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Author Topic: Understanding Basics of LIne Array vs Point source  (Read 8440 times)

Masis Ingilizian

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Re: Understanding Basics of LIne Array vs Point source
« Reply #10 on: November 29, 2021, 01:11:28 AM »

I'm not going say one type of speakers over another however your most likely going to want/need some fill speakers in the side sections. Those could be on a different zone/mix
to control the level and the program content being sent to them independent of the main
system.

Is there going to be a house sound person to run the system, will full production services be offered, stage monitors, mics, cables, stands and all the parts and pieces needed put on an event?

I am presuming there will be an audio engineer setting up the system but perhaps semi production services, and even if there is I doubt it will be as technical or complicated as what you mention. Monitors yes, mics yes, cables yes. Different zone/mix unlikely but this is where I want to understand how much improvement will I get if we go this route? And what for will it improve? If its speech inteligibility let me know cause that is improtant. My goal is to reduce SPL to the sides for guests to chat and enjoy there time on the table while hearing the MC clearly. With enough spray on the dance floor.

Can you tell me exactly what your recommending having side speakers for? Can you please elaborate what your recommending or the best practise in a nutshell?

I hazarded a guess that it might work well to have a seperate system for speech and for music(if that is what your recommending?). And the audio engineer might be able to accomplish that goal, I will find out. But its the setting up from a acoustical perspective and understading the best practise. If need be I will find a better audio engineer, but ultimately I need to know what to tell the engineer if he can't do it will find a better one, if he is more knowledgable then great.

I can probably even work out myself all the delays on a speaker management system worst case I will tell the owner to get a decent audio engineer.

So the side speakers will serve for the MC? What about the vocalist, that will be played through the main speakers right?
 
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Mike Caldwell

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Re: Understanding Basics of LIne Array vs Point source
« Reply #11 on: November 29, 2021, 06:21:13 PM »


Can you tell me exactly what your recommending having side speakers for? Can you please elaborate what your recommending or the best practise in a nutshell?


The side area speakers driven from a separate mix, off of a matrix, ect could have the music
levels much lower so people could sit and talk but any mic inputs used for MC announcements, spoken
word presentation ect. could be ran at a higher level.
Having those speakers closer to the people in those areas would increase the intelligibility.

Jeremy Young

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Re: Understanding Basics of LIne Array vs Point source
« Reply #12 on: November 29, 2021, 09:41:51 PM »

A constant curvature array is a group of loudspeakers that are arrayed vertically, with their sides (tops really) flush against one another (picture a wedge, like a piece of pie) so adding more boxes gives you a taller vertical dispersion pattern, with each individual box providing a fixed vertical dispersion.  Adding loudspeakers to this type of array does not gain you output (where it counts, see below), just increases vertical coverage. 

A line array is a group of loudspeakers that are arrayed vertically, with the faces flush against one another, but with adjustable angles at the rear which allows multiple boxes to direct energy in the same direction, or can be angled such as a constant curvature array.  Angles can be made to suit the space, with multiple boxes summing to give you more output (for example, for the rear of the audience where the distance to the listeners is greatest, and angled down to reach the front rows near the bottom of the array). 

Manufacturer's marketing teams (and thus many users) tend to mix up the terminology, but it's important to note the difference. Constant curvature is more like point-source in the sense that you aim it, and go.  Line arrays require processing, which requires computer simulations to calculate. 

The inverse square law is what dictates sound loss over distance, combined with air loss in the high frequencies based on temperature and humidity. Basically you need energy for distance, but more more in the HF.  Combining multiple identical sources of sound requires that they be within a predefined distance from each other, which is based on their wavelength (frequency). IE its easier to couple low frequencies (longer wavelengths, drivers can be further apart) than high frequencies.  On top of that, using signal delay processing, you can direct sound from a flat front, which is where that processing comes into place. 

The splay angles defined by any loudspeaker manufacturers are not to be taken as exact angles for the entire bandwidth.  Sound waves vary in length based on frequency, and a cabinet/array/horn's ability to control those frequencies is based on it's physical size.  Longer arrays and larger horns can control lower frequencies. Manufacturers tend to use the high-frequencies (easier to control) as the points they base the coverage angle specs on, but the actual frequency varies by manufacturer.  Better manufacturers provide more resolution to their data; lesser ones tend to give you just one number because they don't want to reveal just how poorly they control the spectrum. More data = better results in your predictions. 

