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Old 28th November 2019, 06:46 AM   #11
mayhem13 is offline mayhem13  United States
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Thanks for posting these results! I’ve been an advocate of the Tymphany NE series of tweeters for a while now. Ive not used either the 19 or 25 on a waveguide as of yet and I’ve seen your testing where the larger domes develop a response anomaly related to the dome diameter..............does the 25 behave like this as well?........could a phase plug amorealate this?
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Old 28th November 2019, 11:51 AM   #12
pelanj is offline pelanj  Czech Republic
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Very interesting thread! I just thought a few days ago what it would take to make your own compression driver

I need to order a pair of Vifa's in January, so that they do not get lost in the crazy shipping period before Christmas.
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Old 28th November 2019, 01:23 PM   #13
kipman725 is offline kipman725  United Kingdom
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This is excellent work. The dome is operating above breakup? so the phase plug may not be working as intended? are the phase plugs calculated to equalise the path lengths at the throat from the various points on the diaphragm?
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Old 28th November 2019, 06:42 PM   #14
Patrick Bateman is offline Patrick Bateman  United States
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Click the image to open in full size.

Click the image to open in full size.

I made a new phase plug, what was supposed to be an "improved" version of the tangerine phase plug. But it actually worked WORSE.

In this post I'll take a stab at explaining why.

Click the image to open in full size.

Here is the response of the NEW tangerine phase plug. It uses nine channels instead of six. I copied this from Kef, they use nine channels in the LS50. I thought that perhaps using an odd number of channels might be there for some reason. Celestion (sister company of Kef) uses three channels in the phase plug in my Waslo Cosynes. So they seem to be using an odd number of channels for some reason.

Unfortunately, the new phase plug worked worse than the old, and has a noticeable on-axis dip at 7khz.

Click the image to open in full size.

Here's the six channel phase plug, from two days ago. It not only has superior response, it also uses less EQ.

Click the image to open in full size.

I think the issue is with this curve right here. The curve from the center of the phase plug that leads to the channels of the phase plug.

Click the image to open in full size.

Here's a 2D representation of the two different phase plugs. If you look at the old phase plug (the six channel) versus the new (nine channel), the new one is curved. It's curved because I smoothed all the parts inside of the NEW phase plug. And when I say "curved", I mean that the center piece of the phase plug, which goes right through the center of the device, and meets the tweeter about 2mm from the tip of the dome, THAT part is curved in the new one, but not the old.

Because the old one ISN'T curved, the pathlength from the CENTER of the tweeter dome is longer than in the new one. To be specific, the sound from the center of the dome in the OLD phase plug has to travel 4.5mm. This wasn't intentional, but it happens to be almost *exactly* the same as the HEIGHT of the dome. And this is super important:

In a dome tweeter, the sound radiated from the tip of the dome leads the sound radiated from the edge of the dome.

For instance, the NE19 dome leads the *edge* of the tweeter by 4.5mm.

I think this pathlength difference in the NEW phase plug is leading to the dips on-axis. In the old phase plug, the shape of the center channel adds a delay, which happens to match the distance that the tip of the dome leads the edge of the dome. (Was simply a lucky coincidence that this happened.)

Long story short: it's time to put together a *fourth* phase plug, and see if that works better.
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Old 28th November 2019, 10:15 PM   #15
kipman725 is offline kipman725  United Kingdom
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Click the image to open in full size.

the picture you posted claims the spacing is uneven (and it looks like it) and the plug has 11 channels. I'm guessing its important for this type of phase plug to have no rotational symmetry.
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Old 29th November 2019, 02:25 AM   #16
Pallas is offline Pallas  Pakistan
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Can your printer print something like the Voshvillo (sp?) design used in the better current JBLs?
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Old 29th November 2019, 03:51 AM   #17
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by kipman725 View Post
Click the image to open in full size.

the picture you posted claims the spacing is uneven (and it looks like it) and the plug has 11 channels. I'm guessing its important for this type of phase plug to have no rotational symmetry.
Nice catch. I didn't notice that.
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Old 29th November 2019, 04:07 AM   #18
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by Pallas View Post
Can your printer print something like the Voshvillo (sp?) design used in the better current JBLs?
Click the image to open in full size.

Click the image to open in full size.

IMHO, the new JBL studio monitors are basically biradial.

Click the image to open in full size.

Similar to these JBL 4430s, but truncated, and without the diffraction slot.

Click the image to open in full size.

The JBL Synthesis in-walls are designed to be as shallow as possible, and cannot be modeled in my software. (123D.) The shape of the Synthesis speaker was designed used a BEM optimized, as described here :

https://www.comsol.jp/paper/download...esentation.pdf

This paper is a MUST READ. Probably the best paper on waveguides I've read in the last year.
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Old 29th November 2019, 06:36 PM   #19
Pallas is offline Pallas  Pakistan
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Quote:
Originally Posted by Patrick Bateman View Post
Click the image to open in full size.

Click the image to open in full size.

IMHO, the new JBL studio monitors are basically biradial.
I was referring specifically to the current style phase plug:

Click the image to open in full size.
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Old 29th November 2019, 08:45 PM   #20
Patrick Bateman is offline Patrick Bateman  United States
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Oh, that phase plug will only work on a ring radiator. The Voishvillo phase plug takes a ring and channels it through a square. By doing so, it varies the pathlengths by plus or minus seven millimeters. (I did that off the top of my head, I'd have to take my 2408H-1 apart to verify the pathlength difference.)
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