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21" plans ? anybody got any good ones

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basenote View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote basenote Quote  Post ReplyReply Direct Link To This Post Topic: 21" plans ? anybody got any good ones
    Posted: 13 April 2007 at 8:57am
im about to embark on a journey of passion
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heathrow_B_line Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2007 at 2:00pm
Hi there
 
Have you looked here....
 
 
There should be some good ones there!
Produce a killer sound. Take no prisoners.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote djstefanos Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2007 at 2:23pm
haha
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Post Options Post Options   Thanks (0) Thanks(0)   Quote moray james Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2007 at 11:14pm
A typical 21 inch driver has an Sd of 0.1764 M2 while a 15 inch driver has an Sd of 0.0856, double that value and you get an Sd of 0.1712. So it would figure that a folded horn for two 15 inch drivers would be about right for a single 21 inch driver assuming that the driver T/S values are about equal. There are lots of dual 15 inch horn designs that should be applicable for a single 21 inch unit.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote moray james Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2007 at 10:36pm
Take a look here for some dual 15 inch bass horn designs.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote basenote Quote  Post ReplyReply Direct Link To This Post Posted: 23 April 2007 at 2:35pm
i'm to much of a rookie for the stuff i just want'ed a plan ready made and easy to put into action i have only had a few forays into the build world and i was hoping to come across something simple i may just have to go for the super scooper desgin

scoop chat on here gets amazinly heated
hell hath no fury like a bass junkie without the plan he desires
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Post Options Post Options   Thanks (0) Thanks(0)   Quote moray james Quote  Post ReplyReply Direct Link To This Post Posted: 23 April 2007 at 6:35pm
Well regardless of what 21 inch design you find you will have to find out what driver was to make the design and so find out the T/S numbers of that driver if you want to substitute another brand of your choice. After that you build the box as designed but you cut for a single 21 inch driver rather than two 15 inch units. Unless I am way off base there should be no issues. If any of the guys out there with more experience than me can find a major problem with my assessment  of the situation you should be just fine.  This would get you a lot closer than trying to figure out the whole thing from scratch on your own. Build one up and see what you think about it. It won't be bad and you will get to learn something at the same time. Key parameters will be driver Fs, Qts and Le depending upon how high up you want to cross over. I would imagine that as a sub box that Le will not be an issue in this application.
   Rog pointed out (else where) that this type of design is really just a big vent reflex design (BVR) and as such should be fairly forgiving of driver values just so long as you are close.  Once built you can play with the back cavity volume (add solid fill to make it smaller) and the throat size (use strapping to make it smaller). You should be able to fine tune it to what you want just playing with those two variables. Regards Moray James.

   Next best option would be to rent something that you like for a night then open it up and copy it. Not the classiest thing to do but it will get you where you want to be as fast and as inexpensively as you can.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote moray james Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2007 at 9:22pm
I just discussed this idea with someone who has eperience with cabinets like this and was advised that it would probably be better to scale an 18 inch cabinet design up by three inches overall. Ther are a number of 18" designs atound to choose from. Also you might consider Rog's 21" Super Scooper design (I forgot about it) which ought to give you lots of room to play with with what ever drivers you might consider. I have not searched but I would be surprised if there were not a bunch of threads on Rog's Super Scooper design with respect to driver selection. Hope this is useful informaion. Regards Moray James.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CHAMPION Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2007 at 12:46pm
Just had an idea, reading all this Mini 18" scoop business
 
Can you make a Mini  21" Super scoop version ??
 
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tekasis Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2007 at 12:55pm
One of the members did, which then made them the size of a standard 18'' scoops.
 
 
or do you actually mean as short as the 18'' mini scoops ? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CHAMPION Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2007 at 3:07pm
I mean a 21" mini scoop !!
 
i have 2x PD2150 driver, i would rather make a smaller scoop because of it size and weight and i dont play too much dub roots music


Edited by CHAMPION - 17 May 2007 at 3:08pm
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