Amplifiers

In marine audio equipment, amps drive the speakers and subwoofers, and breathe life into the music. They play an important role in the noisy atmosphere of the sea by continuously supplying raw power to the speakers and subs thereby delivering higher volume and clearer sound. That is why a full-range of marine speakers with built-in amps requires an external amplifier.

To install an amplifier, you may have to make necessary provisions in your boat. The amp should be connected to the battery by a thick power cord. A multi-amp system can be setup using the head unit’s preamp outputs using fewer audio cables than otherwise required. If your amp has speaker level inputs, then you can tap into the boat’s existing wiring.

Anti-corrosion

Continuous exposure to sea water, salt, and wind can cause certain metallic audio components to rust or corrode. By treating the vulnerable parts with suitable anti-corrosive substances, you can protect them against the corrosive effects of sea water. Circuit boards coated with acrylics, epoxies, or silicones and tinned wiring exhibit corrosion resistance.

Auxiliary audio input

Receivers may have a jack provided on its front or rear for connecting plug-and-play devices such as satellite radio tuner, MP3 player, CD changer, or other portable players. These auxiliary audio jacks come in two standard specifications: Mini or RCA.

BlueChart maps

BlueChart maps from Garmin are digital marine maps (available on media devices such as data cards or CDs) that can be read like a paper map. They are typically used with Garmin's line of navigation equipment.

Capacitors

Capacitor stores electricity by drawing from the boat’s electrical system and supplies extra power to the amplifier when there is peak demand. When you are playing music, big bass or kick-drum beat demands more power. The capacitor built into the amplifier is sufficient for most peak power demands but external capacitors add extra punch to the amp. For connecting a capacitor to the amp, you may need to run a cable from the power source.

CEA-2006 compliant

CEA-2006 is a voluntary standard published by the Consumer Electronics Association (CEA) that outlines the standard testing and measurement methods to use for mobile audio amplifiers and receivers. CEA-2006-compliant audio amps are marked "Amplifier Power Standard CEA-2006 Compliant" indicating that the amplifier's RMS power and signal-to-noise ratio can be compared on a uniform scale even if they are meant for different vehicles such as a boat or a car.

RMS power is measured in watts at 14.4 volts by creating a 4-ohm impedance load at 1% Total Harmonic Distortion (THD) and noise. For general purpose amps, the frequency range is set between 20 Hz and 20 KHz. For Signal-to-noise ratio measurement a reference of 1 watt into 4 ohms is used (in weighted absolute decibels).

Connectors

You can choose from a bunch of connectors when hooking up a radio or amp to the speakers.

Spade connectors are suitable for binding port terminals and are easy to hitch. You can simply place the spade over the terminal’s threaded post and press the collar down on the spade to tighten the connector. Some electronic components may not support spade connectors.

Pin-type connectors are best suited for small spring clip terminals that connect heavy-gauge cables. They also hitch to binding posts in a slightly different manner than spade connectors. A five-way binding post terminal’s central post has a hole on its back at the base into which this pin fits comfortably. The collar can be pressed down against the central post to tighten.

Banana plugs are designed to be used with binding posts. They fit snugly into the center of the five-way post with a snap.

Crossover

In a complex audio network, crossover plays an uncompromising role by diverting the signals to the high and low frequency drivers. There are two types of crossovers: active and passive. The crossover that connects an in-dash receiver and amp is the active crossover. A passive crossover connects the amp and the speaker or sub. Apart from the cost difference, active and passive crossovers have different energy requirements as well. Passive crossovers are cheaper but wastes lot of power.

Detachable face

The receiver control panel can be easily removed and carried away with you for safekeeping. In addition to helping you tune your favorite music in the boat, the detachable faceplate is also a way to prevent your receiver from being stolen.

DIN

DIN indicates the size of your receiver. Euro DIN, ISO-DIN, and Double DIN are the most common sizes of receivers.

Euro DIN also known as the “E” fit receiver has frontal mounting points that can be slid into a metal or plastic sleeve. This type of receivers has a rectangular chassis (measuring 7” width x 2” height x variable depths).

ISO-DIN size receivers have two types of fit (“I” and “J”) that differ from each other only in the width of their faceplate. Unlike the Euro DIN, these receivers come preconfigured for mounting on the side support system of the receiver location of the boat. Therefore, your boat should have a factory receiver location for mounting these receivers.

