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How To......Cardioid Sub Arrays

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Topic: How To......Cardioid Sub Arrays
Posted By: kevinmcdonough
Subject: How To......Cardioid Sub Arrays
Date Posted: 17 April 2009 at 9:34pm
Hey

With all the talk of Rog’s Delta Array and the general idea of Cardioid sub arrays I thought it would be good to type up a quick tutorial on the basics of the theory of this technique and how to set it up in the real world, partly for all you good folks but partly for myself as well, as I’ve always found it a great test of your own knowledge if you can explain it to other people successfully.

As a quick introduction for people who don’t know what I’m talking about, the idea of a cardioid sub array is simply to set the subs up in a particular way so as to be able to control the direction of the bass output of your speakers (which is usually omni directional). You use the fact that when sound waves meet out of phase they cancel to create a null of energy behind the subs. You minimise the backwash of sound from the subwoofers and help to stop it travelling towards the stage, which makes your life easier when you have vinyl decks or open mics or anything else that is prone to feedback, and if done properly you can also harness this normally rear firing energy and use it our front.

Most of my knowledge comes from a couple of threads on the PSW forums (Pro Sound Web) which i’ll link at the end, and on there you can see nice MAPP diagrams and people who have actually set these up and taken real life measurements so it all definitely works.

Also note that as Rog reminds us in the other thread, this is all just theory, dealing with a “perfect” subwoofer and “perfect” conditions. In real life subwoofers aren’t perfect point sources and they have ports and group delay and lots of other nice real life issues so the calculations below should be used as a guide, and then when you actually set this all up you should play around with things a little to get the best settings for your particular set up.




OK, so the most common way to do create a Cardioid subwoofer array this is what’s known as an End Fire array (although to be honest I don’t know why, don’t really know what’s so End Fire about it LOL ).

There are a couple of basic variations on how to set it up, but the main idea is that you set up two rows of subwoofers, front and back, and you use a combination of time delay, physical distance and phase inversion to create a situation where behind the array the sound from the two rows meets destructively and cancels out, and in front on the audience side they meet in phase and combine.



Preparation

So the first step is to pick a frequency that will be the centre of your cancelation band. As we know every frequency has its own wavelength and as this trick relies on distance and delay is only properly effective across a band of frequencies, centred around whichever one you pick.  If your playing Dub, D&B, Reggae or anything else with big deep synths and lots of really low energy your gonna wanna move this down a bit, and if your playing more kicky stuff like House or Rock then you’ll wanna take that into account. Some report that you may get as much as an octave either side of the centre frequency although I don’t know if it’d effectively cover just as much as that.

So pick a frequency and work out its wavelength and also 1/2 and 1/4 of this, and also worth working out at this point what times these equate to for setting your delays later. 



Physical Set Up

So you have your frequency chosen, the next step is to set up the array. We need to create a path difference of half the wavelength of your chosen frequency, and to get our ideal conditions we will do this half with distance and half with signal delay. This means we have to set up our two rows of speakers so that there is a 1/4 wavelength physical spacing between the sound sources (drivers for front loaded or horn mouth for horns.)  This second row can also be facing forward if you like and have the space.

If your subs aren’t too deep and you can fit them in and still preserve the 1/4  wavelength spacing, you can spin the second row around and have them back to back which’ll save you a little bit of floor space.

For reflex subs I don’t think it’ll make much difference either way but for horns you will have to consider the fact that because if the nature of the horn they will already have some measure of directivity themselves. If you turn the second row around you may get away with using less in that row because the front row will be putting out less sound towards the back and the back row will be putting its full measure of sound backwards to cancel it. Some experimentation with your particular subs would help confirm this.

Note also however that for one of the two processing methods below we also have to reverse the phase of the rear speakers. If you set it up with both sets of speakers facing forwards you have the option of doing this with processing if you like, but if you reverse the back row to save space this effectively does a phase reversal for you so you are limited to just that method.

(edit: after thinking on this i suppose you could also add a processing phase reversal, flipping your backwards facing speakers back into phase again if you really wanted to use method 2. Might be worth trying to see how effective it is in practice.)


However, as long as the distance between the two sound sources is 1/4 wavelength then your good.



Processing and Delay

Now we come to setting the delays. We must add another 1/4 wavelength delay to one of our rows here, which’ll complete the 1/2 wavelength path difference and get our cancelation going, and again here we have two ways we can do this but in this case it WILL affect the sound you get.


Method 1:  Delay the REAR SPEAKERS by 1/4 wavelength for (theoretically) perfect cancelation.

