Same Song, New Dance: Variation on GM's Jordan ML-TL

[abpea]

Several weeks ago I built a pair of GM's Jordan JX92S ML-TL speakers and continue to be utterly amazed at the sound GM is able to get out of this design.

Soon after posting my impressions of the project on this board discussion began on how to make GM's already excellent design even better

GM's original design features a down-firing port because the box dimensions make it impossible to have a front-firing port. So part of the discussion involved developing a new cross-section that would allow the port to be mounted horizontally instead of vertically. Someone mentioned building a triangular cross-section instead of the original rectaungular.

What I came up with is a 'near triangular' trapezoidial cross-section having the same area as GM's original rectangular cross-section (see attached drawing) that would allow the port to be mounted horizonatally in the baffle.

Here are the cabinet dimensions (all dimensions are INSIDE):

L1 (see drawing) Inside width of back panel = 2.0"
L2 (see drawing) Inside width of front baffle = 6.875"
H (see drawing) Distance between L1 and L2 = 6.770"

L Inside length of cabinet = 31.04"
X0 = L*0.3590 = 11.14"
Vent = 2" x 5" (Cut vent hole 4" above inside bottom edge of cabinet on front baffle)
Stuffing = 0.54lb

I built my cabinet out of scrap 1" (3/4") clear white pine for the back and sides and used 3/4" plywood for the baffle. My drawing shows a 1" front baffle which I'll use when I build the next pair

I thought it was going to be very difficult to improve on the sound of GM's original design because it sounds incredible. However, massaging GM's original design has resulted, in my opinion, in an even better sounding design. The new cross-section definately provides more bass that seems to be tighter and more controlled. The new cabinet seems to be more revealing as well, I can hear more going on in the music, the music and the notes seem to be clearer. Overall the new speaker just seems more emotional.

Jay Fisher told me by eliminating one of the turbulent corners and some of the standing waves he thought the new design might sound a little better than the original and I think he is right.

Someone else needs to build this thing and tell me if it sounds as good as I think it does or if I need to clean my ears

Bruce

[abpea]

Here is a view of the cross-section...

[abpea]

View of the speaker...

[DIAR]

Very interesting but unfortunately impossible for me to build because of the difficult cuts. I don't have suitable gear to make such cuts. Or do I... I have to think

By the way. Have you guys though about using glass to make speaker cabinets stiffer. Epoxy would be suitable for glueing the glass to mdf boards.

[Timn8ter]

Thank you so much for testing the design. I think it makes a lot of sense and am chomping at the bit to try it myself.

I don't have suitable gear to make such cuts.

Most table saws now have the ability to angle the blade to make the angled cuts, of course the main requirement is having a table saw.

[DIAR]

About the construction. How exactly did you attach the parts together. What glue did you use and if you if you pressed the joints while the glue was drying, how did you do it. Did you use screws or dovels or something else.

What do you think. Is it ok to build an enclosure without any screws of dowels. Will the glued joints hold.

What kind of glue do you prefer: Epoxy, PVAc or polyurethane...

Edit: I usually use screws and glue. With one project the filler I added to screw holes first swell and then shrank. No few of my veneered coffee tables look awfull because of the dents above every screw. Dowels are very hard to use bacause the holes must be exactly in the right places. Epoxy would be quite good since it doesn't need much pressure while drying. Polyurethane glue will definitely fill all holes and will definitely make the encluse air tight.

[Timn8ter]

I've found that dowels are very good for helping align joints and a dowel kit helps get it right.
Dowel Kit

[abpea]

Originally posted by DIAR

"About the construction. How exactly did you attach the parts together. What glue did you use and if you if you pressed the joints while the glue was drying, how did you do it. Did you use screws or dovels or something else.

What do you think. Is it ok to build an enclosure without any screws of dowels. Will the glued joints hold.

What kind of glue do you prefer: Epoxy, PVAc or polyurethane..."


DIAR,

I have never used screws in any of my cabinets... only glue. The glue I use is plain old yellow carpenters/woodworking glue, nothing exotic and the glue joints are more than strong enough to do the job.

I have to admit building this cabinet was a little challenging. Gluing the back piece to the first side piece was easy enough to hold with three or four clamps. When I glued the second side onto the back piece there wasn't any good way to clamp it so I ended up just standing there holding the piece in place for about twenty minutes till the glue took hold . Then I braced it with some scrap wood till the next morning. I'm working on a glue jig for the next pair of cabinets I make

After the two sides were on the top, bottom and front baffle were easy, just glue and pipe clamps. If I had to use something mechanical to make a joint it would either be dowels or bisquits. I wouldn't use screws although many people do with great success. I just don't like to.

I had a lot of people over yesterday and last night to do some critical listening tests with the new speakers. I'll post a follow-up with those results shortly.

Please feel free to ask any other questions and I hope you build a pair of these speakers... the sound is astonishing!!

Bruce

[GM]

Originally posted by DIAR
Very interesting but unfortunately impossible for me to build because of the difficult cuts. I don't have suitable gear to make such cuts. Or do I... I have to think

?! What wood cutting tool(s) do you own that can't do angled cuts? Regardless, I built many a cab with other than 90deg corners using only straight cuts without screws/dowels/whatever since I found cutting them with a hand saw was way too tedious. Instead I just glued the pieces to the top/bottom, and once set, glued either square strips or dowels in the corners, finishing them to suit. This way also yields a far stronger joint, a 'big deal' in apps such as touring sound where durability is required, though internal glue blocks will accomplish the same thing if angled cuts are used.

By the way. Have you guys though about using glass to make speaker cabinets stiffer. Epoxy would be suitable for glueing the glass to mdf boards.

It has to be safety plate or tempered and quite thick if used in a LF or wide BW design. Bottom line is it has to be able to be accidently hit or dropped without cracking/shattering.

What kind of glue do you prefer: Epoxy, PVAc or polyurethane...

Early on, traditional PVA wood glue, but once construction adhesive dispensed from a caulking gun came along, it's all I've used except for when I wanted a flexible bond, then I used non-hardening construction adhesive. I used a pipe clamp or two for the long dim. and old belts or tie down straps for holding the sides together while the glue set. If I were still actively building, an air stapler and finishing nailer would be 'must have' tools.

When I wanted some design flexibility, I used pocket screws and Nema 12 rated foam insulation tape for easy assembly/disassembly. I believe they now offer a pocket screw kit that makes it a snap.

With one project the filler I added to screw holes first swell and then shrank. No few of my veneered coffee tables look awfull because of the dents above every screw.

Countersink screws at least 1/3 the material's thickness and either partially fill the holes with PVA wood glue and pack some of the sawdust in or premix the two, and build it up slightly above the surface. Once dry trim flush with a chisel. I've never had any shrinkage problems, even after ~35yrs. I haven't been so fortunate with flushed dowel plugs though.

GM

[6SN7GT]

OK, you have got me interested.

I plan on phoning Ted Jordan when he's back from holiday (14th) to find out more about these speaker units.

Can a standmount version be done ?
What I have in mind is making proper curved sides rather than a trapezoid.
It's easy to do this using 3ply glued a layer at a time over a former.
You just put the lot in a purpose made poly bag and suck out all the air with a 12V car tyre pump and leave overnight.

Problem is, I don't know whether ply is a suitable substitute to MDF, which could well make the idea a complete non-starter.