Now I understand why you insist on your definition of "the Sound power". Acoustic/Sound power has a strict physical and mathematical definition and it is described as [1]
Definitions in some textbooks:
Since we are able to choose any surface for the pressure integration, a spherical one is most convenient. For axisymmetric sources acoustic power curve can be calculated using equations in the picture below.
In turn, you calculate some dimensionless value "SP" using normalized pressure, which is the reciprocal of the directivity index, but noway the acoustic/sound power curve as it is described by ISO standart and acoustics textbooks . It makes sense to name this "SP" quantity "extension/expansion/cea2034power/mabatpower/whatever" index, but actually it is not "Sound Power". But again, this quantity become meaningless if you provide the Directivity Index curve, because it represents essentially the same thing as DI.
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Some remarks on ambiguous moments in CEA-2034-A-2015 standart.
I think that this statement should fixed by CEA-2034 committee. Using generally accepted terms and definitions in the standard at your own discretion is a bad practice. And I don't see why not just bring some equations and definitions into the standard to avoid unnecessary confusion. Why is it necessary to describe in several paragraphs of text what can be fit into one formula.
That sounds like nitpicking to me. The standard constitues a method of practical means of testing loudspeakers to be widely adopted. So it's no wonder it uses only the necessary practical terms it works with. That document is not a physics textbook. And I guess there's nothing in that document that would be in conflict with physics.
If your task was to measure a power response of a loudspeaker and its DI, how would you do it? I think the document is a pretty good starting point.
If your task was to measure a power response of a loudspeaker and its DI, how would you do it? I think the document is a pretty good starting point.
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No, it's not the reciprocal of the directivity index (as I told you already), neither it uses normalized pressure. Sorry, but that's just nonsense. BTW the dimension is dB SPL.
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I would build a spherical test fixture around the DUT. The test fixture would position a large number of microphones in a sphere pattern with a radius of 1 m. To avoid getting into math arguments with people on the internet, I would position the microphones with a spacing of 20 mm. I will require 31,416 microphones. Send the bill to NASA. I will need a 32000 channel measurement system. Send the bill to NASA.
Or, I could follow the CTA2034 standard and make 72 measurements, with a single calibrated mic, and a 2-channel sound card.
j.
Perhaps I should have quoted the whole paragraph to avoid people nitpicking about it. I just didn't expect that they would, especially when they know what it's about.
"Sound power represents all of the sounds arriving at the listening position after any
number of reflections from any direction. It is the weighted rms average of all 70
measurements, with individual measurements weighted according to the portion of the
spherical surface that they represent. Sound power is a measure of the total acoustical
energy radiating through an imaginary spherical surface with the radius equal to the
measurement distance. Thus the on-axis curve has very low weighting because it is in
the middle of other closely adjacent measurement points (see the perspective sketch at
the top of Figure 1) and measurements further off axis have higher weighting because of
the larger surface area that is represented by each of those measurements. Ideally, such
a measurement would be made at equally-spaced points on the entire surface of the
sphere, but this simplified spatial-sampling process turns out to be a very good
approximation. The result could be expressed in acoustic watts, the true measure of
sound power, but for the purposes of this standard it is expressed as sound level, a
frequency response curve having the same shape. Any bump in the curve that shows up
in the other curves (on-axis, early reflections, etc.) and persists through this ultimate
spatial average is a notable resonance. Calculation of the sound power curve begins with
a conversion from dB to a scalar magnitude. The individual measures of sound pressure
are then weighted according to the values shown in Appendix C and an energy average
(rms) is calculated using the weighted values. The final average is converted to dB."
"Sound power represents all of the sounds arriving at the listening position after any
number of reflections from any direction. It is the weighted rms average of all 70
measurements, with individual measurements weighted according to the portion of the
spherical surface that they represent. Sound power is a measure of the total acoustical
energy radiating through an imaginary spherical surface with the radius equal to the
measurement distance. Thus the on-axis curve has very low weighting because it is in
the middle of other closely adjacent measurement points (see the perspective sketch at
the top of Figure 1) and measurements further off axis have higher weighting because of
the larger surface area that is represented by each of those measurements. Ideally, such
a measurement would be made at equally-spaced points on the entire surface of the
sphere, but this simplified spatial-sampling process turns out to be a very good
approximation. The result could be expressed in acoustic watts, the true measure of
sound power, but for the purposes of this standard it is expressed as sound level, a
frequency response curve having the same shape. Any bump in the curve that shows up
in the other curves (on-axis, early reflections, etc.) and persists through this ultimate
spatial average is a notable resonance. Calculation of the sound power curve begins with
a conversion from dB to a scalar magnitude. The individual measures of sound pressure
are then weighted according to the values shown in Appendix C and an energy average
(rms) is calculated using the weighted values. The final average is converted to dB."
