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Jubilee woofer mounting info


grog_b

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i'm building a set of jubilee, and about to start on the woodwork, 

but i can't find anywhere the outside diameter and mounting hole positions of the woofer, 

does anyone have this information?

and what have people used to mount the woofers, T-nuts? i'm concerned that if a T-Nut spins or the thread gets damaged it's impossible to replace, and I've had a lot of issues with T-Nuts in the past, they seem to be made from very soft steel, 

 

thanks

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One way of doing this, I suppose, is to mount the two woofers to the body of the bass bin with wood screws but getting into the back chamber to tighten them would be a real bear.

 

So I used a motor board on which both woofers are mounted with wood screws.  I used all eight holes in each woofer.

 

Then you have a motor board which extends almost from top to bottom of the back chamber. 

 

The problem is how to mount the motor board of course.

 

I used machine screws which fit T-nuts.  This getting hard to explain without diagrams. 

 

But the heads of the machine screws are in the area of the first flare or to a dead area.

 

So I had a big washer on that side of the head of the machine screw and applied epoxy.  On the back chamber side I used T-nuts with epoxy glue to take back chamber side. 

 

That way you wind up with threaded studs protruding into the back chamber and they go through the piece which forms the back side of the initial flare.  .

 

Another issue then is to make sure that the studs and the receiving holes on the motor board line up.  I did that before starting assembly of the bass bin.  

 

Then on final assembly: The bass bin will be on its face.  You can slide the motor board with two woofer attached (and wired) over the studs until they line up and plop down on the studs.  I was worried about that if there is a misalignment the studs can pierce the woofer diaphragm.  But it turns out that is just about impossible. And then I used a washer and Nyloc nuts to secure the motor board to the studs. 

 

This latter issue is a little complicated because I had two studs located between the woofers.  This is to say an arm's length from the hatch on either end.  It is not too difficult because all you have to do is reach in to the central studs, and put on a washer, thread on the Nyloc, and then tighten with a socket wrench.

 

Another issue for me was making sure the diaphragm can't bottom out against the motor board.  My woofers did not have a thick gasket.  So glued a sheet of Masonite cut with 13 inch diameter holes to the woofer side of the motor board.

 

In summary.  Think through how all these mounting systems will work in your design and set them up before assembling the bass bin.  Use epoxy to make sure nothing can back out or become loose.

 

WMcD   

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One important thing is that a great number of the pieces have the same height.  OTOH, these must be cut to the same height.

 

So you can make some careful measurements and rip a 4 x 8 piece of plywood or two (about 39 inches?) and a lot of the precision cuts are done. 

 

WMcD

Edited by William F. Gil McDermott
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i'm building a set of jubilee, and about to start on the woodwork, 

but i can't find anywhere the outside diameter and mounting hole positions of the woofer, 

does anyone have this information?

and what have people used to mount the woofers, T-nuts? i'm concerned that if a T-Nut spins or the thread gets damaged it's impossible to replace, and I've had a lot of issues with T-Nuts in the past, they seem to be made from very soft steel, 

 

thanks

T-nut is the way to go here(or threaded inserts, I used both). If T-nuts are installed properly, they should not get damaged or spin. They are barbed and hammered into place. I use a dab of adhesive on the outside of the barrel before hammering them in place as well. If you are using 13 ply Euro(Finnish, Baltic, whatever)Birch they will never spin. Drill your holes just large enough to where the insert fits in the hole very snug as well. The thread should not get damaged either. Just be careful that you do not cross thread. Also, once the woofers are installed you will probably never remove them. So the chances of T-nuts ever being a problem are slim to none.

 

If you are using K-31's or similar, you will also need spacer rings on the front of the woofer to keep the surrounds from slapping the baffle board when mounted. I will see if I can dig up a few pics of my Jube Clone build.

 

Cut and paste this into your browser to see my entire build. If someone wants to help by creating a link, cool!

 

http://s188.photobucket.com/user/dickweee/library/modified%20klipsch%20jubilee%20build?sort=3&page=1

post-7010-0-93280000-1447992233_thumb.jp

post-7010-0-06760000-1447992257_thumb.jp

post-7010-0-93440000-1447992271_thumb.jp

post-7010-0-63720000-1447992291_thumb.jp

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Here is a page from the SK manual showing how they mount the motor board.

One drawing shows the use of a carriage bolt and another shows a regular bolt.

I used carriage bolts, they are bolts with a square neck.

https://en.wikipedia.org/wiki/Carriage_bolt

I wanted to use a t-nut in place of the jam nut. (You can't turn the carriage bolt to tighten into a t-nut on the other side of the board. SK uses that jam nut with some counter-boring.)

To replace the SK jam nut I put the t-nut upside-down on the carriage bolt so that the prongs are facing the distal end of the bolt. The t-nut is free to turn because the prongs are just in free air. Then tighten the t-nut using some pliers -- the prongs allow you to get a grip. And epoxy on the underside of the t-nut where it comes up against the board. And bend the prongs flat. You have a thin jam nut!

The result is that you've got the stud really securely mounted. The threaded part of the t-nut means the hole in the motor board has to be a bit oversize but I didn't worry.

WMcD

Page from SpeakerLab SK Manual.pdf

Edited by William F. Gil McDermott
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