bigdnfay Posted February 4, 2005 Author Share Posted February 4, 2005 It was stated that the air chamber is one open area. Would there be any harm in dividing it into two seperate ones? It would add extra stability to the cabinet.IMO I do agree with D-man that the mouths should be symetrical and that this was a "money no object" design. Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted February 5, 2005 Share Posted February 5, 2005 ---------------- On 2/4/2005 3:11:22 PM D-MAN wrote: Some guesswork and extrapolations based on PWK's horn designs... PWK had a preference to slightly undersize the back chambers by as much as 15-20% as discussed in his 1970's patent... DM ---------------- D-Man, You have obviously done your homework. My suggestions were just based on the one document that I had reviewed. I look forward to your design. The AES paper has a significant amount of information, but I did not make any drawings and run any calcs to determine if there is enough info to establish the engineering control that I mentioned in my email to you. If you can establish control and get the design right the first time, you will be gold. I am toying with False corners rigth now for my K-horns after I build ALK's but even ignoring the 2-way advantages of the Jubilee design, the elimination of a need for corners makes this design worth pursuing. The K-horns are really a big pain in the butt if you don't have the right room (corners plus seating position at 45 degrees to each). My time is tight, but my offer for CAD work still stands. Let me know. Chris Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 5, 2005 Share Posted February 5, 2005 Whoah, there, big guy! I'm not doing a Jubilee... I'm just blathering incessantly! Probably screwing Big DN up in his design, and he's doing all the real work. I'm waiting for HIS PLANS! DM Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 5, 2005 Share Posted February 5, 2005 Big-D, there is no reason to divide the back chamber. It would just make the cabinet heavier and displace a certain amount of back chamber volume, which you could probably use. I would avoid doing that. Why would you want to? Do you have something "sneaky" in mind? DM Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 5, 2005 Share Posted February 5, 2005 I thought of something that I forgot to mention: The diagrams do not show any bracing in the horn channels, which I think that at least a horizontal brace along each side "inner" horn channel would be advised. One per side ought to work fine, especially for 3/4" ply. DM Quote Link to comment Share on other sites More sharing options...
bigdnfay Posted February 5, 2005 Author Share Posted February 5, 2005 If I don't seperate the chambers, how about dividing the horn from mouth of the motorboard to the 3 inch turn towards the rear of the cabinet. I don't see any seperation in the last leg of the horn, just vibration dampers. D-man you have a PM. Big D Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 10, 2005 Share Posted February 10, 2005 bigd, I was just reading an article. by Bruce Edgar, "The Monolith Horn" which may cast some light on that rear corner you were initially concerned with. Volvotreter is a great resource site, check it out. Go to downloads and scroll down to "The Monolith Horn". Rick Quote Link to comment Share on other sites More sharing options...
Marvel Posted February 10, 2005 Share Posted February 10, 2005 Rick, I'm glad someone else her likes Eric's site as much as I do. I've messed with his spreadsheet of tractrix horns quite a bit. He used to have a link to some mid horns built out of a solid block of wood. Needed a band saw with a huge throat though. Only four saw cuts. Neat stuff -- plus he likes Volvos! Marvel Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 10, 2005 Share Posted February 10, 2005 "Neat stuff -- plus he likes Volvos!" Nobody's perfect. Rick Quote Link to comment Share on other sites More sharing options...
bigdnfay Posted February 10, 2005 Author Share Posted February 10, 2005 3d-Thanks for the info. looking forward to the read. Big D Quote Link to comment Share on other sites More sharing options...
Colin Posted February 10, 2005 Share Posted February 10, 2005 ya better start posting pics... Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 14, 2005 Share Posted February 14, 2005 I am just postulating here, but I don't see where there is much difference here...I could be wrong, but... DM Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 14, 2005 Share Posted February 14, 2005 Some more musings...see what MS Paint and boredom leads to?! DM Quote Link to comment Share on other sites More sharing options...
