Dear Speaker Builders,
I've drawn a double, over/under version of the Alfredo Horn and would like to ask if any of you see a problem with my approach. I've basically duplicated the horn vertically and adjusted the compression chamber to equal the original. The split bass path seems logical to me as it is a shorter path than a longer horn. I like this horn because it's expansion hews so closely to the Fibonacci series. But please if anyone has advice regarding this build please let me know. It's a fair bit of work to build.
Many thanks,
Jim
I've drawn a double, over/under version of the Alfredo Horn and would like to ask if any of you see a problem with my approach. I've basically duplicated the horn vertically and adjusted the compression chamber to equal the original. The split bass path seems logical to me as it is a shorter path than a longer horn. I like this horn because it's expansion hews so closely to the Fibonacci series. But please if anyone has advice regarding this build please let me know. It's a fair bit of work to build.
Many thanks,
Jim
Dividing a horn flare path into two sections should not result in a shorter horn, just two horns each having 1/2 the cross section of the original at a given distance from the throat. If the length is reduced you will have changed (raised) the tuning frequency, which is a function of axial length and expansion. The majority of horns (including this one) are not impedance matched down to F0, relying on resonant action below Fc. So length is important if you wish to preserve as much of the original tuning behaviour as possible. Keep in mind that you will also be changing the loading relative to the original design, since the horn was presumably done with an eye to the terminus having close proximity to the floor, while you may also have some differences through the changed aspect ratio.
Just considering the compression chamber, it looks to me that it is :
1) a funnel, a cone
2) symmetric
3) panels close to be parallel to the membrane
I would avoid all of the three
1) a funnel, a cone
2) symmetric
3) panels close to be parallel to the membrane
I would avoid all of the three
that arrangement will probably have benefits from just one horn branch.
In common living rooms, where ceiling is about 2.5m from floor
Because of the part of the sound wave coming from upper area.
.
Other almost same way, rationally using the space in the room is
with 2 drivers - 2 folded Voigt horns. One standing in opposite way
on another...
In common living rooms, where ceiling is about 2.5m from floor
Because of the part of the sound wave coming from upper area.
.
Other almost same way, rationally using the space in the room is
with 2 drivers - 2 folded Voigt horns. One standing in opposite way
on another...
Like Scottmoose said, if you double up the horn paths that doesn't give you the ability to cut the length in half, just the cross sectional area of each path can be reduced. If you cut it in half, a 50Hz tuned horn will now be a 100Hz tuned horn and will lack bass. Really this needs to be simulated for best results as it is rather a large investment in time and wood to build based on a doubling of the horns and halving the length. I think several packages can simulate this well, certainly Akabak can do it for 2 or more horn paths. I wouldn't worry about the shape of the comp chamber so much as you can line it with felt and it will have a wad of stuffing in there.
If you really want to build it without first simulating it, make it out of foam core and see how it sounds. At least that way you are only out of $10 of foam core and glue and an evening of your time.
I like the name Double Alfredo. "Can I get some extra whipped cream with my double Alfredo Machiato?" 🙂
If you really want to build it without first simulating it, make it out of foam core and see how it sounds. At least that way you are only out of $10 of foam core and glue and an evening of your time.
I like the name Double Alfredo. "Can I get some extra whipped cream with my double Alfredo Machiato?" 🙂
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You guys are up too late but generous to a fault as usual. Thanks for the responses and Nelson's cheer leading.
The horn length is preserved from the original design @ 1932 mm. It's measured on the attachment and I added a diagram of the Fibonacci spiral over the original. The horn length isn't much more than the Alerion horns I built but it is a bit larger volume and takes a spiraling path and I wondered how that would affect the sound. You know - the old mystical power of proportion.
And I wondered if doubling the horn would enhance the base - given that the propagation length is unchanged. Not really clear on that. But isn't that the same with all double horns - like the Spawn series?
OK so I could stuff the compression chamber - or I can reform it. I put a generic 8" speaker in the drawing to see what it looks like. I could also corrugate the sides of the chamber to break up the sound. Does it matter?
This horn would go into a large loft space with 11' ceilings. Do you think that the top horn should be reformed so that the reflector bounces the sound down? Aren't the low frequencies omni directional?
Regarding digital modeling - I suppose I will have to. Has it's predictions worked out for you guys?
The horn length is preserved from the original design @ 1932 mm. It's measured on the attachment and I added a diagram of the Fibonacci spiral over the original. The horn length isn't much more than the Alerion horns I built but it is a bit larger volume and takes a spiraling path and I wondered how that would affect the sound. You know - the old mystical power of proportion.
