SLA pro specs

Short and Transmission Line Arrays for Pros
Post Reply
Message
Author
curtis73
Posts: 7
Joined: Mon Feb 20, 2023 2:34 pm

SLA pro specs

#1 Post by curtis73 »

I did some poking around the main site and didn't find specs like freq response and waveform angles for the SLA pro. Hoping to get some info on them as a possible use for my live theater PA.

There is a photo at the bottom that will give you an idea of the space and I'll add more drawings when I get back to work.

Long story (skip if you don't care). This is a small, non-profit theater black box. 60' long (in the direction the camera is facing) and 50' wide. Grid is installed at about 15' above deck. Important part, the whole theater is modular. I can set up a stage anywhere and seating risers can move to any configuration; in the round, one-sided, two sided on an angle, 3/4 thrust, darn near anything. Even the tech booth on the far left, near, is on casters, so it goes where I want it. Current sound reinforcement comes from a Yamaha 750x2 with a few more amps on standby. They feed four Yamaha 12" cabinets (unseen) just above the lighting grid hanging from swivel links so I can spin the speakers to point toward the audience wherever I put them.

Two of the Yamahas have blown horns, and a third one has a replacement paper woofer that looks like it came from a 1968 Magnavox Phono console. Sound sucks unless I unplug the two with blown horns, but that can only happen for certain seating configurations. I'm also having the trouble of the sound system helping AND hurting simultaneously. It amps voices, but also amps room reverb. It makes it loud, but it also makes the room loud proportionally because they're basically set up in an array as far as possible away from ears.

I'm thinking about making a couple handfuls of smaller active cabinets (maybe 6"/horn) that can hang from the grid much closer to the audience. More speakers closer means less stuff bouncing off walls. It also means (potentially) less opportunity for feedback from the stage mics. It ALSO means that I can toss a digital snake in the grid and XLR each cabinet for ultimate control. That way I can wheel the booth where I want it, plug in a Cat6, re-aim the cabinets toward the seats, done. Depending on how I address the snake, I can just do a couple channels for a regular show, or have SFX routed to a specific one, etc. I realize it can also mean phasing issues, which I already have, but for the most part the audience walks in and sits still.

Long story short: Looking for whether or not some powered SLA pros on a digital snake would be good for hanging in a grid to configure per show. And before you ask: I'm a trained, experienced, and certified rigging specialist, so we can hopefully skip the warnings :D
Also, before you ask, the budget is somewhere between non-existent and shoestring. I know the answer here is to buy 4-6 new QSC 12s, but that isn't the name of the game. This would be partly an attempt to save money (more gear for the dollar) and also an opportunity to give a master class to local students who are interested. Group build with some education kinda thing.
Attachments
krevskypic2023.png

Grant Bunter
Posts: 6915
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
Contact:

Re: SLA pro specs

#2 Post by Grant Bunter »

Hi and welcome :)

Is this what you're after?
viewtopic.php?t=14052

As you can see, SLA pro is pretty good down to around 100Hz and will require subs below that.

As a rigger, you should be informed that the designer categorically states that the cabs cannot be flown relying on the integrity of their structure to hold them up.
A seperate intact frame that holds cabs on all sides is required...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: SLA pro specs

#3 Post by Bill Fitzmaurice »

I'd say SLA pro is a good choice. They have wider horizontal dispersion and narrower vertical dispersion than any twelve inch loaded cab, which should help fix your reverb problems. Dispersion is proportional to the size of the radiating plane, so a vertical line of four sixes will have in the vicinity of twice the horizontal dispersion and half the vertical dispersion of one twelve. The difference in pattern control of the line of tweeters compared to a single HF horn will be even more dramatic.

curtis73
Posts: 7
Joined: Mon Feb 20, 2023 2:34 pm

Re: SLA pro specs

#4 Post by curtis73 »

Grant Bunter wrote: Mon Feb 20, 2023 4:31 pm Hi and welcome :)

Is this what you're after?
viewtopic.php?t=14052

As you can see, SLA pro is pretty good down to around 100Hz and will require subs below that.