This is the method that includes the phase reversal, so we must do that first and then add a delay time that matches up with our 1/4 wavelength, all to the back row of speakers. So In this case whats happening is the sound coming from the rear of the front row of speakers will take 1/4 of a wavelength to reach the back row. We match that with a quarter wavelength delay on the rear speakers so that they would effectively be in phase normally (just like we would delay a delay tower or whatever to match it up) but because we have also reversed the phase of the back speakers either by processing or physically turning them around, the delays now put them perfectly out of phase which makes them cancel out and you get theoretically perfect cancelation and hence no (or in real life much less) sound behind the array.

In front of the array, the sound from the rear speakers travels forward which takes 1/4 wavelength of time, and is also delayed in processing by 1/4 wavelength so it is half a wavelength behind overall and would be out of phase, but the phase reversal puts it back into phase and it combines to add its energy to the front and hence the audience. 

Note however that this changes the nature of the bass sound slightly, because although the waves are combining together in phase out front they are actually half a wavelength behind and then inverted back into phase again so they are not perfect mirror images of each other and there is a subtle but noticeable sound difference. This is reported by actual users as an ever so slight “rounding” off of the sound, a very slight loss in kick or attack, but only really noticeable to a trained ear who has the ability to A/B the two sounds, for the most part it is regarded as unnoticeable to the public.

However if you would like to make sure that you have perfect sound out front then you can use...



Method 2: Delay the FRONT SPEAKERS by 1/4 wavelength for (theoretically) perfect sound out front.

OK so in this case we have NO phase reversal. What happens is now the reverse of what happened in method one. The sound travelling from the rear row takes 1/4 wavelengths of time to reach the front row, and as we have now delayed this front row by a matching 1/4 wavelength they meet exactly in perfect phase and they combine and all our sound out front is  normal, just like delaying speakers or towers to match up. From the perspective of behind the speakers the sound from the front speakers is delayed 1/4 already in processing, and then takes another 1/4 wavelength to travel back to the back ones so when it finally gets there it is 1/2 a wavelength behind and is out of phase. Not that like in the front of method 1 although it is out of phase it is not a perfect mirror image but is half a cycle out, and so will cancel very well but not as good as in method 1.

So method 1 to have maximum cancelation sacrificing a shade of sound out front, and Method 2 to have the best sound out front but loose a little of the cancelation.


Ok think I have that all right although feel free to throw in any comments or tell me i'm all wrong  Tongue


the link that i mentioned to the PSW thread is....


http://srforums.prosoundweb.com/index.php/mv/msg/3954/0/0/0/ - http://srforums.prosoundweb.com/index.php/mv/msg/3954/0/0/0/


where they have lots of pretty pictures to look at and graphs to see Tongue



kev



Replies:
Posted By: jamwa
Date Posted: 17 April 2009 at 10:06pm
or if you use DB you can just point a thrid of your subs 180 degrees the other way run these on seperate amps and switch the CSA mode on - simples!!!!
 
 


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Sound, Light, Projection, Display, Cameras and production support


Posted By: roborg
Date Posted: 17 April 2009 at 10:53pm
For sub-bass control i'm not convinced there is any advantage over just pointing all the subs forward & forming a wide horizontal array, in most circumstances.  IE try to induce as much diffraction directivity as possible & then the radiation pattern tends to be cardioid shaped anyway.
  For really local cancellation, to stop mic feedback for example, it's prolly a really good idea, but i think only if the antisound source is placed close to where the cancellation is needed (like near a drumstack)
  With front & back facing boxes next to each other there is the possibility of good bass & mid-bass cancellation (because it's fairly directional anyway), but sub-bass being omnidirectional will be cancelled in all directions.  Theres no such thing as a free lunch in this application i think, i wish i had time, space & lots of speakers to play with this!


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What I cannot create, I do not understand


Posted By: kevinmcdonough
Date Posted: 18 April 2009 at 1:41pm
Originally posted by roborg roborg wrote:

For sub-bass control i'm not convinced there is any advantage over just pointing all the subs forward & forming a wide horizontal array, in most circumstances.  IE try to induce as much diffraction directivity as possible & then the radiation pattern tends to be cardioid shaped anyway.


While it is true that a large horizontal line of speakers will have significant directivity, it seems to create more of a figure of 8 pattern than a cardioid. You can see it in Rog's bass guide, page 2, where even just a row of 4 subs has a significant figure of 8 shape and there is still a lot of bass directed backwards onto the stage.

Our cardioid array on the other hand, even with just the same 4 subs set up in two rows of 2
you would get something much more like what is shown on Rog's guide page 14. Obviously reflections and real life would mean that it wasnt as perfect as is shown here, but would still be a significant, and often scary, improvement in the amount of bass traveling back onto the stage.

But yeah totally agree, i'd really love a big pile of subs in a field and plenty of time to play about with this all and really get my head around it properly, at the moment its all theory in my head and i've not had very many chances to actually put it into practice.


