Big BenD Bass Horn: Scale Model

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One way to test aspects of horn design which are hard to simulate, is to make a scale model and measure it under similar conditions. A friend with a small CNC machine cut some plywood sheets based on exported on-the-flat profiles of a simplified version of the horn, having only the mouth bend. The scale is 1:5.

Kit

The mouth bend is the most important in this case, as this sets the footprint of the horn, and therefore enables us to position the horn in the same way as it will be positioned in the room.

ScaleModel2

To drive the horn, a scaled down driver is also required. I used a Celestion AN2775 driver, as I had some at hand. 

ScaleModel3

The horn was then placed in a corner, and a few experiments were tried. 

ScaleModel4

Below are frequency response curves for the horn alone in the corner, and with a cardboard baffle flush with the horn mouth. There is a 5dB loss of sensitivity, similar to the simulated loss, so we may assume we will get a similar loss for the big horn in real life.

I also tried making a Helmholtz resonator under the horn, but this only reduced the loss by 1dB. 

ScaleModelFR

 

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