Okay, here's the deal with audio:
One can't just go sticking speakers on amps and expect them to work, ESPECIALLY if we're gonna cover 300 feet and need multiple speakers on 2 channels. Impedances have to match, and the speakers need to be wired in a certain way in order to maintain correct impedance, otherwise the amp can work too hard and self-destruct. On one hand, the idea already crossed my mind to have people stop by thrift stores and pick up a few of the millions of discarded stereo systems made in the past decade. The speakers are generally good; it's usually the LED readout, or the cassette player (!), or the CD player or some other aspect of the main unit that cause people to say 'fuckit'.
I've been investigating car audio options because they use less power and sometimes come in odd impedances; standard home stereo stuff is generally 8 ohms, and car stuff can range from 2 ohms to 16 ohms (many are 8 ), depending on application and manufacturer. What I'm shooting for is a car unit with a CD player at minimum, USB stick would be ideal. Here's why: The CD player, while we could set it on infinite loop, would use more power than a USB stick reader, because there's 3 motors in every CD player. USB = no moving parts, less power use. PLUS--and this is a big one--you could use two or three car batteries in parallel, get longer run times, and use an RV solar charging panel to keep the units close to optimal power all day. If we can assemble a collection of 6x9 coaxial car speakers, or 6" coaxial car speakers, to put in the fake rocks, all the better. We're not trying to achieve sonic masturbation here, just a good playback on ocean sounds.
The only drawback I can see with car audio stuff is avoiding units that require semi-complex interaction with ignition circuits to turn on. I hate that.
Still, I'm optimistic that we can find a wanna-be/no-name brand of head unit, amp, and speakers, used, probably on craigslist or freecycle. The amp needs to have considerable beef... 50, 60 watts isn't gonna cover it. 100 watts, minimum, is what we'll need.
So, alla youse gaiz out dere, listen up: Start putting the word out, keep your eyes peeled, all that stuff. Pick it up cheap or free--I've given you some fairly specific guidelines.
â€¢ In dash head unit that plays USB sticks, CD at minimum
â€¢Â 6x9 coax or triax/ 6" or bigger round coax or triax, speakers. 8 ohms (although 4 ohms is acceptable, too, depending on how it's wired.)
â€¢ 2 channel amp, 100 watts output (not peak output, steady output) or better. Two 2-channel amps will be awesome, less trouble to amplify.
Oh, and wire. The smaller the gauge number, the better; 16 gauge wire is too thin to cover the distances we need, as it'll offer too much resistance to the amp. Better to shoot for 12 or lower. And 300 feet of it should do just fine.