Originally posted by jamwa jamwa wrote:

or if you use DB you can just point a thrid of your subs 180 degrees the other way run these on seperate amps and switch the CSA mode on - simples!!!!



LOL, yeah DB sub users have it easy Tongue    LOL, well for other users, even though we dont have DB's fancy processing and i'm sure staggered delay times to extend the bandwidth, this technique will also work to an extent. If you have relitivly deep subs then reversing one of a stack of 3 is going to move their acoustic sources back a fair bit of physical distance anyway. It probably wont be the proper 1/4 wavalength back and so wouldn't be as effective as having a seperate second row of subs, but in cases where you are really pushed for space if you play with the processing and delay times to make it all match up and cancel properly i'm sure you may get some fairly acceptable results. In most cases anyway there is no real need to cancel ALL of the sub energy going back to the stage just reducing it by a significant amount would be a big help.


k




Posted By: Peter Jan
Date Posted: 28 April 2009 at 11:16am
Originally posted by jamwa jamwa wrote:

or if you use DB you can just point a thrid of your subs 180 degrees the other way run these on seperate amps and switch the CSA mode on - simples!!!!


Well... I do have and use Q-Subs and S2 cabs. The CSA method does work to some extend, but you need more gear ( cabs and amps ) to end up with less SPL than straightforward non-CSA. I tried it several times in various venues from very small to rather big and from my experience it's a small benefit at best at the cost of more gear. The feeling creeps on me that it's a marketting ploy to sell more gear because they ( not only D&B ) convinced you bass splill at the rear is THE BIG problem. But is rear spill really that big a problem ? I admid it can be in some cases, but an environmental problem primarly in open air gigs. Every time I used it, musicians start complaining they need more bass in the monitors... LOL. In small venues CSA is just plain useless. More cabs and amps where you don't have the place for it in the first place and definately a visual problem with one or more cabs facing the public with it's rear... try to sell that to your client... good luck ! Bass spill is slithly less behind the cabs, but nobody talks about what gets thrown in the air or in the ceiling. You have 50% more gear making noise and some of it interacts with the first 100%, but not all of it. In bigger setups I always get better result from stacking and arraying multiple sub and low cabinets and play with fysical positions, (sometimes) frequency overlap and delays between cabs or arrays of cabs. My main goal is allways to get the most possible SPL to the audience and as little as possible EVERYWHERE else, not only at the rear. The dimension and situation of a venue usually dictates placement and I start from there.
For me, CSA is just one of more out-of-the-box solution that 'can' sometimes partly fix a problem or part of a problem. Fine for folks that don't have the knowledge or time to figure things out for themselves in various situations and setups, but I prefer the 'manual' way. Far better result with the same gear instead of limited benefit at the cost of more gear.


Posted By: cnics
Date Posted: 03 May 2009 at 4:41pm
Having done extensive measurements on the style of Cardioid array mentioned here, and CSA, and various other types, they all work differently.  They don't all do the same thing.

The simple array spoken about above will potentially give you more output at the front and less at the back,  the CSA gives you significantly less at 180degrees (directly behind) but also less out front.


It's not JUST about 0 degrees and 180 degrees.  It's often about 90 270 304  201  and every other angle from the cabinet.

For me CSA just doesn't work right in alot of situations.  The cardioid array above can do. though you do need distance from the rear wall.



Rob


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Rob Beech - Technical Director - Cnics Audio


Posted By: Phil B
Date Posted: 04 May 2009 at 10:08pm
This thread...

http://srforums.prosoundweb.com/index.php/t/44778/7154/ - http://srforums.prosoundweb.com/index.php/t/44778/7154/

and back to Dave`s blog for his take on it...

http://ratsound.com/blognav.htm - http://ratsound.com/blognav.htm

Highly informative and some intriguing questions?

.p.

-------------
Mostly harmless.... except if catering is shut.

Solar Sound System Shennanigans.. http://diyhifi.biz/" rel="nofollow - http://diyhifi.biz/


Posted By: Phil B
Date Posted: 15 August 2009 at 8:16pm
Here`s a little piece I wrote today about fun with the world of Cardioid! Apologies to Kevin if I`m repeating some of his stuff!

