opinions wanted.... subwoofer placement etc...

[Shane Presley]

I am planning / prediciting the rig for a ribfest show coming up. I did the show last year, with 4 KF730 over 4 SB1000z. This year the client wants the pa flown to improve sightlines so I plan to do so, but I also thought I'd take a stab at a delayed subwoofer set-up. Here is what I have so far. The top picture is what I intend to go with, it seems to provide the most even coverage (left to right - not front to back) and the most rejection on stage, especially at the lead singer position.

The bottom picture was an experiment to bring the front pair of subs closer to the 2 high sub stack... doesn't look "good" at the singer position as creates power alley....

Notes - frequency is 63hz.

The tops are at 18ft (4 x kf730)
There is one sb1000z on stage (2' high) facing backward in front of the array (delayed 10.99ms, inverted phase)
There are two more subs front firing (delayed 8.49ms) ground stacked.
Lastly a pair of subs in front on the ground, delayed the same as the front firing set ( 8.49), but physically 2ft forward - which will match with the proscenium of the venue.
I plan to tweak all of this onsite to align the subs with the tops, but this is what I'm getting virtually. Does anyone have any suggestions with the equipment I've listed. BTW only one UX8800 - so 2 pairs of channels available for subwoofer delay (3,4) (7,8).

I've attached a pic of the venue, you can see the projected front....

 

[Tim McCulloch]

Re: opinions wanted.... subwoofer placement etc...

I think you're waaaaay overcomplicating this.

Use 3 SB1000, placed F-R-F in a horizontal line (so the "mirror" of the ground plane is uniform for all speakers, you can put the SB1Ks on their sides if you like). Align forward subs/main hang. Turn on reversed sub, flip polarity and start with about 4.5ms of delay. Measure the front and back sides of the array and adjust delay time to give you cancellation at the desired frequency, the 4.5ms should get you around 60Hz. If you want less rear cancellation, turn down the reversed sub.

 

[Shane Presley]

Re: opinions wanted.... subwoofer placement etc...

I think you're waaaaay overcomplicating this.

Use 3 SB1000, placed F-R-F in a horizontal line (so the "mirror" of the ground plane is uniform for all speakers, you can put the SB1Ks on their sides if you like). Align forward subs/main hang. Turn on reversed sub, flip polarity and start with about 4.5ms of delay. Measure the front and back sides of the array and adjust delay time to give you cancellation at the desired frequency, the 4.5ms should get you around 60Hz. If you want less rear cancellation, turn down the reversed sub.

Thanks Tim for taking the time to answer. I modeled this and it doesn’t come out "on paper" nearly as good as it might in the real world. I tried the side by side on ground level F-R-F, and vertically stacked F-R-F, and both of them result in less than favourable conditions. I've seen other providers put thier SB's on thier side, but later hear that the downward firing speakers suffers more fatigue that the one firiing upwards ( probably a wives tale), but if for nothing else, I don't like to put the cabs in thier sides (marks up the paint)...lol Sounds like I have some shop experimentation to do before I go onsite.

 

[Tim McCulloch]

Re: opinions wanted.... subwoofer placement etc...

Outdoors if you can, Shane. I've tried measurements indoors and until I get into airplane hanger-sized rooms it's pretty much a crap shoot... especially when trying to measure the rear output levels of arrays that have rear-firing speakers. If measured in situ at a venue, the reflections easily contaminate the measurement. It pays to take a *really* good look at the impulse response (the magnitude of reflection arrivals) before accepting the measurement as valid, invalid, or conditionally acceptable.

Hopefully Art Welter or Ivan will weigh in on this...

 

[Evan Kirkendall]

Re: opinions wanted.... subwoofer placement etc...

That big 'ol concrete slab of a stage is going to really mess with your predictions. I've been a big fan of either just a straight up cardioid array(though I usually flip the bottom sub) or lately, when I have the room, I have been doing a down and dirty end fire array. It works surprisingly well, and with a few tweaks, I can steer the low end around in the crowd. I like it a lot!





Evan

 

[Shane Presley]

Re: opinions wanted.... subwoofer placement etc...

Thanks everyone for "steering me" in the right direction (wan wan wan)... I re-predicted and end fire situation and it does seem to model a bit better and will be easier to implement. I wish I had more subs.. lol

Looks like about a 1ft apart with 5.45ms (which was just picked out of the blue... I did go in one second increments on either side to review the results, better or worse) So I'll be aligning my tops with the sub closest to the stage, and then adding 5.45MS more to the sub closest to the audience. I'm hoping to test this outside before I actually have to implement it.

 

[Ivan Beaver]

Re: opinions wanted.... subwoofer placement etc...

Thanks everyone for "steering me" in the right direction (wan wan wan)... I re-predicted and end fire situation and it does seem to model a bit better and will be easier to implement. I wish I had more subs.. lol

Looks like about a 1ft apart with 5.45ms (which was just picked out of the blue... I did go in one second increments on either side to review the results, better or worse) So I'll be aligning my tops with the sub closest to the stage, and then adding 5.45MS more to the sub closest to the audience. I'm hoping to test this outside before I actually have to implement it.

It also helps to look at different freq that the subs are reproducing. As you move the spacing and/or delay times-the pattern is going to change at different freq.

One tool I find very useful is the Danley DDT 2D for "faster" answers. Yes it only has Danley subs-but you can get the idea. The 3D works just as well-but takes a bit more "setup" because it is 3D. In the 2D you can add walls-reflections and see how that REALLY starts to change things in the response and mapping.

It is free and it lives on your computer-not on a server-so there is no tracking of what you do with it.

DDT Files | Danley Sound Labs, Inc.

The really cool thing is that you can place mics in front and back of the array (and around etc). So as you move either the delay or the spacing you see in REAL TIME the overall freq response changes. No need to do a bunch of different plots and try to compare. You can also save 3 "views" and compare to a 4th live view.

I find it makes determining the overall distance and spacing much faster.

You can do the same thing with the full range cabinets as well-see how moving them around affects the freq response without having to create a bunch of plots to compare.

 

[Per Søvik]

Re: opinions wanted.... subwoofer placement etc...

With 8 subs, if I counted right, why not just do a 5:3 cardio array in front of the stage and call it a day?