# Arrays vs Horns - Redux



## Patrick Bateman (Sep 11, 2006)

On this and other forums, I've discussed my bias *against* arrays. This morning it occurred to me that there is a potential 'fix' for line arrays, which I'll discuss in this thread.

First off, here are the reasons I don't like arrays, particularly line arrays:

1) They sound mushy and inarticulate, particularly as frequency rises. It's really easy to understand why this is; the sound is arriving from a series of points in space which are seperated by many many wavelengths.








For example, in a megabuck Pipedream line array, the sound of the midrange at the top is one and a half wavelenghts out of sync with the sound of the midrange in the middle. (This is just simple pythagorean theorem; the pathlength from the midrange at the top is 50cm further than the pathlength of the midrange in the middle.)

Due to this 'mushiness', even the world's most expensive line array can't do articulation the way that a $100 Unity horn can:

unity-horn-crummy-xover.mov - YouTube

Although my Unity is rough, it's frequncy response can be fixed, but there's nothing you can do to fix the pathlength problems of the Pipedream.

2) Line arrays make everything sound huge. Whether you're listening to an orchestra or listening to a singer talking on stage, they're all the same size. H-U-G-E. This could be a defect or a feature; although I know it's not realistic, I do find the humongous presentation of line arrays kinda fun. Obviously, not hifi, but fun.

3) Every time I start warming up to line arrays, I remember how awful they sound in every concert venue I've ever been to. *I've never heard a single line array in a concert that wasn't painfully bad.* Line arrays naturally roll off the treble, and tweeters always have lower power handling than woofers. Which means that concert line arrays sound really painful in the high frequencies, because the tweeters are struggling to keep up with the mids most of the time. Plus, the pathlengths suck. (See point 1.)


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## Patrick Bateman (Sep 11, 2006)

The picture above is an illustration of the idea that I had this morning.

As mentioned in the first post, one of the things I really love about Unity horns is *articulation.* I think that articulation is very important for a speaker, because an articulate loudspeaker makes everything sound better. For instance, if you have a speaker with great bass, or great treble, it won't improve the sound of XM Radio, because XM Radio has no bass or treble. But articulation improves everything. Even a crappy internet radio stream, or highly compressed mp3s. Articulation simply makes it easier to retrieve subtle details out of a recording.

The reason that the Unity is articulate is that all of the sound emanates from a point in space that's about the size of a golf ball. So all of those early reflections are basically constrained to a smaller space, where they're less offensive. Another thing that's very important is that the Unity is phase coherent, via the use of carefully optimized crossovers. The audibility of phase distortion is a heated topic, but I'm a believer.


In the pic at top, I've illustrated a horizontal line array, power tapered so that the corners of the car get the most power.

At first glance, this would seem to fly in the face of what the Unity does right. The Unity constrains all of the sound into a space that's the size of a golf ball; this horizontal array constrains all of the sound into a long wide ribbon that's about 60cm wide by 9cm tall.

Here's some reasons I think this *might* work well:

1) No matter what type of speaker you have, there are going to be early reflections. For instance, even my beloved Unity horns will reflect off of the seats, the driver, the center console, the roof, etc.
2) The basic idea of the horizontal array that's pictured above is *to locate the drivers so that the first reflection occurs in a predictable place at a predictable time.* We're basically saying "I know there's going to be a strong first reflection, and I'd like to control when and where that reflection happens.

If it's not clear in the pic, the speakers stretch from one side of the cabin to the other, and the series of images *above* the array are there first reflection. Another idea I had was to fire them right INTO the windshield, so that what we listened to was the reflection itself! This might sound loony, but reflectors work pretty predictably if you size them carefully. (As the Danley Paraline and B&O acoustic lens have demonstrated.)
3) Besides controlling the first reflection, the horizontal array has some other advantages:
a) it should have a strong center, since the speakers are literally from one side of the car to the other
b) although the center is strong, there should be lots of width too, since most of the loudspeaker energy is concentrated on the edges. (IE, the elements of the array in the corners are much much louder than in the center)
c) If everything goes according to plan, it should sound a lot like the entire windshield is a speaker. Might be a neat effect.


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## Patrick Bateman (Sep 11, 2006)

Probably the most radical part of this plan is that it's tweeterless. I would select a driver that could make it all the way to 20khz, and then use sheer displacement to get a xover point as low as possible.

This has some cool advantages:

1) really great behavior in the phase domain. For instance, high order xovers insert quite a bit of delay, and the delay is frequency dependent. By ditching the xover entirely we get the high frequencies and midrange frequencies in-phase, which is very important for articulation.
2) Line arrays can move a LOT of air. For instance, nine of the Dayton ND91s can move as much air as most eight to ten inch subwoofers. So getting down to 100hz is trivial. In fact, my primary goal isn't to play low, it's to play HIGH, so I'm still trying to figure out which driver could be tightly packed so that the high frequency roll off is small .

For some more justification for this scheme, check out the corner-line-array from John Murphy, which was definitely an inspiration for this.


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## chithead (Mar 19, 2008)

Dangit! How come anytime I brought this up in a discussion, it was shot down as un-achievable due to the reflections from the windshield. 

Wouldn't the dash and windshield act as the mouth of horn in a horizontal array? In my mind, I can see it... but in the technical world...


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## Patrick Bateman (Sep 11, 2006)

chithead said:


> Dangit! How come anytime I brought this up in a discussion, it was shot down as un-achievable due to the reflections from the windshield.
> 
> Wouldn't the dash and windshield act as the mouth of horn in a horizontal array? In my mind, I can see it... but in the technical world...












Here's a pic I did, to illustrate various options near the glass. In the pic we see that:

1) arguably the best option is to have the driver pushed all the way back into the corner, and firing upwards a bit. This minimizes reflection *behind* the driver.
2) for those who don't believe in 'keep it simple stupid', a Paraline might be an option 
3) the 'stock' option used in cars like the Chevy Cobalt and the Honda Accord, where the tweeters fire right into the glass, creates a lot of reflections. On the upside, those reflections aren't symmetrical. Symmetry makes reflections a lot worse, so some might argue that this is a viable option.


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