Weird World of Cardioid Subs





Firstly this isn`t some new thing to somehow gain a better sub sound. This is just ways to keep the sub sound you have in the right places. It was born out of one festival where the noise limits were frightening but only to the sides of the stage. There was a block of flats about 70m away from Stage left and a known "complainer"!. And it really only works if you have all the same type of sub with the same type of driver! And if you want to try it with scoops and " W" bins together...good luck & let me know how you get along!
So here`s how we worked out the mad set-up, first the maths! In dry air at 20 °C (68 °F), the speed of sound is 343 meters per second. The centre of our cardioid freq is at 60hz ( this is the freq we want to create the most rear or side rejection at) it can be any freq within the bandpass for that particular box.
There`s a few ways to get a rearward rejection,:
1)     Turn one box in an array around , flip the phase and apply a delay equal to the distance between forward and rear facing drivers, usually you can simply measure the width of the box if you have front loaded subs and apply that delay in mm ( or ms). For horn loaded subs you have to account for the horn path but again if you are using the same type of box ( hopefully!) in your array it`ll always be the distance between the front and back edges of the boxes.
2)     Space the boxes 1/4 wavelength apart (90 degrees apart). Now delay the front box another 1/4 wavelength (90 degrees). The output from the front box takes 1/4 wavelength to reach the rear box, and another 1/4 wavelength you added artificially, so cancellation ensues. The undelayed sound from the rear box takes 1/4 wavelength to get to the front box, so it sums in phase out front.

There are other configurations that use the same principles: a rearward delay to a tombstone etc etc. But we stuck to the two that others seemed to have the best results with

So to work out what 1/4 wavelength is to space the boxes …343/60/4 (Speed of Sound / centre frequency/ 4) = 1.429 m .
And to work out the delay time 1000/60/4 = 4.17 (Period (ms) = 1000 / Frequency)
Keep in mind the speed of sound changes with temperature so that 343m value will change and so the delays and spacings will change. This can be quite a lot over a 5 degree change in temp. I just go for what I think the temp will be during the event. Outdoors get a forecast …indoors have a guess at how hot & sweaty it`s gonna get!

What we did next was to try a few different configs to see what worked best. Excuse the crappy fone fotos…I need a new fone desperately! We only had 4 subs out as we didn`t want to piss the neighbours off too much with constant freq sweeps all day long at a reasonable level. So we laid out a circle and measured at 15 degree intervals around the arrays from front ( 0 degrees) to rear (180 degrees)and swept from 20hz to 200hz at each point. Highly dull and needs two people ( one to walk the mic around the yard and another to shout" ready" about a million times- never knew sound was so much fun!)

First is a straight stack of 3 subs with one inverted

Plot ...... http://img22.imageshack.us/img22/8282/3xvsb218normal.jpg - http://img22.imageshack.us/img22/8282/3xvsb218normal.jpg

The plot shows the standard box as a dotted line at different freqs and the colours correspond to the same freq with the hard line being the interted box measurements. The measurement is 180 degrees around the box so the front of the box is at 0 degrees at the right and the rear is to the left. Db is measured from the centre outwards...further out the louder it was! It`s quite tricky to read what`s going on as the traces all overlap etc etc but we were looking for an overall trend at all freqs. Notice the lump in standard ( dotted line) 30hz @ 30 degrees this is probably down to the ports on the NCA subs being on the outside and it picking up the phase changes at the measured distance 10m. Not a great amount of rear cancellation in fact quite a rag tag response.

In reality we were getting rear rejection but the nature of frontloaded boxes means that just by inverting one box we weren`t getting enough rejection at the rear ( or more especially the sides!)

Then a 2 x 2 Tombstone



Plot..... http://img22.imageshack.us/img22/4733/22vsb218.jpg - http://img22.imageshack.us/img22/4733/22vsb218.jpg

Ver similiar to a standard 3 high stack...? Sounded like we were getting a bit of rejection at 60 and 120 degrees but not much rear rejection.

Then 2 + 1 + 1 - Tombstone



Plot... http://img22.imageshack.us/img22/7830/211delayedvsb218.jpg - http://img22.imageshack.us/img22/7830/211delayedvsb218.jpg

Starting to see a side rejection....

Finally 2 + 1 + 1 ( 1 inverted)



Plot... http://img9.imageshack.us/img9/4323/21reversed11vsb218plot.jpg - http://img9.imageshack.us/img9/4323/21reversed11vsb218plot.jpg

This is now a comination of Tombstoning and reversing a box.
Well that seems to work! We`ve not lost any forward gain and between 60 and 120 degrees we`ve got a good 7-10db gain reduction on all 3 measured freqs. Only problem is we are now getting processor hungry! We need 3 different delays on top of our standard set-up.

So after deciding that a combination of both methods was for us Reay knocked up this little CAD for us to see how mad it looked before the gig!



The only difference on the day was to keep the two inverted boxes on the floor. I don`t like subs firing into each other directly and if it was with hornloaded boxes I would definitly try to keep the boxes from firing directly at each other. It sounded great out front no weirdness with the kick drum and with the two infill stacks covered right across the stage evenly. As you walked off to 40 degrees it started noticably tailing off. At 70 - 110 it was hard to tell if it was on! It didn`t reject at the rear the same as a standard one inverted box array but was still down on the usual standard 4 x 4 sub array.



