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CornScala project....Updated Pics 6/29!!!


jorjen

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Found a local cabinet shop with a CNC router to do the motorbaoards. He charged me $100.00 for four motorboards. That includes setup/labor, material and tax....not bad imo.

I am laminating two 5/8" motorboards together for a nice, healthy mounting. Also, the ones on the right have smaller holes(back piece) and the ones on the left have larger holes(front piece). That takes care of the recess for the woofer to be completely flush so it will not interfere with the Cornwall type grilles I will be making. All drivers will be front mounted. This is going to be a split cabinet similar in appearance to an Altec Model 19. Not sure what I am going to veneer them in yet. May do Rosewood or Ebony with black grilles or possibly Cherry with brown grilles like the Cornwall's I rebuilt.

post-9114-1381929536077_thumb.jpg

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Test fit with a spare K-33-P....

The top sections will ultimately consist of Bob's tweeter and Al's Trachorn. Two piece grille, fit like the Cornwall with Jubilee pie slices in the upper outside corner of the top section grille.

post-9114-1381929536367_thumb.jpg

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Meagain,

It is basically Bob's driver test box with a couple small changes. OD 24"x24"x24". Ever so slightly less interior volume than Bob's due to ID 22.5"x22.5"x22.25". This was due to a change of plans in the baffle design after I cut all my other material. Bob's internal volume is/was about 6.56 ft. or so I believe. Therefore, the decreased cabinet volume of my box still falls perfectly within the Cornwall cabinet range. These are very similar in size to the La Scala bass bin. The finished product will be about the same size as a La Scala, just a bit taller. There will be a 1" riser/collar between the upper and lower cabinets.

Ranjith....Thanks for the comments. I will keep updating this thread with pics as I go along.

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VERY COOL man, that is one stout looking baby!. I too like the idea of 'split cornscalas'. I see that's a double motorboard, very cool.

Do you use any jigs or clamps when you're assembling boxes? I see a pneumatic nail/staple gun there- that must speed things along nicely. You must be acquiring some good woodworking skills and tools by now. It seems you go from idea to prototype in like a week- very proficient Jordan!

Good to see you on the mend man. Tough go there last week.

Michael

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Jordan,

Great craftsmanship as always from you. But I'm kind of lost in this. How are you or bob or? going to make a single ported woofer cabinet K-33 mate with the trachorn and Bob's tweeter efficiency wise? What will the end efficiency be?

What is a K-33P

Craig

Glad to see your Knee deep in audio projects again!!

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J - Thanks for the size info.

I still contend the a "SPLIT" CornScala would be an answer to those of us struggling with a center channel for Khorns/LaScalas for HT. Bass bin on bottom, horns over the tv. In my case, I want a bass bin the depth of a Cornwall as that would better match the depth of gear/TV, but folks tell me the volume wouldn't be right. :( Frustrating.

J - Why the riser between sections? Aesthetics for you? Or to gain a bit more height so the horn section is a bit more in line with ear level? I can't wait to see more pics and how you'll handle the crossover, etc. You are smart to make a split version. IMO.

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Michael,

No jigs, which kind of makes it a PITA. But, the air nailer helps keep the situation well in hand. Jigs would speed the process without a doubt. This project is absolutely helping me feel better after the recent events. Day by day! Thanks man!

Craig,

Thanks for the kudos buddy! Have not gotten as far as efficiency, xo's, level matching, alignment, etc. as of yet, that will come later. Should be similar enough to the Cornwall that it won't be too bad. The only substantial difference would be the Trachorn. I am going to use the same drivers. The K-33-P's came stock in my '75 Belles(another project awaiting my attention). I have not done a search to see who the "P" manufacturer was. Thanks again pard.

Rick,

I AM kicking around the possibility of making my own horn. I will be using some K-400's that I have for awhile, so that would allow me time to build my own. Alot of work, we will see if I am up to it. Thanks Rick.

Meagain,

Aesthetics mostly. I have always Loved the look. "B" style Khorns, Altec model 14's & 19's and so on.

Deano,

Sorry man. John just told me lastnight(you know how kids are)that you called the night before. I will call you tonight!

Mark,

Thanks. I will.

Oh almost forgot. Here is the drawing I did for the cabinet guy and his CNC machine....

post-9114-1381929537066_thumb.jpg

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Great work. Also great to see another one fall into the Cornscala camp. I didn't look back after I built my set. Out the door with the Cornwalls and the La Scalas.

I hope one day to hear Bob's test box or one like this. I do believe the K33 starves for a larger volume than what the cornwall has. However, the characteristic sound would change with increase in volume. I assume you used a 9" shelf for the port? If so, then there is slightly more volume in your port vs the Cornwall port. You internal width of your port is 22.5 inches and the Cornwall one is 22.25 inches. This slight increase with yours may make it just right with your slight increase in cabinet volume. If it sounds anything like Bob's...you should be pleased. I've heard good reports.

Seems ironic that the Cornwall is wider than your box but has a port width less than yours.....this is due to the Cornwall's side support panels within the port.

Nice idea with the dual panel motorboard. Is this gonna be a Decorator? With the CNC cut holes...will be nice.

I too built my Cornscalas with the intent to place a Trachorn in them. I had a thread on it and I have the motorboard cut out for it. Just never got around to doing it. Looks like someone beat me to it.

The network setup should be easy. Just similar to the Cornwalls. however, with you expensive midhorn, you may want a fancier network. ESN's?

Keep the pics coming. This is what makes this forum great.

jc

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Here is a little tidbit for those of you doing the CNC thing on motorboards. I had to work this out last night, so might as well share. This is untested, but the math works, so it should be right.

OK, getting the screw holes right for the K-33 or CW1526 is a bit if a hassel so, if you are getting it done on a CNC router, should be easy to program the holes in. Here is what the CNC program should need.

The spec for the holes is: 8 holes equally spaced on a 14.562 diameter circle. The spec is more precise than I can measure it if your CAD program can allow entry like that. That works out to a distance of 5.573 inches between adjacent hole centers.

Another way to state the hole spacing is a hole every 45 degrees spaced 7.281 inches from the center. Hope I have covered the options on this. I don't know how your program allows data to be entered.

Bob Crites

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Bob:

Will be doing your CAD probably late this evening at the shop. Hope to cut all the panels over the weekend - I know you will like the MDO. I will share some pics here of the motorboard once it is cut. Assembly should occur next week.

Chris

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