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Author Topic: Cardioid array in a 800ppl club. Possible options?  (Read 24083 times)

Tim Steer

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #20 on: February 04, 2016, 06:34:36 am »

It's a fairly common technique. Space the speakers 1/4 of a wavelength at the offending frequency and delay the front speaker by 1/4 of a wave period.

Consider what happens when a sine wave is played through the system at that frequency...

In front of the array: The front sub 'waits' for the wavefront to from the rear sub to 'catch up' before firing - the sound from both subs is in phase and adds constructively.

Behind the array: The wavefront from the rear sub reaches the listener first. The sound from the front sub is delayed by 1/4 of a period, and THEN has to travel and extra 1/4 wavelength - a total time delay of 1/2 a period. The result is that the waves from the two subs are 1/2 a period out of phase, and add destructively.

I've set up two configurations of L'Acoustics subs side-by-side - the L'Acoustics recommended method, with bottom sub reversed and in 'C' mode, and an endfire array as described above, and whilst the 'stacked' method worked pretty well, the endfire array offered much greater rear rejection.
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #21 on: February 04, 2016, 06:37:49 am »

It's a fairly common technique. Space the speakers 1/4 of a wavelength at the offending frequency and delay the front speaker by 1/4 of a wave period.

Consider what happens when a sine wave is played through the system at that frequency...

In front of the array: The front sub 'waits' for the wavefront to from the rear sub to 'catch up' before firing - the sound from both subs is in phase and adds constructively.

Behind the array: The wavefront from the rear sub reaches the listener first. The sound from the front sub is delayed by 1/4 of a period, and THEN has to travel and extra 1/4 wavelength - a total time delay of 1/2 a period. The result is that the waves from the two subs are 1/2 a period out of phase, and add destructively.

I've set up two configurations of L'Acoustics subs side-by-side - the L'Acoustics recommended method, with bottom sub reversed and in 'C' mode, and an endfire array as described above, and whilst the 'stacked' method worked pretty well, the endfire array offered much greater rear rejection.

Yes, that's an endfire array. That's not what we are talking about now. He told me that a normal cardioid array benefits if the box that is flipped around is pushed behind the array. I know how an endfire array works.
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #22 on: February 04, 2016, 08:11:44 am »

There is a confusion of terminology going on here.

A "cardioid" array is where the rear box (facing in EITHER direction) is delayed and has the polarity flipped.

This can be done by turning the rear box around or physically placing it behind the front box.  Either way-the PHYSICAL DISTANCE is the determining factor for the center of cancellation (maximum cancellation) frequency.

An endfire array is where the rear box has no delay and each box towards the front is progressively delayed.

A cardioid setup can only have 2 boxes.  Yes you can use more-but there are only 2 settings that are used.

And endfire can use as many as you want.


The sonic differences are as follows.

In NEITHER cases will the output SPL output out front be equal to the same number of boxes simply facing forward.

It will be always be lower.  Remember you are CANCELLING energy.  You don't get that back.

The cardioid will have more rear rejection at the expense of upper bass rolloff.  This can result in less "punch".

The endfire will have less rear rejection, but will sound like a single cabinet.  So sonically it is better
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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 #23 on: February 04, 2016, 08:17:22 am »


I can't understand why this would be true simply because the flipped box is pushing out everything that i's getting back from the front pointing boxes, just in the opposite phase. Witch means it provides perfect cancelation on all frequencies. That is the point of a normal cardioid array.


Any cancellation by any loudspeaker is freq dependant.

You do not get cancellation across the entire bandwith.

It is all position related.

I don't have the time right now to show you some examples, but can do so later-along with models and freq response .

If you read up on how an endfire or cardioid system works, you should start to get a better understanding that it IS physical distance and freq related.

It is NOT across the whole freq range. No matter what anybody says.  If they tell you that-they are wrong.  Sorry.

Unless the freq range is pretty small.
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Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #24 on: February 04, 2016, 09:56:39 am »

There is a confusion of terminology going on here.

A "cardioid" array is where the rear box (facing in EITHER direction) is delayed and has the polarity flipped.

This can be done by turning the rear box around or physically placing it behind the front box.  Either way-the PHYSICAL DISTANCE is the determining factor for the center of cancellation (maximum cancellation) frequency.

An endfire array is where the rear box has no delay and each box towards the front is progressively delayed.

A cardioid setup can only have 2 boxes.  Yes you can use more-but there are only 2 settings that are used.

And endfire can use as many as you want.


The sonic differences are as follows.

In NEITHER cases will the output SPL output out front be equal to the same number of boxes simply facing forward.

It will be always be lower.  Remember you are CANCELLING energy.  You don't get that back.

