One of the problems with scaling these spiral horns is that, for optimal performance with a given driver, you need to do more than just scale all the dimensions. The good news is that it is easy to design your own custom spiral horn.
1. Use Hornresp to design a back-loaded horn using your driver of choice. You can use whichever horn profile that gives you the response you want - parabolic, conical, exponential, even multi-segment.
2. Work out how deep the horn will need to be. It has to be:
- deep enough to mount the driver
- The right depth to provide the correct rear chamber volume.
- shallow enough so that the throat opening of the horn path(s) is not too narrow - a tiny slit won't work well.
3. You can estimate how big the enclosure will be at this time. Hornresp will tell you the volume of the horn. This will (approximately) be the volume of the final enclosure. Divide by the depth, the result will be the area of the front/rear panels. For a square enclosure, the square root of this area will be the side dimensions. If you don't like the answer, back to the drawing board...
4. Export the horn dimensions. By default, it will export a horn that flares in both width and height. In the export menu, go down either the height or width column and set all the values to your desired depth value. The values in the other column will automatically adjust.
5. Decide how many horn paths you want (one, two, 3, 4 etc).
6. On a large piece of paper, draw a circle corresponding to the diameter of the central chamber.
7. Draw mark(s) on the circle at the point(s) where the horn spiral(s) will start. If more than one, space them evenly around the circle.
8. If you are doing a multi-path horn, divide the dimensions from step 3 by the number of paths. (If a segment point is 5 cm wide, and you are doing a 4 path horn, each path will have a width of 1.25 cm at that point.)
9. Using the width versus length dimensions, start drawing the spiral(s). You'll need to adjust the angle of the inner wall of the first part of the spiral(s) so that they become the outer wall(s) of the next spiral(s). This will make the central chamber slightly larger in area, so you may need to move your inner starting marks in slightly to average out the difference.
10. Continue drawing the spirals, plotting the dimensions every couple of centimetres of length. You can "join the dots" with straight lines if you keep the length increments short, but you'll find it easy to "freehand" draw nice curves. If you're doing a multi-path horn, "sync up" the dimensions every 90 degrees or so in case of accumulated measuring errors. Remember to allow for wall thickness, especially in the inner (narrow) parts of the spiral.
11. When you get to the mouth(s), draw an enclosure shape around the whole thing (for example, a square box around a 4-path horn) and blend the final curve so it fits a side of the enclosure.
1. Use Hornresp to design a back-loaded horn using your driver of choice. You can use whichever horn profile that gives you the response you want - parabolic, conical, exponential, even multi-segment.
2. Work out how deep the horn will need to be. It has to be:
- deep enough to mount the driver
- The right depth to provide the correct rear chamber volume.
- shallow enough so that the throat opening of the horn path(s) is not too narrow - a tiny slit won't work well.
3. You can estimate how big the enclosure will be at this time. Hornresp will tell you the volume of the horn. This will (approximately) be the volume of the final enclosure. Divide by the depth, the result will be the area of the front/rear panels. For a square enclosure, the square root of this area will be the side dimensions. If you don't like the answer, back to the drawing board...
4. Export the horn dimensions. By default, it will export a horn that flares in both width and height. In the export menu, go down either the height or width column and set all the values to your desired depth value. The values in the other column will automatically adjust.
5. Decide how many horn paths you want (one, two, 3, 4 etc).
6. On a large piece of paper, draw a circle corresponding to the diameter of the central chamber.
7. Draw mark(s) on the circle at the point(s) where the horn spiral(s) will start. If more than one, space them evenly around the circle.
8. If you are doing a multi-path horn, divide the dimensions from step 3 by the number of paths. (If a segment point is 5 cm wide, and you are doing a 4 path horn, each path will have a width of 1.25 cm at that point.)
9. Using the width versus length dimensions, start drawing the spiral(s). You'll need to adjust the angle of the inner wall of the first part of the spiral(s) so that they become the outer wall(s) of the next spiral(s). This will make the central chamber slightly larger in area, so you may need to move your inner starting marks in slightly to average out the difference.
