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Old 26th November 2012, 10:22 PM   #371
bwaslo is offline bwaslo  United States
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So... can you do a tapped horn as a Paraline? (possibly an ignorant question, I'm still foggy about paralines).
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Old 26th November 2012, 10:24 PM   #372
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So now that we have a few pieces, we can model our sub in Hornresp. We have assembled the following:

1) we've chosen a target cutoff for the sub
2) we've chosen a sub that will work with that cut off (mcm 55-2421)
3) I've provided a spreadsheet that'll calculate the area of the segments and the cutoff of the horn
4) we have s/w that will model the horn (hornresp)

Using my spreadsheet, I came up with the following sim:

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

Here's some observations about my sim:

1) note how thin the sub is. It's ONE FIFTH of an inch thick.
2) I had to use four subs. Not for power handling, but simply to flatten out response on the low end. Another option would be to use two subs and a thickness of one tenth of an inch, but I don't know anyone that sells wood that thin!
3) The Paraline dimensions are ridiculously large. 24 feet on one side by twelve on the other.
4) Output and efficiency are quite good. Nearly 130dB at 60hz and 125dB at 40hz.




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Old 26th November 2012, 10:27 PM   #373
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Quote:
Originally Posted by bwaslo View Post
So... can you do a tapped horn as a Paraline? (possibly an ignorant question, I'm still foggy about paralines).
You can do a front loaded horn, a back loaded horn and tapped horns in a Paraline.

The output of the tapped horn will be virtually identical to the FLH because the front and the back of the driver are so close to the throat and the mouth, respectively.

Also note that in the real world I'd expect that the 'ripple' would be a lot less severe than hornresp predicts, since the Paraline acts as a baffle seperating the front and the back wave in a manner that's much more substantial and effective than in a typical folded horn.



In a lot of ways I think that Paraline back loaded horns are an interesting alternative to conventional dipoles.
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Old 26th November 2012, 10:34 PM   #374
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Click the image to open in full size.
Click the image to open in full size.


If I didn't make it clear, here's how my spreadsheet 'maps' to hornresp:

1) the area of the fields S2, S3, S4, and S5 are lifted directly from my spreadsheet and pasted into HORNRESP
2) The area of the horn throat is the area of the cone. This one is a bit tricky, because theoretically the area at the center of the Paraline is zero(!) Of course that isn't the case in the real world because there's a volume of air between the cone and the woofer and the Paraline. That volume is fairly substantial; as much as 200-300 sq cm for an 8" woofer. This volume can be reduced if necessary, by putting a baffle in front of the cone.
3) Be sure that the Paraline internal volume from my spreadsheet is in the same ballpark as the volume of the horn from hornresp. If not, you made a mistake somewhere
4) Note that the internal height of the Paraline from my spreadsheet has a direct effect on the overall volume of the horn, and the area of segments S2, S3, S4, and S5
5) The length of the conical segments is constant. It is equivalent to the first value of "X" from cell E4 of the spreadsheet.
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Old 27th November 2012, 07:19 AM   #375
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Thanks a lot for answering many of my questions, PB. While I have learned a lot from your earlier posts about Unity and Paraline, now I am actually left with even more questions.

This may have been addressed earlier, but why do you split the Paraline into 4 segments in your spreadsheet/Hornresp? This is the eye-shaped Paraline?

- Referring to the patent its difficult to see why you split the Paraline into 4 segments, each with a quarter of the total pathlength. Wouldnt the pathlength of section D1 and D2 be close to the total pathlength? If S1-S2 was the entry and rather short, S2-S3 was D1, S3-S4 was the 180 deg. bend and also short, and S4-S5 was D2, I could understand the consept. Could someone please explain?

- If the Paraline horn is a round horn with 360 degree horisontal spread (like the filling in an Oreo cookie) thats folded, why do we need to split the path into sections? Do the folds in the Paraline truncate or in other ways affect the pathway in such a way that we need to section the horn to simulate the effect? If not, then why do we need more than S1 as the entrance and S2 as the exit/slot to simulate a Paraline horn? Is not the pathway expanding in a linear fashion between those two points?

