Tough woodworking question.

[looneybomber]

I want to build Jed's Dynamic 4cc (mk2), but with a profile that of the Paradigm studio series. According to Jed's kit, the baffle needs to be 43" wide and 9" tall, but I'm going to have to widen it to either 48 or 50.5". Whichever the wife decides on.

Here's a profile of the studio series speakers for those not familiar with them.


And Jed's Dynamic 4T and 4cc.



The problem I'm running into is trying to get the binding posts (2 sets) and rear port(s) figured out. I want them both on the apex of that curve that way it's centered/symmetrical, but how? For the center, Jed specifies two 2" ports and for the towers, I think one 3". I can't think of any way to route out those holes.

For binding posts, I never have liked the bare posts surface mounted.
I love the simple recess on the B&W 805's and would like something similar. It's these details that give it that nice finished look.



This is, however, contingent on if I can use a CNC machine. I may have access to one, but if not, I will just go with a square box.

[dsrviola]

If you plan on building this speaker with anything other than the baffle dimensions that Jed has specified, please plan on redoing the crossover as well. The two work together.

Oh dear ops: nvm. I didin't notice that you were building a center channel. All I saw was "changing baffle size of somebody else's design" My bad.

[cjd]

Doing the port opening should be fine if you use PVC - the trick will be doing a rebate on the inside to slide the pipe into, and that could be easy or not depending very much on how you build this. Translam you can just notch a series to a square hole to match the OD of the pipe, leave ~1" uncut, drill through, insert pipe, use flush-trim bit on router to cut through to the outside.

If you use PE's mounting plates you can simply route a flat spot for them.

Neither is a specifically difficult proposition if you have the tools and patience.

[looneybomber]

Doing the port opening should be fine if you use PVC - the trick will be doing a rebate on the inside to slide the pipe into, and that could be easy or not depending very much on how you build this. Translam you can just notch a series to a square hole to match the OD of the pipe, leave ~1" uncut, drill through, insert pipe, use flush-trim bit on router to cut through to the outside.

Not doing translam. Going to make a skeleton of semi-matrix bracing, then layering on the thin, flexible sheets. Trying to get the hole(s) cut in that and then rounded 3/4" or 1" over is beyond me. I think the span will be too far for the jig/guide idea that I have.

If you use PE's mounting plates you can simply route a flat spot for them.

Neither is a specifically difficult proposition if you have the tools and patience.

I have a router, drill, and jigsaw. I may be able to get access to more tools though.

With regards to the binding post plate, it sounds like I'd have to create some kind of guide with a large flat surface that I could attach to the back of the rounded enclosure. This would give me a flat surface for the router to sit on and keep my depth constant.

I have an idea on how to get this to work, but the only thing I can think of would require me to make small drill holes into the wall of the enclosure, but not all the way through...and will be hidden under the veneer.

If I used a flat piece of ply or MDF, I could cut a square hole out of it, a little bigger than the plate. I could lay it on the apex of the box and screw down (recessed) either the top or bottom to hold it. Then use some metal supports on the four corners mounted to the enclosure wall to keep it from moving around. Attach my guides to that and yeah.

*edited and added more info*

[PMazz]

I would make a flat backed enclosure with a separate curved back piece that can be applied later.

[looneybomber]

I would make a flat backed enclosure with a separate curved back piece that can be applied later.

I thought about that and this is likely where my lack of woodworking hinders me. The only way I could see to do this is to build the box as I would normally with the curved back, cut it off somehow, then glue on a translam rear end.



The reason I say this, is because I don't know how I'd butt the lamination sheets up against a flat back board since as the sheets go around a curve, only the corners would touch the back board.

The picture (not to scale) is shown if the back of the enclosure had a 4" wide (or tall since it's a center) flat section. The remaining depth of the enclosure would then only be .75" according to my graph paper drawing of it.

[cjd]

For the port: Cut a square piece, make it ~1.5" thick (double MDF) with a hole that snugly fits the OD of your port on half. Mount it to one of your braces and shape the rest to the curve so your layers are snug right up against it. Later, drill through, use flush-trim with the port in place, apply round-over.

While this is a little bit of work, with MDF it should be do-able with a microplane or an orbital sander and 60 grit quite quickly. And it's a lot less work than trying to make a cap for the whole back.

