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In the Forum: Horn-Loaded Speakers
In the Thread: Midbass Horns and Real Estate.

Post Subject: 13-step programPosted by jessie.dazzle on: 9/5/2009

Though I have difficulties warming to the idea of the "headphone" arrangement for these horns, I do understand that we are talking about loading the room. Similar thinking lead me to consider setting large horns behind the listener in my own longish room... An arrangement that would have probably required something like the proposed Maturation Shields, if not to let the wave mature, then to mask the point of origin of the upper frequencies coming from those horns. Regarding these shields : When used in such close proximity to the horn's mouth, my intuition is that they may subject the exiting wave to a somewhat violent "birth"; I might first attempt a measure of validation by mocking up a pair of mini-maturation shields placed in front of the existing upper-bass horns (I understand that this is comparing apples to oranges, and that the output from a 115Hz horn would be A LOT more affected by such an addition, but it might still be informative if keeping to material that solicits the horn's lower octave).

For outdoor horns, here's a rough, off the top o' my head way I might aproach construction:

1) Design the horn so that it seals to the ground (uses the ground as its lower "wall" or surface)

2) Calculate the sections at 6-inche intervals

3) For each horn, pour a concrete slab large enough to accommodate the "footprint" of the horn as seen when viewing the house from a helicopter

4) From sheets of plywood, cut sections about 3/8 inch inside the line given by the calculation

5) On the concrete slab, set up sections with correct 6-inch spacing

6) Use a nail gun to attach thin wooden lath strips to the sections, leaving as few gaps as possible.

7) Optional : Using a hand-held disk sander fitted with a coarse grit pad, knock down all high spots on the outer surface of the wooden strips (the outer surface of these strips will leave their impression on the inside of your horn, so it pays to be neat)

8) Cover the wooden strips with Visqueen (or some such heavy plastic film), using a staple gun and tape (clear poly tape would be fine) to hold it in place

9) Apply a first layer of (your choice) concrete or Plasticrete. Plasticrete is the way to go if there's any chance you will at some future date want to move the horns (in this case you will need to apply a releasing agent to the plastic film)

10) In the case of concrete, once the first layer has set up (should be at least 1 inch thick), cover the form with 1/4 inch rebar, arranged as a loose-fitting grid (4-6 inch squares. It can be sloppy; you won't see it)

11) Continue building up until desired thickness is attained, finishing off the exterior as desired

12) In the case of Plasticrete, add ribbing (see images of my own 40Hz horns) by laminating spacers between layers

13) Remove all materials from inside of horn

jd*

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