ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: Cardioid Subwoofer Array  (Read 1821 times)

Chris Delcambre

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 52
Cardioid Subwoofer Array
« on: May 22, 2017, 11:11:14 pm »

Hi there,

I am looking for some advice on how to calculate the spacing in between clusters of subs... I am going to be doing a show where I have 4 groups of 3 srx728 subs in front of a stage... each cluster will be setup with forward, backward, forward sub configuration... my question is how do you properly calculate the proper distance in between each cluster of 3 subs... I generally do end fired arrays however at this event I do not have the space available to do this...

Thanks
Chris
Logged

Kevin McDonough

  • Full Member
  • ***
  • Offline Offline
  • Posts: 235
Re: Cardioid Subwoofer Array
« Reply #1 on: May 23, 2017, 04:30:57 am »

Hi there,

I am looking for some advice on how to calculate the spacing in between clusters of subs... I am going to be doing a show where I have 4 groups of 3 srx728 subs in front of a stage... each cluster will be setup with forward, backward, forward sub configuration... my question is how do you properly calculate the proper distance in between each cluster of 3 subs... I generally do end fired arrays however at this event I do not have the space available to do this...

Thanks
Chris

Haha I get to beat Ivan to it and say "it depends" lol!  The distance can be a few cm up to a few feet really, depending on what you're wanting to achieve. In order to couple and appear as one source they ideally need to be within 1/4 wavelength spacing. So if you really start to move them far apart, the wider you make them the more you'll start to lose that coupling and they'll start to act more like 4 individual sources as you go up in frequency towards their crossover to the tops.

However what also counts after that is what delay you give them and how you want them to perform. 

If you don't put any other delay on them other than just that needed to make the reverse sub work as cardioid  (or you maybe delay the whole array to match with the tops, but not delay any of the groups of 3 different to the others) then, again as you start to space wider, they'll start to focus the sound forward more and more into a column of sound up the centre of the venue.

To counter this and to force the sound to spread out again into more of an arc increasing delay is often added to each cluster as you move out left and right from the centre. In your case that would mean maybe adding a little delay to the two outer stacks. Exactly how much will depend on how wide you've spaced the stacks and how much you want to curve the sound outwards.

LOL, so with all that said, by far the easiest way is to use software and get a chance to visualise it.

Ease Focus is free and can be used to calculate arrays, or you could download Meyer or D&B's software among others.

While none of the subs used in the software will match exactly with the subs you're using, they'll be close enough to give you a good starting point. You can have a play in the software and see how adding different spacing and different amounts of delay changes things, and it'll give you an idea of how you want things set up, from which you can tweak on the day to make sure you're happy with the sound.
« Last Edit: May 23, 2017, 06:11:07 am by Kevin McDonough »
Logged

David Sturzenbecher

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1231
    • Sturz Audio
Re: Cardioid Subwoofer Array
« Reply #2 on: May 23, 2017, 07:57:26 am »

I would argue that the delay should really be field verified. No program is going to calculate the propagation delay of the wave around the box.  Programs will get you close, but measurement will get you right on the money.


Sent from my iPhone using Tapatalk Pro
Logged
CTS-D, CTS-I
AES Full Member

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 8172
  • Atlanta GA
Re: Cardioid Subwoofer Array
« Reply #3 on: May 23, 2017, 08:31:15 am »

I would argue that the delay should really be field verified. No program is going to calculate the propagation delay of the wave around the box.  Programs will get you close, but measurement will get you right on the money.


Sent from my iPhone using Tapatalk Pro
Agreed.

The programs "assume" all of the sound radiates from a single small point and goes straight out.

In reality it must take a longer path to "get around" the box in front.

If you put mics in front and behind and look at them as you change the delay, you will come up with the REAL behavior.

Models can be a good thing, but there ARE limitations in how the end result if the real world actually is
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Kevin McDonough

  • Full Member
  • ***
  • Offline Offline
  • Posts: 235
Re: Cardioid Subwoofer Array
« Reply #4 on: May 23, 2017, 11:01:15 am »

I would argue that the delay should really be field verified. No program is going to calculate the propagation delay of the wave around the box.  Programs will get you close, but measurement will get you right on the money.


Sent from my iPhone using Tapatalk Pro

Of course.

The impression I got though was that he already had the cardioid part sorted?  He spoke of making stack of three with the centre one reversed as if he'd done that before (does that model of JBL have it built in?) and it was just the spacing and delay between stacks that he was interested in adjusting?

