2x Jack 12 Lite build

Post your build odyssey here.
Message
Author
User avatar
Strange Kevin
Posts: 161
Joined: Fri May 19, 2017 3:02 pm
Location: Scottsdale AZ

Re: 2x Jack 12 Lite build

#16 Post by Strange Kevin »

Asumming the hols in the baffle are correct,
I'd probably just drill through the spacer in the same place, as it shouldn't interfere with your driver gasket. (You may want to check to be safe)

You can move the holes a little if you want, they are there to vent the rear chamber into the small triangle space in the top and bottom parts of the horn, effectively making the rear chamber larger.
Authorized Builder - Phoenix AZ.
Main Rig - 6 DR200s - 6 T48s (30")
SLA Pros for the smaller stuff.

User avatar
Tom Smit
Posts: 7457
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: 2x Jack 12 Lite build

#17 Post by Tom Smit »

fender3x wrote: Sun Oct 30, 2022 11:20 am Going back to the plans, the holes are in the right place. So I am guessing the ring is the culprit. In the plans, 4 of the straight edges are 5" long, making the other 4 about 5.66" long. Mine are symetric, so they are all about 5.33 in length. I am guessing this is what made the difference?

I cut mine on a chop saw with the blade at 45 degrees. I measured to get the cut line to be 1" from the hole in the narrowest spot on all 8 sides. This produced a symmetrical octagon with the narrow points all exactly the same distance from the circle. I thought I was very clever for doing this...until the holes did not line up.


Option #2 is to remove a little material from the ring so that hole in obstructed. This would be pretty easy to do with the table router, and there should still be 1" or more of ring at every point of the circle, so plenty of ring to mount the speaker on.
Use option #2 since it is the easiest. Also, the dimension is supposed to be 7/8", which would reduce the outside ring diameter by a 1/4". I verified it by using the measuring tape on the Sketchup file.
TomS

User avatar
fender3x
Posts: 647
Joined: Mon May 15, 2006 11:51 am
Location: miami

Re: 2x Jack 12 Lite build

#18 Post by fender3x »

Strange Kevin wrote: Sun Oct 30, 2022 7:15 pm You can move the holes a little if you want, they are there to vent the rear chamber into the small triangle space in the top and bottom parts of the horn, effectively making the rear chamber larger.
That's what I thought, but wanted to be sure. Thanks!
Tom Smit wrote: Sun Oct 30, 2022 8:57 pm Use option #2 since it is the easiest. Also, the dimension is supposed to be 7/8", which would reduce the outside ring diameter by a 1/4". I verified it by using the measuring tape on the Sketchup file.
Sounds like you have the full version of Sketchup. It seems the PC version of Sketchup Viewer does not have tape measure. If you have nothing to do, it would be interesting to use the measure to see if the hole location is correct. In the plans is says 3 5/8" from the lateral edge of the baffle, and 2.5" from the bottom/top. Just eyeballing, the first measurement looks about right, and would put the center of the hole abut 1/2" from where the side sheath joins the baffle. But eyballing sketchup viewer it looks like the center of the holes is about exactly 2" from the top/bottom of the baffle rather than 2.5." The duct is 1.5" and over that is the top/bottom of the duct which is 1/4". The bottom of the vent hole is right on top of the duct top/bottom...which would put the center at 2".

Will most likely put the a new hole closer to the sketchup location so that the chamber is adequately vented. Easy enough to plug the old holes and re-drill. But out of curiousity, is is really necessary to plug the old holes? If all they are doing is venting the chamber, does it matter whether the old holes are open or closed?
One man's magic is another man's engineering. --Heinlein

1 x DR250
1 x T39
1 x Omni 10

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: 2x Jack 12 Lite build

#19 Post by Bill Fitzmaurice »

Leave them open. I use Sketchup Make 2017, which is full featured and should be free here: https://sketchup-make-2017-64-bit.apponic.com/

User avatar
fender3x
Posts: 647
Joined: Mon May 15, 2006 11:51 am
Location: miami

Re: 2x Jack 12 Lite build

#20 Post by fender3x »

Bill Fitzmaurice wrote: Mon Oct 31, 2022 11:54 am Leave them open. I use Sketchup Make 2017, which is full featured and should be free here: https://sketchup-make-2017-64-bit.apponic.com/
Thank you for the advice and link. Downloading now ;-)
One man's magic is another man's engineering. --Heinlein

1 x DR250
1 x T39
1 x Omni 10

User avatar
Tom Smit
Posts: 7457
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: 2x Jack 12 Lite build

#21 Post by Tom Smit »

Bill Fitzmaurice wrote: Mon Oct 31, 2022 11:54 am Leave them open. I use Sketchup Make 2017, which is full featured and should be free here: https://sketchup-make-2017-64-bit.apponic.com/
That is what I have, using Ubuntu OS and WINE.
TomS

User avatar
fender3x
Posts: 647
Joined: Mon May 15, 2006 11:51 am
Location: miami

Re: 2x Jack 12 Lite build

#22 Post by fender3x »

It's hard to get BB plywood here, but a few years ago I was able to get some, which I received in roughly 2'x4' panels. Since then my one-and-only source has dried up, so I am trying to be careful with my cuts to make what I have go as far as possible. I have the pieces mapped out more or less on my panels. Accordingly, I got both baffles and one of the backs out of one 2x4 panel. Since I had one back, I decided to cut the 2nd one as well. The rest of that 2nd panel, a piece about 23" x 30", got used to make horn braces. To waste as little material as possible, I decided to make them with a router. I was able to use the template to trace 12 braces. I cut these out, very roughly, with a jigsaw. Stuck the template on the cut out pieces and cut them out with a small table router.

