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Old 6th October 2012, 01:26 PM   #331
DrDyna is offline DrDyna  United States
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I've been following these Paraline threads with much interest. I'd really like to take a crack at building some.

I do have one question though, everyone seems to be building or testing for > 1 khz response, has anyone tried making a monster one for say, > 100 hz?
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Old 6th October 2012, 02:24 PM   #332
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Is directivity control at 100Hz a problem worth this much effort to fix it?
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Old 6th October 2012, 02:32 PM   #333
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by kenpeter View Post
Is directivity control at 100Hz a problem worth this much effort to fix it?
I wouldn't suspect it is, what I'm interested in is seeing a large (6 or 7 foot?) radiating area, and how it would sound. (plus it would look brutal as f***).
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Old 6th October 2012, 03:16 PM   #334
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Quote:
Originally Posted by kenpeter View Post
I'm just sayin' try the outer edge of the parabola only.
Avoid the "round" part near the middle.

Why? Cause middle part is all nearly the same reflection
distance back toward the driver. Maybe aggrivates dips?

Anyways, also thinkin you might fold this down the
centerline, and then drivers would be on opposite sides,
instead of crowding each other.

Aplologies to drawing above, I totally butchered it...
Click the image to open in full size.

The above measurement is from natehansen66, and gives us some 'food for thought' on the question of reflections causing dips.

The thing about the dips which has me perplexed is that they must be VERY short dimensions. For instance, in nate's measurements we see a dip at 11khz. That frequency is 3cm long. Typically we would expect a dip to be caused by sound reflecting back and being out of phase. IE, it travels one quarter wavelength, runs into something, comes back again, and is now 180 degrees out of phase, which causes a dip.

But if my understanding of dips is correct, that means that the dip at 11khz in Nate's measurement is being caused by a reflection at a dimension that's just 0.75cm in distance.



To me, that seems suspiciously consistent with the *height* of the inner duct. In other words, varying the *shape* of the Paraline won't get us a lot of benefit, but varying the *height* will.

Click the image to open in full size.

The easiest way to vary the height of the Paraline, IMHO, is to dimple it.
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Old 6th October 2012, 05:17 PM   #335
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Quote:
Originally Posted by Patrick Bateman View Post
The above measurement is from natehansen66, and gives us some 'food for thought' on the question of reflections causing dips.
I couldn't remember what exactly those measurements were of, so I had to look at my post that went with it. That Paraline was using a piece of cardboard for the driver mount plate, with 2 FR88's flanking an old 1" soft dome tweeter. There was little to no precision in the mid entrance holes, and they were about .75" in diameter.

I'm making new driver plates right now (had one built but goofed on a measurement and threw the whole thing off center), and I've got a horn shell done. I'll see if I can get some new measurements of a more refined Paraline on a 60x40 conical horn with a 20" wide x 25" tall mouth and see what happens.

What are you thinking with the dimple idea PB?
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Old 6th October 2012, 05:28 PM   #336
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Quote:
Originally Posted by natehansen66 View Post
I couldn't remember what exactly those measurements were of, so I had to look at my post that went with it. That Paraline was using a piece of cardboard for the driver mount plate, with 2 FR88's flanking an old 1" soft dome tweeter. There was little to no precision in the mid entrance holes, and they were about .75" in diameter.

I'm making new driver plates right now (had one built but goofed on a measurement and threw the whole thing off center), and I've got a horn shell done. I'll see if I can get some new measurements of a more refined Paraline on a 60x40 conical horn with a 20" wide x 25" tall mouth and see what happens.

What are you thinking with the dimple idea PB?
Basically there seems to be a dip in the response which correlates with a dimension of about 0.3" or 0.75cm.

That dip may be consistent with the height of the Paraline.

Therefore, dimpling the Paraline might smooth out the response. It basically varies the height of the duct.

The thing that's vexing me is that the dip in response gets lower as the angle varies. And I wouldn't expect that to occur if the dip is caused by the interior height of the Paraline. (IE, if the dip gets lower as frequency gets lower, one would expect that it's due to a reflection that varies based on angle.)
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Old 7th October 2012, 12:05 AM   #337
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I made a single paraline but this time it is all 3/16 to see if the HF improved. Indeed it did, but peaks around 1.5k and 4.5k are prominent. I wonder if these are related to the length of the paraline whose fold is 3 inches long per side. Wavelength of 1.5K is 9 inches, 4.5K is 3 inches. Is this a resonant mode? Maybe it is just a coincidence.
Attached Images
File Type: jpg single paraline.jpg (121.2 KB, 526 views)
File Type: jpg IMAGE_573F065F-2FBC-4EF9-B16A-09072DFEB200.JPG (154.0 KB, 529 views)
File Type: jpg IMAGE_DAD6D673-CD4A-4D9B-87B8-79FD443FB6CD.JPG (141.3 KB, 517 views)
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Old 7th October 2012, 02:21 AM   #338
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Ok, so I ran another test to see the individual FR of the original paraline used in the array. Both single paralines show the bumps. The 3/16 paraline shows extended HF. 3/16 router bit vs 1/4 router bit.

Also, the interaction between the paralines in the array is lowering the HF and bringing up the mids. I don't have any experience with arrays so I can't explain what may be happening. What happens to the phase as you go from the the center of the slot to the ends?
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Old 8th October 2012, 01:53 AM   #339
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Some people like dipoles. Good drivers for dipole use are hard to find - the drivers have to have an equal radiation pattern front and rear. Magnets and other structures get in the way of the rear radiation. So how about a dipole Paraline? The "classic" Paraline folds so that both "sides" of the folded line exit beside each other at the front. How about folding so that one "side" exits at the front and the other exits at the rear? The driver does get in the way for the rear exit, but the mounting and "folds" can be offset so that the exits are still straight. (Same geometry as a classic Paraline with two drivers mounted face-to-face.)

Edit: Oops, the trouble with thinking out loud is that it's easy to forget to remove one's foot first...
the above wouldn't be a true dipole, as the front and rear radiation would be in phase. Shouldn't be an issue for HF use, though.

Last edited by Don Hills; 8th October 2012 at 01:57 AM.
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Old 8th October 2012, 05:58 AM   #340
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Quote:
Originally Posted by Patrick Bateman View Post
Basically there seems to be a dip in the response which correlates with a dimension of about 0.3" or 0.75cm.

That dip may be consistent with the height of the Paraline.

Therefore, dimpling the Paraline might smooth out the response. It basically varies the height of the duct.

The thing that's vexing me is that the dip in response gets lower as the angle varies. And I wouldn't expect that to occur if the dip is caused by the interior height of the Paraline. (IE, if the dip gets lower as frequency gets lower, one would expect that it's due to a reflection that varies based on angle.)

Here is an interesting visual it was just so similar looking I thought I would post it. Please forgive the interuption. Best regards Moray James.
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File Type: jpg Paraline fold.jpg (73.8 KB, 341 views)
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