How to Choose an Amplifier
Features, Channels, and Power Output for Your Car Audio System
Amplifiers are a key part of car audio sound performance. Here are some guidelines to help you choose the right model and features for your vehicle.
Amplifiers are a key part of car audio sound performance. Here are some guidelines to help you choose the right model and features for your vehicle.
Why Add an Amplifier?
Adding an amplifier is essential to experience great sound from your car audio system. An amp adds the wattage (or power) to your audio system that a receiver lacks, leaving your speakers underpowered. An amplifier delivers clean power that drives your speakers and is designed to bring out the best sound from them.
How Much Power Do I Need?
The amount of wattage needed depends on the following factors:
• Electrical Capability of the Vehicle – Make sure the vehicle battery and alternator are in good working condition. The power wiring for an amplifier connects to the battery, but the alternator powers the electrical system and is responsible for charging the battery. Thus, it is important that all elements are working properly. • Speaker Power Handling - Speakers also guide amplifier power needs. Match the amplifier’s per channel RMS power output to the per speaker RMS power handling as closely as possible (+/- 25% per channel RMS power). This ensures the speakers receive the necessary wattage to perform as intended.
o Example: - If an individual speaker’s power handling is 100 watts RMS, choose an amplifier with between 75 and 125 watts RMS per channel to power the speakers.
• Ohm Load at the Amplifier Speaker loads represent the voice coil(s) and are measured in ohms. The rating for a voice coil is called the nominal impedance. There are different nominal impedance values of voice coils (example: single 2 ohm, single 4 ohm, single 8 ohm, dual 2 ohm, and dual 4 ohm ). This nominal impedance is representative of the ‘load’ that the speaker places on the amplifier to do the work of moving the speaker(s) to replicate audio signals. Regardless of amplifier power, 4-ohm or 2-ohm speaker nominal impedance loads (measured at the amplifier terminals) are recommended. Very low impedance loads (below 2 ohms) heat up the amplifier faster and, over time, compromise reliability of the audio or electrical system. Very high loads (over 8 ohms) limit the amplifier from delivering usable power to the speakers.
How Much Power Do I Need?
The amount of wattage needed depends on the following factors:
• Electrical Capability of the Vehicle – Make sure the vehicle battery and alternator are in good working condition. The power wiring for an amplifier connects to the battery, but the alternator powers the electrical system and is responsible for charging the battery. Thus, it is important that all elements are working properly. • Speaker Power Handling - Speakers also guide amplifier power needs. Match the amplifier’s per channel RMS power output to the per speaker RMS power handling as closely as possible (+/- 25% per channel RMS power). This ensures the speakers receive the necessary wattage to perform as intended.
o Example: - If an individual speaker’s power handling is 100 watts RMS, choose an amplifier with between 75 and 125 watts RMS per channel to power the speakers.
• Ohm Load at the Amplifier Speaker loads represent the voice coil(s) and are measured in ohms. The rating for a voice coil is called the nominal impedance. There are different nominal impedance values of voice coils (example: single 2 ohm, single 4 ohm, single 8 ohm, dual 2 ohm, and dual 4 ohm ). This nominal impedance is representative of the ‘load’ that the speaker places on the amplifier to do the work of moving the speaker(s) to replicate audio signals. Regardless of amplifier power, 4-ohm or 2-ohm speaker nominal impedance loads (measured at the amplifier terminals) are recommended. Very low impedance loads (below 2 ohms) heat up the amplifier faster and, over time, compromise reliability of the audio or electrical system. Very high loads (over 8 ohms) limit the amplifier from delivering usable power to the speakers.
How Many Channels?
Channels refer to the number of audio outputs an amplifier supports. One positive and one negative speaker terminal output constitutes a channel. Car audio amplifiers come in several configurations of channels:
• Mono Amps - Mono amplifiers have one channel of output power and are intended for subwoofers. A mono output makes sense for a subwoofer amplifier because bass below 100Hz acts as a mono signal in the small space of a car.
