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Old 5th September 2012, 02:48 AM   #231
JLH is offline JLH  United States
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Quote:
Originally Posted by natehansen66 View Post
I built a Paraline this weekend, and did some quick and dirty testing today. I dimensioned it using Bateman's spreadsheet for 40 deg vertical dispersion, so its "pinched." I'm not much of a wood worker, more of a hack really, but I put a lot of effort into getting these things right. I made the "eye cutout" pieces with 45 deg angles because the abrupt 90 deg corners were bothering me. Unfortunately I made that decision an hour and a half away from my computer and CAD software, so I had to remake the template on the fly. I think it came out ok.

I was eager to see if it worked, so I put a 1" dome tweeter over the 1" hole for the comp driver. This was pretty sketchy, because the dome has a chamfer on its faceplate that the dome recesses into, so I was effectively creating a chamber for the dome. The yellow line is the measurement. I haven't yet made a reflector for the hf driver throat. Measuring with and without the mouth reflector showed that I got me a little smoother hf, with a tad more extension. Either way, I think I'm running into what Don is talking about with the path-length differences. Obviously this thing is low-passing the tweeter. My pathlength difference in the bend (with my angled path) comes out to about .375", which works out to about 12k at 1/3 wl.

I thought that maybe the chamber created by the dome on my driver mount plate was doing the filtering, so I quick rigged up a piece of cardboard with a hole large enough for the tweeter dome to protrude through (I took the faceplate off). That's the red measurement. A bit more extension and less bottom end.

Obviously this setup with the dome is far from optimal, but it'll be interesting to see how the comp driver performs once I get it.
I need to compliment you on your workmanship, well done. Your measurements are much better than you might think. I've played with horn loading Dynaudio soft dome midranges and tweeters like Dr. Edgar did back in the day. These kind of drivers are not really appropriate for horn loading applications. They always rolloff because they lack the motor strength to over come the dome mass at the high end. They are not compression drivers. We also must remember that the radial expansion of the paraline approximates a conical horn. That means it will have a falling high frequency response. Your measurements show a high frequency rolloff, but I would have expected it to be much worse. Quite honestly, what you have there is very good for the limitations you have in play.
Attached Images
File Type: jpg d54a.jpg (164.7 KB, 452 views)
File Type: jpg Dynaudio275Hz3.jpg (15.3 KB, 453 views)
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Last edited by JLH; 5th September 2012 at 03:00 AM. Reason: added pics
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Old 5th September 2012, 02:50 AM   #232
JLH is offline JLH  United States
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Quote:
Originally Posted by Don Hills View Post
So. A Paraline constructed of 1/4" material. Highest frequency 9 KHz or 18 KHz?
Just look at the Danley paraline and that should be obvious.
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Old 5th September 2012, 03:11 AM   #233
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Quote:
Originally Posted by JLH View Post
I need to compliment you on your workmanship, well done. Your measurements are much better than you might think.
Thanks! I gotta say my pic makes them look nicer than they are though.

I was expecting the top end to roll off, but 20db seemed a bit much. Like you say though, a dome isn't exactly a comp driver. I'm not a horn guy and I've never used a compression driver so this is uncharted territory for me.

I wanted to see how a mid performed on the Paraline, and the closest candidate I had was a Fountek FR88 fullranger. I used plumber's putty to seal up the basket, and also to seal it to the throat plate. Graph included.

I eq'd it flat within its bandwidth, then redid the crossover on my Neo8's (the upper mids of my 4-way dipoles) to match the FR88 and listened. The Neo sounded dull and lifeless compared to the Paraline. I guess this is the dynamics you guys keep on about . Then I whipped up a ghetto waveguide out of cardboard and duct tape for the Paraline and listened some more. Very promising! Despite the limited bandwidth and obviously very wrong cardboard waveguide I really like what I was hearing. Definitely potential here.
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File Type: jpg fr88 on paraline.jpg (108.5 KB, 456 views)

Last edited by natehansen66; 5th September 2012 at 03:14 AM.
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Old 5th September 2012, 04:58 AM   #234
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JLH/PB,

I can conceptually see the conical horn approximation from driver to 'edge' of paraline upon which the wave either doubles back and quicklyexits (ends of line) or doubles back and travels some distance prior to exit (i do understand that pathlengths can be adjusted by the width of the eye). During the longer double-backs, does the horn 'area' keep expanding, or is the 'area' getting smaller until the wave hits the 90 degree reflector at the mouth?

I just need to unfold it in my head. A pic/animation here is literally worth a thousand words.

