# Horn Polars



## SSSnake (Mar 8, 2007)

All I am in the process of building some waveguides for my car. I decided to do some measurements between a few horns to see how they matched up. First my measurement setup is NONSTANDARD and attempts to mimic what I will see IN MY CAR. So DO NOT take these as gospel. They are comparative only!

First I have a set of ID Full Bodies and Pyle PH 612s. I am using the same Selenium D210TI driver on each (swapped to different horn for measurement).

Pyle Horn
Pyle Midrange Tweeter ABS Horn Lens Threaded | PH612 | Pyle

ID Full Body
WoofersEtc.com - Ultra ProCompF - Image Dynamics Ultra Competition HLCD Full Size Horn
The one in the back is the FUll Body

Selenium
Selenium D210Ti 1" Titanium Horn Driver 1-3/8"-

This is the measurement of the IDs:









The purple trace is 45 degrees off the horizontal axis and 45 degrees off of the vertical axis. The blue is 30 degrees off horizontal and 45 degrees off vertical. Green is 15 degrees off horizontal and 45 degrees vertical. The red is 0 degrees off horizontal and 45 degrees vertical.

This is the measurement of the Pyle:









The purple trace is 45 degrees off axis horizontal and 35 degrees off axis vertical. The blue is 30 degrees off horizontal and 35 degrees vertical. The green is 15 degrees off horizontal and 35 degrees vertical. The red is 0 degrees horizontal and 35 degrees vertical.


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## SSSnake (Mar 8, 2007)

At first glance I noticed the huge peak at 3.2 khz in the Pyle and the much smoother response of the ID. 

Overlay of the ID and the Pyle:









But if you look back at the Pyle versus the ID you will notice that the pattern control on the Pyle is much more consistent while the ID less so. What I am looking for is something to provide uniform power response. It is not that the ID is bad just the Pyle does a better job in this area. So I decided to see what would happen if measured on axis vertically (the Pyles designed application). The peak disappeared (you'll have to take my word - I forgot to post the pic to my Picasa account). However, in my appication I will not be on axis vertically so I decided to see what a little EQ would do.

Eq'd Pyle Horn:









This was with a single 10db cut at 3.2khz. A much better curve. Notice it also cleaned up a null at approx 12khz (this was a surprise but was repeatable). All in all pretty good response with good pattern control. Now let's see what happens when I start chopping on these things... (Later this weekend)

For John/Patrick - I cut and added some foam to see what the effect would be. No improvement in the 3.2khz peak but it did reduce the output greatly.


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## tRidiot (Jun 29, 2006)

Wow, very interesting graphs... I'll bet those horns sound HUGELY different. I'm thinking I'd hate the Pyles with that ginormous 3kHz peak... although maybe you could EQ that down some...

Just curious why the 35-degree vertical for the Pyle and the 45-degree for the ID? I would think you'd want to try identical points for measurement to get the best comparison?


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## SSSnake (Mar 8, 2007)

The point was to see a comparison of how they would sound in my car... The difference in vertical angle used for measurements was because of the difference in how they would be mounted in MY car. Again I don't claim these are worth a darn to anyone but me. I just thought it might be of interest to others.


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## Eric Stevens (Dec 29, 2007)

You might want to re think your thoughts on power response. If the path lengths were equal or close that is what you would want but they arent, unless you own a Mclaren. The pattern control you see with the ID horn is intentional and necessary to get proper imaging in a car where you have unequal path lengths. 

The idea is to get more volume from the opposite side to compensate for the early arrival of the near side. In addition the near side would have more volume than the far side without the pattern control.


Eric Stevens


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## Patrick Bateman (Sep 11, 2006)

If you're seeing a big drop in output with the foam, that's a pretty good indicator that there's a lot of high order modes. High order modes are simply waveforms which aren't going down the center of the horn. So if the output level is dropping like a rock with the foam, it shows that a lot of the horn's output is going through the foam three, five, or even seven times. (Can you say "group delay?" yuck!)

In a really really good waveguide, the foam barely makes a dent in the output. For instance, with QSC os waveguide clone, the output dropped something like one decibel. (and even that indicates that something like 25% of the output is from high order modes.)