Though yeah, even in that case as I said the software will give a good starting point and then he can tweak on the day.
Logged

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 8172
  • Atlanta GA
Re: Cardioid Subwoofer Array
« Reply #5 on: May 23, 2017, 05:15:49 pm »



Though yeah, even in that case as I said the software will give a good starting point and then he can tweak on the day.
The big issue with "tweaking on the day" is taking into account what is happening out front AND behind the array.

If all you consider is one or the other, there is a possibility that the other position could get screwed up.

That is why it is important to look at both.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Ray Aberle

  • Classic LAB
  • Hero Member
  • *
  • Online Online
  • Posts: 3014
  • Located in Vancouver, WA (and serves OR-WA-ID-BC)
    • Kelcema Audio
Re: Cardioid Subwoofer Array
« Reply #6 on: May 26, 2017, 11:22:05 am »

(does that model of JBL have it built in?)
The 728s do not have front panel speakon connectors. :( At least, all of my old ones don't. I have 6 more en route from JBL; maybe they've added it. That'd be cool.... but I doubt they would. I'll let you know after I pick them up tomorrow!

-Ray
Logged
Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)

Ray Aberle

  • Classic LAB
  • Hero Member
  • *
  • Online Online
  • Posts: 3014
  • Located in Vancouver, WA (and serves OR-WA-ID-BC)
    • Kelcema Audio
Re: Cardioid Subwoofer Array
« Reply #7 on: May 28, 2017, 04:04:48 pm »

The 728s do not have front panel speakon connectors. :( At least, all of my old ones don't. I have 6 more en route from JBL; maybe they've added it. That'd be cool.... but I doubt they would. I'll let you know after I pick them up tomorrow!

-Ray
Nope, just unboxing the new ones now, and they've not added front panel connectors. Boooo!

-Ray
Logged
Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)

Kevin McDonough

  • Full Member
  • ***
  • Offline Offline
  • Posts: 235
Re: Cardioid Subwoofer Array
« Reply #8 on: May 30, 2017, 06:27:09 am »

The 728s do not have front panel speakon connectors. :( At least, all of my old ones don't. I have 6 more en route from JBL; maybe they've added it. That'd be cool.... but I doubt they would. I'll let you know after I pick them up tomorrow!

-Ray

Just to clarify, when I said "does it have it built in" what I was more meaning was the processor settings for reversing the middle sub and making the stack cardioid.

In the set up you're describing, there are two delays to calculate. The first one is within each stack, so that the reversed sub in your stack of 3 has the correct phase/delay settings to make that single stack cardioid.  Obviously just turning the sub around doesn't just do it on it's own, it needs processed differently too.

Then the once you have each individual stack sorted and processed accordingly to make one cardioid block, you then have another set of delays to consider in terms of the overall array: how far you want to space each stack out, and if some delay is then needed as you work your way out from the centre to "virtually curve" the array and spread the sub out around the venue (because, as you space the stacks and widen the group, the sub will tend to form a directional beam down the middle of the room).

Now from reading your initial post, I assumed that you had the first part sorted, and either already knew the correct processor settings for the middle/reversed sub in each stack to make it cardioid, or that the amp/processor has it saved as a preset?

Therefore my advice was more for the second set of delays needed, the virtual ark and the spacing of the stacks.

Again software is the best way to visualise how it works. Create your stacks in the software and try spacing them out and moving them together again, observe the change in the sound. You'll note that the subs will still keep a fairly wide dispersion at the lowest frequencies (would be omnidirectional if not for your cardioid stacks negating some of that), but that as you increase frequency, bigger spacing will make the sub more directional, focusing it down the centre of the room.

Higher up in the sub's range again, if the spacing is big enough, you'll see a point where the spacing is bigger than the distance needed for the wavelengths to couple effectively and they begin to act as 4 individual stacks rather than one array.

Then, by delaying the outer stacks, you can go a little towards reversing that "focusing" of the sub and curve it back out again.


As was said, this won't be exactly applicable to your subs (unless JBL has a model for hat sub in Ease Focus). But by using something similar (another model of double 18 reflex) you'll get a rough starting place for what spacing and delay times might work. You can then make adjustments on the day to get to what you're wanting.

Kev


Logged

Ray Aberle

  • Classic LAB
  • Hero Member
  • *
  • Online Online
  • Posts: 3014
  • Located in Vancouver, WA (and serves OR-WA-ID-BC)
    • Kelcema Audio
Re: Cardioid Subwoofer Array
« Reply #9 on: May 30, 2017, 11:55:33 pm »

I am not the OP. And I was specifically just responding to the Speakon connectors on the front of a sub to facilitate sub arrays; the feature that many sub manufacturers are offering now.

Ray
Logged
Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)
Pages: [1]   Go Up
 


Page created in 0.065 seconds with 20 queries.