OK, thanks Michael. I was hoping for an idea of how much mismatch would give "bad" results.
It would be nice if we could revisit this in a practical sense. E.G., 12.5 deg throat on the CD mated with 25 degree throat on the horn looks like "this" as opposed to 12.5+12.5 etc.
That might be handy for us builders.
If you get a chance.
It would be nice if we could revisit this in a practical sense. E.G., 12.5 deg throat on the CD mated with 25 degree throat on the horn looks like "this" as opposed to 12.5+12.5 etc.
That might be handy for us builders.
If you get a chance.
ScottG said:
If you don't have rigor requirements to the 3-D CAD, I suggest to have a look into ALIBRE (which part of my CAD drawings were made with).
You get it at reasonable prices or even for free with slightly limited functionality. Learning curve isn't exceptionally steep either – if you have some basic knowledge (good tutorial available)
http://www.alibre.com/products/
http://www.alibre.info/alibreversionen/index.php
Its the same as with ORCAD – when I bought it (MicrosSim) back then, it was expensive like hell – now you get great LT-Spice for free...
This is one thing I really like to see developing as some rare spread nucleus – not each, everything and anybody follows the idiot laws of "money making" (god economy - and all its even more idiot science around) that predictable cycles through so called crisis times - creating incredible harm world wide right now!
Michael
panomaniac said:
Sure Pano, this is the idea - but as said - anybody can do...
AxiDriver is available for FREE as well !!!!
http://www.randteam.de/AxiDriver/Index.html
DIY never was more fun - getting almost all tools needed to gain some insight for free (ARTA for measurement as well)
Michael
Lynn,Lynn Olson said:
Thanks for bringing the Newell & Holland book on Loudspeakers to our attention. It very clearly addresses CSDs as I have experience, and provides a lot more information on aspects to consider when designing speakers for different applications. I would put it on the MUST READ list for anyone serious in loudspeaker design.
soongsc said:
Well - we could start on a "simu" group buy - if enough people join, we esily could invest in a "DIY supercomputer" ...
😀
http://en.wikipedia.org/wiki/Supercomputer
Just kidding...
Michael
6 core CPU is probably the latest.😀mige0 said:
I just upgraded from a single core Athelon to a Dual Core Operon, and notice more difference in the speed web pages update. 😉
I thought it would be helpful to point out that baffle location also makes big difference in the accuracy of sim. Below is an onaxis demonstration of waveguide on infinit baffle versus 1M in front of baffle using AxiDriver.
An externally hosted image should be here but it was not working when we last tested it.
I would recommend as many cores in the CPU as you can get. This kind of setup takes probably 4~6 times amount of time.mige0 said:
😀 2GB of memory would do well, you might even get by with 1GB.
Hello,
Vice versa, isn't it? 😉
The vertical scale represents the angle, so the CD speaker should not produce SPL variations over angle _inside_ the coverage area.
A rising amplitude response would produce a variation to deeper colours to the right of the diagram, which represents higher frequencies.
Please compare to the 0° incidence normalisation of that sonogram, you already know, both are of the same presentation type. This type of presentation is very well known in PA, because it is one of the best readable ones and it's not new at all.
Best regards, Timo
Vice versa, isn't it? 😉
The vertical scale represents the angle, so the CD speaker should not produce SPL variations over angle _inside_ the coverage area.
A rising amplitude response would produce a variation to deeper colours to the right of the diagram, which represents higher frequencies.
Please compare to the 0° incidence normalisation of that sonogram, you already know, both are of the same presentation type. This type of presentation is very well known in PA, because it is one of the best readable ones and it's not new at all.
Best regards, Timo
tiki said:
Agree - this kind of visualisation isn't new – I recall Earl having also introduced it in a variant – but around here I only remember soongsc having presented results in this form now and then – hence I thought its worth to write a little explanation around it.
IMO this kind of visualisation too is great as you see both directivity and FR smoothness immediately (*if* you are after directivity at all).
tiki said:
mige0 said:
*If* we would have a ideal constant directivity speaker (one with a certain directivity) we would see no colour changes along the horizontal lines but colour changes in the vertical direction – giving the impression of looking at a "half pipe" - the "half pipe" being orientated horizontally.
*If* we would have a omni speaker with a falling or rising FR we would see no colour changes along the vertical direction but colour changes along the horizontal lines – giving the impression of looking at a "quater pipe" - the "quater pipe" being orientated vertically.
..
Vice versa, isn't it? 😉
The vertical scale represents the angle, so the CD speaker should not produce SPL variations over angle _inside_ the coverage area.
A rising amplitude response would produce a variation to deeper colours to the right of the diagram, which represents higher frequencies.
Best regards, Timo
" Vice versa, isn't it? 😉"
Äähh – no – don't think so.
" so the CD speaker should not produce SPL variations over angle _inside_ the coverage area."
This is a dictum from why CD speakers were invented for in the past – to produce even audience coverage.
But it is not the definition of CD at all – and no requirement if you are after optimisation of advanced EQing, requiring good min phase behaviour.
" The vertical scale represents the angle, so the CD speaker should not produce SPL variations over angle _inside_ the coverage area."
Yes the vertical scale does represent the angle.
But CD speakers usually *do* have variations in SPL over angle – they just have the *same* variation of SPL over angle at all frequencies (or at least should have) – meaning you get sort of "half-pipe" - – the "half pipe" being orientated horizontally – or, more likely - the "whale" seen in my pix.
Some whales are fat – some whales being more lean 😉
" A rising amplitude response would produce a variation to deeper colours to the right of the diagram, which represents higher frequencies."
Yes, kind of "quarter pipe" look – the "quarter pipe" being orientated vertically - as I've put it.
