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Old 30th September 2019, 08:22 AM   #341
mabat is offline mabat  Czech Republic
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I re-read 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. 6-12, then the net effect will be to create adistribution of the velocity at the mouth which has a far more uniform distribu-tion 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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Last edited by mabat; 30th September 2019 at 08:29 AM.
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Old 30th September 2019, 10:40 AM   #342
mabat is offline mabat  Czech Republic
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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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Old 30th September 2019, 11:28 AM   #343
mabat is offline mabat  Czech Republic
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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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Last edited by mabat; 30th September 2019 at 11:49 AM.
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Old 30th September 2019, 02:43 PM   #344
turk 182 is offline turk 182  Canada
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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?
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Old 30th September 2019, 03:03 PM   #345
mabat is offline mabat  Czech Republic
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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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Old 30th September 2019, 03:25 PM   #346
turk 182 is offline turk 182  Canada
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in what sense is it not bad either? i'm trying to understand...
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Old 30th September 2019, 03:41 PM   #347
Ro808 is offline Ro808  Netherlands
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Quote:
Originally Posted by mabat View Post
That would lead me to an idea of making a secondary phase plug to be put at the exit of the existing one that would transform the "flat" wave (hopefully) emanating from a driver into spherical. Maybe it is just nonsense...
The wavefront of an 18Sound 4015Ti/Be is practically spherical at the exit.
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Old 30th September 2019, 03:50 PM   #348
mabat is offline mabat  Czech Republic
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I find that unlikely. What's the radius then?
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Last edited by mabat; 30th September 2019 at 03:53 PM.
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Old 30th September 2019, 04:07 PM   #349
Ro808 is offline Ro808  Netherlands
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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.
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Old 30th September 2019, 04:20 PM   #350
Ro808 is offline Ro808  Netherlands
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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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