As a rigger, you should be informed that the designer categorically states that the cabs cannot be flown relying on the integrity of their structure to hold them up.
A seperate intact frame that holds cabs on all sides is required...
Thank you for the link. Perfect. That looks like they might fit well with some EQing and my Yorkville sub.

I wouldn't build them from traditional materials. I tend to use multi-layer Diab foam and epoxy/glass with known, rated, engineered properties.

curtis73
Posts: 7
Joined: Mon Feb 20, 2023 2:34 pm

Re: SLA pro specs

#5 Post by curtis73 »

Bill Fitzmaurice wrote: Mon Feb 20, 2023 5:21 pm I'd say SLA pro is a good choice. They have wider horizontal dispersion and narrower vertical dispersion than any twelve inch loaded cab, which should help fix your reverb problems. Dispersion is proportional to the size of the radiating plane, so a vertical line of four sixes will have in the vicinity of twice the horizontal dispersion and half the vertical dispersion of one twelve. The difference in pattern control of the line of tweeters compared to a single HF horn will be even more dramatic.
Thanks for the info. I know I'll get into some fun phasing no matter how well I aim it. Fortunately, the audience sits still. The goal isn't Disney-level audiophile, it's making sure our older demographic can physically hear things.

I'm going to spend some time with my CAD of the space to see if I'm better off with a bunch of 2x6s or try to radiate wider with some 4x6s mixed in.

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: SLA pro specs

#6 Post by Bill Fitzmaurice »

2x6s aren't what you want in a reverberant space, having twice the vertical dispersion as 4x6s.

curtis73
Posts: 7
Joined: Mon Feb 20, 2023 2:34 pm

Re: SLA pro specs

#7 Post by curtis73 »

Bill Fitzmaurice wrote: Tue Feb 21, 2023 12:20 pm 2x6s aren't what you want in a reverberant space, having twice the vertical dispersion as 4x6s.
I agree. My concern is with the horizontal. Given the fact that my seating might be sections of 6 chairs wide (in the round) or 25 chairs wide (proscenium), I'm worried about putting all my eggs in one cabinet, so to speak. Two 4x6s would be great for 1/4 and 2/4 seating, but useless for 3/4 and round seating. I was hoping that more (and smaller) dispersion drivers would be more flexible, and that would have to be better than 4 big cabinets on the ceiling.

Let me get a sketchup together quick to demonstrate

curtis73
Posts: 7
Joined: Mon Feb 20, 2023 2:34 pm

Re: SLA pro specs

#8 Post by curtis73 »

A quick and ugly section view of what it might look like in there with proscenium seating. The risers actually go to 5 levels, but I'm lazy. That seating is usually 32' wide, so a couple 4x6 would be perfect in this configuration. The other image shows what it might look like in-the-round, where I'm needing to focus on narrower sections, or trying to pull the cabinets back over the stage to utilize the wider dispersion.

So I think the question is, do I do more 2x6 or fewer 4x6. Which ones (or a mix of both) would be more flexible for this variable configuration?
Attachments
sectionview.png
planview.png

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: SLA pro specs

#9 Post by Bill Fitzmaurice »

You probably don't need as many sources as you think. The beam width of an array of sixes is 100 degrees, so superimpose that on your chart.

User avatar
Tom Smit
Posts: 7457
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: SLA pro specs

#10 Post by Tom Smit »

Welcome to the forum!

I was wondering if a multitude of 2x6s would be the answer. Use as many as you need, where you need, when in the small situations. Then stack a pair of 2x6s to end up with a 4x6 for the larger spaces.
TomS

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: SLA pro specs

#11 Post by Bill Fitzmaurice »

The thing with 2x6 is they have the same vertical dispersion as a 1x12, which as I understand it are causing problems now.

curtis73
Posts: 7
Joined: Mon Feb 20, 2023 2:34 pm

Re: SLA pro specs

#12 Post by curtis73 »

