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Does the criticism of line arrays apply to HORN line arrays of limited length?

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Posted on June 19, 2016 at 17:43:40
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
It has become commonplace to criticize the sound of the line arrays that are frequently used in sound reinforcement. First we must understand that these are direct radiator boxes with limited efficiency and require long lines to reproduce lower freqs in the nearfield. That kind of length really prevents them from functioning as one long speaker which is what they are trying to accomplish in theory.

It has been said by Tomservo that "A true point source in a large horn can have much greater throw, have little or no distance related spectral change, sounds better, is more intelligible and is smaller, with the down side of being a smaller sale for the dealer." And I wonīt disagree with his findings I will only add that in very powerful point source horns not splitting the direction of the output as per using different boxes may result in all in your face sound. But it really depends on the application and with speaker positioning this can be controlled.

But in regards to HORN line arrays the high efficiency associated with these allows a limited number of boxes to be used. These will then perform as a virtual point source while also splitting the output giving easier SPL coverage. I do not believe the above criticisms of direct radiator line arrays apply to horn line arrays for that reason.








Rafaro

 

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RE: Does the criticism of line arrays apply to HORN line arrays of limited length?, posted on June 19, 2016 at 20:45:15
Paul Joppa
Industry Professional

Posts: 7294
Location: Seattle, WA
Joined: April 23, 2001
Sadly, you are mistaken, at least in regards to lobing in the axis of stacking. The same is true of old-style segmented horns. You can find detailed analyses in the works of Harry Olsen from his RCA days.

 

RE: Does the criticism of line arrays apply to HORN line arrays of limited length?, posted on June 20, 2016 at 08:49:58
Don Reid
Audiophile

Posts: 886
Location: Rural NW Georgia
Joined: February 2, 2001
Contributor
  Since:
April 1, 2010
I concede that Paul Joppa is vastly more knowledgeable on this subject than I am, but I am still curious as to the configuration and components and their arrangement you had in mind for a horn line array. Care to share?
I dream of an America where a chicken can cross the road without having it's motives questioned.

 

RE: Does the criticism of line arrays apply to HORN line arrays of limited length?, posted on June 20, 2016 at 11:31:45
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
I heard JBL's latest array at and outdoor live concert. It sounded very good to me, FWIW. Of course this was not a home stereo and it was driven by pro gear, but it did indicate to me that arrays can sound good. I head the Infinity IRS many years ago and it sounded so real it was spooky. So whatever disadvantages there are to arrays, they can be minimized or overcome to the point of having a great sounding speaker.

Dave

 

RE: Does the criticism of line arrays apply to HORN line arrays of limited length?, posted on June 20, 2016 at 15:06:50
Scholl
Distributor or Rep

Posts: 1354
Joined: March 8, 2001
I liked the early 90s Meyer line arrays (haven't heard their latest). Other than that large arrays haven't impressed.

 

RE: Does the criticism of line arrays apply to HORN line arrays of limited length?, posted on June 20, 2016 at 18:09:44
Paul Joppa
Industry Professional

Posts: 7294
Location: Seattle, WA
Joined: April 23, 2001
I think I was a little less than clear. I mentioned multicell horns because some of them (Altec 1505 for example) are much appreciated in spite of having some theoretical lobing issues.

Harry Olson's book is "Acoustical Engineering" (1957, but reprinted in 1991). There's a wealth of cool speaker ideas in it.

 

RE: Does the criticism of line arrays apply to HORN line arrays of limited length?, posted on June 20, 2016 at 22:40:27
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
Hello Don
IN AN OLD POST I discussed the basic design. unable to post pics but you can imagine from the description below.

This is my design of a high power HORN line array cab measuring 22" wide x 16" height x 24" deep in closed position and weighing only 55 lbs with ferrite drivers. It opens to a 70" x 16" mouth at show time. This convertibility makes for easy transport and storage. There are TWO 10 inch drivers each horn loaded into its own exponential 54" length horn designed for a low corner of 75Hz. A curved reflector permits compacting this to a depth of 24" and still passes horn loaded freq up to close to 3KHz. The output of the two horns converge anteriorly to a 70" wide x 16" height mouth. In the middle between the two butt cheeks there is a proprietary designed diffraction horn which being about 12" long appropriately loads TWO high ouput 112dB/W compression drivers crossed over at 2KHz. That much HF output is necessary to keep up with the 2-10" horn loaded drivers!. This being a line array design having cabs above and below puts the cabs in 1/2 boundary space. Using 4 cabs gives a mouth size of 70" X 64" and better than 116dB/W output. From a distance it acts as a point source and avoids the few criticisms made against line arrays yet it avoids the all in your face/ears output as the output can be split and directed as needed as in a line array. The horizontal sound spread is better than -6dB at 90 degrees 70Hz to 16KHz. Although I designed this for linear array use I have found it very useful for a home system as just one cabinet can provide a stereo effect by hooking up Right and Left channels to the appropriate horn of the 10" driver and comp driver. As far as quality of sound it depends on the quality of drivers and amps but the benefits of horn loading are all there. It can make inexpensive drivers sound very good. And yes I have had all kinds of speakers including ribbons electrostatics and horns and all kinds of amps even tube SE 45, SE RCA 845 no power JFET yet. It has the clarity and transient response of electrostatic speakers but with the power of horns. A single amp can easily drive 4 or more of these cabs per side since at only 100 watts per cab the four combined (400W) will do 136 dB. For PA work I biamp with separate amps for the comp drivers and 10" drivers.

