Constant Beam Width Transducers line arrays

My pastor has been hinting that he would like my help upgrading our church PA system. This PE kit has me seriously considering clamping this speaker pair bottom-to-bottom for a flown full-space center array. Horizontal coverage looks good out to the 120 degrees we need.

Your church must have a bunch of money to throw at a sound system. These things are not cheap when you add up cost of eq and amps.
 
Maybe I need to look around more, but I'm not aware of another complete line array speaker with this kind of performance in this price range. I've looked at the JBL CBT70j, but I don't believe it has the same SPL capability.

Happy to hear other suggestions to stretch our dollars farther—because, no, we don't have much money. (compatible DSP and amps are already in place.)

Actually, it's kind of funny how our church buys things. We're a very blue-collar bunch of folks who mostly just scrape by, but one gentleman in particular has been blessed in business. Whenever the church needs something, an "anonymous donor" makes it happen. His name is never revealed, but we all wink and nod. :)
 
I seem to recall seeing their product listing for a half year or so, but it's never been available when I've looked, always seemingly sold out. I wonder if they've EVER had kits for sale yet.

It was never formally listed as a for sale product until just a couple of days ago AFAIK and it's something I've been checking on. They have had the promo shots up for at least a year and a half.
 
Alright, I've been officially asked to get bids on a new speaker system for our church, and my first thought for the center, as I mentioned before, is a pair of CBT36 joined bottom-to-bottom. The church sanctuary has a hexagonal floorplan, about 60 feet across, with a vaulted ceiling about 40 feet at its apex. The array would be hung from ceiling approx. at the red circle.

Any advice--yay or nay? If Dr. Keele is watching this thread, I'd especially value his opinion. :)
 

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Alright, I've been officially asked to get bids on a new speaker system for our church, and my first thought for the center, as I mentioned before, is a pair of CBT36 joined bottom-to-bottom. The church sanctuary has a hexagonal floorplan, about 60 feet across, with a vaulted ceiling about 40 feet at its apex. The array would be hung from ceiling approx. at the red circle.
You could do worse, but a pair of CBT36 joined bottom-to-bottom in the position you show will not provide even coverage left to right and front to back, vertical coverage will be too limited, and the thrust forward puts the outside front row seats, already poor listening positions, outside the cabinets nominal 120 degree horizontal pattern.

Splitting the lower array and making a "J" hang with amplitude shading may solve some of the problems, but will require some crossover re-engineering, the most difficult aspect of most arrays.

Taking an array designed for a home environment and setting it loose in a completely different one will require many "adjustments".

Art
 
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I've heard the CBT and just did a church gig yesterday that used very slim line-arrays (not CBT) I agree with Art, it will work, but you'll need to fool with it. You might need more than one array to cover that big area.

Are you just doing speech, or do you have to play much music thru it, too?
 
I thinks the CBT could work well, but you would need at least two full-arc arrays to cover that area. I'm not sure if the PE kit would have sufficient output (about 105 dB @ 1 m for the tweeter section)

It does have the advantage of an approximate 3 dB loss per double distance, if aimed correctly.
 
Thanks for the input, everyone.

Two more questions:

1) If full horizontal coverage isn't possible with a single array, is it better to cluster two arrays aimed left and right, or to use a single center array with side fills to cover the front corners? I'm leaning toward option B...

2) There is a balcony that wouldn't be covered by the main array. Would using a second center array flown in front of the balcony with appropriate delay be the way to go?
 
Thanks for the input, everyone.

Two more questions:

1) If full horizontal coverage isn't possible with a single array, is it better to cluster two arrays aimed left and right, or to use a single center array with side fills to cover the front corners? I'm leaning toward option B...

2) There is a balcony that wouldn't be covered by the main array. Would using a second center array flown in front of the balcony with appropriate delay be the way to go?
A single center array with side fills to cover the front corners would do less damage to fewer seats than a "cluster" (we know the second word) of side by side mini line arrays.

The mini line arrays have vertical control in the upper frequencies, but still have very little lower frequency pattern control, plenty of sound level wraps around the column. Delayed for the balcony, that wrap-around sound becomes a secondary echo in addition to the back wall echo, helping clarity in the balcony while adding to the general room reverb. One step forward, two steps back.

Line arrays (designed for large rooms rather than small rooms like the ones you are considering) can be a good solution for shoe box shaped rooms.
Line arrays designed to arc can cover tall vertical spaces, the line under consideration is not.

For a wide room with a large vertical coverage angle required like yours, an array of horns with actual pattern control designed for the area they cover is more appropriate, can use far less components, have greater dynamic range using far less amplification and will require less vertical height, though more mouth area.