I`ve picked all of this info up from the net. Mostly from PSW/ SPlans etc etc and am reading Dave Rat`s blog about his Vortex and Slotfire systems with great interest. It is a real world solution to getting sub in the right place ( as long as you have the room to start laying subs out!) . Rog`s article on bass arrays goes into this kind of arrangements in great detail and you can sim up different arrays with Mapp online. But I am always sceptical of how the actual array sounds. The fact you are introducing phase changes (delays) means that even though an array can sim up fantastically it could sound very strange! I have tried a few different set-ups on Carnival floats in an attempt to get more rearward sub ; some have worked, others haven`t. Not because the maths is wrong just the fact that it didn`t sound " right" !

Disclaimer...this is only a rough guide and wasn`t done to exacting standards ( there was a massive chiller unit next to us going on & off which probably was why the 30hz readings were all over the place!). It was a fun afternoon in the sun with some boxes and a few beers!


And maybe next time.....



But that`s another story....


.p.

-------------
Mostly harmless.... except if catering is shut.

Solar Sound System Shennanigans.. http://diyhifi.biz/" rel="nofollow - http://diyhifi.biz/


Posted By: xlogic
Date Posted: 11 January 2012 at 2:26pm
Hi 

To contribute to this thread i'm performing some bass array/cardioid array experiments. Eventually I plan to do tests similar to what phil B has done but first i'm playing around at home.

The test:

Using 2 studio monitors I want to have a play around with an 80hz sine wave using delay and phase to see if I can hear cancellation and eventually measure it with a measurement mic or db meter.

Equipment available:

2 x Genelec 8030A speakers
1 x Motu ultralite soundcard
Logic pro 8

I tried with the 'test osc' on logic one on each of two separate channels playing an 80hz wave but as I am unsure as to whether both the oscillators are in sync ie in phase with each other I tried to bounce a sine waveform to an aif file and use the waveform instead. At the moment im having some troubles getting this sorted but i'm sure i'll work it out soon.

Also with the delay plugin im using the 'sample delay' as this is the only delay without extra gubbins that I don't need. Does anyone know how to get this to have the delay parameters in ms rather than samples or am I just going to have to change the delay in samples and do the conversion myself?

Getting close to just sacking off logic altogether and using a BSS LMS. If anyone has any tips on doing this with Logic that would be appreciated.
Cheers


Posted By: trots
Date Posted: 26 July 2013 at 5:30pm
Hi,

I'm running a small (500 cap) outdoor event on the weekend of 30th Aug - 1st Sept and am looking for someone with good experience of Cardioid arrays either to do a days paid work as a consultant to help setup up cardioid subs in 3 (very small 100 cap) tents or would be interested if anyone with cardioid experience was willing to do (fairly cheap) sound hire for one of the 3 tents in addition to helping with the setup of all tents. Obviously will have crew on hand - this is more an advisory / technical role due to noise restrictions from the council.

The event is 1 hr drive NW of London - please PM me if you have relevant experience and would be interested in helping out - or know of anyone who would.

Cheers!


Posted By: Pasi
Date Posted: 26 July 2013 at 7:43pm
I can sort it out for you ;) Will PM.


Posted By: Ohmen Audio
Date Posted: 10 August 2013 at 3:24pm
After reading this thread i have learned alot about the cardioid sub set ups but i am having great difficulty in figuring how i would apply this to my system in an effective manner considering i am running hogg scoops and 1850's. would i have to have a stack of just 1850's or hoggs or just a certain amount of each. say 1 hogg at the bottom led on its side with one 1850 on top facing forwards and and other 1850 facing backwards would this be applicable?? please excuse my lack of understanding if this seems to be a silly question but if someone could maybe build on this and lend a hand i would greatly appreciate it.

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joints and joinery


Posted By: burningbush
Date Posted: 10 August 2013 at 3:52pm
First be clear on what you want to acheive.  Do you want to reduce the amount of sub on stage, or steer the bass in a given direction?


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music is the message


Posted By: Ohmen Audio
Date Posted: 12 August 2013 at 12:52pm
reduce the sub on the stage mainly. but i suppose knowledge on both would be useful. :)

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joints and joinery


Posted By: Ohmen Audio
Date Posted: 12 August 2013 at 1:05pm
:)

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joints and joinery


Posted By: Pasi
Date Posted: 19 August 2013 at 3:42pm
My solution from the last weekend...
https://www.facebook.com/photo.php?fbid=10201741867414240&set=o.173813726282&type=1&theater&notif_t=like" rel="nofollow - https://www.facebook.com/photo.php?fbid=10201741867414240&set=o.173813726282&type=1&theater&notif_t=like


Posted By: doober
Date Posted: 19 August 2013 at 9:40pm
Good work Pasi! What was the horizontal coverage like with this setup?