Great experimentation going on here with a very novel and interesting idea from TD...

JSS
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Old 5th September 2012, 05:24 AM   #235
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Quote:
Originally Posted by natehansen66 View Post
I wanted to see how a mid performed on the Paraline, and the closest candidate I had was a Fountek FR88 fullranger. I used plumber's putty to seal up the basket, and also to seal it to the throat plate. Graph included.

I eq'd it flat within its bandwidth, then redid the crossover on my Neo8's (the upper mids of my 4-way dipoles) to match the FR88 and listened. The Neo sounded dull and lifeless compared to the Paraline. I guess this is the dynamics you guys keep on about . Then I whipped up a ghetto waveguide out of cardboard and duct tape for the Paraline and listened some more. Very promising! Despite the limited bandwidth and obviously very wrong cardboard waveguide I really like what I was hearing. Definitely potential here.
Unity horns give you the point source radiation of a Lowther, with potentially better directivity and bandwidth.

This is why I've been a lunatic about them for a decade now

https://www.google.com/#hl=en&sclien...teman%22+unity
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Old 5th September 2012, 05:30 AM   #236
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Originally Posted by JLH View Post
... We also must remember that the radial expansion of the paraline approximates a conical horn. ...
??? I thought it was parabolic.

For a Paraline (or its unfolded equivalent), the mouth area for a given length (radius) is pi * diameter * slot width. Double the length (radius), double the area.

For an axisymmetrical conical horn, the mouth area for a given length is pi * radius squared. Double the length, quadruple the area.

It seems counterintuitive to me... what am I missing?
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Old 5th September 2012, 05:53 AM   #237
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Don Hills,
I've been wondering that myself as the expansion rate of the paraline seems like a linear expansion and not conic or exponential. Am I also missing something in my math here?
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Old 5th September 2012, 11:10 AM   #238
JLH is offline JLH  United States
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The key word here guys is "approximates". I know several of us on here are very detailed and analytically minded, but we need to keep this stuff in perspective. I've built so many things I have a feel for what is important and what can be stretched a little bit. My grandfather, whom was a master machinist for Ford Motor Company, had a saying for when people became overly anal-retentive about details. He would tell these people, “Yes you can go ahead and do that, but it’s like picking fly s*** out of pepper”.
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Old 5th September 2012, 11:13 AM   #239
JLH is offline JLH  United States
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Quote:
Originally Posted by natehansen66 View Post
Thanks! I gotta say my pic makes them look nicer than they are though.

I was expecting the top end to roll off, but 20db seemed a bit much. Like you say though, a dome isn't exactly a comp driver. I'm not a horn guy and I've never used a compression driver so this is uncharted territory for me.

I wanted to see how a mid performed on the Paraline, and the closest candidate I had was a Fountek FR88 fullranger. I used plumber's putty to seal up the basket, and also to seal it to the throat plate. Graph included.

I eq'd it flat within its bandwidth, then redid the crossover on my Neo8's (the upper mids of my 4-way dipoles) to match the FR88 and listened. The Neo sounded dull and lifeless compared to the Paraline. I guess this is the dynamics you guys keep on about . Then I whipped up a ghetto waveguide out of cardboard and duct tape for the Paraline and listened some more. Very promising! Despite the limited bandwidth and obviously very wrong cardboard waveguide I really like what I was hearing. Definitely potential here.
As your measurement indicates, you made the mass rolloff even worse by placing a midrange onto the paraline. Being down 20dB with a dome tweeter is quite good. Even a compression driver is down a good 10dB most of the time.
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Old 5th September 2012, 11:31 AM   #240
JLH is offline JLH  United States
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Quote:
Originally Posted by maxmercy View Post
JLH/PB,

I can conceptually see the conical horn approximation from driver to 'edge' of paraline upon which the wave either doubles back and quicklyexits (ends of line) or doubles back and travels some distance prior to exit (i do understand that pathlengths can be adjusted by the width of the eye). During the longer double-backs, does the horn 'area' keep expanding, or is the 'area' getting smaller until the wave hits the 90 degree reflector at the mouth?

I just need to unfold it in my head. A pic/animation here is literally worth a thousand words.

Great experimentation going on here with a very novel and interesting idea from TD...

JSS
Itís always expanding. It is a circle that has two parallel sides folded over. There is no limit to how many times you fold up the sides of the circle. Instead of a single fold like in my attached picture, you can fold the sides into a Z shape.
Attached Images
File Type: jpg paraline_folding.JPG (33.7 KB, 420 views)
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