This is fun!! Just to make my design target clear, the overall goal is to have a FLH bass/midbass 80-400Hz with proper hornloading but I could settle with somewhat less BW. My interest in the Paraline, besides a fascination for brilliant consepts, is the promise of reducing the depth of the horn, and a hope that the folds in the Paraline would not affect the upper bass/lower midrange to much. But if a Paraline mainly is a directivity-device and do not contribute much to the loading in the lower frequencies, I guess I am better of with a "scorpion-style" midbasshorn with only one, gentle bend. My limited experience with folded FLH >250Hz has not been promising.

Like many other, its not the overall bulk of a hornsystem thats the problem, its the depth of proper horns. The system will use distributed subs <80Hz and large horn >400Hz.
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Old 5th December 2012, 11:11 PM   #376
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And the testing continues.......

I had an extra driver plate, so I set it up for 2 mid drivers with the frustrum and port at the center of the mid cone, rather than offset as I have it on my 4 mid Paraline. The central port puts it about 3.5" away from the CD entrance. The first port iteration was a .25" wide x .5" long slot port (red curve), then I went with a .5" dia port (green curve). The lavender curve is my 4 driver Paraline with the offset ports about 2.2" from the CD entrance. These were all taken on the 60x40 conicals I built.

Click the image to open in full size.

The 1khz notch on the centered port versions corresponds pretty well with the 3.5" distance from the CD entrance. You can see a bit extra output past that notch though over the offset port config.

Next, I measured right out of the mid port, not on the Paraline to take that out of the equation. The purple curve is the central port, yellow is the offset port, and red is the mid response on the Paraline attached to the horn:

Click the image to open in full size.

A good bit more hf extension with the centralized port vs the offset port, although the previous test shows the importance of having the mid entry as close as possible to the CD entry. Can't I have my cake and eat it too?

I'm thinking the BMS 4540nd is the answer here. Smaller in diameter than my 4524s, and I can make a screw on adapter that will sit the screen on the driver exit right down into the Paraline itself. This way I can eliminate about 1.25" just with the driver itself, plus I can move the drivers in a bit more and get the mid ports in a more central location without sacrificing the distance to the CD entrance. Total balancing act here!

The deep notches in the CD response have been bothering me as well. I thought I remembered a pretty workable response of the CD on the Paraline and horn with no mid ports but I can't find the graphs. I figured the notches were caused by the mid ports, so I blocked them off and measured the CD on the Paraline on the horn again (green is no mid ports, red is with the mid ports):

Click the image to open in full size.

The ports seem to add to the 5.2khz notch, but not as much as I thought and the others are not affected. I've got my Paralines lined with open cell foam sold for shop vacs. The mid ports and frustrums have the foam as well. Lost the graphs from that bit of testing too, but the foam helps smooth things out a good bit past 8-9khz.
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Old 10th December 2012, 02:26 AM   #377
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Ok, I found this thread following another thread... I had seen the Paraline on the pro website that showed the construction animation some time back. Scratched my head.

Thought it might be cool for PA applications, but maybe not home use...

I agree with Kindhornman's earlier comment that this is a diffraction slot loading... sure looks and seems to act like one.

But all this talk about it has me thinking. Has anyone mapped out the expansions unfolded?? Reading through my swiss cheese synaptic conceptotron auxilliary unit came up with a thought. This looks a bit like the expansion found on the end of a Mantaray horn. That one lets the wavefront expand conically in the "vertical" dimension (assuming you put the horn that way), while actually reducing the dimension, or keeping it almost parallel (maybe it just expands slightly - haven't looked at one for years now), this results in a tall thin slot, which is then loaded into the end of a conical horn (it actually has one or two conical "steps" - but that's not important).

Seems to me that if you made the unfolded paraline you'd have an impossible to make work almost 180 degree vertical expansion and nil horizontal expansion, terminating with that diffraction slot and phase plug thingie...

Ok so you can't build that in practical terms, but if you took two drivers, left and right, aimed them at a center point, and then had an expansion with a slot open in the center, that'd be more or less this paraline unfolded.

