How to determine power needed for speakers?

Whether you go for an amplifier or not, it’s worth understanding the basics of power handling of the speakers and power output of an amplifier. Speakers that you buy will have both RMS and Peak power ratings. These are actually the power handling capacities of the speakers in two different conditions.

RMS Power Rating: The RMS (Root Mean Square) or the ‘nominal’ or ‘continuous’ power rating tells the amount of power that can be applied to the speakers under normal conditions. This power handling capacity is mainly determined by the speaker’s voice coil & the thermal cooling. Speakers that can handle more power will have larger voice coil and better heat dissipation characteristics. In all, the RMS power handling determines the power handling of the speaker for long duration. Hence, we always consider this rating to match the amplifier. For example: If your speakers are rated to handle 75 watts RMS each, then select an amplifier that will deliver approximately 75 watts RMS to each speaker.

Peak Power Rating: The Peak or Maximum power rating tells the amount of power that can be applied for very short time periods without causing the damage to the speakers. This rating is also known as ‘momentary’ power handling and is used by the manufacturers mainly to glorify the speaker’s capacity. If you run your speakers at this power level for long duration, there are chances of smokes coming out of the speakers. For example: If your speakers are rated to handle 100 Watts Max each, and you select an amplifier that will deliver 100 watts RMS per speaker, you will likely apply too much power for the speaker to handle. This can cause a voice coil to literally "burn"!

Now, the question that frequently comes up is: What’s the harm in using an amplifier of very lesser RMS power to power a speaker? And What if I don’t use the amplifier at all?

The answer is: Absolutely no harm!

But, we need to understand few other things. When you go for a powerful speaker, it is usually with a high SPL (Sound Pressure Level) or simply “loudness” in mind. The optimal SPL is guaranteed, only when you sufficiently power the speaker. So, though under powering a speaker doesn’t cause any damage, it doesn’t meet your expectations.

In case of a speaker driven directly from the head unit (No external amplifier), your speakers are not sufficiently powered. Remember that, your head unit can output the RMS power in the range of 17Watts-22Watts. Hence we recommend the speakers to be sufficiently powered with external amplifiers.

With our experience, we have noticed that sufficiently powered speakers will deliver very detailed sound and optimal SPL. And we recommend you to power your speakers to at least 50% of its RMS power handling capacity for a better sound and loudness. For example: : If your speakers are rated to handle 100 watts RMS each, then select an amplifier that will deliver approximately 50 watts – 100 watts RMS to each speaker.