Here's the stack of braces so far ;-)
12_horn_braces.png
Getting as much as possible cut out before opening the PL... Not sure if the next thing will be cutting out more panels or cutting out the horn duct top/bottom. I have a piece of 1/4" BB that is about the right dimensions to get two out. Curious how others have cut the curves on these pieces?
One man's magic is another man's engineering. --Heinlein

1 x DR250
1 x T39
1 x Omni 10

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: 2x Jack 12 Lite build

#23 Post by Bill Fitzmaurice »

I used the method shown in the plans. :roll:

User avatar
fender3x
Posts: 647
Joined: Mon May 15, 2006 11:51 am
Location: miami

Re: 2x Jack 12 Lite build

#24 Post by fender3x »

Ha! That makes sense. I did read the plans. I have a pretty good circle cutting jig on the router, so I thought I might give that a try. If it turns out to be more trouble than it's worth, I'll probably jerry-rig a rotary tool to work as makeshift drum sander, since I don't have a real one ;-)
One man's magic is another man's engineering. --Heinlein

1 x DR250
1 x T39
1 x Omni 10

User avatar
Tom Smit
Posts: 7457
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: 2x Jack 12 Lite build

#25 Post by Tom Smit »

Bill was implying that it is best to build as you go, cutting each panel to final size to fit the current position. Cutting all panels ahead may cause problems because of the possibility that something may be "off" in the build.
TomS

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: 2x Jack 12 Lite build

#26 Post by Bill Fitzmaurice »

I was stating that there are proven methods in the plans for cutting the various parts, proven because I used these methods myself to construct the prototypes. They're not the only possible methods, but I can testify that they work.

User avatar
fender3x
Posts: 647
Joined: Mon May 15, 2006 11:51 am
Location: miami

Re: 2x Jack 12 Lite build

#27 Post by fender3x »

Both points are well taken. The risk is on me. Case in point, I tried *my* approach to making the duct top/bottom last night with a router and a circle cutting jig. It worked, but was probably more trouble than it was worth, and not clearly better than the proven method. ...But now that I have the piece, it occurs to me that it might not be difficult to replicate it on the router table, which worked pretty well with the horn braces. Then again, as Tom suggests, maybe it won't fit that well. I won't know until I get to that point in the build, so I probably won't try to cut any more until I get to that point.

BTW, with the large panels, the only ones I have cut so far are the backs. I cut them a little bigger than I expect them to be in the end. My precision is such that I have had exactly the problem that Tom mentions. So the panels I cut before I need them are a 1/2" bigger or so than I need them.

I try to follow the plans religiously with regard to materials and dimensions. I also try not to deviate from proven methods too mucy, since they are, as Bill notes, proven. If i do try a different approach, I treat it as an experiment. This was a rather low risk experiment since I had the tools out already and it didn't require much material. I'll try to report as faithfully when the experiment is a bust as when it works ;-)
One man's magic is another man's engineering. --Heinlein

1 x DR250
1 x T39
1 x Omni 10

howiez
Posts: 382
Joined: Sun Mar 16, 2014 5:23 pm
Location: Fox Valley, Wisconsin

Re: 2x Jack 12 Lite build

#28 Post by howiez »

fender3x wrote: Tue Aug 30, 2022 3:37 pm Interestingly, I only had one tweeter failure. It was fine for polarity and capacitance, but had a weak sound. Turned out to be a messed up paper cone.

Will go back and give a coat of thicker slurry to the back when I finish the 2nd array.
Same. I had one or two that were dead or quiet. When I pulled them off, paper cone was all FUBAR on both. They were off to the side or scrunched up. Maybe Friday or Monday builds LOL.

As for slurry, I gooped more on, seems fine, plenty sturdy!

User avatar
fender3x
Posts: 647
Joined: Mon May 15, 2006 11:51 am
Location: miami

Re: 2x Jack 12 Lite build

#29 Post by fender3x »

Braces.jpg
Very slow progress. I work outside, and only when I get a chance so I try to use as few tools as possible. Today was primarily the table router. I had previously cut 12 horn braces. Cut the remaining 8 today. Used the method in the plans to cut one throat sheath brace from a circle made of 1/2" radiata pine plywood that was left over from making the woofer spacers. I used it as a template to make 9 throat sheath braces from 1/4" BB. Partly this was to use less BB, and partly it's because I found cutting the horn braces pretty easy with 1/4" it wasn't necessary to rough cut the pieces with a jig saw as I would have done with 1/2" or thicker plywood. However, with the very small throat sheath braces I found the router a bit more difficult. I think this is mostly because tape I used to attach the BB to the template works better on a big piece. With the big pieces I could re-use the tape for three or four braces before replacing it. With the small pieces I found out the hard way that I could only get one or two uses from the tape. After that it did not hold firmly enough. So... to get 9 good ones (8 plus a spare) I made 12 attempts. It saved a bit of wood, and was still pretty easy.
One man's magic is another man's engineering. --Heinlein

1 x DR250
1 x T39
1 x Omni 10

User avatar
fender3x
Posts: 647
Joined: Mon May 15, 2006 11:51 am
Location: miami

Re: 2x Jack 12 Lite build

#30 Post by fender3x »

...accidental post...
One man's magic is another man's engineering. --Heinlein

1 x DR250
1 x T39
1 x Omni 10

Post Reply