Otop phase plug question

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himhimself
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Otop phase plug question

#1 Post by himhimself » Sat Aug 25, 2018 3:59 pm

So, the phase plug extension is a 5" circle of 1/2 of ply (or 2x 1/4") glued to the baffle, with another 1 inch thick circle of foam glued to it. Why not just make the entire thing of foam to save weight? Is there a reason for using plywood? And what exactly does the phase plug do?
thanks
2xT30 (20", 3012lf)
4xOtop Jarray

SethRocksYou
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Re: Otop phase plug question

#2 Post by SethRocksYou » Sat Aug 25, 2018 4:42 pm

Which otop plans are you referring to ?

himhimself
Posts: 276
Joined: Fri Nov 13, 2015 9:34 pm
Location: Bloomington IN

Re: Otop phase plug question

#3 Post by himhimself » Sat Aug 25, 2018 6:10 pm

J-array. <<aha-moment>> Just pulled up the Otop plans and they say you can use all foam discs to save weight. They also give a little more instruction than the j-array plans on sizing the plugs. So that answers my first question. Still curious as to just what the plugs do.
2xT30 (20", 3012lf)
4xOtop Jarray

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Bill Fitzmaurice
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Re: Otop phase plug question

#4 Post by Bill Fitzmaurice » Sat Aug 25, 2018 6:50 pm


himhimself
Posts: 276
Joined: Fri Nov 13, 2015 9:34 pm
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Re: Otop phase plug question

#5 Post by himhimself » Sat Aug 25, 2018 8:56 pm

Good ol' wikipedia...should have gone there first. So the 5" stack of disks with the half ball on the outside of the baffle basically makes what is shown in that illustration in the bottom of the article where it talks about woofers. Thanks, Bill.
2xT30 (20", 3012lf)
4xOtop Jarray

himhimself
Posts: 276
Joined: Fri Nov 13, 2015 9:34 pm
Location: Bloomington IN

Re: Otop phase plug question

#6 Post by himhimself » Sat Aug 25, 2018 9:01 pm

Does the shape of the side near the cone make much difference? Would it work any better if it mimicked the profile of the cone and dustcap, almost like a doughnut? Or is it just the outside that needs to be be spherical, hence the ball? And how close should it be? Gathering from the description in the Otop plans that 1/2" is good, which with xmax around 5mm, would put the cone about 7mm away from the plug at full extension.
2xT30 (20", 3012lf)
4xOtop Jarray

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Bill Fitzmaurice
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Re: Otop phase plug question

#7 Post by Bill Fitzmaurice » Sat Aug 25, 2018 9:09 pm

I actually made a mold of a cone to come up with a 'perfect' plug, but it didn't work significantly better than the design in the plans.

himhimself
Posts: 276
Joined: Fri Nov 13, 2015 9:34 pm
Location: Bloomington IN

Re: Otop phase plug question

#8 Post by himhimself » Sat Aug 25, 2018 9:23 pm

:D As always, follow the plans! Thanks again, my education continues...
2xT30 (20", 3012lf)
4xOtop Jarray

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