In my previous post, I made mention of crazy design for a bass horn to be used as the projection screen in an HT setup. So here it is. If I am correct, this bottoms out around 27Hz. Bracing obviously not shown.
Dimentions == 96"x96"x24"
Throat Area == 144 sqin. (72x2)
Mouth Area == 16 sqft.
Taper Rate == 30"
Horn Length == 126"
Front and Side elevations.
3/4 View
Provided it doesnt collapse under its own weight, I am thinking of using a pair of Assassin 12" drivers for this. Back volume has lots of room to play with. (6 cuft as shown)
My plans on paper have this as two pieces (upper and lower) so it does not have to be build on location, but any way you slice it, its still huge.
Dimentions == 96"x96"x24"
Throat Area == 144 sqin. (72x2)
Mouth Area == 16 sqft.
Taper Rate == 30"
Horn Length == 126"
An externally hosted image should be here but it was not working when we last tested it.
Front and Side elevations.
An externally hosted image should be here but it was not working when we last tested it.
3/4 View
Provided it doesnt collapse under its own weight, I am thinking of using a pair of Assassin 12" drivers for this. Back volume has lots of room to play with. (6 cuft as shown)
My plans on paper have this as two pieces (upper and lower) so it does not have to be build on location, but any way you slice it, its still huge.
so the screen is going to be fastened to it from the top and the bottom edge will be the edge of the mouth correct?
what are you going to do about the center speaker?
reckon with a bit of fudging of dimensions to allow for the box volume you could probably mount it in the box and have it fire directly through the center of the screen
what are you going to do about the center speaker?
reckon with a bit of fudging of dimensions to allow for the box volume you could probably mount it in the box and have it fire directly through the center of the screen
That sure is a big one
I would say if you skipped that od V-shaped start of "line" - you could tilt that rearchamber and get woofers further down and get a longer loadline - that V-shape have wrong angles anyway - too steep, as far as I can see.
And I think you need a V-shape at top of the last folding
Is this both channels or will there be two of them?
I would say if you skipped that od V-shaped start of "line" - you could tilt that rearchamber and get woofers further down and get a longer loadline - that V-shape have wrong angles anyway - too steep, as far as I can see.
And I think you need a V-shape at top of the last folding
Is this both channels or will there be two of them?
I did that with three horns and three JBL 2242H 18's.
It is good.
It is good.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The angles should be correct. They cut the volume in half over a distance of 30 inches. The 12" woofer sits over a 9.6" hole, which give is a throat area of 72 sqin. (which matches the combined area at the bottom of each side of the ^) and a compression ratio near 1.5:1.tinitus said:
I totally forgot to put the reflectors in the upper corners and the top center. Will have to fix. Thanks!
TWO!?Is this both channels or will there be two of them?
Getting my wife to let me build one will be difficult enough. I plan to drive it from a bridged amp, fed by the sub-outs on my HT receiver.
Tehrasha,
Nifty project! I have an idea which may improve room coupling since your horn is a compromised horn with small mouth. You are going to have a 6x8 foot projection screen right? The 2x8 foot horn output at the bottom will be clear of obstacles?
OK. Try to visualize a large triangle shaped flat sheet horn extension (like a raised stage) intercepting the bottom of the screen at the output port, the full width of the port. The stage would be supported on spindle risers 2 feet up from the floor. The pointy edge of the 'stage' faces the audience. This extra slab ought to enhance the LF coupling to the room in this case, I'm thinking an equilateral triangle plate 8 feet on a side. This would double the horn mouth size to 32 sq, ft. while adding a little to the effective path length as well.
If your screen takes up most of the wall then this would be all I would do. If your room is truly huge and you have seceral feet on each side of this screen to the side walls then perhaps putting flares out from each side of the present horn mouth to meet the side walls of the room would provide another matching improvement.
Nifty project! I have an idea which may improve room coupling since your horn is a compromised horn with small mouth. You are going to have a 6x8 foot projection screen right? The 2x8 foot horn output at the bottom will be clear of obstacles?
OK. Try to visualize a large triangle shaped flat sheet horn extension (like a raised stage) intercepting the bottom of the screen at the output port, the full width of the port. The stage would be supported on spindle risers 2 feet up from the floor. The pointy edge of the 'stage' faces the audience. This extra slab ought to enhance the LF coupling to the room in this case, I'm thinking an equilateral triangle plate 8 feet on a side. This would double the horn mouth size to 32 sq, ft. while adding a little to the effective path length as well.
If your screen takes up most of the wall then this would be all I would do. If your room is truly huge and you have seceral feet on each side of this screen to the side walls then perhaps putting flares out from each side of the present horn mouth to meet the side walls of the room would provide another matching improvement.
rcavictim said:
You mean, like the listening audience?
