Ever think of building a Cornu Spiral horn? Now you can!

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I fancy trying the micro version as i have a couple of types of 2 inch drivers. Is there a preferred range of Qts that will work best in the micro cornu?

Mondo,

I am having a blast listening to the Micro's yesterday and today - about 8 hours total now. They sound amazing considering that the sound is coming from a tiny 2 inch driver that I pulled from cheap PC speakers. There is a lot of nice bass down to about 120 Hz I would guess based on the songs that sounded nice. The Micro has the big advantage of being very easy to build as the channels are 2 in tall, the facers are relatively small, and I did the whole thing in hot melt so I did not have to wait for the front face to dry with PVA glue.

Your question of Qts for the 2 in driver: I am using what appears to be a high Qts driver (as most cheap drivers are) that resembles a Visaton FRS5. I thik Qts is of order 0.9. It works great. I think it would work well with a wide range of Qts. If you wanted to get technical, use hornresp to model a long horn, then use some math to divide that and curl it up and come up with your own design. Or just try it - the amount of effort needed to expend to actually build it is very little compared to how much effort might be required to sim and design from scratch. Do you have TS params for your 2 in drivers?

Good luck and have fun!
 
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Cal,

(maybe because it's not a folded horn, not a single horn exit opening/location, Hey ! And so flat)

The multiple horn openings on the edges combined with the flatness which permits wall mounting makes the sound unique - and special. The sound, for the lack of a better word, feels roomy - like it is coming from a much bigger speaker. This probably has to do with the reflected sound from multiple walls ceiling/floor reflections combined with the mids and highs which come from single point source which just anchors the spatial imaging right on. So you get the feeling that it is a roomy concert venue, but you are sitting in the front row because you can localize the lead vocals from the singer or the instrument players.
 
thanks XRK that answered my query perfectly. I have FRS5X (Qts 0.7), TB W2-800SL (Qts 0.25) and some random 2.25" drivers from a JVC surround box of unknown Qts. I was merely concerned that high Qts may not be a good thing, as with other horns. Glad to hear youve tried the 'less hifi' FRS5, results with the X version should be great! Thanks again.
 
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Omar Bose would be proud .. Or might seek legal action
Hey! notice that each Christmas season brings out the Full Page Newspaper adverts for the Bose Wave Radio.

Amar did not invent this, Daniel Ciesinger did - German patent, Planet10 posted It on the foam core thread. The Bose Wave radio patent is very different, as it is not a spiral. Bose does have a spiral horn patent but it is a single horn wrapped like a snail with driver located 1/3 from closed end.
 
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I am thinking of going up to a 5.25" driver. The ever popular RS-1354. Already with planet10 treatment(s). I wonder how big that would be if we kept it at 4.5" walls and did the Pentagon box?

Sounds like fun and it will make some deep sounds like the devil :devilr: :) you are still on this pentagon thing.... You should try your daisy and see which sound better.

Is there enough room in the standard cavity to fit the 5.25 driver? You might need to increase channel depth to 5 inches and then glue strips of foam core braces between the channel walls (parallel to face) every 3 inches or so to keep the radial stiffness. Otherwise, maybe build a double faced spiral for 8 horns like original, more time but lots of breathing room for drivers and you can even flip the handedness of one spiral vs the other side so each speaker contains both clockwise and counterclockwise spirals.

This thing would be only slightly bigger than your current one but take twice the work. However, you are experienced and it goes twice as fast :D
 
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Hi,
i made these drawings to ease scaling and printing.. first one is sebastian's original drawing and the other has more spiral shape. but i don't know if it has any advantages over the original, does it?
i have a pair of 3" full-ranges, may i use them for 70 cm panel or should i scale-down the layout to (3/4) 52.5 cm?
i also hope these pdfs helps to further builders..
xrk971, thanks for the bring us this project..
 

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endia,
Thanks for the drawings! Planet10 actually had made a pdf too but it is buried in the foam core thread. I have made the Cornus with both exaggerated square corners internally (the 20 inch) and also very round spirals on the micro 14 incher. The square shaped with rounded corners was devised by Daniel Ciesinger to reduce the number of cuts they had to make in the wood channels. Since we use foam core board, it is easy to make lots of cuts for a more rounded spiral. I think having the more square shape will help to filter the higher frequencies from coming out the horn. But in practice, the more square one is still quite smooth. If you really want to low pass the sound, make sharp corners.
 
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George,
Thank you for the kind words but...
Regards,
Xrk971


(there was a comma after the inventor :) )

xrk971 I am too for alternative, cheap, easy to work, having some interesting properties materials for speakers. The diy joy for never grown-up boys is the experimentation and learning, not the cash spending.

Regarding positive justification of adding front horn loading to a rear horn loaded driver and some other technical questions asked already regarding cornu multiple horn, here is a series of 3 articles where one can find a lot of relevant answers (bifurcation, equal mouths, throat size effect, rear chamber importance, horn path bending effects ect)and valuable explanations.

http://www.metaleater.narod.ru/Dinsdale_Horns_1.pdf
http://www.metaleater.narod.ru/Dinsdale_Horns_2.pdf
http://www.metaleater.narod.ru/Dinsdale_Horns_3.pdf

Planet10 has wisely noted that with cornu, the lack of baffle step effect and the “on the wall” placement, makes things easy for the bass region, but that the rear horn help should start where the unattended driver’s front radiation –frequency wise – diminishes.

I fully agree with this, but on this important point (integration of front to rear output) I guess, one has to face the complication of the added effect the vibrating large panel surface has on the overall sound.

The “big sound” effect (as I read) with these speakers reminds me of the omni’s same effect. It has to do with the increased amount of indirect sound that is emitted and reaches our ears. This adds "space" to the music (I like it)

I can’t wait till I put my hands on this project!

George
 
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George,
Thanks for the three articles on horn theory and design - very helpful info. I have always wondered if it was the big front baffle acting as a passive radiator that was contributing to the signature of the sound. I think the effect should be more pronounced with the foam core face than plywood faced variants.
Xrk971
 
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Yup.

George, I hope you get the same satisfaction.

I will. The mental exercise has started already (“while counting sheep” as you say). Thank you

George,
I have always wondered if it was the big front baffle acting as a passive radiator that was contributing to the signature of the sound. I think the effect should be more pronounced with the foam core face than plywood faced variants.
Xrk971

Xrk971,
A baffle vibrating when excited through the frame of an attached speaker motor,is nothing like the defined and predicted action of a passive radiator.
I will not use the term “chaotic” (which is not) but the vibration modes become very complex and the resulting acoustic output even more so.
I have a lot of reservations as to whether vibrating panel speakers have been developed based on true analysis rather than experimentally decided “best acoustic results” (not that I reject such an approach).
For me, a panel formed from three layers of corrugated paper (layers oriented 90d/0d/90d for structural integrity and deformation symmetry)glued together with acrylic silicon, provides the quietest reference to which I compare other panel materials/constructions.
http://www.diyaudio.com/forums/construction-tips/98834-discussion-what-materials-build-speakers-out-76.html#post2214653


Very well put,

Thank you jacco. I assume you agree on the “never grown-up” :D

George