BillFitzmaurice.info

I learned of the following video covering sub placement from the face book page for the Behringer XR series mixers (I have an XR18). It is about 6 minutes. What is cool about it is he uses a program that via color shows the sound travel, pressure levels and cancellation area for 4 different setups. It is graphed in a way that shows the distance from the stage.

The person is a pro sound company running some big stuff, but you do get to see the reason for keeping your subs together. He speaks about 2 special setup, Cardiod and End Fire.

I posted this here figuring it's where most of the reading about subs is done.

https://youtu.be/1uD6Szdcqpw

Nice video, very insightful.

Question that I have is since bass is omnidirectional according to physics, how does cardiod and endfire actually control the sound as shown in the depiction?

Another question, has anyone attempted to use one of these setups using BFM cabs?

Interference. When delayed (and placed) properly, the output from subs will reinforce itself in some directions while being reduced by destructive interference in other directions.

whines wrote:Interference. When delayed (and placed) properly, the output from subs will reinforce itself in some directions while being reduced by destructive interference in other directions.

Is there an efficiency drop using interference to force the sound in one direction or is it just that it's putting the normal interference to better use? IOW, does it take more power to get this to work?

Surely the in fire setup will be frequency dependent.

Could anyone suggest a cab separation width for a "Line" setup with 6 (24" wide) T30's?

I reckon a centre stack v-plated would be the best (highest output) outdoor option for T30's, where a boundary other than the ground doesn't exist. Also, I've noticed that in every setup I've done to date with the T30's, that there is not a lot of "bass bleed" back onto the stage area, it's significantly less than around the front of the subs. Is that a characteristic of the FLH?

Dan56 wrote: Is there an efficiency drop using interference to force the sound in one direction or is it just that it's putting the normal interference to better use? IOW, does it take more power to get this to work?

It takes more cabs and more power. In the example he uses eight forward firing subs, which cover the room, and four rear firing subs, which provide the cancellation in that direction. Also note that this configuration is used with the subs in front of the stage, to reduce low frequencies on the stage. It takes a really large stage to make this useful. With average sized club stages the players will be standing where there's a rear wall reflection null zone anyway. If the subs are wall loaded to one side the wall can provide directionality to the rig.

I've noticed that in every setup I've done to date with the T30's, that there is not a lot of "bass bleed" back onto the stage area, it's significantly less than around the front of the subs. Is that a characteristic of the FLH

It's probably the above scenario.

Could anyone suggest a cab separation width for a "Line" setup with 6 (24" wide) T30's?

That arrangement narrows horizontal dispersion by making the source wider. To prevent combing the elements must be spaced less than 1/4 wavelength apart, which is 2.8 feet with a 100Hz crossover. Doing so instead of V coupling would cost you low frequency output. I'd rather the output than the narrower dispersion.

Bill Fitzmaurice wrote:

Dan56 wrote: Is there an efficiency drop using interference to force the sound in one direction or is it just that it's putting the normal interference to better use? IOW, does it take more power to get this to work?

It takes more cabs and more power. In the example he uses eight forward firing subs, which cover the room, and four rear firing subs, which provide the cancellation in that direction. Also note that this configuration is used with the subs in front of the stage, to reduce low frequencies on the stage. It takes a really large stage to make this useful. With average sized club stages the players will be standing where there's a rear wall reflection null zone anyway. If the subs are wall loaded to one side the wall can provide directionality to the rig.

I've noticed that in every setup I've done to date with the T30's, that there is not a lot of "bass bleed" back onto the stage area, it's significantly less than around the front of the subs. Is that a characteristic of the FLH

It's probably the above scenario.

Thank you Bill.

I figured such a set up was for large areas only (like outside, stadiums, and civic center/sports places). I would imagine for an acoustically tuned theater such a setup would not be the best thinking that they are designed to move the sound forward anyway.

With that, we play local bars so this was just a curiosity for me. The wall always does fine.

Thank you.
Dan

This thread got me thinking about my current sub setup and if it could be improved... sorry for the thread jack...

If the subs are placed right up next to a wall (and not firing into said wall) would it be better to have all 4 placed right next to each other like so (pretend the I is a sub): I I I I

or make 2 stacks of 2 with all 4 mouths in the middle like this: ==

Hopefully my stick drawings make sense. right now I have all 4 lined up because it was easy, but it wouldn't be hard to stack them at this point if I can gain some output or horizontal dispersion.

With four subs I'd stack and V-plate them aimed at the wall.

Bill Fitzmaurice wrote:With four subs I'd stack and V-plate them aimed at the wall.

If you did not have the room to V-plate and had to compromise, what would the next best option be?

I simply do not have the depth to V-plate in there current location. The future plan is to move them to a corner and V-plate, so I'm just trying to get the best setup I can at this point in time.

Bill Fitzmaurice wrote:

Could anyone suggest a cab separation width for a "Line" setup with 6 (24" wide) T30's?

That arrangement narrows horizontal dispersion by making the source wider. To prevent combing the elements must be spaced less than 1/4 wavelength apart, which is 2.8 feet with a 100Hz crossover. Doing so instead of V coupling would cost you low frequency output. I'd rather the output than the narrower dispersion.

Thanks Bill. Yeah I think I would also prefer the extra output.

Dan56 wrote: With that, we play local bars so this was just a curiosity for me. The wall always does fine.

The end-fire and cardioid arrays don't work well indoors, especially with a rear wall on stage or low ceiling. My experiments with those arrangements at our venue increased the volume on stage along the rear wall. I've seen a few computer simulations with a rear wall over at PSW and they show that phenomenon as well, the bass builds up along the wall. Also, the cardioid doesn't sound very good out front.

I did find this video educational:

https://www.youtube.com/watch?v=aSZK9Altvm8

He is explaining the "sound sum up" and cancellation in an easy way.