Saturday, April 11, 2015

Getting More Efficiency From A Midrange Horn Using A Corner

The two or three midrange horns I have made work pretty well but they are not as efficient as the bass horns.  It is likely that the small, inexpensive speakers I have been using for midrange drivers are not particularly efficient.  To compensate for this, I decided to try loading a midrange horn with a corner to get the magnification frequently employed by placing bass speakers in room corners.  This required a design that fits into a room corner.  I designed a straight square horn with a cutoff of about 290Hz.  At least on paper, I split the outer eleven inches of horn length in two halves, with each half against a wall of the corner.

To begin fabricating this, I cut out three squares of wafer-board and glued the three together to form a corner.  I have had the wafer-board scraps for about 10 years so it is great that I finally found a use for them.    Here is the corner with two templates:

Wafer-Board Corner For Midrange Horn With Two Templates
Wafer-Board Corner For Midrange Horn With Two Templates
I made the corner a little larger than the horn.  Using the bilaterally symmetrical flare template on the left, I marked and cut two ribs from 7/8" board scraps that I retrieved from a "free wood" dumpster at a local lumber yard a couple of days ago.  I always check this dumpster whenever I purchase anything at this lumber yard.

Here is what the central core of the horn looks like in its approximate position in the assembly:


Midrange Central Core In Approximate Position In Corner
Midrange Central Core In Approximate Position In Corner
Here is the corner turned on one of its sides with a side flare template in position:


Side Flare Template In Position On Corner Side Wall
Side Flare Template In Position On Corner Side Wall
Here is another view looking onto one of the "Wall Half-Horns":

Another View Of One Side Wall Half-Horn Close Up
Another View Of One Side Wall Half-Horn Close Up

After cutting eight side flare ribs, I will be ready to attach them to the corner side walls and bend the panels for the side flares that will join the corner side wall with the central core flare pictured above.

At least in theory, I should be able to fit the throat portion of the horn in two vertical halves set into the vertex of the corner.  This would be my first horn with two drivers.

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