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Danley BC215 Directivity

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Caleb Dueck:

--- Quote from: John Hiemburg on May 11, 2021, 10:34:35 am ---
Great, thank you. The rear cancellation isn't the main consideration, just getting the low end further out front. In other words, I'm only looking at directionality for the sake of getting my 'bass dollars' into the seats.

--- End quote ---

This is a function of vertical pattern control, not rear rejection.  Some types of rear rejection also happen to have side (straight down, for example) rejection, which helps, but vertical pattern control is what you're looking for. 

If you do a model in direct and put a 'wall' right down the center of the speaker - you can see a slice side view, and see what the various frequencies are doing. 

Art Welter:

--- Quote from: Caleb Dueck on May 11, 2021, 05:26:41 pm ---If you do a model in direct and put a 'wall' right down the center of the speaker - you can see a slice side view, and see what the various frequencies are doing.

--- End quote ---
You can also center the speakers in the aisle between seating areas in the "Simple Church" model in the Danley Direct simulator to get an idea of comparative polar response and output. Doesn't seem to show room modes...

The example below uses four of the TH118XL in two configurations compared to the BC215 x2. 
The TH118XL x 4, shows more low end output, the BC215 x2 has a bit more general directivity,  TH118XL, more "variety" in directivity  ;)
Combining the two types with the BC215 reversed polarity is also interesting.

Art

John Hiemburg:

--- Quote from: Art Welter on May 11, 2021, 05:51:53 pm ---You can also center the speakers in the aisle between seating areas in the "Simple Church" model in the Danley Direct simulator to get an idea of comparative polar response and output. Doesn't seem to show room modes...

The example below uses four of the TH118XL in two configurations compared to the BC215 x2. 
The TH118XL x 4, shows more low end output, the BC215 x2 has a bit more general directivity,  TH118XL, more "variety" in directivity  ;)
Combining the two types with the BC215 reversed polarity is also interesting.

Art

--- End quote ---


Thank you all for your help and input. Art thank you for the time and detailed info!

Art Welter:

--- Quote from: John Hiemburg on May 15, 2021, 09:40:40 am ---
Thank you all for your help and input. Art thank you for the time and detailed info!

--- End quote ---
John,

Though you were only considering a pair of BC215, or four TH118XL, thinking about Ivan Beaver’s writing he had measured -10dB at 90 degree off axis around 40-50 Hz with Bdeap cabinets in a 2 over 2 configuration with the "mouths" in a cloverleaf pattern, thought it would be interesting modeling four BC215 configured like that in Danley Direct (DD).

In post #4, Ivan explained that the DD models are based on
“actual measurements of the different configurations (1,2 4) as measured outside on the ground without reflections. They are not simulated.”

The BC215 in DD has interesting anomalies.
The BC215 has a 45 x 45 inch boundary with a small mouth exit in one corner, an asymmetrical cabinet, yet as a single cabinet DD plots it as axisymmetric, left/right being a mirror image with a “pointy” lobe directly in front.
No doubt DD is based on actual measurements, but forward symmetry for an asymmetrical cabinet can’t be valid.

When four BC215 are arrayed in a symmetrical “cloverleaf”, mouths at the four corners, the axisymmetric array’s pattern becomes asymmetrical in DD, a kind of “pinwheel” pattern.

The attached DD models are a 100 x 100 meter area, with 3dB per color change.

The models show a distorted directivity effect, but ignoring the anomalies, demonstrate that four BC215 arrayed in a “cloverleaf” do show directivity similar to what Ivan reported for the Bdeap cabinets 16 years ago.

Unlike Ivan, I never even broke a sweat stacking or flying those 360 pound cabinets!

Art

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