Re: marine amplifier
Installing an amplifier and speakers is very easy. I'll go over the physical connections and then the settings.
Physical connections
before making any connections to the battery disconnect the negative terminal to protect you and your boat!
Battery Positive - You must run a wire from your boat's postive battery terminal to the amps positive battery input. Usually Red in color (other colors are available in kits, and many car audio companies offer a variety, red is the standard). Most amplifiers over 200 watts total you will want to use a minimum of 8awg wire, larger amps may require 4awg, and multiple amps may require up to 0awg. Check your amplifier's manual for what the manufacturer recommends. Also, this wire should be fused within 18" of the battery to protect your boat. Use a fuse that is just large enough to not blow under normal conditions. This way it will blow as quickly as possible if there is a problem. Leave the fuse out until all connections are made and you are ready to fire the system up.
Battery Negative - Run the same size wire as you used for the positive connection all the way back to the negative terminal. Usually black in color, other colors available as mentioned before.
Remote Turn on - an 18awg wire, usually blue in color, connects to the remote output from the head unit. This wire turns the amplifier on and off with the head unit
A pair of output terminals for each channel - Positive and negative for each speaker
RCA inputs for each channel - connectors like those found on your VCR or TV. Usually a red (right) and a white (left). These connect to outputs on the back of the head unit. Not all head units have RCA outputs, and that would necessitate the use of a line output converter (often referred to as a LOC) or an amplifier that accepts high level inputs.
Mounting and running wires
You'll want to mount the amplifier in a place where it will stay dry and is out of the way. Usually they are mounted on a vertical surface tucked up under a console, high and dry so to speak. Although amplifiers may be specifically designed for marine use, that does not make them water proof!
All wires should be run in an out of the way place where they will not get hooked, caught, scraped or chafed. A good idea is to use zip ties every foot or so if you've got multiple wires running together (ie the power and ground wires) and to tie them up to existing structure where they will be out of the way.
All wire ends should be terminated using gold plated spade connectors (if the amplifier accepts them)
and connections should be covered with adhesive lined heat shrink tubing. The less wire that is exposed, the less of a chance of corrosion. Any connection that requires two wires be connected together should be soldered and then covered with adhesive lined heat shrink.
On that note, the type of wire you use is important as well. Many in car audio circles just use welding wire, but there are other options. Oxygen free copper is good, but will still corrode once the wire is exposed. Tinned Oxygen free copper works very well too. Copper clad aluminum is not bad per say, but has less current carrying ability than an equivalent copper conductor, so keep that in mind when you're looking at the prices of this stuff.
I tend to get all of my wire from Knukonceptz.com (a car audio vendor) they have great prices, fair shipping, and good product from my experience.
Settings
Most current amplifiers have a few settings that you will need to make.
Crossovers - Most amplifiers have built in crossovers. Crossovers can be used to protect your speakers from frequencies they can't handle or to filter out frequencies you don't want to hear. Most amps will have 3 settings HPF/FULL/LPF (high pass filter / Full range / Low pass filter). HPF will filter out low frequencies. You use this to protect your full range speakers from possibly damaging low frequency information. full range is simply that, all frequencies are allowed to pass. Low pass will filter out high frequencies. You use this to filter out high freq information from your subwoofers. To put it simple, small speakers can't produce low frequencies at high output. to combat this you use a crossover to filter out the low frequency information and therefore protect your speakers. Look at the published specifications for your speakers to determine the lowest they can safely play, and then use that as a baseline for your crossover setting. A good baseline for 6.5" speakers is 60-80hz. For 6x9 speakers is 30-50hz.
Gain - The most critical setting on any amplifier is the gain setting. There are lots of tutorials and methods for doing this that you can find on the interwebz, but the best way I know of is to do it by ear. This does require that you can identify distortion when you hear it though.
Start by turning the gain on the amplifier turned all the way down (fully to the left) there are different ways that manufacturers mark their gain settings, some use voltage, some use min/max. If it is marked with voltage, note that the larger voltage will be a lower gain setting.
Insert the fuse into the fuse holder and turn on the stereo(keep the volume low right now), check the amplifier's status lights to make sure that it is in fact turning on and operating correctly (RTFM to learn more about this). Once you have verified that everything is hooked up and working, with the gains still set to their lowest setting, raise the volume of the head unit to approximately 2/3. This is basically your rough max setting for the volume. This accomplishes 2 things. 1. it assures that you are not sending a clipped/distorted signal from your source unit to your amp and 2. it allows a little bit of leeway in the volume control for softly recorded tracks.
Now slowly raise the gain on the amplifier until one of two things happens. 1. you hear distortion from your speakers or 2. your ears bleed (ie it's loud enough!)
Bass Boost/Bass EQ/ etc - It's my recommendation to never use these settings as they almost always are used improperly, and WILL result in damage to your speakers.
I think that covers it...
Dave
