# after 20 years of work...



## Patrick Bateman (Sep 11, 2006)

Square Pegs - Page 5 - diyAudio

For literally twenty years I've been trying to come up with a speaker that could satisfy a very specific set of criteria. Basically the ideal loudspeaker is a point source that can play full range. When you go with a two-way or a three-way there's a gazillion problems which are introduced. (directivity problems, it measures like crap off-axis, it doesn't sound 'real', etc.)

BUT

if you can get two drivers within about one-quarter wavelength they'll basically act like one.

If you've followed any of my threads all over the 'net, you'll see that I'm rather obsessed with this goal, and I think I've come pretty darn close this week:

Square Pegs - Page 5 - diyAudio


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## Chaos (Oct 27, 2005)

Caution:

Mad scientist at work!


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## roduk (Sep 19, 2008)

I don't get it Patrick, I want to get it and I'm capable of getting it, but it looks like a rough bit of ply with a joker smile cut into it and a compression driver firing through it?

You then mention connecting it to an ID horn?

Ok, after a bit more reading I understand a bit more (I think) So it's a thin box with two holes, one either side, one with a driver attached and the other, the horn exit (Which you intend to connect to the ID horn input flange.) This thin box contains what looks like a pair of cymbals mounted sort of isobarically? which the sound makes it's way around?


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## jpeezy (Feb 5, 2012)

Patrick thank you for helping advance our hobby/industry for no pay,just sheer curiosity,and desire for the very best.you may also be a little crazy/insane,probably not any worse than most of us please don't stop having fun!


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## Don Hills (Sep 23, 2009)

roduk said:


> I don't get it ...


Try looking at it this way:

Take 2 discs of thin plywood, about 12" in diameter. 
Mount them about 1/4" apart.
Drill a hole in the centre of one piece and mount a compression driver there. 

You now have a horn. It doesn't look like one, but if you think about it you should see that the area inside the horn increases as you move away from the driver, so it's a horn. Trouble is, the horn mouth radiates in a full 360 degree arc, so it's not very useful. 

Now grab two opposite edges of the horn and fold them over until they meet in the middle. If the fold lines were straight, the meeting edges would be curved. But if you can make the fold lines curved, the meeting edges will be straight and parallel. The whole assembly will be "eye shaped". The pictures Fig-4, fig-5, fig-6 in Tom Danley's patent application should help you visualise this:
Patent US20090323997 - Horn-loaded acoustic line source - Google Patents

The trick is to "fold" the horn so that all of the path lengths from the driver to the nearest part of the exit slot are always equal. This gives you:
- constant expansion from the driver to the horn "mouth". 
- identical arrival time at all parts of the "mouth".

This results in a "line source", which is the holy grail of people trying to build large speaker arrays for pro sound reinforcement. 

Patrick's later idea, where the mouth is curved instead of straight, still provides equal path lengths but allows two drivers to be mounted facing each other. Note that the "front" driver, the compression tweeter in this case, has to pass through the "front" of the horn so it can open into the centre of the rear chamber, facing the rear driver.


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## roduk (Sep 19, 2008)

The one thing I don't get is how you are going to mate the curved paraline throat with the ID horn?


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## Patrick Bateman (Sep 11, 2006)

roduk said:


> I don't get it Patrick, I want to get it and I'm capable of getting it, but it looks like a rough bit of ply with a joker smile cut into it and a compression driver firing through it?
> 
> You then mention connecting it to an ID horn?
> 
> Ok, after a bit more reading I understand a bit more (I think) So it's a thin box with two holes, one either side, one with a driver attached and the other, the horn exit (Which you intend to connect to the ID horn input flange.) This thin box contains what looks like a pair of cymbals mounted sort of isobarically? which the sound makes it's way around?


The Paraline is just a plain ol' horn. In this respect, it's little different than the prosound horns from JBL and the HLCDs from Image Dynamics.










Car audio horns have some problems though. (We wouldn't be on this forum if they were perfect, right? We'd just be listening to our music and not wasting time on the internet right?  )

The pathlengths on car audio horns are wonky. For instance, in this pic I've drawn, you can see that the pathlengths vary depending on angle. If you're seated in front of an Image Dynamics HLCD the pathlength from throat to mouth is eight inches or so, if you're in the other seat the pathlength from throat to mouth is something like 16".

And eight inches is quite a bit. Ideally we want all sound sources to be withing one quarter wavelength. At 18khz, that's a margin of error of just 0.1875"!!!


Crazy huh?









In the Paraline, the sound expands in a series of concentric rings. It's not cymbal shaped; it's perfectly flat inside and out.

Because the sound expands in a ring, *the pathlength from the throat to the mouth to the throat is exactly the same at every point.*

This is really important, and kind of a big deal, because you can't say that about any other horn really.









For instance, in a set of horns like this, the pathlengths for the three drivers vary significantly.










The last piece in the puzzle is folding that disc shape. We fold it by taking that circular disc shape, slicing it in two, then stacking the two pieces on top of each other.