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Blahblahblah


Posted By: toastyghost
Date Posted: 19 August 2013 at 9:46pm
Originally posted by Pasi Pasi wrote:

My solution from the last weekend...
https://www.facebook.com/photo.php?fbid=10201741867414240&set=o.173813726282&type=1&theater¬if_t=like" rel="nofollow - https://www.facebook.com/photo.php?fbid=10201741867414240&set=o.173813726282&type=1&theater¬if_t=like


Did you go with end fired just to make sure Dom's ones were hidden at the back away from any potential buyers?


Posted By: kevinmcdonough
Date Posted: 19 August 2013 at 10:33pm
hey

looks great, be interesting to hear a bit more detail about your set up: cab spacing and processing settings etc.  Add some real life info to all the theory Smile


k


Posted By: Pasi
Date Posted: 20 August 2013 at 8:53am
This sort of setup is an extension from normal cardioid where front row is delayed to the back row. The spacing between the cabinets equals to 1/4th of the wavelength where the main cancellation will happen. Another 1/4th will be done with time delay where the bins in front are delayed to the rearmost ones.

In this setup the spacing between the cabinets was 1.35m as i wanted to focus more on lower end cancellation at the back and at the stage. So starting from the back we have 0 time, 4ms delay, 8ms delay and 12ms delay. (rounded up, accurate delay was 3.9xxx). This way sound combines perfectly when going forwards, but adds cancellation when going backwards.



In this pic, green shows the response in front, 2m away from the front cabinets. Pink one is measured at the drum riser with both sides on. And the 3rd whatchammacallit colour is then 2m behind the rear row. As you can see, this resulted to good cancellation at the stage and about 24dB drop @ 40Hz.

Sideways it looked like this:


Number 4 being the front row and number 1 the back row. Green, downstage center is measured again both sides on whilst all others are just one side on.

So this sort of arrangements has many benefits. Good cancellation to the back, perfect adding to the front which keeps the impulse response intact and reasonable cancellation to the stage as well. The negative points are 4 DSP channels needed and quite a lot of space.



Posted By: doober
Date Posted: 20 August 2013 at 9:44pm
Thanks for sharing the plots, very impressive results.

I'd always wondered how beneficial using 4 rows is compared to 2. Others have mentioned that the more rows the better for rear cancellation, but surely cabs 1 and 3 are actually reinforcing each other in both directions due to being 1/2 wavelength apart and delayed 1/2 wavelength relative to each other. I suppose if you always use an even number of rows this won't matter. I also think that the more rows you use the narrower the horizontal coverage will become, I don't have anything to back this up though...

In your photo what is the distance between left and right sub arrays? I like the idea (another one in my head) that if you space them correctly you can have the edges of the coverage just touching, no more power alley!

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Blahblahblah


Posted By: Pasi
Date Posted: 20 August 2013 at 9:54pm
Stage was 10m wide and subs were set about 2m from the stage so distance between the arrays was around 14m.

Power alley effect was quite nicely reduced, not eliminated, but it was acceptable.


Posted By: Timo Beckman
Date Posted: 31 August 2013 at 10:06am
I did a measurement seminar this week in Rimini Italy where i did a end fired configuration :

http://timobeckmangeluid.wordpress.com/2013/08/30/end-fired-with-a-twist-nice-data-from-the-rimini-seminar/" rel="nofollow - http://timobeckmangeluid.wordpress.com/2013/08/30/end-fired-with-a-twist-nice-data-from-the-rimini-seminar/

enjoy


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The sound will be as good as the band play's


Posted By: Timo Beckman
Date Posted: 06 September 2013 at 9:59am
So no simulations on these .

http://timobeckmangeluid.wordpress.com/2013/09/03/gradient-or-reversed-end-fired-sub-array//2013/09/03/gradient-or-reversed-end-fired-sub-array/" rel="nofollow - http://timobeckmangeluid.wordpress.com/2013/09/03/gradient-or-reversed-end-fired-sub-array/

http://timobeckmangeluid.wordpress.com/2013/09/05/gradient-or-reversed-end-fired-as-i-call-it/" rel="nofollow - http://timobeckmangeluid.wordpress.com/2013/09/05/gradient-or-reversed-end-fired-as-i-call-it/

http://timobeckmangeluid.wordpress.com/2013/09/04/end-fired-sub-array-first-with-delay-then-with-2nd-order-all-pass-filters/" rel="nofollow - http://timobeckmangeluid.wordpress.com/2013/09/04/end-fired-sub-array-first-with-delay-then-with-2nd-order-all-pass-filters/

http://timobeckmangeluid.wordpress.com/2013/09/05/end-fired-sub-array/" rel="nofollow - http://timobeckmangeluid.wordpress.com/2013/09/05/end-fired-sub-array/

The allpass thing was something i wanted to try for a long time and finally got around to testing if and how to get it to work .