Here's some thoughts on the polar response:

For such an oddly shaped horn, the Image Dynamics horn is quite consistent off-axis. The easiest way to accomplish performance like this is via the use of a diffraction slot. Do you see any point in the throat where the area of the horn changes dramatically? Here's an example of what I mean:









This is an ElectroVoice Mantaray horn. See how the horn flare rate abruptly changes about six inches from the throat? That's a diffraction slot, and it improves the off-axis response. It works the same way as putting your thumb in front of a water hose. The water coming out of the hose is sprayed into a much wider beam.

Diffraction sounds really obnoxious though.

The easiest way to tell if it's a diffraction horn is to just look inside, and see if there is a point where the flare rate changes abruptly. And diffraction isn't an "all or nothing" affair. All horns suffer from diffraction, and diffraction has a lot to do with the way that a horn sounds.









The Pyle is basically a waveguide, with no diffraction slot. That's why the output of the Pyle begins to decay as you move off axis.

In a nutshell:

Diffraction slots do a good job of making the on and off axis response consistent, and work the same way as fanning water out of a garden hose. On or off axis, it basically sounds the same. This comes at a price though - it creates gobs and gobs of diffraction, and diffraction leads to higher order modes.

The output of a waveguide decays off axis - you see this in the Pyle's response.


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## Patrick Bateman (Sep 11, 2006)

Eric Stevens said:


> You might want to re think your thoughts on power response. If the path lengths were equal or close that is what you would want but they arent, unless you own a Mclaren. The pattern control you see with the ID horn is intentional and necessary to get proper imaging in a car where you have unequal path lengths.
> 
> The idea is to get more volume from the opposite side to compensate for the early arrival of the near side. In addition the near side would have more volume than the far side without the pattern control.
> 
> ...


A couple of years ago I was really obsessed with getting good imaging in the car, but in the past year I've become much more interested in designing a system which is psychoacoustically pleasing.

Or to put it simply, "a system that sounds good" 

I'm still a follower of Geddes, and I think that combating diffraction makes a huge difference. I've become very interested in group delay as well.

Theoretically, diffraction sounds obnoxious. And I found it interesting that a Mantaray diffraction horn scored poorly on a listening test here:

European Triode Festival - ETF 2010 Shootout

Here are the four finalists:


























(the second horn was used by two of the four finalists btw.)

The white EV horn is a diffraction horn too. As noted above, diffraction isn't an "all or nothing" affair, and I think the reason that the white EV horn did so well is that the transition in the white horn isn't as abrupt as the transition in the MantaRay. IE, sharp edges are BAD.

Also, a big mouth goes a long way towards improving a horn. I think this is one of the reasons that the Image Dynamics horns win a lot of contests when the owners put a lot of effort into smoothing the transition from the mouth of the horn to the dash. (the dash extends the horn mouth.)


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## SSSnake (Mar 8, 2007)

> You might want to re think your thoughts on power response. If the path lengths were equal or close that is what you would want but they arent, unless you own a Mclaren. The pattern control you see with the ID horn is intentional and necessary to get proper imaging in a car where you have unequal path lengths.
> 
> The idea is to get more volume from the opposite side to compensate for the early arrival of the near side. In addition the near side would have more volume than the far side without the pattern control.
> 
> ...


Eric,

This is an excellent point and it is the reason the pyle would be mounted on axis with the opposite side listener. This should put the near side listener between 35 and 45 degrees off axis. This should provide some decrease in intensity on the near side. So the critical piece for me is a consistent power response not necessarily an equal power response (less variation in levels across the spectrum rather than constant output level - e.g. less crossing on the FR plots). The big concern with the Pyle horn is keeping the energy off of the center console (my car has a larger center console). The modifications to the horn to accomplish this could cause the polars to go to heck in a handbasket... 

Just so you and everyone else knows, I think the IDs are an excellent solution. I wanted to try my hand at modifying a waveguide to make it a vehicle specific solution. I may end up with a modified Pyle or a modified ID. The ID would definitely require less modifications but that is half of the fun (seeing what I can do with the mods). I expect to use roundovers on all terminated mouth portions of the horn (not done in this round of tests) and I may use some foam. 

So far there appeared to be very little advantage to using foam on the Pyles. I haven't tried on the IDs. I used Open Cell foam initially but I do have some reticulated foam lying around as well (Geddes now says he is using open cell vice reticulated - I could have sworn he said reticulated before).

BTW - no updates from later this weekend. Yard work ate most of my time.


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## thehatedguy (May 4, 2007)

He did say reticulated a long time a go.


