Cardioid Sub Setup Questions

[kirkdickinson]

I have heard about Cardioid sub setups in the past. I just picked up two QSC KW181's and was thinking about figuring out how to set them up that way. I know the new KS118's come with a built in setting for this, but with the older ones, you need some way to precisely delay the signal.


I watched this video yesterday and I was a little confused on why he reversed the polarity and delayed the rear instead of the front facing speakers? I thought that the theory was to slighly delay the front speakers so that the sound wave coming from the rear would travel around and meet the wave from the front at precisely the correct time to increase the volume to the front, and the inverse for the wave from the front to the back.

I’m curious about this. I have 2-KW 181s. My mixing board does not have the capability to delay the signal. I have two questions I guess.

1. What is the cheapest way to create a delay? For instance is there an affordable rack mount or simple in-line box that could be edit?
   
2. Wouldn’t keeping all the polarities the same and delaying the front firing speakers accomplish the same effect?

 

[seamonkey]

This is a good explanation:

 

[Mike Caldwell]

For delay look at a speaker DSP like a DBX 260 or Venue360, you'll get delay on each output along with a bonus of crossover, eq and limiting. It maybe worth while to have
one just to do all the speaker processing outside of the mixer.

Personally I'm not a fan of doing speaker processing with in the mixer.
Over all output EQ is fine.

 

[Scott Shaw]

Go to prosoundweb.com and ask there. Just tread carefully or you'll get some snooty responses! I'm doing an outdoor show this weekend, and I'll be putting the subs in front of the stage together. You get a few extra db's and no power alley.

 

[Mike Caldwell]

Go to prosoundweb.com and ask there. Just tread carefully or you'll get some snooty responses! I'm doing an outdoor show this weekend, and I'll be putting the subs in front of the stage together. You get a few extra db's and no power alley.

How many subs are you going to use?
If you have four....or more you can set the outside subs back some and create a wider pattern by have the outer subs delayed in relation to the inside subs and no DSP needed.

Below is a link to a EV PDF on sub arrays. As with anything audio there is always a trade off though.
https://electrovoice.com/media/downloads/wp_subwoofer_arrays_v04.pdf&ved=2ahUKEwjZsPOt7aT7AhXljIkEHQ4mDZcQFnoECAIQAg&usg=AOvVaw3YQuUa2ys-NIrrGRF3RQ_9

 

[kirkdickinson]

I just picked up 2 used KW181s and was watching the video about the new KS118’s and how the cardioid is busked in. Just gone interested in if I could do it with the 181’s.

I have two KSubs also, but different speakers probably won’t work in an array.

 

[kirkdickinson]

Go to prosoundweb.com and ask there. Just tread carefully or you'll get some snooty responses! I'm doing an outdoor show this weekend, and I'll be putting the subs in front of the stage together. You get a few extra db's and no power alley.

I always try to set multiple subs together. After reading an article about comb effect, power alleys, and null nodes.

I don’t think I’ve ever seen a professional installation with subs together. I wonder why?

 

[Scott Shaw]

I always try to set multiple subs together. After reading an article about comb effect, power alleys, and null nodes.

I don’t think I’ve ever seen a professional installation with subs together. I wonder why?

Most larger sound companies down here do center stack subs, or array them across the front of the stage. I'll leave the cardioid stuff for the pros. It's just too easy to mess up.

 

[Wasnex]

Different types of arrays are used with subwoofers. Most of us use a broadside array. This is essentially the boxes stacked horizontally or vertically. Broadside arrays don't become directional until they are very large, and then they function as dipole radiators.

There are also arrays that use processing and spacing to impact dispersion, which can approximate a cardioid pattern.

The first type is an end-fire array. The boxes are spaced out in a row along the direction you want the sound to travel. Each succeeding box in the array is delayed back to the first box.

This approach reinforces the sound waved as it passes from sub to sub.

There is also the approach you are asking about, which is called a gradient array. The rear woofers are spaced at 1/4 wavelength from the front, and also delayed 1/4 wavelength. The idea is between the electronic delay and propagation delay, the two wavefronts cancel to the back and sum to the front.