If you have a nominal 90 degree wide loudspeaker, that's telling you that 45 degrees off-axis, the sound level will be -6dB from on-axis. Not silent, just -6dB.  Ideally this affects all frequencies evenly, but practically that's not possible so hopefully it's somewhat even (similar tonality but lower in volume). You can use these off-axis points to reduce level in the front rows compared on the on-axis levels because the front row will be closer than the back row (see inverse square law).  Aim the speakers at the rear of the audience where you need the output, and use the right vertical coverage pattern to allow you to reduce level for the front row sufficiently.  This is where different vertical patterns come into play, along with trim height/front to back distance ratios/front to back height variations/vertical aiming etc.

The over arching goal is to give every audience member equal level and tonality, or at least within a small range.  Some would say 4dB maximum variation, some would say 6.  Others are happy with 18dB if you're covering a large outdoor area; this is really up to the budget and client expectations.  When an EQ or level change is made at the FOH console, you want it to affect all seats equally.

I haven't even touched on delay, phase, fills, multi-source driver arrangements versus coaxial arrangements, or anything to do with acoustics yet (just direct sound so far).   And I'm sure I'm missing a lot.   Some pretty slick stuff can be done today to arrange boxes in a seemingly (to the end user) simple fashion, yet carefully balancing a metric shit-ton of compromises to deliver as much direct-to-reverberant energy to where it counts, with less weight/cost/crap thrown back on the stage while avoiding acoustical features like balcony fronts.

I suspect your designer has a few key brands they recommend based on experience with that manufacturer's simulation software, proven support from said manufacturer pre-and-post sale, and experience to say the predictions match the real-world.  Bonus if they have more than one or two cabinet types/styles.   As they say, if your only tool is a hammer, every problem begins to look like a nail. 



Beyond the book I recommended, Nathan Lively (Sound Design Live) has a ton of youtube videos, online courses and podcasts that bring all these concepts together one by one if you have a fews days worth of listening time to spare.  Most are free because he's awesome, but the courses cost (as they should). 
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Masis Ingilizian

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Re: Understanding Basics of LIne Array vs Point source
« Reply #13 on: November 30, 2021, 08:45:02 AM »

Really appreciate the replies. I will definitely read the book. Like I mentioned earlier, I feel if the owner spends say 10k on acoustics and the audio engineer makes a wrong desicion on the speakers and PA system then all my work would be for a waste. I am in an X Soviet Union country with limited skilled audio engineers who understand modern techniques so I just want to make sure the engineer is on the right track. He mentioned QSC so now I am looking at options in QSC line.

My goal is and my current frame of thinking is a point source system with about 70 degrees horizontal or 90 degrees, lets say I go with the QSC AP 5122 or AP 5152 there both a Conical DMT horns with about 90 degree and 75 degree coverage respective. I can toe in the speakers slightly(depends where the side seated guests are at) spraying on axis to the dance floor while reducing about 2db or so to the off axis which is essentially the seated guests on the sides of the dance floor. I want the seated guests to have some comfort from music when not dancing so they can mingle but they also have to be able to hear the MC. The MC will talk when there is no music playing so I figure a stereo pair will suffice. And the guests seated behind the dance floor will also get a reduced dropping off of DB being about 7 metres away on axis but there might not even be seated guests on the back wall and only on the sides. I can keep things simple and stick to the stereo pair idea with 2 subs. I can place the subs on the back wall or if there is a way in front corners and do my best with SBIR with both the speakers and the sub. Use some type of speaker management system to implement a simple autmoated DSP. Go with passive speakers to ensure enough wattage and headroom.

Just to keep this simple

1. Have I got anything fundemantally wrong with this concept? If so what, and I will take a look into it if you can just tell me what Ive missed.

