Inverted subs

[bri4827]

So recently I've seen that with setups with 3 or more subs stacked, one or more is sometimes inverted (sometimes within the box, and other times the whole box itself). What's the benefit of this? is there any special delays that need to be considered when doing it?

[rwhealey]

I think what you might be seeing are "cardioid sub" arrays. The idea is to use the the cancellations and additions to make the sound from a cluster of subs more directional (because you'd need a really, really big horn to do what you can with high frequencies). I believe that there is often processing used. Don't quote me though, I'm not much of an expert.

It's defiantly used above the level of what I usually run..

Here's an interesting sub thread:
PSW Sound Reinforcement Forums: LAB: The Classic Live Audio Board => Amazing bass and Evans gig

and another good one:
PSW Sound Reinforcement Forums: LAB: The Classic Live Audio Board => subs and deploying them 'in the round'

If you want to make the pretty graphs yourself, you can check out
MAPP Online Pro

[museav]

I know several people that implement cardioid sub arrays on a regular basis and had a recent install using the Nexo CD cardioid subs that worked quite well. It is definitely becoming a popular approach for reducing low frequency levels on stage or providing some directionality to low frequencies in acoustically live spaces.

[mixmaster]

While back I stumbled on Dave Rat's blog. He was explaining how he was doing Cardioid subs with 4 stacks in sort of a diamond shape on each side of the stage. There was some talk about the delays between cabinets necessary to make the array work. While it was a way much bigger scale than I'm at it's cool to read about what the big boys are doing with this.

The theory as I understand it is that the rearward firing driver or cabinet is delayed slightly so it's 180 degrees out of phase with the sounds coming off the back of the "normal" drivers. 180 degrees out of phase cancels out the sound going behind the speaker cabinets, which in theory reduces low frequency buildup on stage. We had a guy through here a while back that tried to explain it better than that, but I couldn't wrap my head around the math.

[ChrisPistols]

Cardioid Sub Arrays are a great thing yes it takes a few more subs in order to achive the necessary energy required. The idea is to keep the subs out of phase in order to provide more directionality to your subs and send the low end where you want it. They key is to have the components delayed a 1/4 wavelength apart when flipped out of phase 180º. There is a lot of math behind acheiving this massive amount of enegery. The other cool part about this is it can be ulitilized in power alleys and prevent the low end of the subs when in a L/R setup from phase cancelation you'll have much more even and clear low end rather then different types of low end nodes throughout the room. Meyer sound is big on the cardiod sub arrays and have a lot of content explaining the theory behind it. I am learning more and more about it everyday and utilizing it with my VerTec a lot. You need to have a measurement system of some sort to do this correctly and make sure that there is no latency between different processors because if your timing is off then you stand to lose a large chunk of your low end. I'm not pro with this and I wish I was but I have been doing a lot of research and testing it out on gigs and it works very well. The big benefit though isn't so much the reduction of stage noise but more so controlling the directionalty of your low end and lessening the amount of nodes in a room.

[museav]

It also gets complex in that the relative phase is frequency dependent, two signals that are 180 degrees out of phase at one frequency will also be in phase at some frequencies and somewhere in between for others so simply having two drivers a distance apart or delayed does not necessarily do much.