Speaker efficiency vs sensitivity

[Vaughan Odendaa]

Hi guys,

So I was having this discussion concerning efficiency and sensitivity and some of the guys were lumping the terms together as if they were exchangeable.

I don't agree that it's simply semantic word play. Efficiency is power out/power in. Sensitivity is power out/voltage in. Now in my mind, power and voltage are certainly not the same thing. Clearly, impedance is a factor.

I was in a discussion with a guy who claimed that the more sensitive the speaker, the more efficient it would be. But again, I don't think that's necessarily true. I mean, if you have two speakers with equal sensitivities of 90dB/2.83V and one has a 4 ohm impedance and the other has an 8 ohm impedance, the latter speaker will have a higher efficiency, since the 2.83V will represent half the number of watts. So clearly you can't lump the two terms together. They don't correlate with one another.

So for the technical guys, is it technically inaccurate to mention sensitivity and efficiency in the same sentence to mean the same thing ? I've given you my understanding, as basic it may be, but I believe the terms are completely different and should be treated as such.

Opinions would be appreciated.

 

[Vaughan Odendaa]

Anyone want to bite ?

 

[j_garcia]

The way I see it, efficiency is typically not used for a speaker as a system. I could see it being used for a single driver, but not a complete speaker. Sensitivity is the measure of the speaker as a whole.

They CANNOT be used interchangeably.

 

[gmichael]

An efficienct speaker is one that does a lot of work with as little force as possible.

A sensitive speaker is one that cries at sad movies.



Techniclly they may be different, but they are pretty much used as the same thing in this industry.

 

[sholling]

An efficienct speaker is one that does a lot of work with as little force as possible.

A sensitive speaker is one that cries at sad movies.



Techniclly they may be different, but they are pretty much used as the same thing in this industry.

+1!

I don't understand the need to play word games or pick at nits when in the end those word games just serve to confuse newbs seeking advice. It may make some feel smarter than their neighbor but it's counter productive.

 

[adwilk]

Unlike this post, where's the relevance?

 

[j_garcia]

They don't mean the same thing. I don't need to know how much force a driver delivers, that information isn't useful. How much it outputs is, and that is measured as sensitivity.

 

[GlocksRock]

Wouldn't it be true to say the more sensitive the speaker is, the more efficient it is?

 

[sholling]

Wouldn't it be true to say the more sensitive the speaker is, the more efficient it is?

That kind of thinking makes the hobby far too accessible to the great unwashed. Instead it's absolutely critical to spend hours agonizing over semantics.

 

[j_garcia]

Wouldn't it be true to say the more sensitive the speaker is, the more efficient it is?

Look at a line source array. They have lots of drivers playing the same thing and thus are very sensitive. That doesn't mean the drivers or the speaker as a whole are efficient.

 

[gmichael]

Look at a line source array. They have lots of drivers playing the same thing and thus are very sensitive. That doesn't mean the drivers or the speaker as a whole are efficient.

If they can turn 1 watt into 98 db at 1 meter, I'd say that's pretty efficient.

 

[j_garcia]

If they can turn 1 watt into 98 db at 1 meter, I'd say that's pretty efficient.

And it is measured as sensitivity

 

[Paul_Apollonio]

Efficiency is not sensitivity (except for a point source)

Hi guys,

So I was having this discussion concerning efficiency and sensitivity and some of the guys were lumping the terms together as if they were exchangeable.

I don't agree that it's simply semantic word play. Efficiency is power out/power in. Sensitivity is power out/voltage in. Now in my mind, power and voltage are certainly not the same thing. Clearly, impedance is a factor.

I was in a discussion with a guy who claimed that the more sensitive the speaker, the more efficient it would be. But again, I don't think that's necessarily true. I mean, if you have two speakers with equal sensitivities of 90dB/2.83V and one has a 4 ohm impedance and the other has an 8 ohm impedance, the latter speaker will have a higher efficiency, since the 2.83V will represent half the number of watts. So clearly you can't lump the two terms together. They don't correlate with one another.

So for the technical guys, is it technically inaccurate to mention sensitivity and efficiency in the same sentence to mean the same thing ? I've given you my understanding, as basic it may be, but I believe the terms are completely different and should be treated as such.

Opinions would be appreciated.