Now you might think, 'why not just use a pipe or a conventional horn.' And the answer is *the pathlength is wrong.* For instance, in a piece of PVC pipe the length on the inside of the pipe is longer than the length on the outside.

In a Paraline, there's only ONE way for the sound to expand - radially.
The sound can't go up, can't go down, it can only go out, and along a very specific and measured pathlength.


Stay tuned to the diyaudio thread - I've got some cool stuff coming. I have one running with a ribbon instead of a compression driver (listening to it right now.) And I have a couple more folding schemes that are especially appropriate for underdash horns.


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## roduk (Sep 19, 2008)

What so the slit mouth of the Paraline horn would be where the under dash horn mouth would usually sit? 

Been thinking about it a bit more, if you use a point source dual driver like the BMS, and have a paraline enclosure, but not the eye shape, but round instead with a 1" throat, this could then be mated to the ID horn body, would this work or am misunderstanding how the horn works??


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## onebadmonte (Sep 4, 2008)

A link to animation. 

.:: VTC Pro Audio - Paraline Element ::.


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## pocket5s (Jan 6, 2012)

The animation helps a bit, but honestly the cross section picture in the patent itself explained a lot. Using PB's vids was helpful, but it still didn't quite tell me how it was put together. The cross section confirmed what I thought I was reading.

As to why it works and what it does in a car situation, well I'm still a tad lost


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## thehatedguy (May 4, 2007)

Yeah I'm not really understanding it's use/practicality in a car either.


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## Patrick Bateman (Sep 11, 2006)

roduk said:


> What so the slit mouth of the Paraline horn would be where the under dash horn mouth would usually sit?
> 
> Been thinking about it a bit more, if you use a point source dual driver like the BMS, and have a paraline enclosure, but not the eye shape, but round instead with a 1" throat, this could then be mated to the ID horn body, would this work or am misunderstanding how the horn works??


Trying to figure out where to put the slit has really been maddening, to be honest.









Originally, my idea was to mount the Paraline at the throat of an underdash horn. Normally I am opposed to the use of a reflector in a horn, such as the ones used by USD and Image Dynamics. But I've changed my tune for the Paraline, as the reflector doesn't cause any problems below 18khz, due to the very small dimensions. (Basically you get comb filtering above a specific frequency when you use a reflector in a horn. With a 1" throat, that frequency is 4500hz. There are ways to reduce the damage done, but the best reflector is no reflector at all.)

Keep in mind, the Paraline IS a horn. So you can reduce the depth of that Image Dynamics horn in the pic above by A LOT if you put a Paraline at the throat. For instance, add a Paraline that measures about 8" x 4" x 1.25" and you can reduce the depth of the Image Dynamics horn by 4"!

See where I'm going with this? You can push those under dash horns waaaaaay back. OR you could also play them waaaaay lower.

It's really an incredible invention, I don't think I've been this excited about audio since I built my second Unity horn in 2009ish.




I didn't follow through with an 'Image Dynamics' type of underdash horn with a Paraline though. Basically, it's not impossible, but it's fairly trick to mount the Paraline.


















This is because, ideally, you really want it firing straight into the horn.











The idea that I'm leaning towards at the moment is something similar to a Yorkville Unity horn, like the one in the picture above. But much smaller.

Basically I'd take all the dimensions and scale them down by about 67%. For instance, Yorkville uses a 15" woofer. *I'd use a 5" woofer.* Yorkville has an xover point about 300hz. *I'd use an xover point of 900hz.* Yorkville uses a 15" waveguide that's a Unity horn. *I'd use a 5" waveguide that's a Paraline.*










The end result should be small enough to fit in a kick panel.

Although it might seem a bit absurd to cram one compression driver, four midranges and a midbass into a single kickpanel, I think it's do-able.

Fast forward to 3:50 in this video, and you can see the midrange section of this Paraline is under 2.5" thick : Unity Paraline - YouTube

Another idea I've had - and this definitely gets me my Audio Psychosis award - is the use of FOUR units in the car.



Basically, the Paralines are very 'array-able.' Normally, you wouldn't want to put two tweeters near each other. But the Paraline has *very* narrow directivity in one dimensions, and WIDE directivity in the other.

See where I'm going with this? 










So you take that Paraline, flip it on it's side. Now it's got narrow horizontal coverage and wide vertical coverage. (Just like an Image Dynamics horn.) But since I'm completely nuts, I use TWO of them per side. That's one car with:

four compression drivers at 109dB each (115 db total)
sixteen midranges, at about 87dB each (a total of 99dB efficiency)
four midranges, at about 85dB each (a total of 91dB)

It's semi-absurd. I could make an argument that the use of sixteen midranges allows a low xover point. But mostly I just think it would be silly fun 




Actually though, in all seriousness, two of these per side would basically approximate a single driver that measures 20" x 5". And normally it would be pretty damn tough to fit a 20" x 5" driver in a car. *But the Paraline is super super shallow.* If you design it carefully, you could likely keep the depth down to under 4". So you basically have this awesomely loud array, horizontal, and pushed up against the firewall. Picture something like this, but with an efficiency of about 100dB instead of 88dB:










Now, normally people would say "don't use a horizontal array.' But this is a special case. The drivers are SO CLOSE TOGETHER they act like one. If I was using a dome tweeter and a 4" woofer I'd need to xover at 844hz to pull off this stunt. You can't do that with a dome, but you CAN do that with a Unity Paraline. Plus, it's half the width of the BG array in the picture above.

