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Multi-Way Conventional loudspeakers with crossovers

Phase Plug for Planars
Phase Plug for Planars
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Old 14th February 2017, 11:22 PM   #11
hollowboy is offline hollowboy  Australia
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Quote:
Originally Posted by Patrick Bateman View Post
In the midrange and the lower treble, the Costas phase plug response is virtually the same as the 'bare' NEO8. But in the top octave, the Costas phase plug is doing a couple of things that [are] positive
Since you want the tweak to target top octave problems, foam might be better - something that's fairly transparent in the lower frequencies. Basically clone these:

https://www.madisoundspeakerstore.co...morphous-core/

Foam might allow you to block a lot of area (to widen dispersion), without having an increase in distortion.
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Old 14th February 2017, 11:34 PM   #12
Patrick Bateman is offline Patrick Bateman  United States
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I agree.

Click the image to open in full size.

One neat thing about masking off the NEO8 is that we're not actually eliminating the radiation from that point on the radiator. We're just making the pathlength longer.

For instance, if you mask off one of the "cels", the sound has to travel about one centimeter longer than normal. That doesn't sound like a lot, but it's 180 degrees of phase shift at 17000Hz, and ninety degrees of phase shift at 8500Hz. I believe these random shifts in *some* of the phase is what smooths out the polar response between 7000Hz and 14,000Hz, while leaving the rest of the response curve unmolested.

Obviously, it would be nice if BG would just curve this dumb thing, that would work a lot better But that would easily double the cost.


Long story short: foam may help, but it reduces the efficiency. Phase plug helps, but doesn't affect the efficiency below 10Khz.
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Old 15th February 2017, 12:01 AM   #13
hollowboy is offline hollowboy  Australia
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Interesting points: things that hadn't occurred to me, but make sense now that you've explained.

Quote:
Originally Posted by Patrick Bateman View Post
I believe these random shifts in *some* of the phase is what smooths out the polar response between 7000Hz and 14,000Hz, while leaving the rest of the response curve unmolested.
TL;DR version: I concur.

Long version:

I had one experiment that agrees nicely: as shown in in post 4 of this thread,

Tweeter for coaxial mounting in midrange horn

slapping a 4" driver on a 2" throat horn was OK but gave a ~4.5kHz notch.

I assumed it would be hard (too much work) to eliminate, but found that I could mostly fix it with a few scraps of dense foam stuck just inside the horn throat. The foam broke the symmetry / introduced path length differences, softening the -15dB notch to a much more benign -3dB dip. This allowed the cross point to be lifted from 4kHz to 7kHz ...and was much less effort than the fix I thought this would require: rebuilding the horn with a bigger throat + a proper (lathed / 3D printed) phase plug
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Old 15th February 2017, 01:38 PM   #14
zmyrna is offline zmyrna  United Kingdom
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I can not see the phase plug pictures
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Old 20th February 2017, 01:54 AM   #15
hollowboy is offline hollowboy  Australia
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Good info here (RAAL with/without foam). These look like good, well documented tests.

www.audioexcite.com RAAL 140-15D

"It’s interesting to see is that the distortion is even lower when the “foam deflection pads” are used"
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Old 20th February 2017, 02:41 AM   #16
L.rivera92172 is offline L.rivera92172  United States
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Hey Patrick couldn't you make a Costa array paraline hybrid to combine a 2 way with a 8in and tweeter or with your 8 point star phase plug
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Old 8th November 2017, 09:35 PM   #17
Chris8sirhC is offline Chris8sirhC  United States
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Has anybody tried this with a large esl pannel to control horizontal dispersion?

Last edited by Chris8sirhC; 8th November 2017 at 09:37 PM.
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Old 8th November 2017, 10:08 PM   #18
zmyrna is offline zmyrna  United Kingdom
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i think this is a more successful phase plug experiment with BG planars;
BG NEO 3 FR optimization
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Old 10th November 2017, 10:26 PM   #19
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by zmyrna View Post
i think this is a more successful phase plug experiment with BG planars;
BG NEO 3 FR optimization
That is VERY nice!
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Old 11th November 2017, 06:38 PM   #20
Chris8sirhC is offline Chris8sirhC  United States
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Why not combine them? And have the bars cover both the vertical and horizontal axis (make the entire transition of the oval openings a smooth transition)

Also I wonder how much more quickly distortion ramps up as power levels go up with the costas array vs standard.

Last edited by Chris8sirhC; 11th November 2017 at 06:42 PM.
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