The cardioid will have more rear rejection at the expense of upper bass rolloff.  This can result in less "punch".

The endfire will have less rear rejection, but will sound like a single cabinet.  So sonically it is better

Yes there is a big terminology confusion going here.

In no part of the text i have been talking about about an array where boxes are set one behind another AND some of them are polarity flipped. 

I have been comparing different variations of:  A normal endfire setup where a few boxes are standing one behind another, working in phase, delayed and spaced properly, canceling out ony one frequency perfectly.

And then i have been talking about a cardioid setup. BUT NOT an endfire cardioid setup. I'm talking about a normal, sandard cardioid setup that looks like this:

http://www.ratsound.com/cblog/uploads/2009_04_24_sub_center.jpg

or this:

api.ning.com/files/K5EyQbUmZFDOihL3vM7IYLPZ5*wRx8ADuEJifX4wDkC5HNqJsK0DOvQqBhERjLzhesSxAoooibjO61fcKRj48nubAhTSIqfg/ScreenShot20131001at11.13.31PM.png

or this:

http://www.creativeaudio.us/images/audio/audio4.jpg


In all setups where some of the boxes are turned around, polarity flipped and delayed cancelation occurs at all frequencies. They don't need to be physicaly moved, that makes no sense.
 
However what i think you are talking about is a variation of the endfire setup where the back box is polarity flipped and optimized for maximum cancelation.
I know how that works but i have not talked about that array anywhere in the subject.

Because you wrote:

A "cardioid" array is where the rear box (facing in EITHER direction) is delayed and has the polarity flipped.

There is no rear box in any of the cardioid arrays i have mentioned. The rear box exist only in a normal endfire configuration where all boxes work in phase and point in the same direction.

I am basicaly comparing this: https://www.gearslutz.com/board/attachments/remote-possibilities-acoustic-music-location-recording/296739d1339981762-need-advise-meyer-setup-array.jpg

Versus this:  http://i39.photobucket.com/albums/e194/HarfordSound/cardioidB2.jpg
« Last Edit: February 04, 2016, 10:03:35 am by Eugen Jeličić »
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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #25 on: February 04, 2016, 12:18:30 pm »


I have been comparing different variations of:  A normal endfire setup where a few boxes are standing one behind another, working in phase, delayed and spaced properly, canceling out ony one frequency perfectly.





In all setups where some of the boxes are turned around, polarity flipped and delayed cancelation occurs at all frequencies. They don't need to be physicaly moved, that makes no sense.
 

WRONG WRONG WRONG

No matter how much you "want" to believe it, you MUST have spacing AND it is NOT cancellation across the whole freq band.

I would LOVE to see any simulation or measurement to prove other wise.

I have done BOTH types of setups and MEASURED AND SIMULATED IT, and in NO case did I get cancellation across the whole freq range.

And in EVERY case-the spacing of the boxes made a difference of what freq were affected (ie cancelled)

DO THE MATH (it is very simple) and change things and you can prove it to yourself.

Or you can go on "make believing" that what you think is actually happening.

Sorry to sound rude-but it is evident that you have no practical knowledge or experience with either setup.



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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 #26 on: February 04, 2016, 12:38:59 pm »

WRONG WRONG WRONG

No matter how much you "want" to believe it, you MUST have spacing AND it is NOT cancellation across the whole freq band.

I would LOVE to see any simulation or measurement to prove other wise.

I have done BOTH types of setups and MEASURED AND SIMULATED IT, and in NO case did I get cancellation across the whole freq range.

And in EVERY case-the spacing of the boxes made a difference of what freq were affected (ie cancelled)

DO THE MATH (it is very simple) and change things and you can prove it to yourself.

Or you can go on "make believing" that what you think is actually happening.

Sorry to sound rude-but it is evident that you have no practical knowledge or experience with either setup.

I have no practical knowledge but you are not explaining yours claims either so i don't see how you expect me to see logics in them after seeing normal cardioid arrays with no box spacing at almost every festival where cardioid arrays are used.

Here is a simulation of a cardioid array at 2:10 : 

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

Cancels out everything up to 80hz almost perfectly eaven. After that the cancelation starts dropping of course but we are not talking about sub anymore.

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Ivan Beaver

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #27 on: February 04, 2016, 01:19:31 pm »

I have no practical knowledge but you are not explaining yours claims either so i don't see how you expect me to see logics in them after seeing normal cardioid arrays with no box spacing at almost every festival where cardioid arrays are used.

Here is a simulation of a cardioid array at 2:10 : 

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

Cancels out everything up to 80hz almost perfectly eaven. After that the cancelation starts dropping of course but we are not talking about sub anymore.
Think about it this way.

