Here is my first attempt at building a subwoofer box for my boat- there's a whole new set of challenges when building for a boat- It has to be able to withstand the elements, it has to be loud enough to overcome the ambient noise, it has to be weatherproof, and in my case, it has to be compact so that it can be hidden. This is the box after construction- I love my new table saw. After putting on all the wood putty. I found that putty on the end pieces of mdf works great if you plan to paint your box. Otherwise, the paint will soak in and the ends will be obvious. A lot of primers won't even stay on top. I put on two coats of primer. I had the idea of using the same waterproofing primer that you use on masonry to prevent leaks. Made sense to weatherproof the mdf. I sanded with 220 grit after each coat so the surface was nice and smooth for paint. I put two coats of rustoleum gloss white. Here's the finished piece. I added drawer pulls to use as handles in case I want to remove it. I got these Polk subs at Circuit City for $18 per piece- they were mislabeled. I ended up buying every one they had since they were honoring the price. I gave two of them to a friend for his boat, and they sound great for the price. Maybe one day down the line I'll install some real marine subs, but these will not be exposed to the elements anyway. Underneath I installed these rubber feet to keep the thing from sliding all over inside the compartment where it will be housed. I have to completely disassemble my bridge to get the box into its home, so it would take a good two hours to remove should anyone want to steal it. Too bad it won't be seen, though. I think it came out great. I'll let you know how it sounds.
I have installed many systems myself, and thought I would add that un-enclosed listening areas and/or open spaces eliminate a lot of low frequencies, especially ones that a "subwoofer" would reproduce.
Its a shame, but thats the way it is. Its the laws of physics and nature working against us.
I have tried outdoor systems before, and open air vehicles such as convertibles, jeeps, and boats. Unfortunately they almost always fall short in the bass department.
one way I found that helped eliminate the "dip" was to use low resonant mids. When you have low resonant mids, that means that they do not sound cranky, and/or blasty. prefferably something with a natural dip in the 1000 Hz to 3500 Hz. I know what you may be thinking; Ha Ha good luck, right? Well actually when you use a oversized woofer as your midrange, you get a better response. Larger woofers lack in upper midrange, so thats what I used (12"-15"). I then used drivers that had high QTS (above 60) as my woofer/sub. Using this type of driver allows the driver to maintain lower frequencies even in limited baffle designs. Dont expect mucg below 80 Hz.
Thanks! I can't wait to hear it at the sandbar. you should see this place in Miami. Hundereds of boats anchor up in like 2' of water, ladies making out, and stereos are always blaring. I am in the process of trying to outdo my friends with their boats. They should have sound competitions just for the water. Here's the rest of my system so far.I built this entertainment center out of oak to fit into an unused corner of the cabin, plus it covers a lot of ugly holes in the walls the boat had when I ot it. I mounted a bottle opener on the side (used frequently lol) and mounted a docking station for my laptop on top. Once I snap my laptop in place, I have full acccess to DVD player, all my music, HDTVB tuner, TIVO, etc. I have cellular wireless so if I don't have a song, I can get it. It also has Karaoke software installed so once I get my wireless mike, you can sing along. I hooked up an FM transmitter I got on EBay and it boradcasts in a 150' diameter so any boats around can listen to the same thing. The housing for the head unit unlatches and swings down to access all the complicated wiring, and the center houses two Coustic amps and right now a Sony home theater subwoofer (just for the cabin- nothing huge needed down there to sund good). I mounted a 19" flat screen on the wall and since this picture was taken I have added a blue LED voltage meter, a 1.5 farad cap, and flanked the flat screen with 2 4" Kenwood coaxials. Up on the bridge I have a pair of 6.5" Clarion marine components and a wired remote to control the head unit from up top. Here's what it used to look like before the entertainment center This is the most recent picture, although not a great one. There is a lot of wiring to hide that goes to and from the bridge up top. I'll post more pictures after I tidy things up a bit.