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The sound will be as good as the band play's


Posted By: tall_mike
Date Posted: 06 September 2013 at 4:48pm
I just do this with 8 or more Quakes....



Instant cardoid controlled sub. You could have a conversation behind them quite happily while FOH was getting some serious bass pressure!


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http://www.livesoundhire.co.uk" rel="nofollow - Live Sound Hire Ltd


Posted By: loonie
Date Posted: 07 September 2013 at 9:23am
Nice set-up Mike, what mid highs were you running? Were they in stereo each side?



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Team DB


Posted By: tall_mike
Date Posted: 07 September 2013 at 11:27am
top boxes were EM Acoustics X3, four a side!


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http://www.livesoundhire.co.uk" rel="nofollow - Live Sound Hire Ltd


Posted By: tv00
Date Posted: 31 October 2013 at 11:36pm
How does this works out with horn coupling & mouth area?

If I reverse 2 in a stack of 6 bandpasshorns (bph) will the reversed box uncouple?

If I do end fire distance have to be kept big enough not to "stuff" horn mouth (negative expansion).

I guess end fire could make rear horns see a bigger horn or a corner, front stack is delayed to couple.

I can't really figure out what happens to 2 reversed boxes and the horn coupling? Will it overexcurt fron cancelation or the opposite couple the delayed half wave from front? I'm a little worried about this, no drivers to waste.


Posted By: dymondaudio
Date Posted: 08 May 2022 at 12:54pm
Sorry for dragging up an old thread but I think most of the contributors are still active members. 

I am starting to get into sub arrays and am looking to do a simple set up for a gig in a couple of weeks

My aim is to reduce bass behind the speakers as there are premises quite close by. 

The venue is a big tent. 

I will be using three 18” reflex subs each side of the stage (this is the only config available because of the venue set-up)

So… flip the centre sub, reverse its polarity and delay it by the distance between the rear driver and the drivers in front. 

Is this it or have I missed something? (Seems too simple!)

Cheers all


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If you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid


Posted By: FOO
Date Posted: 08 May 2022 at 5:30pm
The easy way... Nexo CD18, or if your budget is low'ish, Nexo CD12. 
CD18 is a mean piece of kit! But you need some hands to throw them around. Big Box with Big Sound!
CD12 on the other hand.. That is a fun little box which pack quite a good punch without being fridge sized LOL


Posted By: dymondaudio
Date Posted: 08 May 2022 at 5:48pm
Originally posted by FOO FOO wrote:

The easy way... Nexo CD18, or if your budget is low'ish, Nexo CD12. 
CD18 is a mean piece of kit! But you need some hands to throw them around. Big Box with Big Sound!
CD12 on the other hand.. That is a fun little box which pack quite a good punch without being fridge sized LOL

Was this posted in the correct topic?


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If you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid


Posted By: VECTORDJ
Date Posted: 08 May 2022 at 6:40pm
K.I.S.S.


Posted By: dymondaudio
Date Posted: 09 May 2022 at 9:50am
Originally posted by VECTORDJ VECTORDJ wrote:

K.I.S.S.

Could you expand on this, is what I'm saying correct?


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If you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid


Posted By: VECTORDJ
Date Posted: 09 May 2022 at 1:06pm
K.I.S.S........DSP and Digital Mixers have allowed for so much more adjustment then ever before.......Maybe too much...A Friend does Sound and uses EVERY button of his gear...Time delay the Drums to the mains, Gates, Compressor, EQ, Effects on every channel...Some rear facing subs...etc, etc, sounded like Dog Shit.....I went to one of His Shows and turned off most of that stuff...Used Gates on Drums, 2;1 Compressor on Vocals, and a very small amount of EQ and Reverb on Vocals....WOW! His system delivered cranking Sound....He was over Thinking Sound....Sometimes K.I.S.S. is the Best.....


Posted By: KDW32
Date Posted: 09 May 2022 at 1:06pm
Originally posted by dymondaudio dymondaudio wrote:

Originally posted by VECTORDJ VECTORDJ wrote:

K.I.S.S.

Could you expand on this, is what I'm saying correct?

