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Why do line arrays using directional speakers require shorter lines for similar near field performance?

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Posted on April 24, 2017 at 14:08:22
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
 Manufacturers of directional line arrays claim this and it seems to make sense. The more a speaker projects its sound forward instead of to the sides and back the further the near field should extend. Could it be that simple? By directional speakers I an referring to horns or rear cancelling designs as opposed to the typical direct radiating line arrays.


Rafaro

 

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RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 24, 2017 at 16:26:38
Zipcord
Manufacturer

Posts: 707
Location: No. California
Joined: December 19, 2002
 .

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 26, 2017 at 13:56:17
Inmate51
 "Manufacturers of directional line arrays claim this"

Can you cite an example or three?

:)

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 26, 2017 at 18:45:50
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
 About 7 years ago when I investigated this there were several linear array models which had a cardioid LF section in their flown cabs. Because of their improved LF projection it was suggested they would require a shorter line as compared to non cardioid models for similar near field LF performance. I could never understand clearly the science behind it. It would now take considerable time to try to recollect all that info....some models are not even made anymore. But if I can recollect that info IŽll post it




Rafaro

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 26, 2017 at 20:47:34
Inmate51
 ""Manufacturers of directional line arrays claim this"

I asked a simple question: Can you cite an example or three?

:)

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 26, 2017 at 21:48:42
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
 I was suspicious of that claim myself in that the forward efficiency of cardioid designs is usually reduced along with the rear projection. But I do remember the claim being made especially with horn designs. It would take time to recollect that info. But if I can recollect that info IŽll post it. If you desire investigate the subject yourself. It would be models with cardioid or horns in their LF section models. I think Nexo, Meyer? had models with cardioid LF. I would need to locate the manufacturers and the models and read all their literature and fine details again but have no time at present!!






Rafaro

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 27, 2017 at 07:52:16
Inmate51
 "I do remember the claim being made especially with horn designs. It would take time to recollect that info."

I hear ya. Many years ago, I had a Woodwinds Methods instructor in music school (and bowling team partner and pizza/drinking buddy - go figure!) who told me "Remember what's important, and flush the rest".

Still, if you're going to make a public assertion/comment about a manufacturer claim, it's best if you can cite the manufacturer. Otherwise, it's just more Internet bullcrap.

:)

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 27, 2017 at 10:47:27
Paul Eizik
Audiophile

Posts: 2120
Joined: September 15, 2001
 Rafaro

Here's a link taken from the recent "and a lot of lobing" discussion from down page here, which relates to your question.

Paul

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 28, 2017 at 14:11:18
tomservo
Manufacturer

Posts: 8190
Joined: July 4, 2002
 Interesting and wrong in a number of ways technically speaking.

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 28, 2017 at 14:15:45
claudej1@aol.com
Audiophile

Posts: 816
Location: Detroit
Joined: August 17, 2007
 Wrong indeed, to those who have heard or measured line array (with the possible exception of Don Keele's designs that use the Legendre Shading Function).

That's why I hate "cartoon" diagrams as shown there.

Like the "fake news" from political pundits, this one gives "fake data." Since humans are primarily visual creatures, stuff like this does more harm than good to those seeking a better understanding of audio.

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 28, 2017 at 14:17:13
tomservo
Manufacturer

Posts: 8190
Joined: July 4, 2002
 That is a hard question to answer simply.
Line sources use the size of the radiating area (height) to produce a forward beam which is summed form the forward radiation of each source. The problem is 20 hz to 20Khz is a 1000 to 1 span so far as the size of wavelength so a given size line is a different acoustic size at every frequency and so it's vertical behavior is different at every frequency.
Because that effect is so strong and frequency dependent, lines are usually curved to make them more like a point source in the vertical as well as horizontal but the longer you make the line and or the more curved it is, the more radiation is sprayed sideways in addition to rear.
Anyway, the idea of making them short is it will have a wider vertical angle and act less like a line source.
Keeping it short will also minimize the spreading of energy in time as well as there is only a small range of distances from the source to your ears Conversely, line arrays only have a reduced spl fall off with distance when they are acoustically large and are exhibiting destructive cancellation in the near field and then any energy impulse you feed in, will arrive spread out at separate times from each box or source according to the distance. DSP can correct for that in one location but not elsewhere.

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 28, 2017 at 15:17:27
tomservo
Manufacturer

Posts: 8190
Joined: July 4, 2002
 Hey Claude
Check out what we were doing today, a new box.
Use headphones

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 28, 2017 at 17:11:22
claudej1@aol.com
Audiophile

Posts: 816
Location: Detroit
Joined: August 17, 2007
 Holy crap. that's a lot of sound for such a small box so far away. I could tell your lens was zoomed in from compressed perspective. How far?

