Understanding Speaker Sensitivity and Efficiency
Speaker sensitivity (also known as speaker efficiency) can be an important factor when you are looking to buy a new set of speakers.
It is something that can be useful to be aware of when choosing some speakers.
However, in this article we will look at the importance of speaker sensitivity, and why this may be something that is useful to understand.
What Is Speaker Sensitivity?
To put it simply, the speaker sensitivity rating tells you how much power a speaker converts into sound.
An amplifier sends power to the speaker, and in an ideal world all of this power will be used to create the sound that you hear.
However, in reality, most of this power will be wasted and turned into heat by the speaker - and the more power that is wasted means less volume coming from the speaker.
How Is Speaker Sensitivity Measured?
There is a simple way to measure the sensitivity of a speaker.
The standard method is to place a microphone 1 meter in front of the speaker.
This microphone is connected to a sound level meter and this can accurately measure the exact level of noise coming out of the speaker.
The speaker is then sent 1 watt of power, and the sound level that comes out of the speaker is measured (in decibels or dB) - and this measurement gives us the sensitivity of the speaker.
A speaker that is less efficient, or sensitive, will waste more of the 1 watt of power and will therefore create less noise - however a more efficient speaker will turn more of that power into sound and so we will get a higher sensitivity reading.
The specifications you see may say the loudspeaker sensitivity was measured using 2.83 volts at a distance of 1 meter. 2.83 volts is 1 watt of power into an 8 ohm impedance.
Why Is Speaker Efficiency Important?
The whole point of having a good amplifier/speaker system is so we can hear the best sound possible and make the best use of the technology we have.
There's not much point in spending a lot of money on a great amplifier/receiver, if much of the power it sends to the speakers is turned into heat rather than sound (although all speakers will waste most of the power they receive - so this is a relative thing).
However, a more efficient set of speakers will help us get the best out of the amplifier.
More efficient speakers will sound louder as they are able to use more of the power they receive to create sound.
What Do The Numbers Mean?
As we have already said, a less efficient speaker will create less noise, so the lower the dB level then the lower the sensitivity.
Speaker sensitivity for home audio speakers can range from about 84 dB up to about 100 dB.
Therefore, 84 dB speakers are less efficient and require more power to get the same volume as more efficient 95 dB speakers.
Although the numbers don't appear to be very different, the logarithmic nature of decibels actually means that the difference is larger than it may appear.
A 3 dB difference in speaker sensitivity can make quite a difference.
Changing your speakers from 87 dB efficiency to 90 dB will result in an increase in volume that is the equivalent of doubling the power from your amplifier (although that is not the same as being twice as loud, 10 dB is about twice as loud).
Do I Need More Efficient Speakers?
As with all technology, you get what you pay for.
More efficient speakers will generally be more expensive to buy than less efficient ones as they will cost more to manufacture and design - and so your decision may come down to what you can afford to buy - but in general the more efficient the better.
Also bear in mind that the size of speakers will affect the sensitivity, as it is difficult to get small speakers to a similar level of sensitivity as larger speakers - so bookshelf speakers can be expected to be less efficient than floorstanding speakers (go here for more information on speaker sizes).
If you are getting enough volume in your room from your present system then there is little reason to change.
However, if you have a low-powered amplifier which is struggling to deliver the performance you want, then using high sensitivity speakers will enable you to get more volume from it.
So while it may seem obvious that if you want more volume from your system then you will need to buy a more powerful amplifier - maybe all you need to do is get more efficient speakers if you are happy with the sound quality of your amplifier.
Speaker Sensitivity Summary
Hopefully this article will have made it clear why it can be useful to know about speaker sensitivity.
While it is not something that will generally be your main concern when you are buying a new set of speakers - it is a speaker specification which you should bear in mind when you are deciding which speakers are right for your system.
The bottom line is that more efficient speakers should allow you to get more from your amplifier - so try to buy speakers that are as efficient as you can afford.
However, it may not be worth spending a large amount extra just to get more efficient speakers - you can always just turn the volume up on your amplifier (if you have enough power to spare) - and just because they are more efficient, it doesn't mean they sound better!
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