Double DIN receivers are suitable for shallow mounting and they have a larger faceplate. Measuring 4” height, these receivers are also deeper and wider and may have both a cassette deck and a CD player.

Fold-down Face

As the name suggests, the fold-down face of the receiver control panel folds down to expose the CD slot. As a result, the receiver face has more space on the control panel to display instructions and controls. Because the CD slot is hidden, it is protected from dust, dirt, and water.

Free-air Rating

A free-air rated subwoofer should be placed in an airtight chamber because it is designed for flat frequency response and free-air use. In addition to producing excellent bass, these subs also save a lot of space.

Frequency Response

Human ear is programmed to hear frequencies in the range of 20 Hz to 20 KHz. The various sounds reproduced by audio systems, known as its frequency response, falls in this frequency range where bass hits the low frequency notes and treble constitute high frequencies. A bass guitar has its lowest note pegged at 41 Hz where as cymbals produce sounds at frequency levels of 15 KHz.

GPS

The U.S. Department of Defense operates a satellite-controlled navigation system called the Global Positioning System (GPS) that can be used to track the location of vehicles. One or more GPS satellites are sending coded signals every second to your boat that is decoded by the boat’s navigation computer to calculate its velocity and geographic coordinates.

Ground Fault Circuit Interrupters

GFCI are circuit breakers in an electrical system that prevents imbalanced flow of power through the circuit that may cause damage to the audio devices or even electrocution. They are designed to cut off power supply when the resistance to the flow of electricity between the grounded and the ungrounded wires falls below predefined levels.

Grounding and grounding plates

For the safety of your boat and its electronic devices, it’s important that the electrical circuit is only ground at a designated location. In a boat, a grounding plate or electrode is provided to take care of the common grounding for all the wires that are a part of the network. Additional grounding electrode in an undesignated place, faulty wiring, or damaged cables may short an electrical device or the circuit. Ground fault can be detected with the help of built-in indicators in power protection devices. You should only consult a licensed electrician to rectify a ground fault in your electrical system.

Magnetic Shielding

Magnetic shielding of a component pays a crucial role in an electronic system where inappropriately placed magnetic devices may interfere with the neighbors’ magnetic field causing disturbance or in extreme cases destruction to the equipment. In a boat, the magnetic fields of the mariner’s compass placed within a feet-and-a-half distance away from an unshielded speaker tend to interfere.

Magnetic shielding is a way of imprisoning the exuberant magnetic field. This can be achieved in many ways: by coating the speaker cabinet’s inner walls with metal, by placing two speaker magnets back-to-back, and so on.

Marine-rating

If you are shopping for audio equipment for your boat, remember to look for marine-grade or marine-rated product. This label indicates that the product is fit for use in the extreme sea weather conditions, including sun, salt, and water. Even the best unrated audio equipment may not last more than a season.

Navigation

Navigation system is your only hope of returning safely after you have reached unchartered territories and are literally “at sea”. Even otherwise, you’ll need the help of the navigation mechanism to guide you after you have set sail. Most modern navigation systems are equipped with a GPS location and tracking system and a self-regulated gyroscope that prevents the boat from veering off course. An electronic connection to the speed sensor assists in providing information about the boat’s velocity and location.

If the navigation system is a separate box, then it’s placed beneath a seat and connected by a special cable to the radio. Portable, multi-functional systems and all-in-one-box systems can be installed on the dashboard for easy access.

Polypropylene

Polypropylene is a form of plastic that is used to make speakers mainly because of its rigidity, internal damping properties, and weather resistance.

Power inverter

Household appliances and entertainment applications require alternating current (AC) for working. The battery in a boat stocks up direct current (DC) that can be tapped by converting to AC current with the help of an inverter. The power inverter transforms the battery power into 115 volt AC household power.

Preamp Outputs

Oftentimes, you may need the services of an external amplifier to perk up your music in the sea. To hook up the extra amp, you can use a standard RCA patch cable that plugs into the jacks provided on the front or rear of a receiver. There may be two or three sets of preamp output jacks of which two sets are reserved for a single 4-channel amp or two 2-channel amps. A subwoofer amp can be plugged into the third set.

