I'd hold off on the ADSP speaker. You may find that it's not needed.
First, be sure to track down and catalog all noise sources on the boat. Turn off EVERYTHING. Then, switch circuits on one-by-one while listening on the frequency you generally listen to (net freq. probably). There are many sources of noise: alternators
, electric motors, computers, pumps
, friges, digital readouts, inverters
, chargers, etc., etc.
Also, if you can, do this at anchor
. A marina is often a very noisy environment for RF.
Pay attention to the power source for your radio
. It should draw its power directly from the house batteries, not from a circuit breaker on the panel. Use AWG6 wire for runs up to 20', AWG4 for longer runs. A suitable ANL or MRBF fuse should be located close to the batteries on both the positive and negative cables for the radio