I dont have quite -that- much room.
Im actually considering redrawing it a bit thinner so it would act as a wall between rooms. Then I could use wall studs on both sides to reinforce the horn, and simply vent it into the room near the floor.
Tehrasha,
I have a large finished recreation room downstairs which is the full length by half the width of the house. I placed a 6x8 foot screen on one end and built a large set of custom fitted 50 Hz front horns, one on each side. I lost my pictures in a HD crash so cannot show just now. The horns are front loaded Selenium 12CO1P coaxials with a total cabinet depth of 5 feet. Horn mouth is 28" and height is as close to the ceiling as possible, about 7 feet. I was inspired by someone who posted on the web how he had sawn an Altec 210 VOT cabinet basically in two halves. I can appreciate what you are attempting to do!
I have a large finished recreation room downstairs which is the full length by half the width of the house. I placed a 6x8 foot screen on one end and built a large set of custom fitted 50 Hz front horns, one on each side. I lost my pictures in a HD crash so cannot show just now. The horns are front loaded Selenium 12CO1P coaxials with a total cabinet depth of 5 feet. Horn mouth is 28" and height is as close to the ceiling as possible, about 7 feet. I was inspired by someone who posted on the web how he had sawn an Altec 210 VOT cabinet basically in two halves. I can appreciate what you are attempting to do!
Miraculously I was able to recover my pictures recently off that old pooched HD. Here is a picture of one of my large front horns as it was almost at the stage of completion. I don't want to steal any thinder here so I'll perhaps set up another thread with pics and post a link here.
Attachments
Tehrasha,
I can't see those pics you linked.
I'm no horn expert, and don't quite know how much space you have, but I suspect behind a HT screen you could fit in something which could get down lower. The mouth area is larger than mine, but the axial length is less. If you try a longer horn you should get down to 20 Hz without allowing for room gain and the corner extension effect.
I found this helpful in going from hornresp to a model:
http://www.users.bigpond.net.au/ggoodacre/centauri/diy/hornfold.html
I can't see those pics you linked.
I'm no horn expert, and don't quite know how much space you have, but I suspect behind a HT screen you could fit in something which could get down lower. The mouth area is larger than mine, but the axial length is less. If you try a longer horn you should get down to 20 Hz without allowing for room gain and the corner extension effect.
I found this helpful in going from hornresp to a model:
http://www.users.bigpond.net.au/ggoodacre/centauri/diy/hornfold.html
Paul,
You caught my ISP during a maintainance cycle. Web and Mail was down for a few hours. Try looking again.
I chose the 30" (27hz) taper rate becuase it made for easy math and an easy to cut layout. All of the folds occur at 6", 12", 24", etc... and it makes very efficient use of standard 4'x8' sheets of plywood. I'm sure I can make it longer in the space provided, but it will give me alot of odd cuts.
I have even toyed with the idea using thinner wood so I can bend the horn into smooth curves, then backfilling with plascrete (concrete with styrofoam beads as agrigate) to eliminate vibration and resonance.
Thanks for the AutoCAD link for horn folding, it will be most helpful!
You caught my ISP during a maintainance cycle. Web and Mail was down for a few hours. Try looking again.
I chose the 30" (27hz) taper rate becuase it made for easy math and an easy to cut layout. All of the folds occur at 6", 12", 24", etc... and it makes very efficient use of standard 4'x8' sheets of plywood. I'm sure I can make it longer in the space provided, but it will give me alot of odd cuts.
I have even toyed with the idea using thinner wood so I can bend the horn into smooth curves, then backfilling with plascrete (concrete with styrofoam beads as agrigate) to eliminate vibration and resonance.
Thanks for the AutoCAD link for horn folding, it will be most helpful!
Hi,
what experience is there to predict the number of octaves that can be expected from a low frequency horn (not folded).
Starting @ 50Hz upto 100 Hz (one octave) or upto 200Hz (two octaves) or even more? three octaves or four octaves?
If the starting frequency and flare rate are dropped down to 20Hz, can we expect the same number of octaves before the horn starts to lose it's effect?
How much restriction in the wide band performance can be expected due to folding the horn compared to straight?
what experience is there to predict the number of octaves that can be expected from a low frequency horn (not folded).
Starting @ 50Hz upto 100 Hz (one octave) or upto 200Hz (two octaves) or even more? three octaves or four octaves?
If the starting frequency and flare rate are dropped down to 20Hz, can we expect the same number of octaves before the horn starts to lose it's effect?
How much restriction in the wide band performance can be expected due to folding the horn compared to straight?
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