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sensitivity question

A few questions regarding sensitivity.
a speaker with 90db sensitivity means roughly that it will deliver 90db at one meter distance at 1W right?
But if I’m not wrong most speakers are emitting more sound towards the drivers direction. In some way they resemble a light bulb+projector which emits light toward one specific direction. Obviously with speakers the "projector" effect is not as pronounced as with a lighting projector however the sound is mainly emitted toward one specific direction. With light bulbs which have a projector, in order to describe correctly the emitted luminous flux, you have to add the light cone degrees. In fact a spot light which opens one degree and consumes one watt delivers at one meter more lux as a light bulb of 100W at one meter which opens 180 degrees.
Wen measuring the sensitivity of a speaker do they measure only the db at one meter from the front of the speakers or do they make 8 or more measurements at 1 meter around the speaker and calculate then the medium sensitivity? If not is the actual sensitivity measurement not strongly lacking in accuracy? And in a audiophile world which has measurements in such a high regard is that lack in accuracy not wired? Thanks for any info!
daros71
erik_squires
15,675 posts
 
A few questions regarding sensitivity.
a speaker with 90db sensitivity means roughly that it will deliver 90db at one meter distance at 1W right?


You are almost correct. :)  Sensitivity is output vs. 2.83 V, regardless of Wattage.   If your speaker is exactly 8 Ohms then 2.83V would correspond to 1 W.

You are correct that this measurement is from the front of the speaker.  This measure is somewhat subjective as you must eyeball around 1 kHz.

The dispersion of a speaker is a complicated thing, and even within the same loudspeaker it varies greatly from driver to driver and depending on crossover design.  If you are truly curious I suggest you look at the Stereophile speaker measurements for the off-axis measurements.

I think you are asking for sensitivity to do much more than it is intended.  It's basic function is to explain how loud it will be vs. a reference input.  What you seem to be trying to do is use this 1 number to explain the 3D soundfield produced by a speaker.  No, it is not weird.  Sensitivity and efficiency each do what they are intended to do.

If you want to understand the off axis response of a speaker you'll need different measurments, such as what Stereophile provides, and if you want to now how it will perform in your room, well that's something else entirely.
daros71 OP
117 posts
 
Thanks for the exlpaination! This means that lighting fixtures are measured more accurately as speakers? Funny. Now i start to understand from where all this subjectivity cult in the audiophile world comes from.
russ69's avatar
russ69
3,360 posts
 
You can make polar plots of a loudspeaker's output but output generally is measured on axis. To get total output is a complex math and measurement problem but since that is not the industry standard, it isn't used.  
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