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Author Topic: Cardioid array in a 800ppl club. Possible options?  (Read 24460 times)

Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #40 on: February 06, 2016, 10:14:44 am »




I have already done tests like this and tried flipping the phase of one side
You need to be VERY VERY careful when talking about phase and polarity.

In this post you are mixing the two, yet they are COMPLETELY different things.

Phase is a TIME issue.  Polarity is NOT.

Yes it does make a difference.  But many people in our industry are ignorant of that fact.

They brush it off-but it IS important to know the difference and where it applies.

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Ivan Beaver
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #41 on: February 06, 2016, 10:21:06 am »

Just a few more questions:

1. If you take a subwoofer and put it in some kind of a concrete horn that won't allow sub to pass trough it's back side, that does not mean this will make the subwoofer more directional.

3.
The thing i hate the most about this cw218v yamaha subs is how sloppy they sound. Slow drivers, shitty transient response.
Maybe getting amps with better dampening factors and getting them as close as possible to subs to connect them with short neutrik cables?

Yes a large concrete horn will be able to make the bass directional.

HOWEVER-due to the wavelengths-it is going to be larger than the space you are in.

A VERY IMPORTANT fact to realize is that sound wave have size-based on freq.  The lower the freq-the longer they are.

So what it takes to control them get larger and larger as you go lower and lower.

For the most part-don't waste your time/money on getting amps with larger damping factor.

There are many posts on here talking about that.

Use short cables of a large ga is your best best.

But part of the "sloppy sound" is also due to the cabinet/loudspeaker design.  It is all a trade off of one thing for another.

You can only "fix" something so much with outside parts. 

Sooner or later you need to look at the real issue and what you are trying to achieve.
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Ivan Beaver
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #42 on: February 06, 2016, 10:40:17 am »

You are right but most sound engineers call the polarity flip switch on a channel on a mixing board: "A phase flip switch". So this wrong terminology got in my head. I meant polarity.

I understand. So tehnicaly if i wanted to make a subwoofer directional down to 20hz i would need a 17 meters long concrete horn that wont let the sound penetrate to it's back. Then the wave would exit it only once it's fully formed.
Then basicaly what is the cause of sub omnidirectionality? A driver is pushing air and the pressurised area starts to go not only in front of the box with drivers but also on the sides and back of the box.
Why does this happen from the aspects of physics. Where can i read about this?

Also why is it a rule with horn loaded subwoofers, that if you wan't a subwoofer to effectively reproduce sound down to XY hertz, it's horn need's to be long at least 1/4 of the wavelenght of the XY frequency.
Why is it 1/4, why not the entire wavelenght?

And yes, i understand that i can't do much about the fact that those yamaha subs are simply not very good. But at least i will try with shorter cables.
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #43 on: February 06, 2016, 12:24:02 pm »

You are right but most sound engineers call the polarity flip switch on a channel on a mixing board: "A phase flip switch". So this wrong terminology got in my head. I meant polarity.

I understand. So tehnicaly if i wanted to make a subwoofer directional down to 20hz i would need a 17 meters long concrete horn that wont let the sound penetrate to it's back. Then the wave would exit it only once it's fully formed.
Then basicaly what is the cause of sub omnidirectionality? A driver is pushing air and the pressurised area starts to go not only in front of the box with drivers but also on the sides and back of the box.
Why does this happen from the aspects of physics. Where can i read about this?

Also why is it a rule with horn loaded subwoofers, that if you wan't a subwoofer to effectively reproduce sound down to XY hertz, it's horn need's to be long at least 1/4 of the wavelenght of the XY frequency.
Why is it 1/4, why not the entire wavelenght?

And yes, i understand that i can't do much about the fact that those yamaha subs are simply not very good. But at least i will try with shorter cables.
There are 2 aspects to horns and people often get them confused.  Like polarity and phase.

BTW the console manufacturers don't help any when they put a "phase" symbol on the polarity button.

