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One Box Array - The Church Speaker

A look at Speaker Coverage Angles


. Church sound starts with the speakers. Some discussion has been given to a so called "Sweet Spot". While somewhat relevant, this disregards the most important factor - Coverage Angles.
 
. The fact is, No combination of conventional speaker cabinets will ever properly cover a typical rectangular church from an oblique angle. In other words, hung overhead and aiming down.
. Conventional speakers typically have a coverage pattern of 90° wide by 40° high. This is designed to be used at slightly above head height, like on a tripod speaker stand, and vertically straight. Tilting down creates a narrow stripe of coverage that will only reach a few rows of pews in a church. Stacking these will increase the vertical coverage, but will not provide the increased projection needed for the back of the room. Hanging them sideways will give a taller vertical pattern, but will NOT give the increased directivity needed for the back rows. Placing them side-by-side will only make matters worse than ever.
 
. The One Box Array was conceived to address the coverage angle requirement for MOST typical churches of rectangular shape with a high ceiling. By combining three DIFFERENT horns; 90°, 60° and 40°, the front, middle, and back of the room can be uniformly covered with a minimum of cost, weight, and size.
 
What about a line array?
. With the exception of the very expensive "Room-Match" series from BOSE, which are so expensive that most churches cannot even consider them, most "Line Array" cabinets do not have different directivity. They are designed for concerts and outdoor applications.
. To cover the rectangular church, the front must be wide and the rear must be narrow and the middle must be, well, medium. This is clearly very simple with 3 horns of different patterns, all using the same drivers, and same filter frequency too.
 Room Coverage - The 3 shaded areas show the coverage patterns of each horn. . The cabinet is tilted about 15°.

The Room:

From the point of view of the speaker, the seating area is not a square or a rectangle, it's a trapezoid, wide at the bottom and narrow at the top.

And farther away to the back requiring more projection or higher directivity, therefore a narrower pattern.

This is why no conventional speaker will give proper coverage at all.

The 1BA, One Box Array, hung in a typical "A" frame sanctuary.

The resulting coverage was pleasantly uniform from front to back and side to side, even in the balcony.

It is hanging 2 feet down from ceiling to reduce resonance and reflections.

Frequently we see speakers hung too high, thus creating unwanted interaction with the ceiling and beams


The Box:

Side view of the cabinet.

The slanted speaker boards are 20° apart. This gives enough overlap between patterns for smooth coverage.

The horns are rated for 40° vertical, but the primary on axis pattern is really more like 20°.

The grille frames are 3 separate frames with tapered sides and the outside edges can be chamfered or rounded for a better look.

Then they are covered together as one large frame. This allows them to bend around the front 3 faces for a nice finished look.

The cabinet side layout dimensions.

The front speaker boards are recessed an extra 1/8" for the carpet on the speaker board.

I always carpet the speaker board instead of paint. It creates a nice gasket for the speaker and horns plus it eliminates reflection and refraction from the speaker board surface.

Note: These sketches are not meant to be complete plans, but if you know woodworking you should be able to build one easily enough.

I mostly filled the cabinet with fiberglass insulation to reduce standing waves and increase internal air density.

I used a little push terminal cup for wiring. This is much easier than a connector, and makes a better contact too.

Each speaker board with dimensions and speaker/horn placement and spacing.

 

These are the 3 horns I used.

Sadly no company makes a consistent series of horns of 90, 60, 40 degrees with matching size and mounting cutout.

Note: If you need a 120° horn, the Selenium HC23-25 is a really nice sounding choice, perfect for smaller or wider rooms, or with a lower ceiling.

 

A simple filter design: . (I never liked the term crossover since nothing really "crosses over" anyway.)

More complicated filters just waste power. There is no reason to keep the highs out of the 15" speaker, and this gives plenty of protection to the HF drivers. . It actually comes out with a pretty flat response.

If you use good components, you will have a good sound.

3.3 mfd 400 volt Polypropylene capacitor

The finished cabinet with speaker and horns mounted.

Note: Middle horn shown is Eminence LT-250, now discontinued.

It looks like it is mounted the wrong way but is actually correct. . The PRV WG17-25 is functionally the same.

Finished cabinet with grille.

The grille is attached with finish nails right through the cloth.

 

And another thing . . . This is a driver

This is a speaker, NOT a driver