BR928 Posted February 13, 2011 Share Posted February 13, 2011 I have been lurking on the forum on and off for years with special interest the the custom speaker builds. I have been building speakers since the 70’s when I build a set of K-Horn clones from some planes that were published by EV in the 50’s. If I recall, those bass bins had close to 80 pieces in them. My last build was about 8 years ago with some la scala bass bins, EV511B/Atlas squawkers, EV T35 tweeters and ALK Universal crossovers. The bass response was lacking so I augmented that with a RSW 15 subwoofer. That filled it in nicely. These speakers weigh a ton. I moved them once for a party and swore I would never move them again! A friend of mine recently rekindled my interest in new building project. Naturally I came back here for some inspiration. After reading the forum for days the most promising seemed to be the Cornscala configuration with a wooden tractrix horn. The hardest part was the tractrix horn so I started there. Using the forum, I found ALK’s trachorn.exe program to calculate the dimensions. I decided to go with a mouth of 7” x 20” and 1” driver since that seemed to be one of his proven standard horns. After looking at the others construction technique, I decided I would try something a little different. I have a CNC router. I cut the pieces for la scala I build with this 8 years ago. Using the ability of the CNC to cut in 3D, I cut the top and bottom plates with a dado to accept the flared sides. By placing the top and bottom plates on the CNC at the proper angle, cutting the compound angles is eliminated. By using the 3D cutting ability, the round to square transition piece between the driver and mouth was made. At this time I discovered that the exit of the Atlas PD-5VH & the EV K-55 drivers were ¾” and not 1”. The throat of the K-400 and the adaptor for my 511B horns are also ¾”. To use one of these drivers I would have to make a round to square adaptor almost 2 ¾” thick or redesign the horn from scratch. A suggestion to use a true 1” driver was taken and I bought the JBL 2426H. The next step is the bass bin. I like the Cornscala idea if I can get good bass response from it. The consensus on this forum says it will. I want to keep these as small as possible, for a large speaker, so I want to stay away from the split design. By staying with the original Cornwall dimensions, or close to it, I can mount the tractrix horn lens through the cabinet and mount the driver externally. The round to square transition piece of the horn would actually be part of the rear wall of the enclosure. If the speaker does not need to be flush against the wall I see no problem with this approach. Quote Link to comment Share on other sites More sharing options...
BR928 Posted February 13, 2011 Author Share Posted February 13, 2011 pic2 Quote Link to comment Share on other sites More sharing options...
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Guest David H Posted February 13, 2011 Share Posted February 13, 2011 Very nice, Keep up the fine work. I am anxious to see the rest of your build. Dave Quote Link to comment Share on other sites More sharing options...
BR928 Posted February 13, 2011 Author Share Posted February 13, 2011 Thanks Dave. I remember discussing this technique with you early on. Quote Link to comment Share on other sites More sharing options...
BR928 Posted February 16, 2011 Author Share Posted February 16, 2011 After chatting with a few people I have decided to stay with a standard Cornwall II enclosure with a slotted port. To get the wooden tractrix to fit inside I will have to make the enclosure about 3/8" deeper. That would add about 300cu in to the internal volume. The horn probably will take up that much more space so I figure it's about a wash. How critical is it to keep the original volume? Quote Link to comment Share on other sites More sharing options...
Johnny's Jill Posted February 16, 2011 Share Posted February 16, 2011 After chatting with a few people I have decided to stay with a standard Cornwall II enclosure with a slotted port. To get the wooden tractrix to fit inside I will have to make the enclosure about 3/8" deeper. That would add about 300cu in to the internal volume. The horn probably will take up that much more space so I figure it's about a wash. How critical is it to keep the original volume? It's a good idea to keep the internal volume close.Sweet horns. Craig 73 Quote Link to comment Share on other sites More sharing options...
TheEvan Posted February 17, 2011 Share Posted February 17, 2011 Amazing-looking horn! Keep us updated. Can I see & hear them when you finish? Did you build the Universals yourself? Nice to see another Red-Sticker here. Quote Link to comment Share on other sites More sharing options...
