Cardioid Subs

[dnathan]

I'm looking into cardioid subs to create a quiet stage. I like the KS212C for portability. I just came across a deal for a Bose L1s with two subs. Can I position those to mimic the KS212C cardioid pattern? Would the cardioid pattern vary per the room I'm in? Also, how would I measure accurately? Thanks!

I plan to use a column speaker of some kind for the highs.

 

[MNicolai]

The cardioid efficiency will vary per room, particularly in small reverberant rooms where the room modes may cause interesting phase cancellations and additions.

You can't create a directional subwoofer array with 2 subs. You end up with a starburst of phase cancellations and additions. Really any horizontal array that's 1 cabinet tall will produce this effect unless you've got a lot of subs deployed and are delaying them from the center outward.

The best you could hope for is an end fire array where you put the first sub several feet in front of the second sub and delay the second sub to the first. The effectiveness of this is frequency dependent. The first image below is 80 Hz. Then next one is 125 Hz (using a completely different sub for the purpose of some quick visualization). Usually you don't have the luxury of sticking a sub in front of the lead vocalist and then another one several feet in front of that, so there are practical limitations to this scenario as well.

You would be better served by the KS212C's. Whether that's one or two, you will experience better directivity than a couple of omni's.

 

[dnathan]

Thank you Mike! Great info!

 

[DrewE]

Respectfully, it is possible to get a more or less cardioid response out of two closely-spaced subs if you apply a delay that varies with frequency (i.e. a bunch of DSP processing, typically) and are wiling to sacrifice some efficiency. There are some available that do this, such as (pairs of) the Yamaha DXS series and apparently the KS212C. Having them spaced further mainly just makes the signal processing a good bit simpler. Room reflections can wreck havoc in any of these situations, of course, particularly when close to the speaker(s).

 

[FMEng]

Like the others mentioned, my EV ETX-15SPs can do cardioid as a stacked pair, and as a horizontal or vertical trio. The appropriate placement is in front of the stage, so that the performers are in the null.

 

[TimMc]

Like the others mentioned, my EV ETX-15SPs can do cardioid as a stacked pair, and as a horizontal or vertical trio. The appropriate placement is in front of the stage, so that the performers are in the null.

In addition, there should be no obstructions of the subwoofer(s) for 1 metre all the way around, and above, them. IOW, give 'em room to breathe.

 

[gafftaper]

Just wanted to note that while It's possible to create a cardioid sub pattern if you are highly skilled and have the right gear, many of us don't have the time or skills to do it right. The KS212C is magic on that it's all done for you and it just works in a cardioid pattern out of the box.

Also, my impression of the KS212C is that it's really designed for small clubs and other locations where you need to control the direction of the bass but you probably don't have the staff, budget, or even the space to create a cardioid sub pattern the old fashioned way.

 

[MNicolai]

Circling back on this, I would agree that yes, technically, you can create cardioid subs with 2 sub elements. I wasn't aware of the models entering the marketing that are omni's with special presets if you park them near other cabinets, but I would still consider those the exception and not the norm. The odds that the deal the OP was presented have that feature are unlikely. If you have 2 standard omni subs and are trying to make them a cardioid setup, it takes a lot of technical skill and DSP to achieve a less effective rig than something prepackaged by the manufacturer and that was measured and tuned in a laboratory environment.

 

[gafftaper]

Circling back on this, I would agree that yes, technically, you can create cardioid subs with 2 sub elements. I wasn't aware of the models entering the marketing that are omni's with special presets if you park them near other cabinets, but I would still consider those the exception and not the norm. The odds that the deal the OP was presented have that feature are unlikely. If you have 2 standard omni subs and are trying to make them a cardioid setup, it takes a lot of technical skill and DSP to achieve a less effective rig than something prepackaged by the manufacturer and that was measured and tuned in a laboratory environment.

Also, those KS212C's really do work well. I heard them at NAMM last year and it was stunning how much of a difference there was from front to back. Where doing it yourself you might be always fighting to sort of get the results you really are hoping for.

 

[Ben Stiegler]

It depends if you have the luxury of time and measurement tools onsite when setting up the event as well. More advanced system engineers might have luck with the roll your own than someone just beginning with CS. I took a 2 day Meyer class on this and there’s a lot to be aware of when tuning

 

[TimMc]

It depends if you have the luxury of time and measurement tools onsite when setting up the event as well. More advanced system engineers might have luck with the roll your own than someone just beginning with CS. I took a 2 day Meyer class on this and there’s a lot to be aware of when tuning

The good news is these behaviors can be modeled (Meyer's tool for modeling their loudspeakers is great stuff) without needing access to physical equipment. Much experimentation on site can be reduced to a some quick a/b tests in a throw and go live environment.

My shop started doing "reversed, polarity flipped and delayed" directional sub arrays for Weird Al Yankovic, who does not like to be shaken on stage (stirring may be out, too!). This was prior to JBL having presets for this sort of thing so it involved a calculator, the speed of sound, and the location of the *acoustic center* of the subwoofer we used. We proved it in situ with Smaart. Not a Bob McCarthy-level endeavor, trust me, but it kept the Stomach Steinway guy happy, we didn't beat up the monitor guy or guitar tech as bad as usual. It was a successful deployment for portable use, and we've kept using this type of deployment unless something different is requested in the advance.