The Importance of Speaker Watts

Everybody wants a great, high quality sound from their audio system. Usually people want a sound to fill the room and have a deep bass, a clear treble and a rich middle range. The sound quality should not deteriorate when you crank up the volume and you certainly don’t want insane vibrations, static hiss or smoke coming out of the speakers at any point!

Speaker watts are only one figure to think about in your quest for quality. Other important values are the sensitivity of the speakers and total harmonic distortion (THD). If you read through this page you will get a good idea of how to work out what a sound system will deliver just from the manufacturer's specifications.

Loudness in Decibels (dB)

This is a measure of loudness and is important for choosing speakers, especially if you like to listen at high volume. Something to remember about decibels, is that for every 10 decibel rise the noise is twice as loud- so small increases in decibel levels= a big impact on the ear.

Power in Watts (W)

A watt is a measure of electrical power. The output of an amplifier is measured in watts. All loudspeakers have a maximum number of watts that they can cope with and the manufacturer will tell you what this is.

It is important to make sure that your amp does not put out more power than your speakers can handle or they can be damaged.

Usually, the manufacturers give 2 figures for power for both amplifiers and loudspeakers

For Amplifiers

RMS = the power an amplifier can put out over a long period

Peak = the power an amplifier can put out in short bursts.

For Loudspeakers

Nominal power= what a speaker can handle long term without being damaged

Peak power= what a speaker can handle in short bursts without being damaged,

Speaker Sensitivity

Very good speakers are more sensitive than mid-quality speakers and can deliver a lot of sound with only a little power coming from the amplifier. Mid price range speakers need more power to give you the same volume.

Usually speaker sensitivity is expressed in terms of the number of decibels (dB) of sound pressure level (SPL) per 1 Watt of amplifier power measured at 1 meter from the speaker. Usually manufacturers drop the 'SPL/W/M' and just say ‘db’.

Most loudspeakers have sensitivities in the range of 85 to 91 dB.

So a sensitivity of less than 85dB is not so hot.

How Watts translate into Loudness

A pair of reasonably sensitive speakers deliver the following decibel levels at a distance of about one meter.

Power/ Decibels

2 Watts = 93 decibels
4 Watts = 96 decibels
8 Watts = 99 decibels
16 Watts = 102 decibels
32 Watts = 105 decibels
64 Watts = 108 decibels
128 Watts = 111 decibels
256 Watts = 114 decibels
512 Watts= 117 decibels
1024 Watts = 120 decibels

For Comparison

10db = normal human breathing
60db = normal human conversation
110db = power saw, car horn, shouting in ear,
120db = jet aircraft close to, emergency vehicle siren, rock concert

If you like really loud music, you are looking for between 85dBs and 110dBs. Anything louder than this and you will be destroying your hearing. So 120 watts is about the most you should ever need for mid-price speakers in the home.

When you move up the price range and get to the super-efficient speakers then the power needed to get a big volume goes right down.

Total Harmonic Distortion (TDH)

This is a measure of how faithfully speakers translate what is on a disc or hard drive into sound. The lower the figure, the less distortion there is. Usually the values are between 0.05% and 0.08% THD for a quality "clean" system but any figure below 0.1% THD is pretty good.

Speaker Impedance

This tells you how much current a speaker will draw. 8 ohms is standard. 4 ohms is very good and usually a lot more expensive. If you are buying 4 ohms speakers you need a very good amplifier to get the most out of them.

Headroom

This is a measure of what a system can deliver in short bursts. A large headroom figure is important if you have a home cinema system and want to get a jolt from the explosions in action movies.

Buying Loudspeakers online

Amazon and EBay are great places to buy audio equipment at a good price but they often fail to give all the stats you need to make an informed choice. The best way round this is to find something that looks about right at one of these sites then check out the details on any of the many hi fi review sites.