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Author Topic: Cardioid sub worth switching to?  (Read 1902 times)

Russell Ault

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Re: Cardioid sub worth switching to?
« Reply #40 on: April 10, 2021, 01:39:32 am »

Surely we are talking about small rooms?  If this is the case, Id say forget it.  Boundaries are going to play hell with your array cardioid or whatever.  Im sure this has been discussed at length as to why cardioid subs need free space to do their thing. {...}

In my experience the free-space requirements for cardioid arrays aren't quite so black-and-white as that (especially when it comes to the space behind the array). I've deployed more than a few two- and three-box arrays in small venues to good effect although, as I mentioned above, they do take up physical space. As one example, 12" subwoofers are often small enough that they can sit right up on the front stage (where there's plenty of open air) and be no more visually obtrusive than stage wedges.

It's definitely not always the right solution, but there certainly are times that it can be (even in small spaces). It just depends on your goals.

-Russ
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Luke Geis

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Re: Cardioid sub worth switching to?
« Reply #41 on: April 10, 2021, 02:32:47 pm »

There are multiple approaches to cardioid arrays and the required time alignment.

I won't say one is more conventional than the other since each has its own pro and con.

Let's just assume you have a 2 sub cardioid deployment where one is facing forward and one is facing backward. You can either A) Delay the front-firing sub, or B) You can delay the rear-firing sub. Which one is best? Depends on what your needs are.

Delaying the front-firing sub provides the best quality of sound in the forward plane of interest. The downside is that rearward rejection is reduced. Delaying the rear-firing sub provides the greatest rearward rejection, at the cost of mucking up the sound in the forward direction. Delaying the rear-facing subs puts the forward energy about 1/2 of a wavelength behind in time, but due to the reversed polarity of the rear sub, it is in the same polarity as the forward-facing sub's energy. So while technically the sounds combine effectively in the forward plane, the sound you hear is the combination of the original signal and the delay of that signal 1/2 of a wavelength behind it.

Conversely, if you delay the forward-facing sub, the forward energy of the rear-facing subs is allowed time to meet with the front-facing sub. The result is two subs that combine in polarity and phase, BUT, the rearward energy is not truly ever nulled. Since the forward-facing sub's energy now has to wrap around to the rear, it will be 1/2 of a wavelength behind in time. So while it may be in polarity and phase, it is 1/2 of a wavelength behind in time. This reduces the effectiveness of the array's ability to cancel rearward energy.

I did an outdoor show where I had a long enough line of center clustered subs to have good side rejection. I had another area off the side that needed some low-end coverage still, so I deployed a two-box cardioid sub-array. I got some strange looks from my stagehand when I placed a random stack of subs off in the distance. When asked what the hell I was up to, his query was met with technical jargon he didn't understand until he heard it. When the main PA was on and no " sub fill " it was as expected. No bass in the " money seats ". Turn on the " sub fill " and the boom is now in the desired room. So why cardioid he asks? Turn off the rear-facing sub of the " sub fill " and you get the weird phasey not quite right sound in the area between the to subs arrays. Turn the rear-facing sub back on and it suddenly sounds more correct over a larger area. He looks at me, laughs, and says " holy S*&t, that's why you get paid the big bucks ". This same stagehand is the shop manager for another local production company in my area. He had a newbie in his shop that was asking why I was changing equipment and making odd requests to do a show they hired me for. His response: " because he is Luke and he has earned the right to do whatever the hell he wants, just listen and do what he says " was his response :) 
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Rick Powell

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Re: Cardioid sub worth switching to?
« Reply #42 on: April 10, 2021, 03:13:02 pm »

I will say this for the TH 118's. In certain rooms we play in, using one per side, I am asking my son the soundman "where's the thump" because I expect the kick drum and bass to be throbbing out front. He assures me it's there out front and I trust him. We always seem to hear more lows on stage when we use dBTech S30's on the low end (another local sound co and a local place with a house system have them).
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Ivan Beaver

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Re: Cardioid sub worth switching to?
« Reply #43 on: April 10, 2021, 05:16:13 pm »

There are multiple approaches to cardioid arrays and the required time alignment.

I won't say one is more conventional than the other since each has its own pro and con.

Let's just assume you have a 2 sub cardioid deployment where one is facing forward and one is facing backward. You can either A) Delay the front-firing sub, or B) You can delay the rear-firing sub. Which one is best? Depends on what your needs are.


