Australian Jack Stack

[NeilD321]

Hi Folks,

I found BFM on the net a couple of weeks ago and immediatley ordered a bunch of plans. So I thought I'd introduce myself and show a few pictures of my first build.

I'm starting off with a stack of Jack 12s. 4 to be precise. 2 for our bass player and two as PA tops (until I build some DR200s and Titan 39s).

I have purchased 2 Eminence 2012s for the bass player, but have pulled 2 Celestion Rock Drivers out of a cab I currently have for the the other 2 Jacks. No idea how they will sound because finding a spec sheet on these drivers is impossible as they were produced by Celestion exculsively for Hughes and Kettner and they wont release the specs. None the less, I'm going to shove them in and just see what happens. If they really are terrible I'll save up and grab some more Eminence speakers and swap them over.

Please be nice, I'm a newby at this. I've already learnt an enourmous amount just by reading through many of the threads and hope to learn a lot more.

[NeilD321]

Glueing up the baffle and throat plates

[NeilD321]

Waiting for the glue to dry and brilliantly glueing them to the floor because of the weird glue I've never used before. Man that stuff expands everywhere. Big lesson learnt here!!!

[Jon Barnhardt]

Set wax paper underneath them to guard from gluing them to the floor. But you probably already learned that

[NeilD321]

Adding mouth plates

[spongebob1981]

Bass cabs tend to have the nasty way of blowing up drivers not suited for them (tuning, that is). If I were you, I would'nt risk it. If I had no use for such rare drivers, I'd ebay'em out and get the good Eminence stuff.

[jswingchun]

Bass cabs tend to have the nasty way of blowing up drivers not suited for them (tuning, that is). If I were you, I would'nt risk it. If I had no use for such rare drivers, I'd ebay'em out and get the good Eminence stuff.

You make a valid point, but he did say he was going to use the celestion drivers in the PA jacks, not the bass cabs.

If you are going to use them, make sure the bolt holes in the celestion drivers line up so when you decide to swap out to the eminence drivers you don't have to mess around with the baffle. It's not as big a deal as it would be in a sub, but still worth checking.

[NeilD321]

Thanks for the feedback guys.

jswingchun is correct, I'm only using them in the PAs and wont be driving them hard.
The good thing is I'll have a direct comparison as one of the bass cabs will have a switchable melded array in it so they can come straight back out if it all goes pear shaped.
The cab they are in wasn't expensive so I doubt I'd get much for them, hence this trial.

[NeilD321]

Forgot to mention that my next build is 2 XF12s so the Celestions could well end up in one of those.

[spongebob1981]

Don't you love when you actually get to use the old gear you refused to sell just in case some need arises?

I like what jswingchun added, just in case =)

I'm building a couple of J12s myself. Wished I'd seen your pic on clamping the 45deg pieces in the throat before. Mine were not bad but not great either; but only because spent a lot of time sizing them up just right.
Bookmarking for next time ...

[NeilD321]

Thanks,

those 45 degree blocks actually have a V cut out in the middle of them so they sit over corners and allow a 45 degree clamp. You can just make this out in the pics. I made four of them a while back. Very useful clamping caul for all of 10 cents worth of timber

Tested the fit of the Celestions and they are EXACTLY the same as the 2012s in size and hole placement so replacing them if neccessary will be a sinch. Yay!

Here are the next shots...

[rogerc]

I put a pair of guitar speakers in my PA Jacks as I was impatient to hear what they sounded like. They were dreadful!! So I saved up for a pair of Deltalite 2512. They now sound excellent!!

Roger

[NeilD321]

Has anybody else noticed how easy it is to accidentally build wind (twist) into the cab using Bill's method? I.e. Attach the bottom, attach the top THEN attach the sides.

I'm a fairly experienced hobbist cab builder but as it's my first BFM build I followed the instructions to the letter (I think) and one of my cabs has about 2mm of wind in it. Nobody but me will notice, but it's not square

Wondering if anybody has a good tip for attaching the top square to the bottom before adding the sides?

In hindsight I think I'd attach the bottom then, once the glue is dry, temporarily attach the top. Trim the mouth plates then attach the top and sides at the same time and square the whole thing up before the glue sets.

[BoostFab]

it helps to keep everything in line with the use of a square guide to brace the panel down while the glue dries

[rogerc]

I had the same issue with my Jacks. In the end I constructed the shell base and both sides and braced the sides square to the base with temporary battens. That way it was easier for me to then fit the baffle and horn throat and the horn mouth panels could be planed to be an exact fit within the shell. It made the fitting of the braces a bit tricky but I'd rather spend a little more effort here that have an out of square cab. The only other solution I could think of was to build a substantial jig to hold the various parts in place but it wasn't worth the effort fo just a couple of cabs.

Roger