Hi Marcel,
Following your last Saturday PM about T34B, I sent you an answer, did you get it ?
Following your last Saturday PM about T34B, I sent you an answer, did you get it ?
I ordered a pair (Radian 760NeoPB). These are strange drivers, hardly usable for anything else, IMHO, due to the extremely wide exit angle (60°). But when used directly from the phase plug with a more typical waveguide, they seem almost perfect. I say almost because the phase plug terminates at ~33mm (1.3") diameter. A little smaller would be even better.
I am sure you saw it but just in case:
https://audioxpress.com/article/tes...eering-950pb-and-760neopb-compression-drivers
For the HF range It will be an interesting comparison to the https://www.eighteensound.it/en/products/horn/2-0/0/XR2064C
https://audioxpress.com/article/tes...eering-950pb-and-760neopb-compression-drivers
For the HF range It will be an interesting comparison to the https://www.eighteensound.it/en/products/horn/2-0/0/XR2064C
Yeah, I expect a plug version to be considerable smoother. Such a wide-angle exit section will form a concave contour with most of the available horns. That can't be a good thing.
This is what I'm going to use with the 760NeoPB. This time with a segmented/octagonal horn but that's still not fully implemented.
(The ring plug apparent on the left picture.)
(The ring plug apparent on the left picture.)
Of course it could be made more flat. I'm still not convinced what's the better choice.
- Would love to be able to listen to these two side by side. Maybe some day... 🙂
- Would love to be able to listen to these two side by side. Maybe some day... 🙂
In this post I'd like to share some early results, comparing simulation to actual measurements.. I also have a question about an inconsistency in the ATH report.
--
After playing around with ATH a bit, I decided it was time to find out how well an ATH simulation holds up in practice. Although I've recently discovered that the R-OSSE functionality works really well, in the past - when I didn't have access to advanced simulation software like ATH - I always tried to break up the design process into the smallest possible steps. With fewer degrees of freedom, it's easier to narrow down cause-and-effect relationships. Therefore, the waveguide of the Dutch & Dutch 8c was first optimized in an infinite baffle, and only after that did I work on optimizing its interaction with the actual speaker baffle. I decided to take the same approach in validating ATH.
The waveguide we'll be looking at here, I designed about a month ago, presumably with ATH version 4.8.3 beta.
This is the ATH report I generated at the time:
Yesterday I measured the WG in what is generally referred to as an infinite baffle. The mic distance was 1 meter.
These are the normalized results of the gated measurements, from 0 to 90 degrees in 15-degree steps. Please ignore the irregularity below about 2500 Hz in the 90 degrees measurement. It's caused by the relatively early and not perfectly gated-out reflection that results from diffraction at the closest edge of the not-quite-so-infinite baffle.
There are some small differences, but overall I'd say the measured response tracks the simulation very well. Great!
Now the funny thing. I simulated the same waveguide again with ATH 4.9.0 pre-230518, and now the report looks like this:
Everything seems to look the same, except for the directivity. It seems to be 3 dB higher across the board in the report I made today. I'm afraid I've overwritten the original config file I used to make the earlier report. Has the way directivity is calculated been changed, or did I change something in the config file?
This is the complete config file:
--
After playing around with ATH a bit, I decided it was time to find out how well an ATH simulation holds up in practice. Although I've recently discovered that the R-OSSE functionality works really well, in the past - when I didn't have access to advanced simulation software like ATH - I always tried to break up the design process into the smallest possible steps. With fewer degrees of freedom, it's easier to narrow down cause-and-effect relationships. Therefore, the waveguide of the Dutch & Dutch 8c was first optimized in an infinite baffle, and only after that did I work on optimizing its interaction with the actual speaker baffle. I decided to take the same approach in validating ATH.
The waveguide we'll be looking at here, I designed about a month ago, presumably with ATH version 4.8.3 beta.
Code:
Throat.Profile = 1
Throat.Diameter = 25.4 ; [mm]
Throat.Angle = 7 ; [deg]
Coverage.Angle = 41 ; [deg]
Length = 130 ; [mm]
Term.s = 1.1
Term.n = 3.2
Term.q = 0.995This is the ATH report I generated at the time:
Yesterday I measured the WG in what is generally referred to as an infinite baffle. The mic distance was 1 meter.
These are the normalized results of the gated measurements, from 0 to 90 degrees in 15-degree steps. Please ignore the irregularity below about 2500 Hz in the 90 degrees measurement. It's caused by the relatively early and not perfectly gated-out reflection that results from diffraction at the closest edge of the not-quite-so-infinite baffle.
There are some small differences, but overall I'd say the measured response tracks the simulation very well. Great!
Now the funny thing. I simulated the same waveguide again with ATH 4.9.0 pre-230518, and now the report looks like this:
Everything seems to look the same, except for the directivity. It seems to be 3 dB higher across the board in the report I made today. I'm afraid I've overwritten the original config file I used to make the earlier report. Has the way directivity is calculated been changed, or did I change something in the config file?
