Square Pegs

[Patrick Bateman]

Originally Posted by Naturlyd

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.

Hornresp has no way to model the bends in the Paraline.
I'm modeling the Paraline using the volume of the radial rings in the wavefront expansion.
So my model doesn't include two things:

1) it doesn't account for the reflectors. We have no way to account for it, so we have to pretend it's not there, unfortunately. In the real world, the reflectors appears to roll off the highs.
2) My model uses an arbitrary size for the horn throat. This is a bit tricky also, since the "true" value of the throat is somewhere between zero and the size of the radiator that's driving the Paraline. For instance, if the radiator at the apex of the Paraline is a 10cm compression driver dome, then the 'true' size of the throat is somewhere between zero and 10 cm.

If you really want to go crazy with this, the docs for Akabak describe a model for a compression driver that includes virtually everything. Hornresp is easier to use of course, and gives results that get us 'in the ballpark.'

[Don Hills]

Originally Posted by bear

s ... 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...?

Good point... a horn formed from 2 discs has a mouth area of 3.1416 * diameter * plate spacing. A Paraline has a mouth area of 2 * diameter * plate spacing.
It's hard to model though, because the distance from the throat to the fold varies from half the horn length to the full horn length.

[Patrick Bateman]

Originally Posted by Don Hills

Good point... a horn formed from 2 discs has a mouth area of 3.1416 * diameter * plate spacing. A Paraline has a mouth area of 2 * diameter * plate spacing.
It's a diverging horn from the throat to the old and then converging from the fold to the mouth. It's hard to model though, because the distance from the throat to the fold varies from half the horn length to the full horn length.

I posted the math for how wide the Paraline mouth should be. It's somewhere in this thread. IIRC, it's (pi * internal height.)

For instance, with an internal height of 0.635cm, the Paraline mouth measures 1.99cm wide.

Note the width will be wider due to the reflector that's typically placed in the mouth.

[Don Hills]

Originally Posted by Patrick Bateman

I posted the math for how wide the Paraline mouth should be. It's somewhere in this thread. IIRC, it's (pi * internal height.)

For instance, with an internal height of 0.635cm, the Paraline mouth measures 1.99cm wide.

Note the width will be wider due to the reflector that's typically placed in the mouth.

Making the mouth wider doesn't compensate for the different expansion rate in the post-fold part of the horn. You'd need to make the plate spaciing divergent in the latter half of the horn. (It would have to taper from 0.635 cm at the fold to 1.99 cm at the centre of the mouth slot, tapering back down to 0.635 cm at the ends of the slot.)

[Patrick Bateman]

Originally Posted by Don Hills

Making the mouth wider doesn't compensate for the different expansion rate in the post-fold part of the horn. You'd need to make the plate spaciing divergent in the latter half of the horn. (It would have to taper from 0.635 cm at the fold to 1.99 cm at the centre of the mouth slot, tapering back down to 0.635 cm at the ends of the slot.)

The expansion rate isn't different after the fold.

The horn expands in 360 degrees in one dimensions, and zero degrees in the other. It expands out like rays of sunshine. That's one of the reasons I named my thread on the Paraline 'Sunshine'

[Don Hills]

Originally Posted by Patrick Bateman

The expansion rate isn't different after the fold.

The horn expands in 360 degrees in one dimensions, and zero degrees in the other. It expands out like rays of sunshine. That's one of the reasons I named my thread on the Paraline 'Sunshine'

You might care to re-evaluate your conclusion.
The expansion rate from the throat to the fold is standard radial horn parabolic. The expansion rate from the fold to the mouth is somewhat less.
More specifically, the expansion rate from the throat to the ends of the mouth line is standard radial horn. Now look at 90 degrees, from the throat through the fold to the centre of the mouth line.

Simple math, just compare the mouth areas.

Standard radial horn formed of 2 parallel discs, 20 cm diameter, 2 mm apart:
Mouth area = 3.14 * 20 * 0.2 = 12.56 cm2.

Paraline with 20 cm diameter (mouth length) and 2 mm plate spacing:
Mouth area = 2 * 20 * 0.2 = 8 cm2.

(Making the mouth slot wider does not compensate for lack of expansion earlier in the horn.)

Simulating this is difficult, because the point at which the expansion rate changes varies from half way down the horn to its mouth. Probably the best that can be done with Hornresp is to use a 2-segment horn with the expansion rate of the second half chosen as an average of the two limit cases. The attached image shows the two limit cases - the expansion rate from the throat to the ends of the mouth line versus the expansion rate at right angles to the mouth line. (The mouth areas follow the two calculations above.)

[kenpeter]

Styrofoam Smith Horn

Wow, look at that date, 29 Oct 2009...
Too bad I never followed up.
Totally forgot I ever had the idea.

Originally Posted by kenpeter

I'm now thinking Unity here as well...

An if that news weren't strange enough. I'm also thinking what-if
you fold a Smith horn???? Folded on a parabolic curve... Can it be
tricked to exit from a flat front slot in one phase, as-if a line array?
Does the non-expanding part (after the parabolic) serve as a plane
wave tube?

And if that still ain't strange enough. Also thinkin Smith Unity to
replace the driver in a Karlson type enclosure. That would mean
loading the backs of the cones to the K box. Not sure how thats
gonna mess with EBP??? As most advice I've heard is to seal the
backs of such cones in attempt to raise both Fs and EBP.

I don't think Styrofoam will be the material of choice, but might
still get abused here and there...
Last edited by kenpeter; 29th October 2009 at 02:56 PM.

[kenpeter]

Danley filed in June 2009, but wasn't published till Sept 2012.
Rats! There goes my braggin' rites...

[Patrick Bateman]

Originally Posted by Patrick Bateman

On this forum, Tom Danley has given us some information on some interesting new ways to fold a horn. These new horns include the VTC Paraline, which combines two compression drivers on one horn, and the Jericho J4, which uses what he calls a 'layered combiner' to load 64 compression drivers on one horn.

Unity Paraline - YouTube

I decided to build one this week.

Once you figure out how they work, they're a lot of fun to build. They're waaaaaaaaaay easier to assemble than a Synergy horn, that's for sure. I built this one in under two hours.

The device that I built is neither a Paraline nor a layered a combiner. For the most part, it's a simplification of the Paraline. (I could build a *real* Paraline, but I didn't want to for this project, I wanted to do a 'proof of concept' first.)

As usual, my projects are completely kludgey and rushed and crude, but you get the general idea.

In the video, I think you'll notice a few things:

#1 - Although my compression driver appears to be firing through a block of wood, I have extension out to at least 18khz
#2 - Have you ever seen a horn that was less than four centimeters deep?
#3 - Have you ever seen a Unity horn that was smaller than a 8" woofer?

Hope you enjoy the vid.

Diagrams of the layered combiner are now available. The patent number is US20120328140 A1

[Patrick Bateman]

Here's the link:

Patent US20120328140 - Horn enclosure for combining sound output - Google Patents