And I wondered if doubling the horn would enhance the base - given that the propagation length is unchanged. Not really clear on that. But isn't that the same with all double horns - like the Spawn series?
OK so I could stuff the compression chamber - or I can reform it. I put a generic 8" speaker in the drawing to see what it looks like. I could also corrugate the sides of the chamber to break up the sound. Does it matter?
This horn would go into a large loft space with 11' ceilings. Do you think that the top horn should be reformed so that the reflector bounces the sound down? Aren't the low frequencies omni directional?
Regarding digital modeling - I suppose I will have to. Has it's predictions worked out for you guys?
Simulations are quite accurate at predicting the response for the bass below 500Hz. Even the effects of baffle step losses and back walls and floor bounce can be accounted for quite well.
If length is per the original, then notwithstanding the altered aspect ratio and terminus positioning, it will in free-space behave more or less like the original. Altering the folding geometry will likely have an effect on the details of the acoustic low pass.
Up to a point -not a lot. Up to a point. This varies with specific circumstances, but with a reasonable aspect ratio approximating a Fibonacci spiral isn't likely to cause problems, though it's not likely to bring significant gains either, acoustically speaking at any rate.
If you have simply doubled the cross section of the horn, then you'll be impedance matched down to a lower frequency -whether it's optimised any longer is another question. Depends if the original was, or, to put it another way, how badly compromised the original was in the first place.
All of my double-terminus designs were developed to have that configuration from the off to best exploit it. But in a very general sense, the bigger the horn, the less compromised it can be.
Providing you understand the limitations of the software package, i.e. what it doesn't do / show, as well as what it does, then yes. It is, or can be, an extremely powerful tool. Not a panacea, but very useful.
Ah, I was not thinking to double the width of the horn but to make it a double terminus horn as you say. But the aspect ratio is a longstanding question for me. Since many horns are constructed in parallel sided boxes the throat of the horn changes aspect as it enlarges. It would be simple enough to at least vary the width of throat as it progresses so that the aspect ratio remains more constant. A Kleinhorn in a box lets say. Has this been attempted? Would the simulations show an advantage - or do you think you could hear the difference?
Nothing like being put on the spot. 😉 Only answer I can give really is 'it depends' -this is very much circumstance / design detail dependent, so generalising too far is problematic. Most simulation software does not account for issues relating to aspect ratio for instance, but practical differences can exist, and may be both measured and heard. Generally speaking, providing you don't go to extremes the effects are not overly significant, but exceptions exist.
I very much doubt anybody has tried to build a Kleinhorn in a box -if they have, I haven't heard about it anyway. Nelson's probably in a better position to know about other builds.
I very much doubt anybody has tried to build a Kleinhorn in a box -if they have, I haven't heard about it anyway. Nelson's probably in a better position to know about other builds.
This foam core KH might fit in reasonable box.
http://www.diyaudio.com/forums/pass-labs/166784-pictures-your-diy-pass-amplifier-182.html#post3438566
http://www.diyaudio.com/forums/pass-labs/166784-pictures-your-diy-pass-amplifier-182.html#post3438566
So it does appear that there is a problem with the way I set up the Double Alfredo. I understand that the two exit passages leading from the compression chamber should match the total cross sectional area of the single exit passage in the original horn. The way I set it up the double exit passages double the exit area coming out of the compression chamber. I see that in the Spawn speakers the first passage goes a short distance then splits into two somewhat smaller passages. That seems like a good way to set it up. In the attached drawings I narrowed the two exit passages but I could also reduce their area by blocking them in the third dimension. I could also reconfigure the horn path so that there is a single exit passage that splits further along its path. It looks as though Ill just have to learn the simulation software and try the build.
I built the original Alfredo horn and you say, its a good deal to build. The biggest problem for me was setting up all the cut angles. A lot of them were cut larger and sanded down close to the proper angles. Once glued up, with one side only clamped on for tuning, I opted for felt lining on the top of the main manifolds and light stuffing (about 300g) behind the speaker. Without the driver in the cab the whole thing is a little back heavy, not to mention a little narrow. Perhaps you'll do up some outriggers?
Horn speakers certainly are complicated builds. I have a cabinet shop cut the sides and guide mortises with a cnc router. That vastly simplifies the process - though it still requires cutting several fussy miters (unless one has access to a five axis machine) I've drawn the Alfredo in CAD so if anyone wants to build one they're welcome to the files. I've been working on a double mouth version in tower form for a friend. I've been putting three point outriggers on my narrow speakers. Seems to do the job. But beyond all of that how do your Alfredo's sound? I've been interested in them because the Alfredo geometry so closely follows the golden section spiral and I wondered what effect that might have. People on this site say the effect will be minimal but I wonder. What driver are you using?
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