Also, you can put the BG drivers *in* a Paraline. I'll post some pics of that at diyaudio.


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## lucas569 (Apr 17, 2007)

my head hurts


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## Patrick Bateman (Sep 11, 2006)

lucas569 said:


> my head hurts


When I first saw one of these, that was my exact reaction:










I Don't Understand. - diyAudio

Literally, WTF is going on here?

That was four years ago, I've been thinking about this for a while


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## lucas569 (Apr 17, 2007)

needs a sub, only goes down to 90hz.


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## marvnmars (Dec 30, 2011)

holly cap batman, if this works the way my feeble mind perceives and believes this could be wayyy cool. thank you for the work and effort..


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> Yeah I'm not really understanding it's use/practicality in a car either.












Here's an idea of what a three-way might look like under the dash.

It has four midranges and a compression driver, mounted on a 900hz Paraline, which then feeds a 15 degree horn. The horn has two midbasses. Frequency bands would be approximately 225hz to 900hz for the midbasses, 900hz to 1800hz for the midranges, and 1800hz - 20000hz for the compression driver.

On the left is my horn idea, on the right is the footprint of an ID CD1-PRO, for comparison's sake.



There's half a dozen different ways you could tweak this, depending on your car:


Obviously, this thing is big. I have a lot of room *under* the dash of my car, but not much room on the floor. I don't really like kick panels bcuz I'm 6'3" tall. I've managed to fit underdash horns that were 4" tall by 20" wide by 16" deep under my dash. (There are subs smaller than that!)

If someone is using a car that can't provide that much space, just remove the midbasses and shorten the depth. So you'd have a two-way horn that runs from about 900hz to 18khz.

While that doesn't sound like much of an improvement over an ID horn, keep in mind that those midranges have as much surface area as a subwoofer - so you get big dynamics in the midrange.

Another option would be to use a different compression driver, and larger midranges. For instance, a two-way with a B&C DE25 and two or four 4-5" midranges. A combo like that could do about 300hz to 16khz.

You can bend the wavefront, so if you want a super stealthy install, you could likely take the design on the left and squash it down to about 2-3" in depth.

The way that this works is that the drivers enter the horn pointing straight forward and then the geometry of the Paraline itself bends the wave to the right or to the left.

In that pic of the Genesis horn, it's doing that. See how the compression drivers are mounted flat, but the midranges are at an angle? That's because of the wave bending. The Genesis horn bends the wave *down*. We can do the same thing, only our devices are flipped on the side so we can bend it right or left.

As with all these devices, they're 'fractal' in nature. I know the Genesis horn looks a little daunting due to it's size, but you can scale all of this down by changing the frequencies. For instance, if you move the frequencies up by one octave, the box size drops by 75%.

And of course, the car dash extends the curve quite a ways.


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## thehatedguy (May 4, 2007)

The stage would only be as wide (roughly) as you could get the horns apart. If you are 6" inside the car to the edge of the horn, the stage wouldn't really get much wider than that. As drawn it looks like the stage would start near or close to where the steering wheel is at.


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> The stage would only be as wide (roughly) as you could get the horns apart. If you are 6" inside the car to the edge of the horn, the stage wouldn't really get much wider than that. As drawn it looks like the stage would start near or close to where the steering wheel is at.


True.

In the pic above, I have the midbasses covering two octaves from 225hz to 900hz, and the midranges covering one octave from 900hz to 1800hz.

I just pulled up some measurements of the 'squaraline' that I put on Youtube, and it's measured response begins to decay about 800hz with two midranges and a 2.25" mouth.

But conical horns are very very 'arrayable.'


So...

What if we ditch the midbasses, and then do one constant line, from one side of the car clear to the other side?

In this configuration, we'd have two compression drivers per side, flanked by four midranges. If one pair of GT25s goes to 800hz on a 2.25" mouth, I guarantee that eight GT25s on a 16" x 2" mouth would go to 450hz easy.










The pic above is a rough idea of what I am talking about. I've ditched the midbasses, and doubled down on everything else.









Obviously, the next step would be to ditch the angled entry of the conventional underdash horns, and use a flat surface. By using a flat surface, we have a much much better match for the dash. Basically the car dash is our horn.

A flat front doesn't work too hot for conventional horns; it's like you're getting blasted in the face. Too hot, and you can't hear the other side.

But we can actually delay the signal by manipulating the Paraline path. Basically we manipulate amplitude and pathlength and end up with the same wavefront of a horn that's cross-fired, even though it's physically facing us. (IE, we're looking right at it, but the sound is bent 45 degrees to the right.)


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