Is the speaker good to 50 Hz? Hard to tell from the program material. BTW, I got a Double CD set of Essential Boz Scaggs music after hearing your last demo.

I can can see why you use "Thanks to You" Great vocal, bass, a treble extremes in that one. Very clean commercial recording, one of the best.

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 28, 2017 at 18:42:54
Rafaro
Audiophile

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

Glad to have you join in. Linear arrays can be messy audio affairs especially the longer they get. It seems that it�s the ease of mounting and dismounting as well as the alledged ease of coverage that has kept them in the business. I for my needs went with a "linear array" but a DIY using exponential horns. Because of the efficiency I can limit the column length to just 4 cabs. It really functions more like a point source because of the nature of horns combining their output and the limited number of cabs limiting time smear. Some of the idea came from one of your patents. Sound source having a plurality of drivers operating from a virtual point US4845759A.
The Ureda article quoted in your "Why Danley does not build linear arrays" article was very useful in designing the exit angle of the horn cabs. A common mistake in stackable horn cabs is to have too great a vertical exit angle which can cause lobbing problems in the MR and more so in the HF.
In regards to the topic in question your reply "Line sources produce a forward beam which is a summed form of the forward radiation of each source." So theoretically the more the forward radiation of each cab the stronger the beam the longer the nearfield. Kind of reminds me of pushing back the critical distance in reverberant rooms by using more directional speakers !!

Thanks for the input


Rafaro

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 30, 2017 at 06:12:44
tomservo
Manufacturer

Posts: 8190
Joined: July 4, 2002
 Hi Claude
I had the camera at 100 meters from the source (and well past the usable distance for large line arrays) which makes a sound level measurement -40dB re 1 meter (easy to keep track of).

That recording was hitting peaks approaching 90dB fast and avg more like 80dB slow but it hit 105dB A slow at the point the limiters start to get tickled using the stadium type test noise signal. Good catch, the knee in the lf response is -3 @55Hz.
Yeah Boz has some great recordings, I like to use the same material I would use to evaluate speakers in my living room although others play more classic, less subtle PA test program like AC/DC or EDM which I find enjoyable in smaller quantities.
Best,
Tom

 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 30, 2017 at 06:19:51
tomservo
Manufacturer

Posts: 8190
Joined: July 4, 2002
 "Kind of reminds me of pushing back the critical distance in reverberant rooms by using more directional speakers !!"

When one wants to understand the words in a large space, then Hopkins Styker equation points the direction (the same direction as it deals with preserving information).
An example is in the link;

"The direct field can be improved by

Increasing Q (loudspeaker directivity, difference between what's radiated forward and what is radiated outside the pattern)
Move the listener closer to the source
Increase absorption
Reduce the number of sources
Aim the loudspeakers at the listener

Note that by increasing "N" from 1 to 2 will also increase the level of the reverberant field by 3dB. Keep the number of loudspeakers to an absolute minimum in difficult acoustic environments."


 

RE: Why do line arrays using directional speakers require shorter lines for similar near field performance?, posted on April 30, 2017 at 09:40:04
claudej1@aol.com
Audiophile

Posts: 816
Location: Detroit
Joined: August 17, 2007
 "others play more classic, less subtle PA test program like AC/DC or EDM which I find enjoyable in smaller quantities.
Best,
Tom"

OMG, "classic?", LOL. I do believe your tongue if firmly implanted in your cheek as you write this. Too funny.

I think you once described your TH-50's "as subtle as a pair of Humvees in the living room."..........which, BTW, prompted me to buy/trade for a bunch, since subtlety is not my strong suit!

So you get sales and marketing credit for that one!!

As to "enjoyable in smaller quantities," I concur. The full band, high dynamics, high resolution of microdetails in your speakers means that "micro quantities" of rock music should apply.

Across the board, fully resolving high distortion guitar effects can be quite irritating in a short period of time. BUT, as old Rockers with Garage Band experience, we do love to crank it up once in while, especially when the right social circumstance meets the perfect alcohol tolerance level!!

As I've said before, the Direct Radiator guys don't have both the high and low decibel options that the Horn Guys have, only the low AND at higher IM distortion. A 650 Horsepower Corvette can outrun most of the others, but it can also drive slowly through a parking lot. Those overpriced little boxes at Axpona can only do parking lot driving. I'd rather have the 200 MPH option on the right road.

Cheers!

 

Thanks Tom crystal clear and concise nt, posted on May 2, 2017 at 00:35:31
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
 nt
Rafaro

 

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