audio-talk

Thought I would plagiarise Mark's thread, as this is a long project ( hopefully not as long as Marks )

I am building a new pair of midrange horns, but this time I have got for an elliptical one to get better vertical integration. I have had the definition of the horns for a number of years curtesy of JMLC who gave me a spreadsheet. After a few years of wondering how to make them, I decided to CNC them. So about 18 months ago I started building a CNC router, with a bed big enough to machine the 200hz horns. After commissioning the machine and learning how to write Gcode, I started the horns.....

Decided to machine them in slices and glue them together, using a watermark aproach machining in 1mm steps for the inner and 2mm steps for the outer. Here's some pictures of how far I have got .....

Very impressive Steve... building a cnc router too, wow !!

Thanks Steve, The aim is to have them finished for the next Owston meet. The next sections start to get big and have a re-enterant feature so there will be some hand shaping too as I only have 3 axis. Widest point is about 800mm, so reckon I will need a couple of sheets more of birch ply.

Phwwwwwwwwworrrrrrraraaaaa(h)!

Bonkers and ace at the same time. Respect.

Nice one !
I wondered what you were up to.
Something good about the title too....
Reminds me I must talk to Chris V about how his mate down South is doing with some elliptical JMLC's , they are probably a bit smaller , maybe 350 or 400Hz.

Done a bit more machining and gluing. On the final leg now. Just got the ears to do. Had to get into more complex machining to get the re-entering features. Changed to a ball nose cutter which gives a better surface finish.

Now you've got me confused. What's with the ears ?

The bits that go on the top and bottom of the horn, another 250mm of material to add.

Something like this...

Ah yes, of course. Makes more sense when the full top/bottom flanges are there.
What Hz is the little one ?
Wondering about trying the Radian 745Be on a small elliptical some time, around 700Hz to 1000Hz exp.

Finished matching and gluing all the sections together now. Next step involves a Japanese rasp... got to decide if I want wood finish of a lacquered finish, if later need to use glass fibre tissue and gel coat.
Was hoping to get a room at the Scalford show but out of luck will have to audition them at Owston instead,

Phwoaaaaaaaaaaaaaar (etc!).

Outstanding work!

vinylnvalves wrote: ↑Sat Jan 20, 2018 6:40 pm ...if later need to use glass fibre tissue and gel coat.

If you're talking about polyester gel coat I wouldn't go there; it's quite viscous and it'll be really hard to get a smooth finish. Personally I would use some glass or carbon tissue wetted out with low viscosity epoxy, something like this;

https://www.bucks-composites.com/produc ... -cure-time

I've use it for finishing model boat hulls (and mould plugs) and if you remove all the excess resin you can get a paint like finish.

Thanks for the info on the finishing epoxy, yes this probably what I meant, coloured gel goats do allow you to sand and buff it to a mirror finish though, without needing to spray it. Have some bits of tissue and epoxy left over that I might practice with first.

Good lord.