For this, as well as flattening a spot for terminals, you'll need to have a flat-surface that fits over the speaker - you do not have to mount it with screws, though that can certainly make it simple and secure (and you can easily patch holes, I've put 1/4" holes to run wires through sealed boxes when I'm measuring, plug 'em with a dowel)

[looneybomber]

CJD, I like that method you mention, but I'm worried about my abilities to hold a router with a largish roundover. Without the entire router base against a flat surface because of that big cutout in the middle, it could be prone to tilting on me. I'll just have to get a piece of plexy and make a larger router base just for the port flaring.

...Ok, slowly the whole build process is coming together in my head.

I may even toy with the idea of making my own "race track" shaped port so that it doesn't extend towards the side (top and bottom since it's a center) of the enclosure as much. I could make that with multilayers of MDF. As it is, 2" from center will be, depth wise, .75" away from the apex. If I use a .75" roundover on a flat surface flush with the apex, it won't even touch. I do have a 1.25" roundover. Yeah, I think I'll look into this racetrack port more.

[cjd]

I would NOT try to do a perfect round-over all around, but let the flare cut short on the sides. In other words, use the same flat secure mounting you use to cut a spot for the terminals.

[looneybomber]

Yeah, that's what I was going to do. But if doing a 3" port with a .75" flare, at the edges (away from apex), I'll hardly get anything. In order to get more of a flare, if I do a 2x4" race track, I will have a similar port area and can get a little more flare on the edges.

[cjd]

It would certainly be possible to make a modified base for the router that would allow it to follow the surface, though it would still not be perfect. Add outriggers that allow it to sit flush at the deepest part - it will lift as you go around, but not nearly as much as flat.

Part of making more complex projects like this, though, is being able to make the tools you need to be safe. And that can make a project take longer than anticipated, not to mention the possibility of screw-ups.

Not sure where you would find "racetrack" tube to match such a port.

[looneybomber]

I think you're not following me all the way.

The larger router base is to sit on my flat surface that will be mounted (screwed) to the speaker. I don't want to put the router on the curved speaker wall. Without the larger base, I'm scared I won't have enough skill to keep it steady when using a roundover.

The race track port would have to be created using multiple layers (8-9 depending on length) of MDF cutout and glued together. No plastic tube used, just MDF.

Yeah, I'm trying to keep mess-ups to a minimum by not having to shoot from the hip. And, when I eventually create a complete 5.0 Dynamic MK2 setup, all the enclosures should be darn near identical.

[cjd]

Ahh, I understand now. Yeah, I use a base made up with 1/2" birch ply and a nice big handle for when I use the monster chamfer bit.

Regardless, you should be able to make a custom base (make it wide with handles on the ends) that will follow the curves much closer if you so choose.

[Martyn]

I was recently faced with the problem of mounting a 4" diameter port plus flare (making it ~6") in the back of a similarly curved cabinet. Eventually I compromised and took PMazz's way out and redesigned the cabinet with a flat back (although I didn't go on to add a separate curved piece - I just left it flat). Although this introduced some interesting new construction challenges, it had the additional benefit of increasing the internal volume (which I needed to do anyway).

I could have considered two 3" ports or even four 2" ports, but this was getting too complex and I would still have to come to terms with the strange shape of the intersection between a cylinder piercing a curved wall. Beauty is in the eye of the beholder, but I didn't feel happy with this.

You could also try adding a separate curved back and machining a flat spot on it (like Sonus Faber). I discounted this as being too much extra work...

[Biff]

Hybrid idea?

Consider building your cabinets as you want curved back and all. Then use a band saw to cut off the back as in the nice diagram instead of making it as a separate piece. You can now reapply sections above and below the flat area that carry binding posts, whatever, as a nice flat recess.

[looneybomber]

You could also try adding a separate curved back and machining a flat spot on it (like Sonus Faber). I discounted this as being too much extra work...

Oh yeah, those look nice (Cremona's), but far too much work. This will be my first speaker build and mimicking the Paradigm Studio's will be hard enough.

Speaking with the guy's wife, she said it's a 3 axis CNC machine, so I hope I can use it! I guess he's having difficulties with the software though.

[shon35us]

MDF Translam

I thought about that and this is likely where my lack of woodworking hinders me. The only way I could see to do this is to build the box as I would normally with the curved back, cut it off somehow, then glue on a translam rear end.



The reason I say this, is because I don't know how I'd butt the lamination sheets up against a flat back board since as the sheets go around a curve, only the corners would touch the back board.

The picture (not to scale) is shown if the back of the enclosure had a 4" wide (or tall since it's a center) flat section. The remaining depth of the enclosure would then only be .75" according to my graph paper drawing of it.

I was thinking of making something similar, by glue 5 pcs of 3/4" MDF and cutting them down with a band saw or a table saw, not sure if this would work?