rest of the time, when the speakers aren't used just stow them below deck. Also, the speaker cones and voice coils will like being out of the elements too.