I know it sounds weird, but you will get more rejection if the rear sub is ALSO facing forward, NOT facing to the rear.

I have measured this both ways (granted not with every type of speaker out there), and always got better overall response out front and more rejection to the rear.

If you break down why delaying the rear speaker and inverting the polarity works, it will make sense.

You are NOT trying to send energy to the rear, but tying to get the energy to the rear to be 180* out of polarity.  The actual phase will be WAY more than that (due to the physical positioning and the delay used), so it is polarity we are talking about.  The phase response will be different at each freq.  Polarity is the same phase difference at all freq.

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Russell Ault

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Re: Cardioid sub worth switching to?
« Reply #44 on: April 10, 2021, 06:52:07 pm »

I know it sounds weird, but you will get more rejection if the rear sub is ALSO facing forward, NOT facing to the rear. {...}

I've always figured that this has to do with the fact that subwoofers in the real world aren't quite omnidirectional. Especially with gradient arrays, where the cancellation goal is "equal in time and level but opposite in polarity", it makes sense that you'd want the two sources to be as close to the same as possible, which for any real-world subwoofers means pointing them all in the same direction.

(Of course, if my figuring is correct, then strictly speaking "all the same direction" doesn't necessarily mean "forward", although "forward" will often make sense for other reasons.)

-Russ
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Luke Geis

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Re: Cardioid sub worth switching to?
« Reply #45 on: April 12, 2021, 12:55:39 am »

While I have not tried a cardioid array with two forward-facing subs, the theoretical possibility that it is more effective makes 100% sense. Since the energy behind each sub should be identical, if one sub is exactly 180* shifted in phase and polarity, it will be more equal on both ends of interest. I.E. more cancellation in the rear and more complete summation in the front.

While I have not spent much time trying to A/B exactly how much better one is at one task over the other objectively, I know that when I deploy one method, I spend the time to A/B the effected vs. the non effected deployment to see if I truly have improved the result. I may have to introduce the all-forward-facing cardioid array sometime to see what I get. I find myself to be pretty crafty and clever with most of my deployments in order to solve a problem and yet stay within a certain aesthetic. I find I can often get what I want without the end client ever knowing I did anything tricky to get there. My experience is they often don't care what your reasoning is for why you did X, Y, or Z, so long as they see what they like. Yes, I have had 6 speakers splayed across the front of a stage and only had 1 or 2 per side turned on... Yes, I have had 6 subs deployed across my stage and turned half of them off... Yes, I have actually placed a speaker in a spot and only turned it on just enough to prove sound was coming out of it with ZERO intention of it ever actually doing any real work for me... Always looking for a new trick to get what I need without having to explain to the client why I did it.
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Ivan Beaver

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Re: Cardioid sub worth switching to?
« Reply #46 on: April 12, 2021, 08:20:05 am »

While I have not tried a cardioid array with two forward-facing subs, the theoretical possibility that it is more effective makes 100% sense. Since the energy behind each sub should be identical, if one sub is exactly 180* shifted in phase and polarity, it will be more equal on both ends of interest. I.E. more cancellation in the rear and more complete summation in the front.


The spacing is the critical thing.  You need the space distance between the radiating elements.

All facing forward (but one physically behind the other) will take up more real estate than stacking them and facing one towards the rear.  But the performance (out front and greater rejection in the rear) is often worth it.

Every situation is different, with different constraints and requirements.

In order to have the most rejection in the rear and the most summation in the front, the response from each of the subs needs to be the same in each of those areas.

Think of combfiltering, you get the greatest rejection when the signals are the same.  When they are not the same, you get less cancellation.
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Ivan Beaver
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Debbie Dunkley

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Re: Cardioid sub worth switching to?
« Reply #47 on: April 12, 2021, 10:13:52 pm »

As always you guys have given me plenty of info to consider. I am undecided but now I know what NOT to do - LOL. Thanks Peeps!
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Caleb Dueck

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Re: Cardioid sub worth switching to?
« Reply #48 on: April 13, 2021, 10:56:54 pm »

I am undecided but now I know what NOT to do - LOL.

More TH118XL's, the universal answer.   ;D  That way you can try cardioid, end fire, delay arc, and various other directional methods.
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Re: Cardioid sub worth switching to?
« Reply #48 on: April 13, 2021, 10:56:54 pm »


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