• 2-Channel Amps – Dual or 2-channel amplifiers are stereo channels (one left, one right). Although 2-channel amplifiers are usually called ‘stereo’ amplifiers, the channels can be used in other ways as long as the outputs match the inputs.
o Example - Two separate 2-channel amplifiers can power ‘left channel only’ and ‘right channel only’ component separates. Channel 1 on each amplifier connects to a midrange, channel 2 to a tweeter. By separating the left and right sides into separate amplifiers, the stereo separation is maximized and can utilize active crossovers before the amplifier.
• Multi-Channel Amps - Multi-channel amplifiers have 3, 4, 5 and sometimes 6 channels in a single chassis. This configuration makes it convenient to power an entire audio system from a single amplifier. Many multi-channel amplifiers have staggered power that provides more power on one or more channels. This allows the amp to drive a subwoofer (higher power needs) and component speakers from the same amplifier, but on separate channels.
• Mono Amps - Mono amplifiers have one channel of output power and are intended for subwoofers. A mono output makes sense for a subwoofer amplifier because bass below 100Hz acts as a mono signal in the small space of a car.
• 2-Channel Amps – Dual or 2-channel amplifiers are stereo channels (one left, one right). Although 2-channel amplifiers are usually called ‘stereo’ amplifiers, the channels can be used in other ways as long as the outputs match the inputs.
o Example - Two separate 2-channel amplifiers can power ‘left channel only’ and ‘right channel only’ component separates. Channel 1 on each amplifier connects to a midrange, channel 2 to a tweeter. By separating the left and right sides into separate amplifiers, the stereo separation is maximized and can utilize active crossovers before the amplifier.
• Multi-Channel Amps - Multi-channel amplifiers have 3, 4, 5 and sometimes 6 channels in a single chassis. This configuration makes it convenient to power an entire audio system from a single amplifier. Many multi-channel amplifiers have staggered power that provides more power on one or more channels. This allows the amp to drive a subwoofer (higher power needs) and component speakers from the same amplifier, but on separate channels.
Number of Channels versus Number of Speakers
The speaker(s) connected to a channel depend on the system design and the equipment configuration.
• Example 1 – A mono amplifier with a single output channel can drive multiple subwoofers as long as the group of speakers is wired in a series or parallel combination to a safe load on the amplifier, typically 2, 4 or 8 ohms when measured at the amplifier output terminals.
• Example 2 - A 2-channel amplifier powering component speakers with a midrange in the front door and a tweeter in the windshield pillar panel separated by a passive crossover would mean four total speakers on a 2-channel amplifier. The passive crossover separating the frequencies allows the 2-channel amplifier to drive the component set in this configuration. One channel is the left side; one channel is the right side.
• Example 1 – A mono amplifier with a single output channel can drive multiple subwoofers as long as the group of speakers is wired in a series or parallel combination to a safe load on the amplifier, typically 2, 4 or 8 ohms when measured at the amplifier output terminals.
• Example 2 - A 2-channel amplifier powering component speakers with a midrange in the front door and a tweeter in the windshield pillar panel separated by a passive crossover would mean four total speakers on a 2-channel amplifier. The passive crossover separating the frequencies allows the 2-channel amplifier to drive the component set in this configuration. One channel is the left side; one channel is the right side.
Bridging Channels
Amplifier bridging combines pairs of channels into a single, more powerful output channel. This increases amplifier flexibility, for instance bridging channels to power a subwoofer. The amount of power increase is at least double the single channel rating, but can be up to four times the single channel rated power at the same load.
• Example - A 2-channel amplifier can deliver 100 watts per channel into 4 ohms for a total of 200 watts. When it is bridged, the power output on the single bridged channel becomes 400 watts into 4 ohms.
• Bridging Considerations - To accommodate the added current capacity when bridging, choose adequate power and ground wire for the amplifier. Also select a mounting location that allows adequate cooling from the added power output.
• Example - A 2-channel amplifier can deliver 100 watts per channel into 4 ohms for a total of 200 watts. When it is bridged, the power output on the single bridged channel becomes 400 watts into 4 ohms.
• Bridging Considerations - To accommodate the added current capacity when bridging, choose adequate power and ground wire for the amplifier. Also select a mounting location that allows adequate cooling from the added power output.
Amplifier Classes
Amplifiers are classified by letters (also called ‘topology’). The main differences are efficiency, size and cost.