It seems like everyone has an opinion about this. The accepted usage is that efficiency is a measure of power output/power input. (we assume this is constant, but like all speaker parameters, it is not) Efficiency refers to the radiated power, over all angles. Sensitivity is often shorthand for axial sensitivity, which means what the driver or system (either term can apply to either form of speaker) puts out on the central axis, i.e., directly in front. One can take a compression driver, and put the same compression driver on two different horns, The horns have a different directivity index (DI) which is unfortunately sometimes also called (Q) (as if we don't use that letter for enough crap already). One horn might radiate into a 40 by 90 degree arc, which the other horn is a 120 degree by 60 degree horn. That compression driver will have different axial sensitivities on the different horns, but the exact same efficiency. (The difference is how the sound power is spread out). IF we have a speaker which is practically a point source, radiating its sound in every direction equally and simultaneously, then the efficiency can predict the axial sensitivity. If it is directive (which is usually a function of frequency vs source size) then the sensitivity will be higher than the efficiency would predict. This is ONE reason we use horns.

Sincerely, Resident Speaker Guru, and Weeper at sad movies...
Paul Apollonio

 

[mtrycrafts]

... also called (Q) (as if we don't use that letter for enough crap already). ...
Paul Apollonio

Yes, we do. It even made it to a character on one of the Star Trek series

 

[Vaughan Odendaa]

Wow, thanks guys for the discussion. I've been discussing this with an EE on one of the forums and he tells me that if you double the efficiency and you increase sensitivity by 3 dB's and that Sensitivity(dB) = 112 + 10*log(efficiency)

That is a direct relationship without other variables. He doesn't seem to think that there is much of a difference between efficiency and sensitivity because both variables are average values integrated over a frequency band.

I'm no EE. But from discussions with other guys, both terms mean two different things. There is no water tight relationship between the two.

 

[Vaughan Odendaa]

Wouldn't it be true to say the more sensitive the speaker is, the more efficient it is?

I think this might have truth to it assuming two speakers with differing sensitivity levels but with identical impedance curves throughout the range (hardly ever the case). But the moment you alter the impedance you also alter the wattage draw. If you have two speakers both with the same sensitivity of 88dB/2.83V and one has a 4 ohm impedance and the other has an 8 ohm impedance the latter speaker, in my mind, would have a higher efficiency since the 2.83V will represent half the number of watts in that case.

The EE I've been discussing this with, his argument is that sensitivity (dB)=112+10*log as a way of saying that the two are scalable I think and then he goes on to suggest that this is a direct relationship not taking any other variables into account. That, to me, would suggest that the relationship is not scalable, not interchangeable.

Is this correct ? I mean, the guy is an EE, I'm not but then I've heard some EE's give contradictory information in the past.

 

[gmichael]

And it is measured as sensitivity

Very true, but I don't see why anyone would need to take exception to using the word efficient. It may not be the term that is supposed to be used but it sure fits. (Maybe not in EE speak, but in good old Average Joe speak)

 

[Vaughan Odendaa]

It may not be the term that is supposed to be used but it sure fits. (Maybe not in EE speak, but in good old Average Joe speak)

Well according to the EE I've been talking to, the term efficiency can be used instead of sensitivity. The thing I don't agree with is that he tells me that doubling of efficiency equals greater sensitivity (+3 db in fact) but doesn't that assume identical impedance curve in the speaker ? Or is it just a blanket statement ? Two speakers with the same efficiency could have different sensitivities and vice-versa. I mean, if one speaker was 2 dB's more sensitive than another speaker, that doesn't necessarily mean that it's more efficient. It could be slightly less efficient if the nominal impedance is halved (8 ohm to 4 ohm).

As I understand it, efficiency does not scale with sensitivity in a linear fashion right ? Impedance throws a spanner in the works.

 

[gene]

Well according to the EE I've been talking to, the term efficiency can be used instead of sensitivity. The thing I don't agree with is that he tells me that doubling of efficiency equals greater sensitivity (+3 db in fact) but doesn't that assume identical impedance curve in the speaker ? Or is it just a blanket statement ? Two speakers with the same efficiency could have different sensitivities and vice-versa. I mean, if one speaker was 2 dB's more sensitive than another speaker, that doesn't necessarily mean that it's more efficient. It could be slightly less efficient if the nominal impedance is halved (8 ohm to 4 ohm).

As I understand it, efficiency does not scale with sensitivity in a linear fashion right ? Impedance throws a spanner in the works.

I suggest reading Paul's posting above that clearly explains the difference between efficiency and sensitivity. He is an actual loudspeaker driver engineer whom is more well versed than a EE in this field. I am a EE myself and have had no training in transducer engineering in school and only know some of this stuff b/c of the fact I am in this field and running this site relying on people like Paul to educate me.

 

[gmichael]

I suggest reading Paul's posting above that clearly explains the difference between efficiency and sensitivity. He is an actual loudspeaker driver engineer whom is more well versed than a EE in this field. I am a EE myself and have had no training in transducer engineering in school and only know some of this stuff b/c of the fact I am in this field and running this site relying on people like Paul to educate me.

I read it, but about half way though everything got fuzzy and I forgot what I was reading. I understood a little of what he was saying but not enough to be able to,.... well, understand the overall picture.