The 2 aspects are pattern control and horn gain.

You can have one without having the other.

The pattern control (which does not stop the sound-just reduces the level at the edges and beyond) is based on the wavelength-the pattern of the coverage and the physical size.

As the pattern get narrower the size MUST get larger.  As the freq goes lower the size MUST get larger.

The other aspect is horn loading or acoustic gain.  It is a common misconception that putting a loudspeaker on horn will make it louder.  Well it will-but ONLY over a limited range of freq.  A simple horn is not a broad band device.

Once the freq get to high for the physical size entrance to the horn-no more gain can be had (except from the narrowing of the coverage pattern)

It is for this reason that smaller HF drivers can take advantage of horn gain to a higher freq than larger exit drivers.

On the bottom end you have things like expansion rates and the physical size of the horn to limit how much gain can be had

Lower freq need slower expansion rates than higher freq.

The reason that most subs are omni directional (yes there are exceptions) is simply due to the fact that the size of the wavelength is large as compared to the radiating source.

Think of it like this.  Go to the ocean and find a pier or piling sticking up.

Look at the waves-there are basically 2 sizes the large waves that you surf on and the little waves that are caused by the wind.

Now look on the backside of the piling.  Notice how there is a smooth area of the smaller waves?  This is because the piling is large as compared to the size of the small waves.

ALSO notice that the large wave size is completely unaffected by the piling.

This is because the size of the wave is LARGE as compared to the size of the piling.

If you want to control large waves (low freq) you MUST use large things.

Just like small acoustic materials can only control the smaller high freq0they do nothing for the larger low freq.

When you start to think of things in terms of physical size vs freq, you start to get a understanding.

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Ivan Beaver
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Art Welter

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #44 on: February 06, 2016, 12:46:02 pm »

Just a few more questions:

1.  As soon as a low frequency wave is free in open air, it starts getting omnidirectional, there is no way to stop this by physicaly enclosing subwoofers right?

2. The mid-high boxes we have, the yamaha c215v, they are not "arrayable" ..We have 3 a side so you can hear this problem quiet a bit.
Is there any way to partialy stop this? Getting the boxes further apart, getting the boxes one on top of each other, putting some of them as a delay stack further in the club, what are my options?

3. The thing i hate the most about this cw218v yamaha subs is how sloppy they sound. Slow drivers, shitty transient response. You can't feel sharp kick in your chest from them, it's just a mass of molded energy compared to a good sub. What can be done on this quiestion?
Maybe getting amps with better dampening factors and getting them as close as possible to subs to connect them with short neutrik cables?
I usually try boosting the 40-31.5 hz area to extend low end. Then keep them flat at 50 and 63hz because they have quiet decent sensitivity there and can overload the room. Then sometimes i try slightly boosting the 80-100hz area to make kick slightly sharper but the room is very ringy at 100hz so this can become a problem...
1)When the sound wave is large compared to the exit (or baffle) size, it diffracts around the exit, similar to the difference in pattern between a garden hose, and a garden hose with a small exit (like your thumb pressing over the exit), the small exit sprays wide. Bass horns start being effective in output down with 1/4 wavelength, so are generally not made longer. To be effective in controlling directionality the diameter would need to approach the wavelength, obviously not possible in a typical venue.
2)Vertical stacking with the HF horns together will reduce horizontal lobing, and (in general) reduce vertical dispersion, though with a pair of 2x15" it may not be possible to get the HF horns high enough to be above head height. Delayed speakers may be a better option, but introduce off axis timing and phasing problems due to path length differences at various off-axis time of flight differences.
3) Much of the "sloppiness" of the subs is likely directly due to your EQ approach. BR (bass reflex) enclosures rely on the phase inverted port output around Fb (box tuning frequency) to reinforce the front output. At Fb, the driver's excursion is at minimum, and port output (Helmholtz resonance, like blowing across a jug mouth) is at maximum. Below Fb, excursion (and distortion) increases rapidly, and port output also rapidly drops. You are boosting below Fb- which will waste power, and make the rest of the output sound sloppy, because the cone is "flopping around", not doing useful work. Put a dot (white out, silver Sharpie) on the cone, run a sine wave sweep (use about 10 volts) from 100 Hz down, you will see the cone excursion start to increase, then it will decrease to it's minimum at Fb, then rapidly increase again. Once you determine Fb (probably around 45 Hz) set the HP on your DSP to a LR 24 filter a few Hz below Fb to keep the excursion under control. If excursion exceeds Xmax (one way linear travel) the driver's output will start sounding like crap. Cheap(er) speakers generally have only half (or less) Xmax than state of the art speakers- doubling Xmax (and power) allows 6 dB more clean output.