Found my answer, it looks like changing weight=0 in the observation.txt file is one method according to post 9,879
In addition, we need to change the solving.txt to file to add Direction=z for the low frequency source according to post 9,881
However, best practice might be modifying the drive groups in observation.txt as explained in post 9,892
So, for the sake of the google search engine spiders: how to simulate two (or more) drivers in an enclosure, cabinet, speaker box with an ATH waveguide using ATH software and an additional midrange or low frequency driver source in ABEC or AKABAK.
BTW, regarding the power response, I believe it's the red curve in this Earl's graph as well: http://www.gedlee.com/Loudspeakers/NS15.aspx
Now I wonder if Earl knew what he was doing.
Edit: - Indeed it is: "The red curve is the power response and the white curve is the Directivity Index (DI)"
Now I wonder if Earl knew what he was doing.
Edit: - Indeed it is: "The red curve is the power response and the white curve is the Directivity Index (DI)"
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So room traps dont work? Why is even the word "room" used in that definition - unfortunate.
Sound Power is how much water is boiled by the energy emitted by a DUT, as collected by a spherical energy collector, for each frequency. The unit is indeed Watt. If one have a destructive out of phase situation in a certain direction and frequency region, it will show as a dip in a SP trace - for the specific frequency, the spherical energy collector did not see the same amount collected of energy as for other frequencies - like for a D'Appolito MTM configured speaker for example - its inherent in the architecture and cant be completely fixed.
//
Sound Power is how much water is boiled by the energy emitted by a DUT, as collected by a spherical energy collector, for each frequency. The unit is indeed Watt. If one have a destructive out of phase situation in a certain direction and frequency region, it will show as a dip in a SP trace - for the specific frequency, the spherical energy collector did not see the same amount collected of energy as for other frequencies - like for a D'Appolito MTM configured speaker for example - its inherent in the architecture and cant be completely fixed.
//
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To combine in the same definition:
"Sound power represents all of the sounds arriving at the listening position after any
number of reflections from any direction."
and
"Sound power is a measure of the total acoustical
energy radiating through an imaginary spherical surface with the radius equal to the
measurement distance."
... do not show, as I see it, proof of very high level of stringens. But one might have different requirements on things...
//
"Sound power represents all of the sounds arriving at the listening position after any
number of reflections from any direction."
and
"Sound power is a measure of the total acoustical
energy radiating through an imaginary spherical surface with the radius equal to the
measurement distance."
... do not show, as I see it, proof of very high level of stringens. But one might have different requirements on things...
//
It seems that Fusion 360 Surface Import script crashes when adding a rollback.
After adding a rollback to Tritonia and exporting resulting surfaces into Fusion, I get the following error:
I opened the script file and add "if" condition on the line 56 (spaces preserved - forum engine removes them):
This suppressed the exception, but Fusion now isn't able to generate a shape for thickening. It thickens part of the horn before rollback:
I don't know Fusion API and don't understand the CSV data good enough to figure out what part is breaking. If there is something I have to change in the configuration file, let me know, please.
After adding a rollback to Tritonia and exporting resulting surfaces into Fusion, I get the following error:
I opened the script file and add "if" condition on the line 56 (spaces preserved - forum engine removes them):
This suppressed the exception, but Fusion now isn't able to generate a shape for thickening. It thickens part of the horn before rollback:
I don't know Fusion API and don't understand the CSV data good enough to figure out what part is breaking. If there is something I have to change in the configuration file, let me know, please.
I told you maybe five times what that quantity ("SP") means. It is the frequency response of an ideal point source radiating the same total sound power as the source with the given/measured polars. What's not clear on that?
And it's exactly this quantity that's needed to calculate the DI in practice. And why not to show it when I already have it. It gives a nice insight into how the radiation pattern and the power response relate to each other.
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Thank you for the suggestion! I just started using the app, so I took the first presumably good cfg from here and started playing around. Will experiment with round waveguides.