The gradient array reinforces the sound moving to the front.

If you view the phase relationship from the front, you get this:

The top is the front sub and the bottom is the back sub. The back sub has 1/4 wavelength of propagation delay and also 1/4 wavelength of electronic delay.

So essentially you hear the front sub start 1/2 wavelength before you hear the rear sub. But because the rear sub is setup with reverse polarity the, two signals sum.


From the rear things work a bit different.

The drivers in the subs are spaced at 1/4 wavelength, and the rear sub is delayed by 1/4 wavelength. The idea is the propagation delay for the front sub is 1/4 wavelength, and then the rear sub is delayed by 1/4 wavelength, so you hear both start at the same time. But since they are 180 degrees out of phase they cancel.

End Fire and Gradient arrays have different pros and cons. End fire arrays take up a lot of space but have better transient response and higher SPL out front. I believe the sound behind the array is uneven/peaky, especially with small endfire arrays, which is bad for the band.

Gradient arrays take up less space and have worse transient response and lower SPL out front. Also they are only effective over the range of about 1 octave. But I believe the sound behind the array is more even, which is better for the band.


How do you calculate cardioid subwoofer spacing? (gradient array) (sounddesignlive.com)
Microsoft Word - wp - Subwoofer Arrays v04 .doc (electrovoice.com)

 

[Zooberwerx]

I always try to set multiple subs together. After reading an article about comb effect, power alleys, and null nodes.

I don’t think I’ve ever seen a professional installation with subs together. I wonder why?

It’s largely argued that these sonic quirks & speed bumps become a secondary concern when also weighing the affect of boundaries and associated reflections in a given venue (enclosed). Outside applications are a whole ‘ other ball game.

Riis

 

[kirkdickinson]

Different types of arrays are used with subwoofers. Most of us use a broadside array. This is essentially the boxes stacked horizontally or vertically. Broadside arrays don't become directional until they are very large, and then they function as dipole radiators.

There are also arrays that use processing and spacing to impact dispersion, which can approximate a cardioid pattern.

The first type is an end-fire array. The boxes are spaced out in a row along the direction you want the sound to travel. Each succeeding box in the array is delayed back to the first box.

View attachment 4870459
This approach reinforces the sound waved as it passes from sub to sub.

There is also the approach you are asking about, which is called a gradient array. The rear woofers are spaced at 1/4 wavelength from the front, and also delayed 1/4 wavelength. The idea is between the electronic delay and propagation delay, the two wavefronts cancel to the back and sum to the front.

The gradient array reinforces the sound moving to the front.

If you view the phase relationship from the front, you get this:
View attachment 4870535

The top is the front sub and the bottom is the back sub. The back sub has 1/4 wavelength of propagation delay and also 1/4 wavelength of electronic delay.

So essentially you hear the front sub start 1/2 wavelength before you hear the rear sub. But because the rear sub is setup with reverse polarity the, two signals sum.


From the rear things work a bit different.

View attachment 4870536

The drivers in the subs are spaced at 1/4 wavelength, and the rear sub is delayed by 1/4 wavelength. The idea is the propagation delay for the front sub is 1/4 wavelength, and then the rear sub is delayed by 1/4 wavelength, so you hear both start at the same time. But since they are 180 degrees out of phase they cancel.

End Fire and Gradient arrays have different pros and cons. End fire arrays take up a lot of space but have better transient response and higher SPL out front. I believe the sound behind the array is uneven/peaky, especially with small endfire arrays, which is bad for the band.

Gradient arrays take up less space and have worse transient response and lower SPL out front. Also they are only effective over the range of about 1 octave. But I believe the sound behind the array is more even, which is better for the band.


How do you calculate cardioid subwoofer spacing? (gradient array) (sounddesignlive.com)
Microsoft Word - wp - Subwoofer Arrays v04 .doc (electrovoice.com)

Thanks for the explanation. I think I kinda understand that.
Kirk

 

[seamonkey]

Alpha Sound has several great videos on cardioid. This one really hits the "spot".

 

[musicman7722]

watching