But, like I said before, a mini line array will work...
 
Thanks for the input, everyone.

Two more questions:

1) If full horizontal coverage isn't possible with a single array, is it better to cluster two arrays aimed left and right, or to use a single center array with side fills to cover the front corners? I'm leaning toward option B...

2) There is a balcony that wouldn't be covered by the main array. Would using a second center array flown in front of the balcony with appropriate delay be the way to go?

To answer the second question: "Yes".

JBL has some great software called "JBL CBT" for hanging, aiming and EQing the CBT units. I have done simulations of multiple CBTs (in this case as lateral surround speakers firing across the audience. If the software is to be believed (and I have no reason to doubt it), then you can hang well spaced arrays and use time delay and get a very smooth blend across the area with no ill effects.

Download the software and draw in a side view of your seating area and balcony (just lines for the string of listener locations) and you will be able to play around and get surprizingly uniform response and level for most seats.

David S.
 
For a wide room with a large vertical coverage angle required like yours, an array of horns with actual pattern control designed for the area they cover is more appropriate, can use far less components, have greater dynamic range using far less amplification and will require less vertical height, though more mouth area.

But, like I said before, a mini line array will work...

Good point about the horns and the possible pitfall of delayed second array for balcony. Perhaps a two-way box hanging in the front with a ~60x25 deg. treble waveguide aimed at the balcony, and then hang a J-array like the JBL CBT70je from the bottom of that to cover the lower area with the help of front side fills...
 
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To answer the second question: "Yes".

JBL has some great software called "JBL CBT" for hanging, aiming and EQing the CBT units. I have done simulations of multiple CBTs (in this case as lateral surround speakers firing across the audience. If the software is to be believed (and I have no reason to doubt it), then you can hang well spaced arrays and use time delay and get a very smooth blend across the area with no ill effects.

Download the software and draw in a side view of your seating area and balcony (just lines for the string of listener locations) and you will be able to play around and get surprizingly uniform response and level for most seats.

David S.

Thanks, Dave. Just last night, I downloaded that CBT app and played with it. It's a great looking tool. I wish it incorporated information about the max SPL capability of the CBT units, though.

It got me thinking that a CBT70JE might be a good choice for the center array, but I still have a question about max SPL.
 
If you are interested in CBTs for your church, you should contact Marshall Kay of www.audioartisty.com and Rick Craig at Selah Audio. They cooperated on a CBT system for the Cary (North Carolina) Church of God a few years ago. While there are references to it on the audioartistry.com site, most of those papers address the electronics setup vs. the speaker design/implementation aspects. Marshall worked with Don Keele on the implementation of the Parts-Express CBT kit.
 
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Here's a screenshot of the sim I did last night.

The balcony array is -6dB wrt the front array. Maybe this would make the echo potential less of a problem?

Good program and it leads to endless dabbling to get things just right. Can you aim the arrays farther back into the seating areas to get more uniformity of level (without losing too much at your front point)?

Do you have a specific echo problem or are you talking in general? Of course the program just deals with the level of the direct sound and your acoustics will respond to the overall radiated power.

I do a lot of system design with level vs. distance trading to get uniformity across the depth of an audience. You end up aiming a lot of energy at the back wall, because you are using the bottom half of the polar pattern to place people in the fall off of one side of it. It would be usefull to have more assymetrical polar patterns. The CBT goes a little in that direction, but not enough.

David S.
 
Can you aim the arrays farther back into the seating areas to get more uniformity of level (without losing too much at your front point)?

Do you have a specific echo problem or are you talking in general? Of course the program just deals with the level of the direct sound and your acoustics will respond to the overall radiated power.
David S.

I'll try simming a little less tilt. The front seats are already at about the lowest relative SPL, though. The coverage would be more uniform if I could hang the front array lower and aim at the back wall, but at some point it would become an unacceptable aesthetic tradeoff. There is a high stained-glass window behind the platform, and also a projection screen and wall-mounted plasmas that cannot be obstructed.

Weltersys brought up the possibility of echo trouble resulting from spillage from a delayed balcony array. As-is, the sanctuary doesn't suffer from echoes. The faceted walls and ceiling seem to break things up enough.
 
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Weltersys brought up the possibility of echo trouble resulting from spillage from a delayed balcony array. As-is, the sanctuary doesn't suffer from echoes. The faceted walls and ceiling seem to break things up enough.

The delay is what is preventing echo in the overlap regions. You can see a little bit of cancelation (dip in the response curves) in some of the measurment points below the balcony speaker. Play with the delay to see if you can minimize it. You can also see strong interference (if it exists) in the color map of the combined polars. Try different frequencies for that.

A useful tool.

David S.