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Author Topic: Cardioid pattern.  (Read 2200 times)

Al Rettich

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Cardioid pattern.
« on: August 24, 2023, 09:18:57 PM »

In my background I was trained that to properly do cardioid you needed more forward pressure that rear pressure.  Today I saw a set up that puzzled me.  Six stacks of L’Acoustic KS28’s. Two high.  Bottom cabinet turned around.  Total of twelve subs.  On top of that he had them in a 70 degree sub arc.  I was watching soundcheck and my friend was pushing the low end. Much harder than normal he said.  Can you do cardioid with just two cabinet stacks?
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Chris Grimshaw

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Re: Cardioid pattern.
« Reply #1 on: August 25, 2023, 08:59:28 AM »

Yep!
Just turn the front-facing cabinets up a bit, or the rear ones down.

Chris
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David Morison

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Re: Cardioid pattern.
« Reply #2 on: August 25, 2023, 09:12:36 AM »

In my background I was trained that to properly do cardioid you needed more forward pressure that rear pressure.  Today I saw a set up that puzzled me.  Six stacks of L’Acoustic KS28’s. Two high.  Bottom cabinet turned around.  Total of twelve subs.  On top of that he had them in a 70 degree sub arc.  I was watching soundcheck and my friend was pushing the low end. Much harder than normal he said.  Can you do cardioid with just two cabinet stacks?

Yes, you can do cardioid with only 2 boxes per stack.
The more common ratios (2:1 or 3:1, forward to rear) are done because in many situations, getting several dB of rear attenuation is enough to be useful, and having more forward boxes gives a bit more forward level.
If you had a really important reason to try and get more rear attenuation, then 1:1 forward to rear would actually help achieve that, at the expense of a bit of forward output as your friend found.
Whether or not combining that with an arc is at all useful would be beyond my current knowledge though - modelling would almost certainly be required.
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Ivan Beaver

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Re: Cardioid pattern.
« Reply #3 on: August 28, 2023, 12:15:30 PM »

In my background I was trained that to properly do cardioid you needed more forward pressure that rear pressure.  Today I saw a set up that puzzled me.  Six stacks of L’Acoustic KS28’s. Two high.  Bottom cabinet turned around.  Total of twelve subs.  On top of that he had them in a 70 degree sub arc.  I was watching soundcheck and my friend was pushing the low end. Much harder than normal he said.  Can you do cardioid with just two cabinet stacks?
You will get the most rear rejection when you use the same number of cabinets for both the front and rear cabinets.

Many cases you see do not take full advantage of the possible rear rejection, if some are turned backwards.

For the most forward output and rear cancellation, both cabinets MUST be facing forward, with the proper spacing, and proper DSP applied.

For cardioid that in the rear cabinet is reversed polarity and delay added.  But you pay a price for that extra cancellation, which is a rolloff of the low end and the top end (less punch).

An endfire situation (physically the same setup), has better overall fidelity and greater output, but does not have as much rear rejection.

It all depends on what you are trying to achieve and what is most important for that particular situation.  One size/application does not fit all usages
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Al Rettich

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Re: Cardioid pattern.
« Reply #4 on: August 30, 2023, 04:44:49 PM »

Ivan,
This venue the promoter doesn't like giving up space for subs. When I tried to get him to pay for flying them, he didn't want to pay, and told me to stack them as far away from center as possible. However, all the acts have complained of all the low end on stage. We have twelve subs, in carts stacked two hight. Everything I've been taught has that two facing forward, and one flipped. I was always able to "play" and get a bit more rejection by moving the delay time around. (and flipping out of phase) I keep wanting to learn about end fire, but if you search youtube there are quite a few folks who go against each other. My goal has been to get even coverage, and try to have a bit less low end onstage.

You will get the most rear rejection when you use the same number of cabinets for both the front and rear cabinets.

Many cases you see do not take full advantage of the possible rear rejection, if some are turned backwards.

For the most forward output and rear cancellation, both cabinets MUST be facing forward, with the proper spacing, and proper DSP applied.

For cardioid that in the rear cabinet is reversed polarity and delay added.  But you pay a price for that extra cancellation, which is a rolloff of the low end and the top end (less punch).

An endfire situation (physically the same setup), has better overall fidelity and greater output, but does not have as much rear rejection.

It all depends on what you are trying to achieve and what is most important for that particular situation.  One size/application does not fit all usages
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Tim McCulloch

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Re: Cardioid pattern.
« Reply #5 on: August 30, 2023, 05:07:58 PM »

Ivan,
This venue the promoter doesn't like giving up space for subs. When I tried to get him to pay for flying them, he didn't want to pay, and told me to stack them as far away from center as possible. However, all the acts have complained of all the low end on stage. We have twelve subs, in carts stacked two hight. Everything I've been taught has that two facing forward, and one flipped. I was always able to "play" and get a bit more rejection by moving the delay time around. (and flipping out of phase) I keep wanting to learn about end fire, but if you search youtube there are quite a few folks who go against each other. My goal has been to get even coverage, and try to have a bit less low end onstage.