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## SSSnake (Mar 8, 2007)

OK guys. Maybe I'm not explaining myself or maybe what I am after is just not possible. Anyway here is another attempt. I would like the SPL at all freqs to be higher for the passenger to offset pathlength differences. I would like the SPL to be consistenly lower for the driver (assuming we are discussing the driver's side horn). For example if you look at the Pyle horn measurements at 0 and 45 degrees. the output is consistently lower at 45 degrees with one exception at 5.6khz (this is a good thing if I am aiming the horn at the passenger).










However, if you look at the ID horn you notice the traces aren't very consistent (they cross each other indicating a different listening positions the output will sound different).

ID at 0 and 45 degrees









What you see with the ID is between 900hz and 2.3khz the off axis response is greater than the on axis (a good thing). However, between 2.7khz and 4khz the on axis response is higher. Then between 4khz and 7khz off axis dominates. Finally, on axis dominates between 7khz and 20khz.

With the Pyle you don't have this switching back and forth between the dominate listening location. Therefore you should end up with a more consistent power response (I hope that makes sense).

I realize that the ID is optimized for off axis listening and in a car with their mounting directions this is a good thing. However if I used the Pyle I could aim the horn at the opposite side and make sure the closest listener was listening off axis. This would give the opposite side listener the greatest output but keep the consistency that I want.

The problem I am running into is that I need to keep the radiation off of the center console and the Pyle *will not* do this. I likely need a 45 degree horizontal coverage pattern for this to work (the Pyle is roughly 90 degrees). I also have to address pattern flip in the vertical axis. If I go the ID route I will need to minimize the vertical dimension as much as possible (likely one inch). I could go the opposite direction and try to move the horn's vertical pattern control down in freq but this would mean a very large vertical dimension (around 12 inches for 1100hz). This would be WAY TOO BIG.

I hope that makes sense.

BTW - the more and more I try to attack this thing the more and more it looks like a straight entry ID horn.


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## SSSnake (Mar 8, 2007)

> my take on your desire for an even power response, is that you sort of answered your question with the center console comment. A horn that throws the sound out evenly will have a much higher ratio of reflected energy from the car interior reaching your ears in conjunction with the direct energy from the horn's mouth.


Only if the reflective surfaces are in the coverage pattern. In this case I hope to tighten up the coverage pattern so they are not (45 degrees horizontal coverage pattern vs 90). Again, the mods that I make to limit the coverage pattern and keep the radiated sound off of the console may screw things up dramatically. BUT, I won't know until I try (unless John/Patrick sends me his modeling software).


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## SSSnake (Mar 8, 2007)

A strict OS will not work due to the size constraints you noted. The ID rectangular approach does seem to offer quite a few advantages. As I mentioned before the theory keeps pointing to something similar to the ID solution. I would love to see something with an OS throat blended to a rectangular mouth. The issue I see is if you use a one inch throat you don't have the vertical room to build the OS throat and keep the vertical pattern flip freq high enough. Would one of the new small diamater throat drivers like the DE5 or DE7 help this? Probably...



> you see certain principles at work, that can't be commutated any other way without a dash rebuild or a non-functional seating area, or a not drivable car.


Which principles can't be properly executed in a car? We're not talking midbass or bass horns. This is a horn for upper mid and tweet. I'm not looking for a Mark Eldridge style solution. Maybe all of the possible tricks for horns have been executed already. It is definitively a possibility but I would be surprised if everything that could be done to a horn to adapt it to a specific vehicle has been implemented in a commercial product. Like every other commercial product it has to fit a wide variety of applications. Now I could be drinking my own kool-aid but as someone who has spent most of my adult life providing engineering solutions to a variety of customers on an equally wide variety of products, I am convinced that there can be modifications made to commercially available products to better adapt them to my application. Will I find the beneficial modifications? Maybe, maybe not. Either way I won't be upset with myself unless I admit defeat before even trying.

BTW - If you have any suggestions, other than not trying, I am all ears.


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## Patrick Bateman (Sep 11, 2006)

SSSnake said:


> Only if the reflective surfaces are in the coverage pattern. In this case I hope to tighten up the coverage pattern so they are not (45 degrees horizontal coverage pattern vs 90). Again, the mods that I make to limit the coverage pattern and keep the radiated sound off of the console may screw things up dramatically. BUT, I won't know until I try (unless John/Patrick sends me his modeling software).


What software?

I use akabak and hornresp for just about everything

both are free (well akabak isn't free if it's for commercial use)


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