I'm going for it being an acronym for keep it simple stupid. Or maybe he was listening to the hair metal band. Either way very helpful lol


Posted By: dymondaudio
Date Posted: 09 May 2022 at 1:19pm
Originally posted by VECTORDJ VECTORDJ wrote:

K.I.S.S........DSP and Digital Mixers have allowed for so much more adjustment then ever before.......Maybe too much...A Friend does Sound and uses EVERY button of his gear...Time delay the Drums to the mains, Gates, Compressor, EQ, Effects on every channel...Some rear facing subs...etc, etc, sounded like Dog Shit.....I went to one of His Shows and turned off most of that stuff...Used Gates on Drums, 2;1 Compressor on Vocals, and a very small amount of EQ and Reverb on Vocals....WOW! His system delivered cranking Sound....He was over Thinking Sound....Sometimes K.I.S.S. is the Best.....

I understand what KISS means and I completely agree with you regards to keeping the signal chain clean etc. but this is not what I'm suggesting here. 

I'm looking to set-up cardioid subs to mitigate/reduce a possible noise complaint issue, not because I think it's fashionable ;)


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If you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid


Posted By: jeddere
Date Posted: 09 May 2022 at 5:23pm
Originally posted by dymondaudio dymondaudio wrote:

So… flip the centre sub, reverse its polarity and delay it by the distance between the rear driver and the drivers in front. 

Is this it or have I missed something? (Seems too simple!)

That is essentially it however the required delay will not be exactly equal to the measured direct path difference. Ideally you would setup up a mic behind the speakers (where you want the cancellation to occur) and measure the forward facing speakers to get a phase response. Then measure the rearward speaker (polarity reversed) and adjust the delay until they are 180 degrees out of phase. Alternatively stand some distance behind and adjust the delay until it is quietest. I've not tried this but I'd start with the measured path difference and increase from there.

Summation on the front side is not going to be perfect but you are sacrificing sound quality out front to get the reduction behind.

EDIT: to avoid confusion my reply relates to a inverted type of cardoid bass array which it seems you are proposing. Other posts earlier in this topic relate to different types of cardoid bass array.


Posted By: dymondaudio
Date Posted: 09 May 2022 at 7:16pm
Originally posted by jeddere jeddere wrote:

Originally posted by dymondaudio dymondaudio wrote:

So… flip the centre sub, reverse its polarity and delay it by the distance between the rear driver and the drivers in front. 

Is this it or have I missed something? (Seems too simple!)

That is essentially it however the required delay will not be exactly equal to the measured direct path difference. Ideally you would setup up a mic behind the speakers (where you want the cancellation to occur) and measure the forward facing speakers to get a phase response. Then measure the rearward speaker (polarity reversed) and adjust the delay until they are 180 degrees out of phase. Alternatively stand some distance behind and adjust the delay until it is quietest. I've not tried this but I'd start with the measured path difference and increase from there.

Summation on the front side is not going to be perfect but you are sacrificing sound quality out front to get the reduction behind.

EDIT: to avoid confusion my reply relates to a inverted type of cardoid bass array which it seems you are proposing. Other posts earlier in this topic relate to different types of cardoid bass array.

Thanks for this :)

To clarify regarding summation at the front, as long as I'm not going to loose output at the front then it's fine.  Main concern is rejection behind the system.




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If you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid


Posted By: jeddere
Date Posted: 10 May 2022 at 10:14am
Summation at the front will be roughly 1.5 dB below what you would have if you faced all 3 cabinets forward, with up to approx. 6 dB ripple in the response as some frequencies will be closer in phase than others when comparing the signal propagating forward from the rear facing and front facing cabinets.

The delay time that you set needs to be long enough so that you do not get cancellation out front at the lowest frequency your cabinet will play. This means making sure that the signal out front from the rear facing and forward facing cabinets has a phase difference of less than 120 degrees either side of 360 degrees. For example:
Cabinet low cut off: 30 Hz
Period (time taken for 1 wavelength of 30 Hz), T=1/f = 33 ms
120 degrees at 30 Hz = (120/360) x 33 = 11 ms
The rear signal is 180 degrees out of phase (polarity flipped) = (180/360) x 33 = 16.5 ms
When this combines with the signal from the front facing cabinets it needs to be at least 33-11 = 22 ms behind them. This will then sum with the signal from the front facing cabinets, but 1 phase wrap later.
There is already 16.5 ms of delay, or offset due to the polarity flip, so only another 22-16.5 = 5.5 ms is required.
The rear facing cabinet is delayed twice by the time its signal combines on the frontside, once by the delay setting in LMS and once by the physical path length. Therefore the minimum delay setting is 5.5/2 = 2.75 ms.

TLDR: If you end up with a delay setting for the rearward facing cabinets of less than about 3 ms then the bottom end of the bass frequencies are not going to sum as well as they could out front. Solution: move the rear facing cabinets backwards to increase the physical path length delay to about 3 ms.



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