diy transducer experiments

[Fatrecco]

I got two 40x23x6mm ring-neodym magnets (realy strong!). The area in the ring are magnets. The rest is steel.

ringmagnet.jpg

transd1.jpg

t8.jpg

I got a bad frequency response. only up to 5khz

t10.jpg

The whole coil+cone+rod+spring weight about 2.35g.
Its 0.2mm wire.

Now I try thinner wire + rubbermembran instead of a spring.

Fat

[grooveguy]

Hey, Fatrecco,

Looks like you're off to a good start. Nice job winding that coil; is there clearance for it in the gap or does it rub? I would think it needs 3-point support to keep it from being angled against one side of the magnet assembly.

What are you using for a cone? Is it hollow or solid? The weight you show isn't much, but at high frequencies even a light static load is formidable. You should be able to sweep that assembly with an oscillator and determine pretty quickly what the resonance is. Response above resonance is going to drop quickly, and you'll have to use motional feedback or lots of EQ to overcome it. Best performance is probably going to be achieved with a very stiff assembly and lots of watts.

Best of luck, keep us informed, please!

[Fatrecco]

thanks,
the gap is 1.5mm. The cone is out of copy-paper which is saturated with cyanacrylat.
In my first build, I use two v-springs to avoid a rubbing coil. But I removed one of them, cause I thought it will block higher frequencies. I testet it with white noise and found no high freqs excluded of a 10khz peak. When I put single sinus signals into the transducer, I got them in the output When I play music over the transducer(with RIAA) and hear the result with a phono-amp, it sounds holow.

Try

[Bahndahn]

Hey friend,

Have you tried making the bottom-most portion aluminium? This might help saturate the flux where you want it, in that gap.

Try it our on the simulator and see if it does anything!

[EpicenterBryan]

Hey Fatrecco,
You might want to ask "Fela Borbone:" about this. He did some great simulations on the Groove Scribe thread.

Bryan

[Fela Borbone]

Hi,
You have agood start! I like westrex like suspension too! It should feel stiffer than a speaker.maybe you want to add something else to keep coils clearing the gap when in action, other spring or silicone.
Magnetic things seem ok., maybe the gap toobi g. I prefer less turns and more current,but theres lot of trade offs.
are you using cianocrilate to bond the coil? If so be avoid breathing the vapours it prodoce when heated!!
Good luck with the project!!


..and have fun!

[Fatrecco]

Thanks,


@Bahndahn: I don't understand what you mean with the aluminium in the bottom plate. The iron/steel should be nearly at the point of magnetical saturation. I think FEMM doesn't consider about saturation.

@Fela: ok I try to make it stiffer. And yes I use cyanacrylate.


fat

[opcode66]

Hey friend,

Have you tried making the bottom-most portion aluminium? This might help saturate the flux where you want it, in that gap.

Try it our on the simulator and see if it does anything!

Not quite as simple as saying aluminum bobbin.... There is a trick to it to avoid eddy currents in the aluminum that will negate high frequencies. The aluminum will fight the drive coil.

https://en.wikipedia.org/wiki/Eddy_current

[Bahndahn]

Not quite as simple as saying aluminum bobbin.... There is a trick to it to avoid eddy currents in the aluminum that will negate high frequencies. The aluminum will fight the drive coil.

https://en.wikipedia.org/wiki/Eddy_current

Copper shorting ring

[opcode66]

Even simpler