How Many Watts Do I Need For My Speakers?

Question from the title is one of the most common ones that any sound consumer will, sooner or later, ask. Whether you are a hormone-driven teenager, an audiophile with hypersensitive eardrums, or just an average Joe, you will crave to get the maximum pleasure out of your sound system.

So, what do the Watts do for You in that respect?

Watts represent an amplifier’s power output and the maximum power your speakers can handle without breaking or distorting the sound. You can’t just hook up a 100W speaker to a 300W amplifier and turn the volume all the way up. You will end up distorting the sound and eventually destroying the speakers.

The main features of every speaker are speaker sensitivity and power handling. The first one relates to the speaker‘s sound pressure or volume after imputing 1 Watt of power at a distance of 1 meter. The other refers to the speaker‘s ability to handle the wattage.

Speaker sensitivity

This feature shows the sound pressure level in decibels (dB), and it is vital in figuring out how much power you will need to get to optimum sound volume. This feature is also known as SPL. The most common speaker sensitivity is anywhere between 80 -100 dB. That is the amount of sound pressure or how loud the sound will be after imputing 1 Watt of power, measured from a distance of 1m. 

More sensitive speakers require less power to reach the same volume level. This influence of sensitivity to the power requirements becomes more apparent when you know that, for every 3dB increase in SPL, you need to double the input power. For example, if your speakers have a sensitivity of 80 dB, that means 2W of power will give you 83 dB. 4W will produce 86 dB, 8W equals 89 dB, and so on. To reach 101 dB of volume, you will need the input of 128 W, which is a pretty hefty amount of power. On the other hand, if you get very sensitive speakers with, let’s say, a rating of 100 dB, you will get 103 dB with only 2W of power.

Power handling

When you are shopping for the speakers, you will regularly find Watts, either expressed as RMS values or PEAK values.

RMS stands for Root Mean Square and represents the amount of power a speaker can handle continuously.

PEAK stands for the highest possible power a speaker can handle for a short time.

When buying and comparing speakers, you should always pay more attention to the RMS number because it says how much power that speaker can regularly handle. Most manufacturers and their marketing departments will confuse you by flashing PEAK, MAX, or dynamic power rating. This number can be a few times bigger than the RMS, but keep in mind that this is the max power that the speaker can handle, and it can do it only for a very short time.

Some manufacturers, like Klipsch, will publish both power values – RMS and PEAK (Klipsch RP-280F specs)

How loud should your speakers be?

The answer to this question is very subjective because we all have different perceptions of sound and distinct thresholds. Still, anything above 85 dB is considered loud. Here are some known sound levels for comparison:

At this point, you need to figure out how and where you will use your speakers. If you plan to install them indoors, then you should be just fine with levels up to 105 dB to fully enjoy those loud sound effects. On the other hand, if you plan to cover bigger, open-space areas with some crowd, you will need a rock concert kind of loudness (120+ dB).

This difference in max required volume is because it drops over distance. For every meter of the distance, you will lose 6 dB of SPL. So, it is something you need to take into account as well.

How will all those watts, dBs, and distance work in practice?

Let’s say you have a room 15x20ft and you want to put your speakers on the narrow side to cover the whole room.

That means you will need speakers that can reach 105 dB at full volume. Now, let’s take three speakers with different SPL and PEAK power ratings as an example.

1. Speaker with SPL 80 dB, RMS 16W, and PEAK of 60W

This speaker will peak around 98 dB, but you will regularly get not more than 92 dB at a distance of 1m. That means you will have 68 dB at the end of the room for most of the time (3 dB for every doubling of power – 6 dB for every meter of extra distance)

 2. Speaker with SPL 90 dB, RMS 16W, and PEAK 60W

This speaker will regularly produce 102 dB and around 108 dB at PEAKS. Subtract 6 dB for every meter of the room, and you will get 72 dB at the end of the room or 78 dB at peaks.

 3. Speaker with SPL 100 dB, RMS 16W, and PEAK 60W

Much greater sensitivity means you will get a significantly louder sound for the same wattage. In this case, 112 dB regularly or 118 dB on peaks. At the end of the room, that would go down to 82 dB and 88 dB at peaks.

In this example, only speaker number 3 would give you close to optimal peak volume at the room’s center.

Conclusion

The answer to how many watts you need depends on the space you need to cover, on the speaker‘s sensitivity, and power handling. 

Hopefully, this text provided you with all the necessary information required to make an accurate estimate of what you need and how to find the best speakers and best amp for your needs.

If possible, before buying any specific speakers, we recommend trying them in the store. 

Looking up the reviews is also a good alternative if you are shopping online. An impression of sound quality is very subjective, and experience may vary depending on your preferences.