Rerurn to Romy the Cat's Site
In the Forum: Horn-Loaded Speakers
In the Thread: Jessie Dazzle Project
Post Subject: Bass horn : Throat transition & construction.Posted by jessie.dazzle on: 7/23/2008
I've continued thinking about construction since posting my previous laser-cut hallucination (titled "Painless mid-bass horn"...).
Thinking mostly about the transition from round driver to rectangular horn...
I don't know how important it is at these sorts of frequencies, but I have an "aesthetisophical" problem with a driver firing directly into a square throat.
I would prefer a round throat that "transitions" to a rectangular section over the length of the horn. This was the main advantage offered by the laser-cut hallucination (BTW, cutting via hot wire is more appropriate when dealing with foam).
The image below shows one of what seems to be few rectangular horns where there is an attempt to make a transition from round to rectangular... You have to look deep into the dark throat of the left horn to see what I mean (these are Ulf's horns... Where are you Ulf... Did you manage to keep the girl?)
Below is a close up of the same horn with a phase plug.
I would probably bring the transition all the way out to the mouth of the horn. The horn I am conceiving will have around a 7 inch throat... My thinking is to cut a 7 inch disc and use it as a template to "drag in" the fillets over the entire length of the horn :
I just feel this is right.
Klaus wrote :
"...why you dont make it from carbonfiber on a foambase?..."
Klaus,
Thanks for the suggestion.
Maybe things have changed, but thirteen years ago I priced a roll of woven carbon fabric; at that time it cost about the same as a small car.
"...im also just working on a "surfboard" horn, but i make the bent sides with layers of depron boards and carbon..."
I have continued to think about it since posting my previous laser-cut hallucination (titled "Painless mid-bass horn"...). With the exception of your choice of carbon, what you describe in the above quote is exactly one of two possible directions I had recently been considering. The only difference being that I was going to use glass fiber (because its cheap). I sort of abandoned it because the stacked-section approach facilitates incorporating the round-to-rectangular transition; you don't have to add it after the fact.
The other idea involves making the walls of the horn as follows:
1) Bend a thin sheet of plywood to a template (corresponding to the profile/curve of the horn), and clamp it in place
2) Glue several 3-inch-thick spacer blocks to the outside surface of the plywood and let the glue set
3) Glue another sheet of plywood to the spacer blocks and let the glue set
4) Drill holes in the out side sheet of plywood (the last one attached) and inject expanding foam completely filling the space between the two sheets of plywood
5) Add fillets in corners of horn by dragging circular template (see above) over a mix of resin and the maximum dose of microballoons (http://en.wikipedia.org/wiki/Glass_microsphere)
jd*Rerurn to Romy the Cat's Site