How do I choose the right amplifier for my speakers?
To choose the right amplifier, mainly consider the speakers’ power handling, the total impedance (ohms) per channel and how many speakers you want to connect. Confirm the models, speaker quantity and wiring before choosing an amplifier.
A correctly sized amplifier helps the speakers deliver high sound quality and sufficient power without unnecessary distortion.
1. Check the speakers’ RMS power rating
RMS power indicates how much continuous power an amplifier can deliver or how much power a speaker is designed to handle.
For example, if your speakers have a stated power handling of 100 W RMS, an amplifier delivering around 100 W RMS per channel at the correct impedance may be suitable.
An amplifier with higher RMS power than the speakers’ stated power handling is not necessarily a problem, but places greater demands on correct settings.
Do not compare only MAX or Peak power, as these figures do not give the same information about continuous power.
2. Check impedance (ohms)
Impedance describes the speaker’s electrical load and is measured in ohms (Ω).
Common car speaker impedances are 2 and 4 ohms, while subwoofers are also available with other impedances and dual voice coils.
The amplifier must be designed to handle the impedance presented by the speakers.
If several speakers share a channel, the wiring affects both impedance and power per speaker. Two identical 4-ohm speakers in parallel give a total of 2 ohms. If the channel delivers 1,000 W RMS at 2 ohms, they share the power: approximately 500 W each, not 1,000 W each. To target 1,000 W per speaker, the channel must be able to deliver a total of 2,000 W at 2 ohms.
Check the model’s RMS output at the actual load, permitted impedance and usable frequency range in the product information or manual. Do not convert a 1-ohm power figure to 2 or 4 ohms without verified specifications. If information is missing, obtain confirmation before promising a particular output.
Excessively low impedance can overload the amplifier and cause overheating, protection mode or damage.
3. Choose the correct number of channels
The number of channels determines how many speakers or speaker groups you can drive individually.
Monoblock: Usually for one or more subwoofers.
Two-channel amplifier: Suitable, for example, for a pair of coaxial speakers or a component system with passive crossovers.
Four-channel amplifier: Suitable, for example, for front and rear speakers, or front speakers together with a bridged subwoofer.
Multichannel amplifier: Suitable for larger systems with several speakers and possibly a subwoofer.
If you plan to expand the system later, choosing more channels than you currently need may be sensible.
4. Check crossover filters and adjustment options
Many amplifiers have built-in crossovers that let you adjust the frequencies the speakers reproduce.
For example, a high-pass filter (HPF) often limits the lowest frequencies sent to standard car speakers, while a low-pass filter (LPF) is used for subwoofers.
For more advanced systems, an amplifier with a built-in DSP or a separate audio processor can provide additional adjustment options.
5. Ensure a suitable power supply
An amplifier needs sufficient current to deliver its stated output.
Use correctly sized power cables, a suitable fuse and a proper ground connection. We recommend 100% copper (OFC) cables for good conductivity.
More powerful installations may also require reviewing the car’s battery, alternator and other electrical systems.
Does the amplifier need the same RMS rating as the speakers?
No. A speaker’s RMS rating is its power handling under specified conditions, not a requirement for constant power. The amplifier’s rating describes possible output, not how many watts the speaker automatically receives.
A more powerful amplifier can provide headroom, but, for example, 5,000 W into two identical speakers does not automatically mean 1,000 W to each. Signal level, gain, filters and any limiter must suit the speakers’ limits; ask a knowledgeable installer for help if unsure.
The most important thing is compatibility with speaker impedance and correct adjustment of gain, crossovers and other settings.
An amplifier rated below the speakers’ stated power handling can also work well, but if pushed too hard it may clip and cause severe distortion.
Unsure which amplifier you need?
Contact our customer service team or visit one of our stores. Tell us which speakers you have, their impedance and RMS rating, and which car stereo you use, so we can help find a suitable amplifier.