This is the complete config file:
Code:
; Device width x height = 439.60 x 439.60 mm (17.307 x 17.307")
; Device length = 130.00 mm (5.118")
Throat.Profile = 1
Throat.Diameter = 25.4 ; [mm]
Throat.Angle = 7 ; [deg]
Coverage.Angle = 41 ; [deg]
Length = 130 ; [mm]
Term.s = 1.1
Term.n = 3.2
Term.q = 0.995
; -------------------------------------------------------
Mesh.AngularSegments = 100
Mesh.LengthSegments = 40
ABEC.SimProfile = 0 ; CircSym
ABEC.SimType = 1 ; Infinite Baffle
ABEC.f1 = 250 ; [Hz]
ABEC.f2 = 20000 ; [Hz]
ABEC.NumFrequencies = 100
ABEC.MeshFrequency = 40000 ; [Hz]
ABEC.Polars:SPL = {
MapAngleRange = 0, 90, 19
NormAngle = 0 ; [deg]
Distance = 3 ; [m]
; Offset = 0 ; [mm]
}
; -------------------------------------------------------
GridExport: = {
ExportSlices=1
ExportProfiles=1
}
Output.SubDir = "demos"
Output.STL = 0 ; bug, can't output https://www.diyaudio.com/community/threads/acoustic-horn-design-the-easy-way-ath4.338806/page-635#post-7365338
Output.ABECProject = 1
Report = {
Title = "BOVRIE2_Old_report"
NormAngle = 0
Width = 1024
Height = 768
SPL_Range = 50
MaxRadius = 90
PolarData = "SPL"
}
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That happens between versions. For example, the rollback feature was eliminated for free standing so you can't use it between versions. I place a commented line in my config file to help me remember which version I originally designed a waveguide like this...
Then I keep the executable files named like this...
The STL files may look different when generated between different versions. Mine do because I try to use the newly added features of later version executables. Although, I haven't tried designing in an older version and generating in a newer version.
Others may have a more efficient way of doing things. However, I do like formatting the version comment line so I can copy and paste into the command line prompt "ath_490_230531.exe 46_8inch_DE250.cfg" without needing to type it out.
Then I keep the executable files named like this...
The STL files may look different when generated between different versions. Mine do because I try to use the newly added features of later version executables. Although, I haven't tried designing in an older version and generating in a newer version.
Others may have a more efficient way of doing things. However, I do like formatting the version comment line so I can copy and paste into the command line prompt "ath_490_230531.exe 46_8inch_DE250.cfg" without needing to type it out.
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Thanks for sharing the data, the results look quite nice.
Yeah, we had a side discussion here recently about how is the DI defined for half-space conditions. Basically, a source radiating equally in all directions in a half space should have DI = 3 dB, according to the common definition (there's no right or wrong, it's just a matter of consensus). So I changed this in the latest versions and the DI curve is now shifted by 3 dB as a result (what was 0 dB is now 3 dB). Also, the values at high frequencies now agree to what you would get in a free field, which makes a better sense after all.
Yeah, we had a side discussion here recently about how is the DI defined for half-space conditions. Basically, a source radiating equally in all directions in a half space should have DI = 3 dB, according to the common definition (there's no right or wrong, it's just a matter of consensus). So I changed this in the latest versions and the DI curve is now shifted by 3 dB as a result (what was 0 dB is now 3 dB). Also, the values at high frequencies now agree to what you would get in a free field, which makes a better sense after all.
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As for the backward compatibility, also some might have noticed that it's now possible to define an OSSE horn simply like this:
So there are the OSSE and R-OSSE profiles now (as described on my website), both using a similar notation.
(The parameter 'q' meaning different things in both but I won't change that...)
I see no need for the old rollback feature anymore. If you still want or need it, just use the old version...
Code:
OSSE = {
r0 = 19 ; Throat.Diameter/2
a0 = 41.0 ; Throat.Angle
a = 71.25 ; Coverage.Angle
k = 1.3 ; OS.k
L = 19 ; Length
s = 1.12 ; Term.s
n = 2.467 ; Term.n
q = 0.999 ; Term.q
}So there are the OSSE and R-OSSE profiles now (as described on my website), both using a similar notation.
(The parameter 'q' meaning different things in both but I won't change that...)
I see no need for the old rollback feature anymore. If you still want or need it, just use the old version...
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I generated two DI reports, one for ATH 490.122 and one for ATH 490.230531 in ABEC.SimType = 2 (free space) rather than 1 (infinite baffle). I see a small change in high frequency simulation as a result of the update.
Extremely small but since I generated the reports I thought I'd post them in case anyone else was curious about the update.
Extremely small but since I generated the reports I thought I'd post them in case anyone else was curious about the update.
Attachments
At some point I fixed a bug regarding the weighting of the last polar, maybe that's the difference.
Anyway, the more recent release, the better it should be 🙂
Anyway, the more recent release, the better it should be 🙂