• Class A – Class A amplifiers are rarely used in car audio because of high current draw. Class A is roughly 25% efficient, meaning for every 100 watts of electrical power consumed, it provides only 25 watts of output power to the speakers.
• Class A/B - Class A/B amps are 50-60% efficient. These amps use less power and are smaller and less expensive than Class A designs. Advanced Class A/B designs use faster Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) output devices instead of bipolar transistors. Most car audio amplifiers use Class A/B amps because of the efficient, proven design.
• Class D - Class D is a switching amplifier popular for subwoofer use. The advantage is greater efficiency and a smaller amplifier size for a given output power when compared to Class A/B. Class D designs are 70-75% efficient.
• Class G/H - Class G/H designs are 75-80% efficient and use multiple output voltage levels for greater efficiency. At low volume levels, the amplifier remains at the lower voltage. When output increases, the second (higher) voltage level takes over, and at the highest outputs all voltages combine for maximum output. This allows a small amplifier size and relatively high power output when compared with Class A/B designs.
• Class T (Tripath) - This is an integrated circuit (IC) chip design (not a switching power supply amplifier like the others in this section). Tripath – the company whom originally developed this ‘Class D’ like integrated circuit – is where the term Class T originates. Class T integrated circuit chips are used in small devices like iPod docks, computer speakers or portable electronics with an internal speaker. Although they have been used in the past, Class T based ICs are seldom used in car audio products today.
• Class A – Class A amplifiers are rarely used in car audio because of high current draw. Class A is roughly 25% efficient, meaning for every 100 watts of electrical power consumed, it provides only 25 watts of output power to the speakers.
• Class A/B - Class A/B amps are 50-60% efficient. These amps use less power and are smaller and less expensive than Class A designs. Advanced Class A/B designs use faster Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) output devices instead of bipolar transistors. Most car audio amplifiers use Class A/B amps because of the efficient, proven design.
• Class D - Class D is a switching amplifier popular for subwoofer use. The advantage is greater efficiency and a smaller amplifier size for a given output power when compared to Class A/B. Class D designs are 70-75% efficient.
• Class G/H - Class G/H designs are 75-80% efficient and use multiple output voltage levels for greater efficiency. At low volume levels, the amplifier remains at the lower voltage. When output increases, the second (higher) voltage level takes over, and at the highest outputs all voltages combine for maximum output. This allows a small amplifier size and relatively high power output when compared with Class A/B designs.
• Class T (Tripath) - This is an integrated circuit (IC) chip design (not a switching power supply amplifier like the others in this section). Tripath – the company whom originally developed this ‘Class D’ like integrated circuit – is where the term Class T originates. Class T integrated circuit chips are used in small devices like iPod docks, computer speakers or portable electronics with an internal speaker. Although they have been used in the past, Class T based ICs are seldom used in car audio products today.
When to Consider Professional Installation
Vehicles are complex machines. Before attempting any DIY installation, assess your comfort level with the installation of electronics and mechanics of your vehicle.
Consider a professional installer if:
1. You are not comfortable disassembling vehicle interior panels.
2. You do not have a suitable work area available.
3. You do not have the recommended tools for the job.
4. You do not have the necessary installation accessories specific to your vehicle year/make/model.
Many independent retail installation shops welcome jobs with products purchased on Amazon.com. Professional installers can also provide many of the installation accessories you need for jobs that are covered in this guide. Always look for a Mobile Electronics Certified Professional (MECP) installation technician to handle your most challenging installation needs.
Want to purchase installation now? Find an InstallerNet card on Amazon.com that corresponds to your job type.
Consider a professional installer if:
1. You are not comfortable disassembling vehicle interior panels.
2. You do not have a suitable work area available.
3. You do not have the recommended tools for the job.
4. You do not have the necessary installation accessories specific to your vehicle year/make/model.
Many independent retail installation shops welcome jobs with products purchased on Amazon.com. Professional installers can also provide many of the installation accessories you need for jobs that are covered in this guide. Always look for a Mobile Electronics Certified Professional (MECP) installation technician to handle your most challenging installation needs.
Want to purchase installation now? Find an InstallerNet card on Amazon.com that corresponds to your job type.
THANKS: amazon.com