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jc's tractrix bass bin


jwc

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The top section hasn't been completly lined up. I have Crites tweeters here with the tractrix 223Hz horns and JBL 2446. I also has Gothover's fastrac la scala horns with K55's. Gonna mess with it some... will see.

I also have ALK's ESN5800 for use with 3 way setup..

Of course....the original plan was to put my K402's on there...The width of this bass bin is 45". The K402 would look good there wouldn't it? ...

jc

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I just found this, I don't know how I didn't see it before ?

That is the horn you had in your garage, wow it looks different than when I see it. I looked at it when we went through the garage, that sucker is built like a tank the way you designed the laminating is very strong and solid. It also looks bigger in person and heavy.

I do a little woodworking and I have to say you are very talented and patient with your building and designs. When I seen the way that horn was constructed I was just amazed at what you went through to get that design completed just to that point, that's alot of laminations. How did you get all of the square corners smooth like that, especially the outside, I had seen it when it was just glued together, with all the individual corners from each layer sticking out ?

Very nice work.

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Thanks guys.

The option for now is this. I haven't put the crites tweeter in there. Gothover put together the 223Hz tractrix and the "tweeter baffle". He does great work.

jc

post-16499-13819474820622_thumb.jpg

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I dig the idea of a removable rear chamber...I might borrow that idea actually. Is the motorboard removable too?

Maybe you already mentioned it, but what was the motive for using two drivers? Was it to get the horn shorter?

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The baffle isn't removeable.

OK. The use of the two drivers with K31's is the intent. Reason being...I borrowed some "knowns" with those drivers. I've read and milled over the Jubilee AES article so much that I have derived other ideas. We know the T/S of those drivers. Klipsch has used those paramenters to configue the optimal throat and the optimal cabinet size. For instance...calculating the "annul" for horn loading those drivers. OK..well, I knew the cabinet volume to annull at 38Hz for the jubilee. Well, I wanted a straight horn and I didn't want it to be 55 inches long like the jube (the physical horn length...not the cornner loaded extended length). Well, that formula for calculating the annul is changed for this design by using 80Hz instead of 38Hz. So again.....less room for error knowing these things. So the total throat is 90 sq in like the jubilee to achieve...theoretically...maximum midband efficiency.

The mass roll off of K31's..if I remember correctly...is somewhere in the upper 300's Hz. Now I could load some other 12" drivers in there that would go higher. This cabinet can also accomidate two 10" driver........I don't plan on doing that anytime soon.

Now...this is a full space horn...not 8th space. I want this to be able to get down to 80-100Hz no matter where I put it....such as sitting on top of MWM's away from a wall or corner. OR.....sitting on the floor out of a corner away from a wall and mate with a horn sub.....which is in the works right now.

So.....I'm relying on previous experiences with those drivers to give me confidence on getting this to work. As I build more stuff....I get more into the unknowns. I don't have the experience to do "everything" from complete scratch and go in with confidence on the success. I may get there someday. I have already used a dual K31's loaded on a straight horn already and was astounded with the results. So I went further with it "building on that same concept".

Yes...the horn is shorter with a larger throat. However, I could have used a large throat with one driver such as a 10 1/2 inch circle and achieved the same calculated length. I believe using a different 12" driver would have worked better for that. Such as those pro "mid-bass" drivers out there with a higher Fs and smaller VAS. Using a driver such as that.....wouldn't go "low enough" for what I'm trying to do here. I think this would be something to try but I actually have other things I would like to try before diving into that.

Building stuff like this is time consuming...so I can just take a leap and start building all those great ideas. I have to "build" on previous experiences....

This horn is 24" long and with the removeable cabinet...about 30 inches total. It will snug into the corner some as the back part of the design is only 18". The sidewalls are 1" MDF. This isn't the "bendable" MDF that you can buy. It is solid. The top and bottom is 3/4" MDF with another layered 1/4" MDF for a total of 1" there to0. The baffle is plywood.

Several coats of "outdoor primer and outdoor paint". That way...if they end up in a garage or shop....will possibly be more humidity resistent.

jc

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lol

I like how you work JC - I was just curious about the design intent as I feel that's what the final result should be compared against. The rough plans I'm drawing up right now are very similar, except I'm planning to use a single 12" driver (that B&C to be exact). The thing frustrating me now is getting the horn to load into a room corner, but I don't think it is possible to optimize without folding. I think I might end up going your route and designing for full space....does the mouth area really come out that small?

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Bentz. Have you heard any of the horns from Ramsdell Pro? I exchanged emails with them about their midbass horns. They are tractrix. The 10 and 12" have a phase plug. I thought that was interesting. Of course....none of them will go as low as what you are looking for.

http://www.ramsdellproaudio.com/products/midbasshorns/MBHs.html

The 15" 90 Hz Cut Off Horn and the 12" Phase Plug are the exact same width and height and are used in one of their speaker sytems....

http://www.ramsdellproaudio.com/products/fullrange/cph3.htm

As far as drivers.....

RCF makes a 10" driver in its own sealed chamber that will mount to a horn. You can buy the phase plug that goes with it. I thought it would be cool to build a tractrix horn and try out that driver and phase plug.....see attached....

jc

MR10N301_spec_sheet.pdf

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