Okay, here's a bunch of pics.
Inside dimensions of the compression chamber are 13.5 cm wide x 17.8 cm high x 6.5 cm deep. The vent opening dimensions are 13.5 x 4.5 cm.
The internal layout of the baffles are that the first length is 8.5 inches down from the top of the vent. Then up 20.5 inches to the top of the speaker, then down 48 inches to the bottom, giving a total horn length of 77 inches. The port cutouts at the bottom of the speaker are the same dimension as the base of the speaker. Mine was 382 sq. cm., or 191 sq. cm each.
The forumla for figuring the area of a triangle is height x width x .433. Ex: A triangle with a base width of 8 cm and a height of 8 cm would be (8x8) x .433 = 27.71 sq. cm.
Pic #1: The compression chamber and vent opening
Inside dimensions of the compression chamber are 13.5 cm wide x 17.8 cm high x 6.5 cm deep. The vent opening dimensions are 13.5 x 4.5 cm.
The internal layout of the baffles are that the first length is 8.5 inches down from the top of the vent. Then up 20.5 inches to the top of the speaker, then down 48 inches to the bottom, giving a total horn length of 77 inches. The port cutouts at the bottom of the speaker are the same dimension as the base of the speaker. Mine was 382 sq. cm., or 191 sq. cm each.
The forumla for figuring the area of a triangle is height x width x .433. Ex: A triangle with a base width of 8 cm and a height of 8 cm would be (8x8) x .433 = 27.71 sq. cm.
Pic #1: The compression chamber and vent opening
Attachments
Pic #2: The first baffle.
The small triangular hole at the top must be heavily stuffed and sealed. I think ultimately using expanding foam will work the best. The top of the compression chamber and vent hole must extend deep enough to touch the back of this baffle. It's pretty obvious when building this part.
The small triangular hole at the top must be heavily stuffed and sealed. I think ultimately using expanding foam will work the best. The top of the compression chamber and vent hole must extend deep enough to touch the back of this baffle. It's pretty obvious when building this part.
Attachments
Pic #4: The back ready to go on.
Notice how the second baffle stops short of the top. It's width is exactly half the distance between the first baffle and the back of the speaker. How far short of the top you make this determines the line area necessary to keep an expanding horn.
Notice how the second baffle stops short of the top. It's width is exactly half the distance between the first baffle and the back of the speaker. How far short of the top you make this determines the line area necessary to keep an expanding horn.
Attachments
Some thoughts so far:
This will not be easy to build in wood. I would strongly advise doing this first out of foam. Build it so the blue side is facing out. The tape seems to release better from that surface when you want to take something apart. Most of the parts in prototype #3 are from the pieces of prototype #1.
Minimum tools needed are a straightedge, two spring clamps, a square, a long sharp knife (I use an Olfa retractable with breakaway tips, works perfectly), hot melt glue (lots), masking tape, and something to measure with.
Helpful tools: Two large 45 degree angles to clamp to the large baffles while building. If you can find a knife that cuts at a 45 degree angle, I would love to hear about it. I think with wood, I would cut the baffles to size and then use a router with a 45 degree chamfer bit. Much easier than trying to cut compound angles.
This is a true expanding horn. There are no parallel surfaces.
I have used 2.5 sheets of foam for five prototypes, and I can take all these apart and reuse the pieces. I have only thrown away one small bag of scraps so far. My costs so far are about $45 US.
Thanks for reading this far. I've had great fun. Maybe this will ultimately work out as a viable design. I think it's to the point where others can start playing with it. Thanks for everyone's help, encouragement, and input.
Doug
This will not be easy to build in wood. I would strongly advise doing this first out of foam. Build it so the blue side is facing out. The tape seems to release better from that surface when you want to take something apart. Most of the parts in prototype #3 are from the pieces of prototype #1.
Minimum tools needed are a straightedge, two spring clamps, a square, a long sharp knife (I use an Olfa retractable with breakaway tips, works perfectly), hot melt glue (lots), masking tape, and something to measure with.
Helpful tools: Two large 45 degree angles to clamp to the large baffles while building. If you can find a knife that cuts at a 45 degree angle, I would love to hear about it. I think with wood, I would cut the baffles to size and then use a router with a 45 degree chamfer bit. Much easier than trying to cut compound angles.
This is a true expanding horn. There are no parallel surfaces.
I have used 2.5 sheets of foam for five prototypes, and I can take all these apart and reuse the pieces. I have only thrown away one small bag of scraps so far. My costs so far are about $45 US.
Thanks for reading this far. I've had great fun. Maybe this will ultimately work out as a viable design. I think it's to the point where others can start playing with it. Thanks for everyone's help, encouragement, and input.
Doug
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