Speaker Efficiency or Reference Efficiency, is a calculated parameter in percent that uses the electro-mechanical parameters of a speaker that include the resonance frequency (Fs), the speaker’s electrical damping (Qes) and the equivalent volume compliance (Vas).
The relationship that I have found is that if the resonance frequency (Fs) or the equivalent volume compliance (Vas) was to increase, the Reference Efficiency will increase.
The odd one is the speaker’s electrical damping (Qes), so if this parameter was to increase, the Reference Efficiency will decrease.
The Reference Efficiency numbers will be in a range of 1 to 4 %.
This is why I have seen many times that it has been recommended that the Qes parameter should be 0.40 or less when selecting a speaker.
Trying to provide some relationship with four variables will require that two of these be constants.
I have chosen for the Reference Efficiency to be 3.00 +.02 and the Qes parameter to be .40.
This will allow for me to plot the resonance frequency (Fs) and the equivalent volume compliance (Vas).
The relationship shows that a decrease in the equivalent volume compliance (Vas) will require an increase in resonance frequency (Fs) to maintain the Reference Efficiency of 3.0.
Something I have seen recently, is the parameter SPLO that I have never seen before. I cannot get a straight answer from anyone because they do not know, and all I get is bullshit. These same people is trying to tell me that the sensitivity parameter is the efficiency of the speaker and this is another bullshit statement.
First, the only thing that I found is that this is a SPLO measurement is specific to subwoofers with a measurement in the range with the application (40 to 250 Hz). This parameter is sometimes larger than the sensitivity and can be deceiving. This is because averaged test output for sensitivity is from 500 Hz to 2.5 kHz vs the focus on subwoofers low frequency.
Now the important thing, is to understand the differences between sensitivity and efficiency, and how these are derived.
Sensitivity, sound pressure in dB, is a physical measurement of the on-axis output, using the reference of 1 watt of pink noise in the range of the resonance frequency (Fs) times 10 with a Crest Factor of 6 dB applied and measuring the average sound pressure level at 1 meter. This parameter may not relate to the low-frequency efficiency level of a speaker.
η0 or Efficiency, is referred to as the Reference Efficiency and specified in percent. Comparing drivers by the calculated reference efficiency is more useful than the sensitivity parameter. This reference efficiency, is a calculated function of the electro-mechanical parameters of the loudspeaker and represents the low frequency output range of 300 to 400 Hz range for 12 to 18 inch speaker drivers that directly correlates with the efficiency ratings.
This efficiency calculation used the electro-mechanical parameters that include the resonance frequency (Fs), the speaker’s electrical damping (Qes) and the equivalent volume compliance (Vas).
What are the effects of the parameters associated with port sizing and the tuning of a ported speaker cabinet? I was using an app on my tablet and thought I would improve on my understanding of these parameters.
Speaker Cabinet Port Parameters Relationship
For explanation, the first port length effect is saying that a decrease in cabinet volume, a decrease in tuning frequency, a increase in port diameter or increase in the number of ports will effect the port length by increasing length requirements of that port.
As I found some online calculations that can be used for design or to double check yourself as I do from time to time.
Great online calculations for Speaker Design that I recommend.