First build - have CNC, modest budget

[momerath]

Greetings!

I'd like some advice on choosing my first project. I'd rather not spend >$500 all-told, and cheaper is better. It probably won't be my last speaker build, but I wouldn't want to be feeling the upgraditis immediately. I have a nice source (Ack! dAck!), but only a pioneer receiver as far as speaker-amps go. Full-range appeals to me conceptually; I'm into detail, and can live without deep bass. My room is ~15x12(x8), and I'll mostly be listening to instrumental post-rock (esp. strings-oriented), though I wouldn't want other genres to suffer too much from the trade-offs.

I belong to a "makerspace" with a small CNC (can handle 24"x32") and a _ton_ of other tools. My own woodworking experience is minimal, but I'll have experts on-hand. I'm not averse to a difficult/time-consuming build, and I don't mind the cabinets being sizable (huge even). My biggest concern with what I've seen so far is a lack of detailed instructions; something with .dxf and/or gcode files would be ideal.

[454Casull]

How do you have a CNC (mill?) and not know how to generate your own G-code?

Anyway, the ER18DXT build is simply (mostly) impeccable. http://www.audioheuristics.org/proje...XT/ER18DXT.htm

[momerath]

As I said, I belong to (am about to join, actually), a "makerspace." Also, I _do_ know how to generate gcode, but most of the projects I've seen out there don't even have vector-format plans.

[454Casull]

Originally Posted by momerath

As I said, I belong to (am about to join, actually), a "makerspace." Also, I _do_ know how to generate gcode, but most of the projects I've seen out there don't even have vector-format plans.

It's a little overkill for most speakers since a table saw and plunge router takes care of most work.

However, if you like, I can generate DXFs or other 3D files.

[454Casull]

Oops... just realized this was the full-range forum. Never mind my suggestion then.

[talaerts]

I cannot find the theory of the "Big Fun Horn" anymore, I remember it was on a Norwegian site. The author did calculate the expansion of the horn, and then approximated it with dividing panels in the enclosure. What you could do is use CNC'd layers of a perfectly formed cut out horn path.
There was a Japanese kit maker who offered exactly such layered kits for Fostex, but I can't find the link back. Someone else can, perhaps?
Here is a similar illustration from someone who made a Tannoy coaxial horn with CNC'd layers:

[Zen Mod]

Talaerts - is there any link for page with more information about that Tannoy horn?

[planet10]

Originally Posted by 454Casull

It's a little overkill for most speakers since a table saw and plunge router takes care of most work.

This is very true. With most speaker builds the only part that would benefit from a CNC is the rebate on the baffle, and even then, only when the driver basket is non-circular. If would also be useful for tedious jobs like holey braces.

A project that can take big advantage of the CNC are things like Frugel-Horn 3 where side panels are rebated and the rear curve done (see here for some pictures) It isn't necessary to rebate the sides, but it makes assembly a breeze. The inner panels are still best done with a tablesaw.

IMO, using a CNC to do somethinglike talaerts posted is a waste. A waste of material, a cabinet that is not as strong, the swoopy curves look cool, but theu degrade the performance suffers because the horn is better able to pass midrange which you don't want coming out of the mouth.

I can supply dxfs of any of the box designs i have drawn (will say drawn by dld), but no g-code, the CNC we have access to only speakers some weird Italian dialect.

dave

[owenhamburg]

Dear momerath,

Because people don't have a CNC milling machine typically people don't make designs for them. When I have seen speakers that use CNC techniques most show the designer had a lack of imagination for what the tools may be used for. Please remember that a speaker is also a sculpture, you will have in your house maybe for years to come.

A clone of a nice looking speaker in my opinion is here, based on transmission line design, I suspect..

For sealed speakers it would be nice to break out of the grim box like shapes of conventional speakers and look into Icosahedron based shapes. In Germany and much of northern Europe their is a tradition of filling Star Dipyramids with lights before Christmas, why not make a speaker this shape ? But why limit your self to regular geometric shapes, why not curve the edges, or use the golden ratio to the length of the points on your star?

Even if you favor boxes, and spheroidal shapes for their the lower surface area to volume ratio, you could also use the great features of CNC for other benefits, why make speakers with thick walls if you can use other approaches. In my opinion you could make a excellent project using CNC milled bracing and the speaker walls relatively small and thin (back to stars). You could even go further and allow the speaker walls to be sand filed, or even three layers thick, in Germany these days energy efficient houses have triple or even 4 layers of glass in their windows, providing heat and sound insulation.

As I started the reason people don't make CNC based designs is mostly due to not having the tool in their possession, and secondly because they don't have the skills to program a CNC system and the tooling costs for every piece a different shape may be prohibitive. For commercial speakers its all about cost. I think you have options.

Regards

Owen

[454Casull]

Originally Posted by planet10

IMO, using a CNC to do somethinglike talaerts posted is a waste. A waste of material, a cabinet that is not as strong, the swoopy curves look cool, but theu degrade the performance suffers because the horn is better able to pass midrange which you don't want coming out of the mouth.

dave

Nothing a little stuffing couldn't fix.