TheEvan Posted February 17, 2011 Share Posted February 17, 2011 Wait...Baton Rouge, a 928, home-built Klipschorns. I'm betting we know each other. That you, Stan? Quote Link to comment Share on other sites More sharing options...
BR928 Posted February 17, 2011 Author Share Posted February 17, 2011 Another Sherlock Holmes! Very good Evan. You can listen any time you want. Quote Link to comment Share on other sites More sharing options...
BR928 Posted April 11, 2011 Author Share Posted April 11, 2011 I am ready to build my Cornscala enclosures. I have downloaded many versions of Cornscala enclosures. Each one has somewhat different internal volume, port volume and port opening. Using a K-33E or CW1526 what should the internal volume of the enclosure be? Most have around 6.5 cu ft. What should the port volume be? Most have around 650-715 cu in. What should the port opening be? Most have around 48.7-49 sq. in. Tuned to 30- 40 Hz? How critical are the dimensions and what side should you err on? Quote Link to comment Share on other sites More sharing options...
bigrfish Posted April 17, 2011 Share Posted April 17, 2011 I am ready to build my Cornscala enclosures. I have downloaded many versions of Cornscala enclosures. Each one has somewhat different internal volume, port volume and port opening. Using a K-33E or CW1526 what should the internal volume of the enclosure be? Most have around 6.5 cu ft. What should the port volume be? Most have around 650-715 cu in. What should the port opening be? Most have around 48.7-49 sq. in. Tuned to 30- 40 Hz? How critical are the dimensions and what side should you err on? I inherited (by way of a mutually-beneficial trade) the CigarBum's CornScala cabinets and learned a lot about the genre in a short time. After mulling it over a great deal, I have about decided that if I ever built some myself, I would pattern them after the work of Dr. Cullison with his Double Bass Bin, corner ported, slightly pointy-in-the-back Cornscala design. With it you get positional latitudes, solid bass that is both room-filling and chest-thumping, less distortion in the bass, and the novelty factor is way cool. Quote Link to comment Share on other sites More sharing options...
moray james Posted April 17, 2011 Share Posted April 17, 2011 interesting, do you have links to the good Doctors work? Best regards Moray James. Quote Link to comment Share on other sites More sharing options...
BR928 Posted May 7, 2011 Author Share Posted May 7, 2011 I received my ALK crossovers so now the ball is back in my court. I finalized the design and was able to cut the parts for the enclosure out today. It may be next week before I can start assembling them. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted May 7, 2011 Share Posted May 7, 2011 How critical is it to keep the original volume? you can change the shelf length to compensate for volume variations. there are numerous on line vent port calculators. Quote Link to comment Share on other sites More sharing options...
tomlang Posted May 8, 2011 Share Posted May 8, 2011 Nice work. Am I seeing screws holding the wood panel to the spoilboard? Are the parts now loose or did you leave "tabs" to cut manually? Will this have a "curved" front? Quote Link to comment Share on other sites More sharing options...
BR928 Posted May 8, 2011 Author Share Posted May 8, 2011 Nice work. Am I seeing screws holding the wood panel to the spoilboard? Are the parts now loose or did you leave "tabs" to cut manually? Will this have a "curved" front? The sheet was screwed to the spoilboard. The larger pieces that that I could not put holes in were just cut free. Smaller pieces that the dust collector would pick up were cut with tabs to hold in place. The front will be curved that the grill cloth will follow. Quote Link to comment Share on other sites More sharing options...
Crossman Posted May 8, 2011 Share Posted May 8, 2011 Very nice build. I have two questions if you don't mind - 1. Which CNC system do you use? 2. The curved sides of the horn appear to be oak plywood or oak veneer covered and not bendable plywood. What exactly are they made of and how did you bend them? Thanks, Quote Link to comment Share on other sites More sharing options...
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