All midrange and high frequency speakers have a few common behaviors. The polar pattern will be such that you will get a lot of off-axis radiation in very close proximity that will narrow considerably as you raise the frequency and also as you increase the distance. So when the speakers are just a few feet overhead, regardless of type, you can't avoid the in-boat impact. An HLCD will have somewhat of a narrower dispersion pattern versus a dome tweeter for example. But in the final analysis, an HLCD is simply much louder, which is essentially why it projects farther, and will just be louder in the boat when played louder for the rider. There are a few things you can do like raising the height of the speakers if you have those options, mount the speakers on the rear crossbar so they are closer to the rear and tilt the tower speakers up slightly so that they project out versus down when the boat is squated and pulling. Past that the best way to make loud tower speakers more tolerable in the boat is to go with a larger tower speaker/pod that has a much warmer balance. Its often the overly aggressive high frequency stridency that is more taxing in the boat than the amplitude.

David
Earmark Marine