The use of horns in line arrays has been limited because the too large vertical exit angle of the MR horns causes MR interference patterns when cabs are stacked as in linear arrays. In this design that has been avoided. Of course HF interference patterns is avoided by the design of the HF horn and itīs very small exit angles. The directionality of horns enable near field Low Freq control to be maintained using much shorter columns. And horn loading causes a great increase in driver output. You would need 64 direct radiation linear array cabs with typical output of 98dB/W to match 116dB/W. The large JBL VerTec, or L Acoustics are direct radiators require 2x15", 4x8", 3 comp drivers 350 lb cabs and cost thousands of dollars and actually have less output in the low and mids than this design. The Martin Audio WL8 although a horn loaded design also do not equal this performance because of too short a horn and too small a mouth. I am very happy with this 55 pound compact cabīs remarkable performance.





Rafaro

 

RE: Does the criticism of line arrays apply to HORN line arrays of limited length?, posted on June 21, 2016 at 14:14:53
tomservo
Manufacturer

Posts: 8149
Joined: July 4, 2002
Hi Rafaro
The simple imaginary "point source" radiates like ripples in a pond except horizontally and vertically and so as you move away, the spl falls according to the inverse square law.

A point source placed on the other side of an open window, radiates a patch or section of that spherical radiation through that window but not the entire sphere and this is what our horns do, they radiate a section of a sphere.
To the degree one can make a horn that has "constant directivity" the height and width of that beam stay at the same angle over a wide range of frequencies.
What is not obvious is that when you move off axis of such a horn, the SPL falls accordingly BUT the frequency response stays the same. This means that if one places the horn up in the air and aims it at the right angle (the simple version is to aim the horn at the farthest seats) then one can make the response and spl very much closer to constant over a large rage of distances and this is what the Direct design program at the web site allows one to do. It is pretty easy to produce a much more even coverage and have it "sound the same everywhere" this way than with a line array.

In fact, a well known California line array only several years old was replaced with several of our Synergy horns at Penn state stadium and the installer (Clair bros) said the following regarding the large difference

"Everything worked out very well," says Devenney. "Coverage is excellent: plus/minus 2 dBA throughout the stadium, except in club areas where I intentionally made things quieter. The system has good articulation, nice fullness, great dynamics, and impressive vocal clarity.
http://www.danleysoundlabs.com/danley-jericho-horns-cover-south-to-north-at-penn-state-universitys-beaver-stadium/

Also, as you have observed with your horn, horn loading can give one a great deal more acoustic power than direct radiators, in fact the in many stadiums a J-3 has replaced 12 to 16 box hangs of large format line arrays with greater fidelity, a larger working distance and greater intelligibility.
If you double the number of drivers in a synergy horn, you get +6dB more energy, if you double the number of boxes in a line array you get about 3dB.

Line arrays are a great way to sell a lot of boxes, amplifiers and processing, the only down side is for the customer / listener as the large array will never sound like a good studio monitor and of course the cost and comlexity.

Part of the reason is they radiate an interference pattern and they are dispersive in the time domain. A single impulse as an input will deliver a train of arrivals spread out in time because there is a different path length between your ears and each source, the bigger the array, the worse it sounds.
While marketed as being narrow vertical patterns individually, a look at the vertical beam width which shows the truth and that the pattern is lost when the frequency falls (pattern loss frequency is 1,000,000 / angle / divided by horn mouth size in inches)
This is why we make large very horns. A single source full range horn delivers a single impulse to your ears in addition to having the same spectral content over a much larger area.

We don't advertise, a part of the reason is the huge effort that has gone into marketing line arrays in live sound so instead we have focused on the most difficult audio tasks where the limited throw distance and bad fidelity of the line arrays are already problems.
In the last 6 years since the Jericho Synergy horns were developed, they have been put in 4 of the 10 largest stadiums (100,000+ seats) with another one next season as well as many smaller ones and that based on side by side listening.

It's not just large stadiums where they are used but where the best sound is desired, here is an example of the largest surround sound system I know of, the listening area is about 250,000 square feet and the speakers your hearing are all more than 300 feet from the audience, a line array, no matter how large cannot do this and with 12 X bc218's, the lf corner is about 25Hz. Don't know who recorded this, try with headphones.

https://www.youtube.com/watch?v=BtAyOeUn3wc

A couple stadium video's too for reference.
Penn state demo walking the field (the 3 speakers are the little black glob under the scoreboard)

https://www.youtube.com/watch?v=e_usTlJi2NA

At about 300 feet
https://www.dropbox.com/s/oyosfc3adc6j1du/20130723135350.mts?dl=0

at about 700 feet
https://www.dropbox.com/s/ykq1y2ugesok2se/20130723141759.mts?dl=0

at about 700 feet
https://www.dropbox.com/s/6ohyjninxzu2fjo/20120726122124.mts?dl=0

at 800 feet
https://www.dropbox.com/s/9bsr2bnrjrr24cq/20140805175937.mts?dl=0
Best,
Tom

 

RE: Does the criticism of line arrays apply to HORN line arrays of limited length?, posted on June 21, 2016 at 22:56:46
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
Hello Tom:

As always crystal clear presentation of complicated topics. Thanks for clearing up question of the stability of the SPL coverage in your horns. As you point out the shorter the line array the less the interference field and the less the time difference between boxes which would represent more intelligibility and clarity in the presentation. Unfortunately the low efficiency of direct radiation linear arrays limits this where horn line arrays being much shorter would limit this time differential between boxes and would approximate a point source.

Thanks for taking the time to answer


Rafaro

 

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