Second problem is alignment- your top cabinets are also BR, and have a phase inverted output at the lower end of their range, but the sub's upper range phase is not- to align the phase of the two in the crossover region may require delaying either the sub or tops slightly. Since your crossover is likely in the 80-100 Hz range where "punch", and "tight" (as opposed to "sloppy" response lives, proper phase alignment is crucial in that region.

That said, the third problem of room modes and L/R distance relationships will dominate LF response, a perfectly aligned system will still not "win" over a bad room. Reduction of the most offensive frequencies (after system alignment and properly setting HP filters) will "clean up" the sound a bit, but only provides a compromise,  the "greatest good" for the most will still result in some areas that are no good.

Art
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #45 on: February 07, 2016, 06:34:05 am »

Ivan:

So about horns. I'm not exactly understanding what you are trying to say.
Small drivers like compression drivers/tweeter usually have a horn in front of them
and the reason for that horn is pattern controll right? It controls how a tweeter covers the area in front of it. Under which angle.

But on the other hand, that tweeter won't get much when talking about horn gain?
Once you remove the horn from it, it doesn't really get much quieter right?

The way i see it... those waves are too small to make a horn usefull for them when talking about gain. The membrane is moving so fast that the air in front of it does not have the time to escape, a tweeter effectively compresses that air even if it's completly free right?

On the other hand, that big 18 is moving slow compared to the tweeter membrane. So if it's free with no box, the air will simply move away from  the membrane and it won't effectivley compress it. When you then put that driver in a horn, the horn keeps the air in place allowing the driver to compress it.

Am i seeing this right?

If i am then, the way i understand it is, if the horn is too short the air will start beeing free and exiting the horn while the driver is still pushing it. Which will drasticaly drop the effectivenes of the horn. That's all understandable but why then is there that rule that if you want a horn loaded subwoofer to be effective at let's say 40hz. The horn needs to be 1/4 of the 40hz wavelenght long?
Why wouldn't it need to be as long as the entire wavelenght of 40hz? If it's only 1/4 the air will still start escaping the horn when the driver is still pushing it. That will drop the pressure inside the horn and make the driver a lot less effective?

The other thing is, how can a bass reflexx box go lower then a horn while staying relativley small. The bass reflex box also wouldn't be able to keep the air inside during the entire cycle that a driver does.
This is obviously because a bass reflex box works on a totaly different principal of a horn. Where can i read more about this?
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #46 on: February 07, 2016, 06:53:56 am »

Art:

1) I will go read about wave diffraction now, i want to know how it works.
Talking about horns, the same thing that i just asked Ivan.
So i understand that in order to control directionality a horn needs to be as long as the wavelenght which is not possible.
But why does it only need to be 1/4 wavelenght to be effective for horn gain? Shouldn't it be keeping air in place during the entire cycle of a driver?
And why does if need to start narrow and then keeps getting wider. I understand that this is because it slowly changes the impedance of air but i don't understand how it works. Why wouldn't it work if it was just a straight tunnel in front of the driver, the same size during the entire path of the horn.