Receivers

Receivers are where you insert your CD or another media source or tune the radio to play your favorite music. Their control panel provides an interface for selecting songs from a list, shuffling the songs, tuning a radio station, and other audio configurations. When they are connected to speakers, the receiver diverts audio signals to them for louder sound. Preamp outputs may be provided on the face or rear of receivers to plug an external amp, which perks up the signal up a couple of notches before diverting to the speakers.

RMS power

Amplifier performance is measured in watts using the continuous average power (a.k.a. the root means square (RMS) power) that the amp is capable of producing. When selecting an amp, you must look for higher RMS so that your music is loud and clear.

Satellite Radio

If your receiver can be equipped with a tuner and antenna for receiving satellite audio signals, you can subscribe to the satellite radio broadcast for a fee. Otherwise, you may need to buy a receiver that accommodates a tuner for tapping satellite radio signals and tune into over 130 channels. The receptivity is extended to 200 miles offshore.

Signal-to-Noise ratio

This value indicates by what measure (in decibels (dB)) the audio signal is better off than the background noise in a marine environment. CD and MiniDisc are more effective in drowning the noise at 90 dB when compared to a 70 dB or 80 dB Cassette Player.

Speakers

A music system is unthinkable without speakers. Your music takes on life only when they emerge from the four or six or more speakers you have placed in strategic locations of your boat. An in-dash receiver can power a couple of general purpose speakers and play to your tastes but if you are looking for heart thumping effects, then you must engage external amplifiers to pull it off. If you are not satisfied with the way your music sounds, then your present speakers should make way for new ones.

Submersion

No. These are not your under-water audio system but they can be restored and used in case one or more components drown in the water. But not all marine equipment can withstand submersion. Only waterproof components come protected against submersion, but the depth and duration of submersion vary with the make and brand of the equipment.

Subwoofers

Subwoofers are speakers specially designed for turning on low frequency bass. Subs measure 8” or 12” or more and guzzle more power to reproduce the low frequencies. Except the free-air subs, the others are installed in a specially designed box and hooked to an amplifier for that extra power. Subs with built-in amps are easier to install and use when compared to the ones that require an external amp.

Tinned Wire

Copper wires coated with tin are used in marine applications because they last longer than aluminum and steel wires when faced with the ravages of the sea. Tinned copper wires are more resistant to the corrosive and rusting effects of the sea water.

Universal cover

If you are worried that continuous exposure to the rough sea weather damages your marine grade audio gear, then you should buy a universal cover to add an extra layer of protection to your equipment against wind, water, and sun. You can flip up the transparent cover along its hinges in order to access the receiver’s controls.

UV-Resistant

Like the ozone layer in the atmosphere that protects our skin from the harmful UV rays, marine audio gear also needs protection from the harmful effects of sun rays. Audio equipment rated for protection from ultraviolet (UV) rays does not bleach, crack, or overheat under the intense heat of the sun and due to the constant exposure to sun rays.

WAAS

GPS satellites are continuously orbiting the earth looking for signals of natural disturbances and tracking the various objects on the earth. There are reference stations in the ground that monitor these satellites and create GPS correction messages. Using a network of 25 reference stations spanning the US, Canada, and Mexico, Wide Area Augmentation System creates a GPS correction message with information about the disturbances in the ionosphere and timing and satellite orbit errors. The corrected message is relayed to the GPS system for more accurate positional information. As against a normal GPS’s position accuracy level of 6-12 meters, WAAS-enabled navigation gives you an accuracy of less than 3 meters.

Wakeboard tower

Many sporting boats have a tall crossbar to which the buoyant wakeboard is hitched. This tower can be used to mount speakers and other audio components.

Waterproof

Waterproof equipment withstands water splashing and to some extent submersion. Such equipment is not among a boater’s hot favorites but is good to have. The levels of submersion as indicated by the duration and depths that the equipment can survive under water vary with the marine audio manufacturer.

Water-resistant

Water-resistant marine audio gear is ubiquitous. Water-resistance is in fact a basic feature of marine audio components because they are constantly threatened with water splashing or rain or humidity. Receivers meant for boats have coated circuit boards, faceplates with rubber gaskets, or protected chassis. Plastic and other anti-corrosive materials are preferred in speakers in the place of paper and metal. Similarly the other marine grade components use water-repellant materials for protection.