Thanks for posting your directivity sonogram – looks like the bones of a really fat whale 😀
What does it show?
Michael
I run it on a P4 3.2gHz with 2GB of ram. It takes ~1-2 hours to do the steady state response, 2-3 hours to do the transient response. The bigger the model, higher the frequency, more frequency points, longer the time after impulse, the longer it takes.
I'm using ANSYS Mechanical which costs ~$36k.
Very fascinating! I've bin following this discussion for a while now.
My current setup is 2x peerless sls12 and a Fostex FE166E per speaker. This is in a OB and the weight is about 30 kilo's per speaker 🙂
Anyway a would like to convert this setup. The mid and high is going to be driven by the Fostex (horn) and Im keeping the low in OB setting.
I used the excelsheet to calculate the profile, i used the 2007 version is that the latest?
The setting i chose are as followed:
- cut off frequency 300 Hz
- diameter of the throat 130mm
- angle of exit of the driver 2 degrees
- and the "T" coefficient 0
I think these are the right settings???
I also found a nice way to import the profile into autocad:
http://autodesk.blogs.com/between_t...t-xy-coordinates-from-excel-into-autocad.html
This is really perfect after you put in the first hundred value's in manually
My current setup is 2x peerless sls12 and a Fostex FE166E per speaker. This is in a OB and the weight is about 30 kilo's per speaker 🙂
Anyway a would like to convert this setup. The mid and high is going to be driven by the Fostex (horn) and Im keeping the low in OB setting.
I used the excelsheet to calculate the profile, i used the 2007 version is that the latest?
The setting i chose are as followed:
- cut off frequency 300 Hz
- diameter of the throat 130mm
- angle of exit of the driver 2 degrees
- and the "T" coefficient 0
I think these are the right settings???
I also found a nice way to import the profile into autocad:
http://autodesk.blogs.com/between_t...t-xy-coordinates-from-excel-into-autocad.html
This is really perfect after you put in the first hundred value's in manually
Hello,
Regards, Timo
I do not want to bother the other readers, because it was already shown and shortly discussed with Earl. Look through the "neighbour" directory, it is not only a simulation.mige0 said:
Regards, Timo
With my next BEM simulations I'd like to show how Oblade Speroide contour, LeCleach contour and direct radiators compare with respect to sound field defects.
Again this is visualised by showing their behaviour in the powerful directivity sonogram. The resolution is a moderate 100 points through the 1000 – 20kHz range.
In order to get a idea how the sound field at a certain frequency would look like, I added a sound field graph at 4kHz (two octaves above 1kHz) - also showing the contour used and how it is "attached" to an infinite baffle.
In addition to that this allows to get an idea of the process of "what is cooked inside the horn spills out into the room"
Direct radiator of roughly 10cm / 4"
Direct radiator of roughly 20cm / 8"
Direct radiator of roughly 40cm / 16"
Oblade Spheroide with 1 ½ " entrance
LeCleach with 1 ½ " entrance
soongsc's contour (or at least kind of "reverse engineering" 😉 ) with 1 ½ " entrance
All "drivers" are actually plain wave fronts that are injected (piston diaphragm).
The OS contour is deliberately shown without any rounding of the mouth to make clear the effects when not taking seriously the issue of mouth diffraction (as seen in many, many commercial designs) and also to provide an easy comparison to the issue of throat joint diffraction shown earlier (the "moon racer" pix)
In case you get lost in trying to decode the highly concentrated information content in the directivity sonogram I'd recommend to reread my short introduction on "how to read" directivity sonogram.
http://www.diyaudio.com/forums/showthread.php?postid=1888195#post1888195
Michael
Again this is visualised by showing their behaviour in the powerful directivity sonogram. The resolution is a moderate 100 points through the 1000 – 20kHz range.
In order to get a idea how the sound field at a certain frequency would look like, I added a sound field graph at 4kHz (two octaves above 1kHz) - also showing the contour used and how it is "attached" to an infinite baffle.
In addition to that this allows to get an idea of the process of "what is cooked inside the horn spills out into the room"
Direct radiator of roughly 10cm / 4"
Direct radiator of roughly 20cm / 8"
Direct radiator of roughly 40cm / 16"
Oblade Spheroide with 1 ½ " entrance
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
LeCleach with 1 ½ " entrance
soongsc's contour (or at least kind of "reverse engineering" 😉 ) with 1 ½ " entrance
All "drivers" are actually plain wave fronts that are injected (piston diaphragm).
The OS contour is deliberately shown without any rounding of the mouth to make clear the effects when not taking seriously the issue of mouth diffraction (as seen in many, many commercial designs) and also to provide an easy comparison to the issue of throat joint diffraction shown earlier (the "moon racer" pix)
In case you get lost in trying to decode the highly concentrated information content in the directivity sonogram I'd recommend to reread my short introduction on "how to read" directivity sonogram.
http://www.diyaudio.com/forums/showthread.php?postid=1888195#post1888195
Michael
mige0 said:
Direct radiator of roughly 10cm / 4"
I'll take the 4" driver below 2 kHz. 😀
Very nice, thank you! 🙂
Michael,
Care to show us the OS version *with* roundover into the baffle? Otherwise this again is sort of unfair.
And please normalize the directivity plots to the 0° on-axis SPL (only a few mouse clicks away, "normalize --> to curve in x-graph"). EDIT: Then again, we know that 0° not necessarily is the optimum angle, for OS....
- Klaus
Care to show us the OS version *with* roundover into the baffle? Otherwise this again is sort of unfair.
And please normalize the directivity plots to the 0° on-axis SPL (only a few mouse clicks away, "normalize --> to curve in x-graph"). EDIT: Then again, we know that 0° not necessarily is the optimum angle, for OS....
- Klaus