Re: Need help building marine speaker boxes??
Comparing an audio system used in studio environment to a boat or car is like comparing a pogo stick to a hovercraft, they are totally different worlds. A car has a much higher noise floor than a studio or even your living room. You're already competing with road noise, rattles, the engine, and other cars. In a boat this is even more of a problem! A studio environment typically has walls covered with sound absorbing materials and or special wall coverings that aren't flat and won't bounce sound back at you. Cars and boats don't have this option, they have flat surfaces with minimal sound absorption capabilities.
In most cases boat speakers are laid out similar to car speakers meaning you're probably sitting right next to one while you're driving. So the only high frequency sound that you hear is the coming from speaker closest to you. Since the sound waves are actually hitting your ears at different times your brain detects the slower waves and ignores them, otherwise you would be hearing an echo effect.. (Ever been to the beach or a concert where they have speakers that are several hundred feet apart? You can stand in spots and hear sound coming from one speaker and then hear it again from the next? The sound left the speakers at the same time however the distance was great enough that your brain no longer thinks they are the same transmission.) Short of sitting the exact same distance from every speaker in your setup or investing in specialized time alignment processors you're not going to get the proper sound image coming from your mobile system anyways.
In a car or boat environment just to overcome the natural ambient noise you're going to have to have more power, if you're trying to put a stereo in that you're going to be able to hear clearly over a loud boat engine you're going to have to have even more. The higher you crank up the volume control the more power required to push the speakers, running a speaker with not enough power will destroy them. Getting into selecting a proper amplifier is an entirely new ballgame. Home and mobile audio again differ here as the law doesn't really require mobile amplifier manufacturers to list every detail about their power ratings on the box, so lots of times it comes down to price when people go about selecting an amplifier. Some companies use a dummy load rather than an actual speaker to measure power, they also use non realistic power supplies while they are measuring the maximum power output. Say for example while testing they ran the input voltage at 20 volts, then blasted the amp with a single note and it lasted for half a second before it let the smoke out. They could then legally record this as the maximum power output of the amplifier and market it this way, ignoring the fact that your 12 volt system is not going to be capable of putting 20 volts into the amp. (Ever notice how a system will sound louder with the engine running? The reason for this is the amplifier instead of running at 11-12 volts with the engine off is now running at around 14 volts due to the alternator charging the battery) That being said when you go out shopping for an amplifier don't just jump on the one that is on sale that claims 200 watts for 90 bucks.. The old saying here about being too good to be true always applies, if an amplifier costs less than a dollar per watt you're throwing your money away. You would get more power buying a quality 50 watt amplifier that cost 200.00
While you can have good sound in a car or on a boat it is silly to compare a car or boat stereo or any component in it to a closed studio or even a good home theater system. You have to be practical, choose a material that is going to hold up good for the life of the system. MDF and Plywood have their uses but their lifespan is limited on a boat. Your speaker & subwoofer locations are also quite limited to the available space you have. If it's mounted near or pointed at a vertical surface on your boat the sound waves are going to reflect off of it and there will be places in the boat where there is a noticeable difference in the sound.
Another major contributor to good sound will be the enclosure size itself, it has to have volume or air space normally measured in cubic feet. Ideally you would measure the airspace requirement for each subwoofer but most people aren't going to go to the trouble to do that so checking with the manufacturer for their recommendation of airspace is the other option.
In conclusion build your sub box out of something that is going to last, the thicker the material the better. 1/2" material will actually resonate and you'll hear the wood vibrate.