2. How do I work out how much wattage I need for a room of about 3000m2 which will have its reverberation time reduced? I am sure there some calculator I can use. There is a Crown calculator but I need to know what DB i will need with say to 12inch speakers in a hall that size so I can use it, i mean im getting 38000 watts from 7m away. Lol

3. There was a mention of having side speakers and even if all the delays were set up well, there is speakers overlapping and not sure how much of a problem that would create. But, if my goal is to reduce the db going to the seated guests on the side and if the MC will talk when the music is not playing then what other reason would there be to have side speakers other than increasing SPL? The only thing I can think of is have increase the vocal volume from the side speakers with the music slighlty lower and using the main pair for music in turn giving less distortion.

If I can just get on the right track, I can keep reading and learn more concepts. I know there is a lot to read on, but other than ensuring the correct dispersion characteristics of the speaker is chosen and maybe the use of DSP on a DBX or speaker management system the audio engineer will do the rest just making this clear don't want you gusy to think I will be setting anything up so I think with these concepts covered I am on right track, well I hope I am. I can worst case always get some online email consulting, ultimately its not my job but the sound system has to sound good and complement the acoustics this is the predicament  I am in. There might be good audio engineers in my country to rig up the system but DSP, dispersion characteristics, line array they might know what they are and how to set it up but matching to a hall using DSP I doubt it. Hence why I am scrambling to pick up at the very least the basics and with a home 2 channel background with digital filters and DSP I hope I am not too far off.

 
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Doug Fowler

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Re: Understanding Basics of LIne Array vs Point source
« Reply #14 on: November 30, 2021, 09:59:43 AM »

What is your budget for this?
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Dave Garoutte

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Re: Understanding Basics of LIne Array vs Point source
« Reply #15 on: November 30, 2021, 12:10:45 PM »

What is your budget for this?
+1

Getting the (point source)mains up as high as possible and aiming them down can go a long way to minimize room problems.
Also, look at speakers with serious pattern control.  I just got some Danley SM96 and the drop off as you leave the pattern is impressive.

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Masis Ingilizian

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Re: Understanding Basics of LIne Array vs Point source
« Reply #16 on: December 02, 2021, 08:51:47 AM »

What is your budget for this?

Lets do it this way. This way I can get an idea of what a decent sounds system for PA costs so I can provide an overview to the owner. A step up from the JBL VRX would be ideal.

Pair of speakers will be at least 2k
Amplifier will be at least 1k and need 3, one for sub and two if I biamp the mains.
A mixer have no idea what a decent one costs for this appliciation.
Speaker management controller again about 1k depending how ths is implemented
A monitor at least one, $500
Minimum two subs again at least $500 each

What else am I missing?

Am I right in hazarding a guess at 10k which should give me good speakers and decent amps. Most PA amps don't have third party measurements so will never know what we are really getting so I wouldn't go all out on the amps

I am sure we can save on the 10k but is this about right?

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Masis Ingilizian

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Re: Understanding Basics of LIne Array vs Point source
« Reply #17 on: December 02, 2021, 08:53:07 AM »

+1

Getting the (point source)mains up as high as possible and aiming them down can go a long way to minimize room problems.
Also, look at speakers with serious pattern control.  I just got some Danley SM96 and the drop off as you leave the pattern is impressive.

A decent drop off will come in handy. But still need good pattern and frequency control in the range.
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Dave Garoutte

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Re: Understanding Basics of LIne Array vs Point source
« Reply #18 on: December 02, 2021, 12:42:16 PM »

I am sure we can save on the 10k but is this about right?
I think you're two to five times too low on price.
You could easily spend $10k on mains and subs for something decent.
As far as amps, nowadays lots of them have DSP built in, saving $ and complication.
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Mike Caldwell

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Re: Understanding Basics of LIne Array vs Point source
« Reply #19 on: December 02, 2021, 04:17:39 PM »

I think you're two to five times too low on price.
You could easily spend $10k on mains and subs for something decent.
As far as amps, nowadays lots of them have DSP built in, saving $ and complication.

I agree,for a proper installation in the room that you linked to the pictures $10,000 would not get you a system to fill all the needs you listed.

Don't forget the cost of room acoustic treatments to make it workable.
« Last Edit: December 02, 2021, 04:37:54 PM by Mike Caldwell »
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Re: Understanding Basics of LIne Array vs Point source
« Reply #19 on: December 02, 2021, 04:17:39 PM »


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