I don't have a problem with vertical dispersion necessarily. I'm trying to remember, but I think they are 40-degree vertical and 90 horizontal and they're hung angled to point at where I usually have audience set up. I think the primary problem with the four 12s way up high is that I'm driving them hard enough to reach 40 feet away from the most distant ear. By the time I make enough dB, I'm adding to the reverb. The closer I am to the individual ears, I need proportionally fewer dB to accomplish the same volume reaching the people, and also firing toward soft seats and soft bodies. Part of what I'm experiencing with the 12" cabs is that it kind of blasts everything in the room. I'm hoping for some discrete focusing on people. I think the lower SPL will make the reverb a hundred times better, and getting it closer is key to that. I'm not sure (given the angle at which they're firing) if broadening the horizontal is going to work in the round seating without pulling the sources back away from the seating and putting them over the stage, which could contribute to feedback.

I'll amend the previous drawing. Please note that the drawing IS to scale as it pertains to seating and the section dimensions of the space, but NOT as it pertains to speaker placement or the angles. I just drew in the speakers and the angles as a demonstration of what I'm looking for.

Also... I'm never challenging any of you when I ask this stuff. I'm pretty good behind the console, and I'm pretty good with acoustic theory and the general physics behind it, but most of my experience is as a sound board op, not a sound engineer. When I ask, I'm truly asking for advice from someone who knows more than I do.

curtis73
Posts: 7
Joined: Mon Feb 20, 2023 2:34 pm

Re: SLA pro specs

#13 Post by curtis73 »

Here is what I was thinking. I know I'm over-explaining, but imagine you're amping a cathedral. If you hide the speakers in the top of the clerestory, you are just adding to the reverb. Until you drive them loud enough to be heard, all you hear is the whole church bouncing back. Now put the speakers on the pillars of the ambulatory about 20' from everyone's ears and drop volume proportionally. They can still hear reverb, but they're getting the clear voice primarily. Then send it through headphones to everyone and drop another chunk of volume. Suddenly zero reverb.

I'm not necessarily concerned about reducing vertical dispersion, although that DOES contribute to reverb, I'm looking to add discretion. Half way between a big driver in the rafters and wee little headphones 2" from your eardrum. I'm thinking (maybe incorrectly) that it should make it much better, regardless of if I use one bigger box to cover 100 degrees or 2 smaller boxes to cover 50 degrees each. The 4x6 has tighter vertical, but I'm not sure it will make much difference the way I would aim them.

In the photo below, I'm getting more discretion and a tighter pattern from the same vertical dispersion angle because they're closer to the humans in the audience. My problem with the big speakers is that they're so far away they just fill the whole room. That is to say, I feel like my current setup is great for a basketball game or a dance party, but not good for vocals to a small audience.

Thoughts?
Attachments
section.png

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: SLA pro specs

#14 Post by Bill Fitzmaurice »

The reason I mention vertical dispersion is that sound that reflects off the ceiling and/or floor contributes to early reflections, and doesn't end up in the audience as direct radiation. You're on the right track with your diagrams, you just need to refine them. The dispersion figures you mentioned would be for the HF horn, not the woofer. It would have the same beam width on the horizontal and vertical planes. Typical beam width of a twelve in the mids is 60 x 60 degrees. Speaking of churches, the first major implementation of line arrays was in St.Paul's Cathedral in London in 1949. They were used until about ten years ago, when they were replaced by new line arrays.

Grant Bunter
Posts: 6915
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
Contact:

Re: SLA pro specs

#15 Post by Grant Bunter »

I hope there is some merit in your thinking about distance.
IIRC, SPL drops by 6dB with each doubling of distance, ie 3,6,12,24 feet roughly.
With 40 odd feet, you have around 3 1/2 doublings, or -21dB from a 1meter SPL reading.
Moving your cabs forward towards your audience by 14 feet would see that back to -18dB.
Not a large saving by any means, but also means a possible 3dB reduction at 1 meter, which may be enough to help some more...

That makes me wonder if some 2 x6's as rear fill/satellites may allow an even greater overall reduction in dB in the mains...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

Post Reply