Speaker designer Colin Whatmough explains how to pair your speakers with an amplifier.

The usual approach to buying an audio system is to first choose your speakers, which must fit your budget and lifestyle.

However, you must love their sound quality.

Of all audio components, your speakers will have the most influence on your system. For this reason, when buying a new system you should decide on the speakers first.

Once they have been chosen, you need to decide on the amplifier that best suits the speakers. Not the other way around. This is where the fun begins.

Specifications rarely give much indication of an amplifier’s sound quality. Most modern high-quality amplifiers have very low distortion figures and a very flat frequency response, yet they can still sound different from one another.

You need to listen to several different amplifiers driving your chosen speakers.

To save yourself some time, find a good audio dealer who has spent a lot of time listening to amp/speaker combinations and can make recommendations based on experience.

The most obvious amplifier specification to look at is power. The power you need will depend on the sensitivity of your chosen speakers and how loud you want your music.

The standard way of describing speaker sensitivity is the speaker’s volume in decibels (dB) at a distance of one metre, when driven with 2.83V which gives 1W into an 8Ω speaker.

Speakers with sensitivity less than 86dB are considered to have low sensitivity; 86¬-90dB medium sensitivity; 91-96dB high sensitivity; and above 96dB very high sensitivity.

Most high-quality speakers these days have medium sensitivity. This usually needs 70-100W RMS (continual power) to operate properly, but people who listen at fairly low volume may be quite happy with 35-50W.

Conversely, those who want very high volumes may need 200W or more, provided the speakers can handle that much power.

To increase the volume by just 3dB requires double the amplifier power. To increase the volume by 10dB, which is twice as loud, requires 10 times the amplifier power.

From this you can see that those who like to play at very high volumes using medium-sensitivity speakers will need many hundreds of watts.

Having established how much power is needed to drive your speakers at the volumes you want, the next consideration is sound quality.

For this you need to listen to various combinations. Again a knowledgeable dealer can save you a great deal of time by pointing you in the right direction to suit your musical tastes.

The decision may come down to a choice between a lovely sounding amplifier that does not quite have the power you need and a powerful amplifier that doesn’t sound particularly refined.

I would choose the more refined sounding amplifier and keep the volume down.

My advice is to listen to amplifier/speaker combinations and buy the one that appeals most. Choosing a speaker from one dealer and an amplifier from another and presuming they will work well together is fraught with risk.