A try at ascii art:


C|< | >D

A little imagination required. Left and right compression drivers C| and D, the conic expansion with nil expansion in the direction perpendicular to this page are < and > and the exit on one side only is | . Hope this makes some sense.

Actually this double driver version can be built... the thing that can't be gotten without the folding is the equal distance to a vertical slot from a single point! That's the beauty of Danley's idea it seems to me.

This assumes that the air in the chamber acts in a fashion that actually requires or creates equal path lengths and that it doesn't act as a single hydraulic volume. There's some question there... but I can accept the idea of equal path lengths.

Anyone see it this way besides me?

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Old 10th December 2012, 02:39 AM   #378
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Originally Posted by bear View Post
... Has anyone mapped out the expansions unfolded?? ... Seems to me that if you made the unfolded paraline you'd have an impossible to make work almost 180 degree vertical expansion and nil horizontal expansion, terminating with that diffraction slot and phase plug thingie... ...
An unfolded paraline is 2 circular disks mounted a short distance apart, with a driver attached to a hole at the centre of one of the disks. 360 degree expansion in one plane and none in the other plane.
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Old 10th December 2012, 04:05 AM   #379
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sure, two discs, hole in the center of one, 1/4" apart, exit on the edges... except that does not converge to a straight line. Even cut in half.

And actually, only the first part of the expansion is 360 degrees... the second fold is not, otherwise it would not converge on a straight line...?
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Old 10th December 2012, 07:55 PM   #380
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Originally Posted by natehansen66 View Post
And the testing continues.......

I had an extra driver plate, so I set it up for 2 mid drivers with the frustrum and port at the center of the mid cone, rather than offset as I have it on my 4 mid Paraline. The central port puts it about 3.5" away from the CD entrance. The first port iteration was a .25" wide x .5" long slot port (red curve), then I went with a .5" dia port (green curve). The lavender curve is my 4 driver Paraline with the offset ports about 2.2" from the CD entrance. These were all taken on the 60x40 conicals I built.

Click the image to open in full size.

The 1khz notch on the centered port versions corresponds pretty well with the 3.5" distance from the CD entrance. You can see a bit extra output past that notch though over the offset port config.

Next, I measured right out of the mid port, not on the Paraline to take that out of the equation. The purple curve is the central port, yellow is the offset port, and red is the mid response on the Paraline attached to the horn:

Click the image to open in full size.

A good bit more hf extension with the centralized port vs the offset port, although the previous test shows the importance of having the mid entry as close as possible to the CD entry. Can't I have my cake and eat it too?

I'm thinking the BMS 4540nd is the answer here. Smaller in diameter than my 4524s, and I can make a screw on adapter that will sit the screen on the driver exit right down into the Paraline itself. This way I can eliminate about 1.25" just with the driver itself, plus I can move the drivers in a bit more and get the mid ports in a more central location without sacrificing the distance to the CD entrance. Total balancing act here!

The deep notches in the CD response have been bothering me as well. I thought I remembered a pretty workable response of the CD on the Paraline and horn with no mid ports but I can't find the graphs. I figured the notches were caused by the mid ports, so I blocked them off and measured the CD on the Paraline on the horn again (green is no mid ports, red is with the mid ports):

Click the image to open in full size.

The ports seem to add to the 5.2khz notch, but not as much as I thought and the others are not affected. I've got my Paralines lined with open cell foam sold for shop vacs. The mid ports and frustrums have the foam as well. Lost the graphs from that bit of testing too, but the foam helps smooth things out a good bit past 8-9khz.
If you mess around with hornresp, you'll notice that you get peaks and dips in frequency response when a horn is too small. If that's the thing that's causing the peaks and dips in your response, there's a couple of ways to fix it:

1) use a horn with larger volume (IE, use a Paraline with an internal height that's larger)
2) use a compression driver with higher BL; IIRC motor force is able to smooth out the peaks and dips in a horn that's too small

If the BMS 4524 is a ferrite compression driver, than the neo 4540 may help here. I wish I had a proper testing rig set up here; I have both the neo 4540 and the neo Celestion CDX1-1425 here.
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