bigdnfay Posted February 15, 2005 Author Share Posted February 15, 2005 I took 3D's advice and read the Bruce Edgar article "The Monolith Horn". It really shed some light on my question. The bends work as diagonal reflectors,hence the narrowing of the turn.The bend in the Jubilee is about 48 degrees,but still effective enough to allow the wavefront to reflect off of the first diagonal reflector to the second reflector with no backward traveling waves. The picture(fig.6)in the article only shows a 90 degree turn. By using a mirror image, it makes a 180 degree bend which is what I think PWK intended. Obviously PWK knew what he was doing.Who am I to question? So it will be built "as is". Once the 2-dimensional model is finished, I'll use a laser pointer and a few small mirrors to check the bends. Sorry about the diagram. Another question. Has anyone had any experience with a B&C DE-900 drivers. This may be a possible candidate for the HF. Big D Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 15, 2005 Share Posted February 15, 2005 I also read that. Apparently appropriate for "reconstituting" smaller wavelengths, but what about the larger (lower) ones? I don't know. However, the "4 horn" corner fold validates the design as being effective AND maintaining an expansion all the way. I agree that it IS a good design. I would think that people would want to modify their Khorns to use this approach, too... One of the ramifications of squeezing the channel will increase the reactance at the throat to a degree. On the other hand, it is interesting that the La Scala/Belle has unmodified 90 deg. corners (which is "unusual" to say the least), and they also put out alot of upper-bass frequencies. This could be due to the single 90 deg. fold and a very short horn length, though. But it too could be modified in the same way towards the same end. DM Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted February 15, 2005 Share Posted February 15, 2005 ---------------- On 2/15/2005 12:25:11 AM bigdnfay wrote: I took 3D's advice and read the Bruce Edgar article "The Monolith Horn".... ---------------- I have been reading an interview with Edgar that is posted on Volvoteer's website. Two points of interest: 1) Edgar builds all of his horns out of MDF because he says that plywood resonates. He learned this long after PWK had been using plywood. Will you be using plywood of particle? I am building false corners and want to use Maple plywood (part will be exposed), but I can use particle and veneer with tigerwood if necessary. 2) Edgar's "ultimate speaker" was actually a four way. He recommends what is essentially a horn subwoofer, horn bass, swuaker and tweeter, all horn loaded. The reason is that the woofer can either be in a corner and function well for low bass, to the detriment of mid-bass, or moved out into the room a few feet to help the mid-bass but to the determinent of the low bass. Comments? Chris Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 15, 2005 Share Posted February 15, 2005 The work that I was interested in concerning horn folding technique was evidently done by Huygen, and was referenced in the Edgar article, the only place that I've seen it. I did not see a bibliography on it, though, but I'd like to find it and check it out. {edit} found a bunch of stuff on the internet; Dutch mathematician, wave propogation. I think Edgars' choice of wood is at least partially dependent on the type of horns he is making and how much he pays for it (the MDF). It is not good overall horn-making advice. It is well know that MDF does NOT take edge screws very "nicely". For simple box-like horns, it's probably fine, but for the more complicated structures requiring lots of edge screws, it should not be used, IMO. DM Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted February 15, 2005 Share Posted February 15, 2005 ---------------- On 2/15/2005 3:22:03 PM D-MAN wrote: The work that I was interested in concerning horn folding technique was evidently done by Huygen, and was referenced in the Edgar article, the only place that I've seen it. I did not see a bibliography on it, though, but I'd like to find it and check it out. I think Edgars' choice of wood is at least partially dependent on the type of horns he is making and how much he pays for it (the MDF). It is not good overall horn-making advice. It is well know that MDF does NOT take edge screws very "nicely". For simple box-like horns, it's probably fine, but for the more complicated structures requiring lots of edge screws, it should not be used, IMO. DM ---------------- He stated that the reason is doe dampening purposes. Plywood tends to resonate while part MDF is "dead". Because every structure has a natural frequency, my guess would be that the linearity of the fibers in plywood make it more readily resonate (hit its natural frequency) at bass notes in music. Plywood is going to be much easier to construct my false wall out of (and cheaper - $32 for a sheet of maple vs $24 for MDF + the cost of the tigerwood veneer and the hassle of veneering). As far as the edge screws, I can use wood glue and L Brackets on the inside (although this would be imparcticle for teh Jubilee build). Of course predrilling pilot holes and countersink pits helps too for edge screws. Chris Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 15, 2005 Share Posted February 15, 2005 Chris, the notion that the random fibers in MDF are less prone to vibration might be true, but consider that in the case of plywood, each ply layer is alternately layed 90 deg. grain pattern "out" from the previous ply, which would also cancel vibration as long as you have at least 4 plys worth, I would guess. The more plys the better, so 5-7 ply is about as good as anything else. Granted 1/2" ply is probably not the best choice, but a 13 ply 3/4" is pretty vibration resistant. Plywood is also more bendable under a load and will support much more weight than MDF by weight/size. I prefer plywood in anything that I build, and your blades will stay sharp longer, too, compared to MDF. DM Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted February 15, 2005 Share Posted February 15, 2005 ---------------- On 2/15/2005 4:00:09 PM D-MAN wrote: Chris, the notion that the random fibers in MDF are less prone to vibration might be true, but consider that in the case of plywood, each ply layer is alternately layed 90 deg. grain pattern "out" from the previous ply, which would also cancel vibration as long as you have at least 4 plys worth, I would guess. The more plys the better, so 5-7 ply is about as good as anything else. Granted 1/2" ply is probably not the best choice, but a 13 ply 3/4" is pretty vibration resistant. Plywood is also more bendable under a load and will support much more weight than MDF by weight/size. I prefer plywood in anything that I build, and your blades will stay sharp longer, too, compared to MDF. DM ---------------- I will probably use 3/4" plywood to avoid haveing to veneer the backs. A coat of urethane over maple should look really nice. I think that the natural frequency has more to do with the length of the fibers than their orientation. I may be wrong (going off of memory from materials science classes that I took 15 years ago). In any event, I would like to build one (OK 2!) of these some day. Looks like a fun project. What is the advantage to using a 2 way speaker (limiting the crossover to one frequency)? Chris Quote Link to comment Share on other sites More sharing options...
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