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30th September 2019, 08:22 AM  #341 
diyAudio Member
Join Date: Sep 2004
Location: Prague

I reread the Chapter 6 and it makes much, much more sense to me now (even though the math itself is still above my head to a large extend). It's almost an intuitive reading now
It states (p.145), among other things: "If instead of driving the throat with a wavefront of constant amplitude we taper this amplitude as shown in Fig. 612, then the net effect will be to create adistribution of the velocity at the mouth which has a far more uniform distribution than one fed with a flat throat velocity distribution" Would it make sense then to try to damp the phase plug exit this way? I'm thinking about putting an open cell foam (the right amount and density) into the exit rings openings. The 18Sound ND4015 seems like a good candidate  laying on my bench right now. It has four slits for a 1,4" throat, reaching the exit of the driver.
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www.athorns.eu Last edited by mabat; 30th September 2019 at 08:29 AM. 
30th September 2019, 10:40 AM  #342 
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Join Date: Sep 2004
Location: Prague

Another excerpt (p.148):
"...The only way for this higher order mode creation to not occur would be for there to be a wavefront radius source point which did not move in space, as opposed to one that is changing in each section. It is now readily apparent that any waveguide which has a changing location of the origin for the wavefront radius will require the presence of higher order modes to account for this changing origin." It seems that this (i.e. the wavefront origin shifting) is exactly what happens for larger throats. For a smaller throat it takes less of the contour to approach a cone, more for the larger.
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30th September 2019, 11:28 AM  #343 
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Join Date: Sep 2004
Location: Prague

Now when I think about it more, it can't be the explanation as simply as it is stated. By this reasoning a straight cone directly connected to a flat wavefront would be even better, which I assume is not.
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www.athorns.eu Last edited by mabat; 30th September 2019 at 11:49 AM. 
30th September 2019, 02:43 PM  #344 
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Join Date: Oct 2012

sorry to butt in but as the math is dumfounding to me, i hope i can ask a few questions to gain some understanding (and hopefully start to make a math to english bridge for myself)
currently these equations are plotting a particular curvature with the intent of doing so with a minimum of problems in the field of interest(i.e. a field defined by the directivity) or am i out to lunch? 
30th September 2019, 03:03 PM  #345 
diyAudio Member
Join Date: Sep 2004
Location: Prague

These equations (if you mean what I have presented) are just an attempt to cover the whole WG contour in one formula, as smooth as possible. Just a mathematical exercise, really. It has no status of being optimal in any sense... It's not bad either.
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30th September 2019, 03:25 PM  #346 
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Join Date: Oct 2012

in what sense is it not bad either? i'm trying to understand...

30th September 2019, 03:41 PM  #347 
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Join Date: Mar 2010

The wavefront of an 18Sound 4015Ti/Be is practically spherical at the exit.

30th September 2019, 03:50 PM  #348 
diyAudio Member
Join Date: Sep 2004
Location: Prague

I find that unlikely. What's the radius then?
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www.athorns.eu Last edited by mabat; 30th September 2019 at 03:53 PM. 
30th September 2019, 04:07 PM  #349 
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Join Date: Mar 2010

This was confirmed by 18Sound to someone I know.
You could enquire once more to be sure. I have no clue about the radius. Last edited by Ro808; 30th September 2019 at 04:11 PM. 
30th September 2019, 04:20 PM  #350 
diyAudio Member
Join Date: Mar 2010

Would it be too much hassle to pinch the 2" throat to 1" and stretch the throat accordingly?
It is then of course no longer an OS throat, but I wonder what the sims would look like. 
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