The quarter-wave spaced array (with or without delay arc) across the front of the stage can even out coverage left to right, but puts a whole lot of energy back on the stage.  It also eats 6 feet or more of downstage space, which is what your promoter doesn't want to do.  Taking out space:  smaller capacity; flying:  more expense (riggers) for the in and out.  And the promoter doesn't give a shit about what the bands might like or prefer unless it's a show-stopping issue with the act.  Trust me, sub placement won't be THAT issue for any gig most of us will be doing.  Promoter: "fine, don't play, pack up your merch and get the hell out, and no, I'm not paying the balance, sue me."  When artist management hears about it, they'll be screaming at the band and the PM/TM "what the fuck did you just do? It's gonna take years to repair the relationship with that promoter."

When the BE comes to me with this kind of stuff, especially if it wasn't advanced, I usually suggest that they immediatley involve management and the promoter rep - because I know what will happen.  My alternate is "well, what you want will reduce the ticket inventory by 10% and show is sold out, so we need the promoter to decide who gets refunds..."  Guess what ain't happening?  Now if everyone (promoter, venue, house manager, security, etc) is on the same page - in advance - about sub deployment, it will be done and ready when the BE arrives.

That all said, I'm not talking about U2 or Adele or other international or national level performers, as this was all worked out months prior when the show was designed.

The tl;dr
If you're still with me, Al - thanks for caring, really.  The things that will make the most difference either reduce revenue or increase costs, or possibly become security or safety concerns.  Usually those decisions are above our pay grade.
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Helge A Bentsen

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Re: Cardioid pattern.
« Reply #6 on: August 31, 2023, 05:10:10 AM »

What you can do if time and space permits it, is to do a cardioid stack or end fire solution L/R and angle them outwards.
That way the rear cancellation lobe points toward the stage. This might help, how much is dependent on the venue acoustic and physical placement.
Done it a couple of times with good results and a few times with little or no effect due to placement issues and venue acoustics.

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John Schalk

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Re: Cardioid pattern.
« Reply #7 on: August 31, 2023, 10:34:48 AM »

This venue the promoter doesn't like giving up space for subs. When I tried to get him to pay for flying them, he didn't want to pay, and told me to stack them as far away from center as possible. However, all the acts have complained of all the low end on stage. We have twelve subs, in carts stacked two hight.

I keep wanting to learn about end fire, but if you search youtube there are quite a few folks who go against each other. My goal has been to get even coverage, and try to have a bit less low end onstage.
Al,
You may want to install Meyer's MAPP 3D software (it's free) and use it to model different subwoofer configurations in this venue.  MAPP 3D only has speaker files for Meyer's powered products, but if you own front loaded double 18" bass reflex subs then you can use Meyer's 1100 LFC for you models.  Heck, if you post the venue's dimensions including the stage size, I might have time to play around with some options.  Another source for real world experience with different subwoofer configuration options is Dave Rat's YouTube channel.  He has I think three videos in a subwoofer series where he goes through a bunch of different subwoofer setups that he's tried over the years.  He uses L-acoustics SoundVision software to show the results for the various configurations.

By the way, I'm a very small operator so I have no practical experience with any kind of subwoofer deployment beyond one on either side of the stage or two in the middle.  Maybe one of these days I can get a third sub matching subwoofer to play with!
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Al Rettich

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Re: Cardioid pattern.
« Reply #8 on: September 02, 2023, 05:41:16 PM »

I've done this with both SoundVision, and ArrayCalc. Thursday we had a show there, I had some time to play a bit with subs. I tried both a sub arc, then a sub arc with stacks of two subs. Bottom sub turned around, flipped out of phase. 4.1ms I found that dead center onstage was the quietest. But not as much as I've had with stacks of three.

Al,
You may want to install Meyer's MAPP 3D software (it's free) and use it to model different subwoofer configurations in this venue.  MAPP 3D only has speaker files for Meyer's powered products, but if you own front loaded double 18" bass reflex subs then you can use Meyer's 1100 LFC for you models.  Heck, if you post the venue's dimensions including the stage size, I might have time to play around with some options.  Another source for real world experience with different subwoofer configuration options is Dave Rat's YouTube channel.  He has I think three videos in a subwoofer series where he goes through a bunch of different subwoofer setups that he's tried over the years.  He uses L-acoustics SoundVision software to show the results for the various configurations.

By the way, I'm a very small operator so I have no practical experience with any kind of subwoofer deployment beyond one on either side of the stage or two in the middle.  Maybe one of these days I can get a third sub matching subwoofer to play with!
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ProSoundWeb Community

Re: Cardioid pattern.
« Reply #8 on: September 02, 2023, 05:41:16 PM »


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