What are the STEPS in doing a directional sub array (either type)

STEP 1 Determine what the 1/4 wavelength distance is for the freq of interest.

If this didn't matter-then WHY is it STEP 1?

You CANNOT go to step 2 until you have done STEP 1.

Yes you don't HAVE to figure out step one-but there ARE consequencies.

For example-if you just turn one sub around and let's say it is 2' deep.

You set your delay for around 2ms.

Sure you will get cancellation behind- BUT ALSO there will be LESS SOUND out front than if you just used ONE speaker-at certain freq.

There ARE tradeoffs, and you have to realize there is no "free lunch".

But people often like to "forget" the things that they don't want to talk about.

It just makes their case "stronger".

But it is the OVERALL situation that should be considered-NOT just one little aspect.  But if that is all you want to consider-then sure-it is fine.
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Jay Barracato

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #28 on: February 04, 2016, 02:50:51 pm »

Eugen,

A couple of reality points. I understand what you are trying to ask without forcing absolutes onto your words which really aren't helping.

I have set up the two forward/one reversed setup you are asking about any number of times. These comments are based on my observations and measurements.

1. The best center frequency cancellation I achieved was about -18 db at 70 hz in open air. 12-15 db is much more typical.

2. This comes with a 3-6 db reduction out front that is delayed by 1 wave. You still have the initial impact on the initial wave.

3 The cancellation tapers off (as you asked) as you move outward from the center frequency. This is because of the range of phase angles around 180 where cancellation occurs.

4. The rate at which the cancellation falls off depends on the phase response from f the speakers. The steeper the change in phase of the speakers, the narrower the frequency range that will cancel is.

5. Indoors primary reflections from walls especially at the back of the stage throw a monkey wrench into all this and really affect what is heard at each listening position.

I work every week in a similar 700 capacity club and my inclination would be to use bass traps to control low end reflections on stage rather than trying to create a zone of cancellation.

If you go to www.bennettprescott.com
He has a couple of articles posted about smaller subwoofer arrays.


Sent from my XT1254 using Tapatalk
« Last Edit: February 04, 2016, 02:57:43 pm by Jay Barracato »
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Jay Barracato

Eugen Jeličić

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Re: Cardioid array in a 800ppl club. Possible options?
« Reply #29 on: February 04, 2016, 06:59:09 pm »

Eugen,

A couple of reality points. I understand what you are trying to ask without forcing absolutes onto your words which really aren't helping.

I have set up the two forward/one reversed setup you are asking about any number of times. These comments are based on my observations and measurements.

1. The best center frequency cancellation I achieved was about -18 db at 70 hz in open air. 12-15 db is much more typical.

2. This comes with a 3-6 db reduction out front that is delayed by 1 wave. You still have the initial impact on the initial wave.

3 The cancellation tapers off (as you asked) as you move outward from the center frequency. This is because of the range of phase angles around 180 where cancellation occurs.

4. The rate at which the cancellation falls off depends on the phase response from f the speakers. The steeper the change in phase of the speakers, the narrower the frequency range that will cancel is.

5. Indoors primary reflections from walls especially at the back of the stage throw a monkey wrench into all this and really affect what is heard at each listening position.

I work every week in a similar 700 capacity club and my inclination would be to use bass traps to control low end reflections on stage rather than trying to create a zone of cancellation.

If you go to www.bennettprescott.com
He has a couple of articles posted about smaller subwoofer arrays.


Sent from my XT1254 using Tapatalk

Thanks.
So if i understood this right, with a standard cardioid array i also pick the most problematic frequency and tune the array according to that?
It will of course give me more overall 30-100hz cancelation than an endfire array witch will be effective only around one frequency. But i still have to pick the area that creates the most problems because i can't cancel out everything.

How do i set up a standard cardioid then? I flip one box, flip it's polarity, and then i delay it how much? I tought i need to find the time that sub from the front boxes needs for reaching their back side/the front side of the flipped box.
I didn't think that this time was frequency dependant?

Also i can't improvise bass traps. It's not my club, i won't invest my money in acoustical treatment of a club i only work in.

And yeah, the sub from the flipped box that is getting back in front will be out of phase and delayed in comparison to the sub from the boxes radiating directly into the room, witch will decrease the quallity of what goes in front, right?
And talking about power, when i flip one box in a mono block to make a cardioid array, i quiet much loose most of the power, if not all of the power from that box if talking about what i'm getting outside. That sub that goes to the back side of the flipped box is going to be late and do more damage than good right?
« Last Edit: February 04, 2016, 07:04:32 pm by Eugen Jeličić »
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