10. Continue drawing the spirals, plotting the dimensions every couple of centimetres of length. You can "join the dots" with straight lines if you keep the length increments short, but you'll find it easy to "freehand" draw nice curves. If you're doing a multi-path horn, "sync up" the dimensions every 90 degrees or so in case of accumulated measuring errors. Remember to allow for wall thickness, especially in the inner (narrow) parts of the spiral.
11. When you get to the mouth(s), draw an enclosure shape around the whole thing (for example, a square box around a 4-path horn) and blend the final curve so it fits a side of the enclosure.
Don,
Thanks for the design sequence! We can all run off and see what we come up with using our Favorite driver. One thing we have notice is that the driver choice and exact spiral dimensions are not so big a deal. The cornucopya is very forgiving. I just figured out how to model an arbitrary spiral in Solidworks... But I still think hand drawing is best way to get going on new designs.
Thanks for the design sequence! We can all run off and see what we come up with using our Favorite driver. One thing we have notice is that the driver choice and exact spiral dimensions are not so big a deal. The cornucopya is very forgiving. I just figured out how to model an arbitrary spiral in Solidworks... But I still think hand drawing is best way to get going on new designs.
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What will you name the thread? I think we can start it off with a summary howto and cool photos.
Ken Peter,
Thanks for the tip! This could just be made into a circle with driver pointed into circle plane and directed out to perimeter. This is good as waveguide but doesn't have long path unless made big in diameter. Nonetheless, gives me ideas.... How did your Smith Horn sound?
Regards,
Xrk971
Thanks for the tip! This could just be made into a circle with driver pointed into circle plane and directed out to perimeter. This is good as waveguide but doesn't have long path unless made big in diameter. Nonetheless, gives me ideas.... How did your Smith Horn sound?
Regards,
Xrk971
instead of clouding up this thread with my questions on cabs, i started a new thread.
http://www.diyaudio.com/forums/mult...ng-reference-speakers-please.html#post3284246
http://www.diyaudio.com/forums/mult...ng-reference-speakers-please.html#post3284246
It depends on whether it was designed to be a full range or a tweeter. For example a 2 inch Visaton FRS5 had an fs of 180 Hz, so yes. But I have also seen 3 inch tweeters that wont go below 2000 Hz.
Then the Sony's are full rangers. The value of the cap and the impedance of the drivers will let you calculate the cutoff freq of the drivers as Sony had designed them for. If those are 8 ohm drivers, I think the cutoff frequency is about 200 Hz. Usually, the cutoff will be higher than what they are capable of going down to in a proper cabinet and direct driven without the cap. I see you are doing the trading sleep for speaker building.... it is about midnight in Sydney right?
http://www.parts-express.com/resources/crossover-component-selection-guide.cfm?AID=1457483&PID=3696791&SID=skim1010X497171X0de51a97ee736fa86b8d187d07c44e28
it is about midnight in Sydney right?http://www.parts-express.com/resources/crossover-component-selection-guide.cfm?AID=1457483&PID=3696791&SID=skim1010X497171X0de51a97ee736fa86b8d187d07c44e28
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Adason,
Here are the mp3 sound clips of the difference between what comes from the mini Cornucopya (20 in) for the direct driver radiation plus the horns, versus the horns only. I did this the lazy way by laying it flat on the floor face up for the combined output, and the placed it on a pillow on the floor face down to block the direct output for the horn only output. I placed the XY mic about 1.5 meters above the speakers which were spaced 1 meter apart (center to center).
Obviously, there is quite a bit of output from the horns as you can tell (there is a small rattling on the horns only clip because the hanging wire is resting on the back of the box when it is face down and I did not bother to silence it). At high volume, I can feel the pressure wave coming from the horn mouths similar to the effect you get when you place your hand at the port of a bass reflex woofer.
Hope this is convincing enough for you to build.
Enjoy.
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