Another DIY Ribbon thread

[babblefish]

I've been reading with great interest the information on this thread (all 55 pages ) - thanks to all who have contributed. One re-occuring question is where to get aluminum foil that is thin enough to be useful and I think I may have found an unlikely source. Firstly, I found a "house" brand of kitchen foil here in the States sold under the "Target" brand name. I measured it's thickness to be 0.0005" with my Mitutoyo digital caliper. Fairly thin, but maybe not thin enough. Recently, while shopping at a discount store, I came across several unknown brands of aluminum kitchen foil and noticed that one 25 sq/ft roll (12"/30.48cm wide x 8.33 yards/761.7cm long) felt unusually light so I bought a roll on a whim. When I got it home, I found that indeed it was very light - lighter than the "Target" brand plus it was too thin to measure with my digital caliper. I cannot imagine using this stuff for anything in the kitchen as it seems too thin to be of any use. I have a machinist friend that I'm going to ask to measure the foil for me and will post his findings.

I'm going to try and build a 6" maybe 8" long tweeter using this foil and will "corrigate" it with a jig that uses gears from a radio control toy car:

Tamiya P/N 50794, (Tower Hobbies - Radio Control ( R/C or RC ) Cars, Trucks, Airplanes, Boats and Helicopters)

The big gear is 21 mm wide which should be enough for anything I plan to make.
I've already ordered some N45 magnets for this project. I'm hoping my DIY tweeter will at least come close to the Aurum Cantus G1 which uses what appears to be a 6" ribbon and is rated for a Freq. range of 900-40K Hz and a SPL of 102.0 dB 2.83V/1m with a minimum suggested x-over of 2,000 Hz.

[brunob]

There is a relative simple way to measure the foil thickness using a ruler and a small scale.
Cut about a 1 m long 30 cm wide alu foil. Fold it and weight it using a scale with a 1 gr or better precision.
The surface S of the piece of foil is 30 x 100 = 3000 cm2
The volume V of the piece of foil is equal to its weight in gr divided by 2.7 , which is the density of aluminium.
In our example, the weight is 8 gr.
The volume V is then 8/2.7 = 3 cm3.

We have now V and S. The thickness is then V/S: 3 / 3000 = 0.001 cm = 0.00001 m = 10 microns


When I was in the US, I bought foil at different places. The thinner alu foil I found was at the dollar store (brand was "Utra foil"). Thickness was about 9 to 10 microns.

Bruno

[tinitus]

Managed to get on with it

[a.wayne]

Ahhh, errr, what is it , tinny ? .....

[tinitus]

Baffle for a 8mm x 170mm ribbon

Not a well planned project, just some parts I had around

[tinitus]

A bit more work

[Audiofanatic]

Cute !



Audiofanatic

[brunob]

I am trying to reproduce the FEMM simulation that dhenryp has posted at the beginning of this thread (2nd post). A question to FEMM users: How can I specify the magnet thickness?
dhenryp used magnets that are .25 X .5 X 1.75", N40 Neodymium. The thickness is .5" and I don t see how to enter this parameter in the program.

Bruno


FEMM link: Finite Element Method Magnetics: HomePage

[båndsei]

You only need 2 sizes.Not length.

[brunob]

Here are the pictures of my first ribbon tweeter.

I have three versions:
1) without steel bars
2) two steel bars on the side of the magnets
3) four steel bars (loop).

Bruno