2.
Those boxes wouldn't be on the floor. The first one would allredy have the horn/tweeter above heads of people. The second box on top of it would then get very high and maybe improve the throw of the PA. It would maybee loose less SPL over distance which i could use.
But you are saying that if i stack them on top of each other i would get less comb filtering/lobing horizontaly?
Verticaly it's not that important. People don't walk up and down in the room, they walk from left to the right. But what did you mean by reducing vertical dispersion?

3.
Very interesting. I'm doing a big mistake then, probably because i mentaly trick myself into believing these subs are actually giving me decent pressure at 35-40hz.
The thing is, when i take the parameter eq on the behringer x32 i use for control, and boost the 40hz area to make their sub extension go lower. What that probably does if not actually giving me anything much usefull at 35-40hz but does boost the 50hz area because i use wide Q when i do the boost. And then it tricks me into thinking they are giving me pressure at 40hz. I will definitly test this the way you told me. If i lowcut them properly, they will be under less load and start working more precise. Basicaly i shouldn't make them to any work under tuning frequency right?

Yes the crossover is around 100hz and yes i have been thinking about this buy tought that the entire PA is a yamaha club series and should be designed to work well with a top box on a subwoofer with no delay, i tought it's logical they both push frequencies aroung 100hz in phase when they are physicaly aligned. That's obviously wrong so i will try delaying them.

Thanks!

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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #47 on: February 07, 2016, 09:10:52 am »

Art:
 
Talking about horns, the same thing that i just asked Ivan.
So i understand that in order to control directionality a horn needs to be as long as the wavelenght which is not possible.

No.

The length of the horn has almost nothing to do with the freq for directivity.

Here is the basic formula for figuring out pattern control.

Of course the sound does not stop at those angles-but is generally considered to be 6dB down.

Freq of control=1,000,000/(size of horn exit in inches x rated pattern in degrees)

Of course the length will be what it needs to be.

But if you run the numbers you will see that a wider coverage horn will be smaller (for a given freq) than a narrow coverage horn.

Or looking at it a different way- for a given freq a narrower horn will be deeper than a wider horn.

The 1/4 wavelength has to do with HORN LOADING-NOT pattern control

Those are different things that require completely different approaches in the design.
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Ivan Beaver
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #48 on: February 07, 2016, 09:37:01 am »

No.

The length of the horn has almost nothing to do with the freq for directivity.

Here is the basic formula for figuring out pattern control.

Of course the sound does not stop at those angles-but is generally considered to be 6dB down.

Freq of control=1,000,000/(size of horn exit in inches x rated pattern in degrees)

Of course the length will be what it needs to be.

But if you run the numbers you will see that a wider coverage horn will be smaller (for a given freq) than a narrow coverage horn.

Or looking at it a different way- for a given freq a narrower horn will be deeper than a wider horn.

The 1/4 wavelength has to do with HORN LOADING-NOT pattern control

Those are different things that require completely different approaches in the design.

Okay so if i wanted to make a 20hz wave directional i wouldn't need a 17 meters long horn. I would need to take that formula and see how big the horn will have to be?

And yeah, time to go read about horn loading. I understand that it has nothing to do with pattern control because the point in this case is increasing efficiency, not directing sound.
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #49 on: February 07, 2016, 10:19:39 am »

Okay so if i wanted to make a 20hz wave directional i wouldn't need a 17 meters long horn. I would need to take that formula and see how big the horn will have to be?


I gave you that formula in my last post.

The formula describes the size of the mouth for normal pattern control

Then all you have to do is to determine what length at the specific ANGLE of the direction that it needs to be.

A wide horn will not be as deep as a narrow horn.

But FIRST-YOU have to say how much directivity or what angle you are interested in.

Is it 40* or 90* or 180* etc.

You could "argue" that 300* is more directional than 360*.

So defining the parameter you want is the first step in ANY audio design.

If you don't do that-it is like saying "I want a powerful amp".

So how do YOU define powerful?

Is it 1000 watts, 10,000 watts, or 20 watts.

It all HAS to be based or referenced to something else.
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Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!
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