I know what you mean, bro- you are absolutely right. It is definitely a challenge. My first box was 16 years ago and it housed one Kicker 12 in the convertible well of my 71 Cutlass. When the top was down, all you could do was feel the bass. There was no hearing it. I now have a 68 Fury convertible (many sub boxes later) and am now pretty happy with the way it sounds with one 10" Puch sub. I had to play around a lot with ethe placement to get it to sound right, though. My friend using this same Polk sub had the same problem- unless he was at the marina, it was like the sub wasn't even there. Just nothing for the sound to reflect off of. The best we could do was put it into a corner in the back of the boat, and it sounds decent. I'm crossing my fingers that where this sub will be will bear fruit. It will be housed in a massive fiberglass enclosure that goes in the front of my bridge underneath the controls. Plenty of surfaces for it to reflect against and plenty of areas for air to escape, but again it could be a matter of placement. I am using Clarion marine 6.5" compnents for the mids and highs- I might look into doing what you were talking about. There is still room to build a box just for a mid bass. Are you saying use a sub in a smaller enclosure to attain this or cross the sub over at a higher frequency?
how big is that boat? it doesnt seem like it will be parked on the sandbar bro the water is only like 2.5 feet deep in most parts unless you go off to the side, maybe its deeper then when i used to go but as far as i remeber that doesnt seem like itll be floating
It's a 32 Carver Aft Cabin cruiser. You're right. It gets dicey around 4', but I anchor into the wind in front of the sandbar so that my swim platform is facing the fun. You may have to swim up to the action, but it's worth being able to watch the game inside in the air conditioning or showering if you need to.
I spent until 2:30 in the morning putting the sub in and then putting everything back together again. It was well worth it. I have a few gain and crossover adjustments to make, but the sound was gorgeous. The bass was clean and actually much more pronounced than I expected. I had to actually turn the gains down on the amp to get it to sound right. I am pleasantly surprised, but we'll see what it sounds like on the water.
Here are the latest pictures Head Unit- I set the system up so that it can be faded from outside to in as opposed to rear to front. Great if you just want to lock yourself inside and watch a movie. I built this entertainment center to be able to unlatch and give me access to the extensive wiring for the wired remote, usb gadgets, neon lighting, terminal blocks, aux inputs, etc. I know, I know. The wiring's a mess. Every time I needed to add another gadget it went in here and further complicated things. Everything works and I know where everything is, though. Kind of like that guy at work with piles of paper on his desk but still gets things done. Here you can see the pin switch I installed with the white neon light to illuminate everything when the hatch is opened. 17" flat screen.
It is. Pioneer is the only manufacturer I could find with auxilary in and wired remote capability. This is my second one- my first one developed a loud hum. I'm also kind of bummed that you need to buy a seperate component to accept the auxilary input. Now that things are all connected, I'm happy with the unit. Nice features nd easy to use, plus I like that display with the power meters.
This is the box after construction- I love my new table saw. 
After putting on all the wood putty. I found that putty on the end pieces of mdf works great if you plan to paint your box. Otherwise, the paint will soak in and the ends will be obvious. A lot of primers won't even stay on top. I put on two coats of primer. I had the idea of using the same waterproofing primer that you use on masonry to prevent leaks. Made sense to weatherproof the mdf. I sanded with 220 grit after each coat so the surface was nice and smooth for paint. I put two coats of rustoleum gloss white. 
I built this entertainment center out of oak to fit into an unused corner of the cabin, plus it covers a lot of ugly holes in the walls the boat had when I ot it. I mounted a bottle opener on the side (used frequently lol) and mounted a docking station for my laptop on top. Once I snap my laptop in place, I have full acccess to DVD player, all my music, HDTVB tuner, TIVO, etc. I have cellular wireless so if I don't have a song, I can get it. It also has Karaoke software installed so once I get my wireless mike, you can sing along. I hooked up an FM transmitter I got on EBay and it boradcasts in a 150' diameter so any boats around can listen to the same thing. The housing for the head unit unlatches and swings down to access all the complicated wiring, and the center houses two Coustic amps and right now a Sony home theater subwoofer (just for the cabin- nothing huge needed down there to sund good). I mounted a 19" flat screen on the wall and since this picture was taken I have added a blue LED voltage meter, a 1.5 farad cap, and flanked the flat screen with 2 4" Kenwood coaxials. Up on the bridge I have a pair of 6.5" Clarion marine components and a wired remote to control the head unit from up top. 
