Building a field coil FR driver

[michabass]

btw those molds will need some bleeder holes and grooves machined to hold some heaters.Next thing I would look into is:http://www.papiermache.co.uk/articles/papier-mache-paste/if you're going to make the cones out of paper, which I sincerely hope you will... now I wish I had access to a lathe myself...

[Zen Mod]

cones will be made of carbon fiber ( if I remember well)surround - leatherspider - dirt cloth :shakehands:basket - plastic reinforced with fibers

[Magura]

cones will be made of carbon fiber ( if I remember well)surround - leatherspider - dirt cloth :shakehands:basket - plastic reinforced with fibers

That's pretty much the plan for now. I may decide to use clean cloth for the spider later on, if not for other reasons, then just as an experiment.The cones could also be paper or Kevlar, as the mold is to be lined with film. For heating the molds, I'm simply going to mount an iron to each half, hence the thick block of aluminium for spreading the heat even.Magura

[andrics]

Hi For cone I use rohacell . Sounds better then fiberglass . carbon or aramid(kevlar).Making mold for thermo forming is not problrem for you .http://www.clarasonic.com/en/rohacell.php:hammer:

[Magura]

Hi Andrics,Thanks for the suggestion, I sure will try and see if I can get some of that material. To make a test should be quite easy, as the mold will actually work for thermo forming as well.Can I see the drivers you've made? Magura

[andrics]

[Sipi]

E Slobo, ovo nisi pominjao Svaka cast !

[Zen Mod]

[Magura]

Nice design, I feel like stealing a few ideas Have you made other drivers?I now have an ongoing correspondence with Nick at Clarisound about Rohacell. It sure could turn out to be interesting.Magura

[andrics]

I buy rohacell directly from factory. I give you clarasonic web address only for information. For your driver I suggest you 2mm thick ROHACELL® 31 IGF . If you have problem to buy rohacell i can give you few sheets for testing 2mm thick ROHACELL® 51 or 71 IGF. I don't buy 31 because i made woofer and for me few grams more-less is not problem .What is diameter of your cone ?I have only one driver more . Ribbon 1.7 m long . Prototype working in my friend setup with 2 woofers like on picture. Cutoff frequency is 200 Hz active crossover set at 200Hz 24 db linkwitz filter.

[michabass]

Isnt rohacell only suitable for bass units? I thought the goal here is to produce a FR speaker?@andricsovaj tvoj zvučnik izgleda fenomenalno!

[Magura]

I buy rohacell directly from factory. I give you clarasonic web address only for information. For your driver I suggest you 2mm thick ROHACELL® 31 IGF . If you have problem to buy rohacell i can give you few sheets for testing 2mm thick ROHACELL® 51 or 71 IGF. I don't buy 31 because i made woofer and for me few grams more-less is not problem .What is diameter of your cone ?

I would sure like a few sheets of 2mm thick ROHACELL® 51 for a test. And if possible a few small pieces of scrap for getting a feel for working with the material, as I'm new to this material. My cone is 150mm diameter. How much is 2mm sheet directly from the factory? CheersMagura

[Magura]

Isnt rohacell only suitable for bass units? I thought the goal here is to produce a FR speaker?

They claim it's suitable for FR drivers as well. Time will show if their claim hold true.Magura

[andrics]

I don't see any reason why is rohacell or any other material, not good for FR cone . This is very good,ligth, hard, sound-neutral material. My woofer is 12" with 113 mm coil . Moving mass include spider and surround is around 55 - 65 gram depending of laminating material . For laminating I use aramid (kevlar ) 69g/m2 or glassfiber 35 g/m2 from both side of cone and still have low mass. For 150 mm cone diameter friom rohacell 51 mass of cone will be around 5 gram. This is a very good starting point .Sorry for my Tarzan English i learn English from movies and internet .

[Zen Mod]

...Sorry for my Tarzan English i learn English from movies and internet .

still in better position than Metaldanske ...... he learned his Engrish from Russians

[andrics]

@magura Did you have magnetic simulation of your magnet motor?

[Magura]

This is a very good starting point .

I would think so too. What is it you have covered the face of your cones with? Aramid? Magura

[Zen Mod]

pics of today's work ?

[Magura]

@magura Did you have magnetic simulation of your magnet motor?

No, I have simply copied a known design for the motor, and given it a bit more power. I made most of the parts for the motor yesterday, so in short time, I should be able to test.It's just like Christmas Magura

[Zen Mod]

which design - if that isn't secret ?

[Magura]

It kinda is secret by now, cause i can't remember what I copied. Magura

[andrics]

What is it you have covered the face of your cones with? Aramid?

On picture front is aramid back is glass fiber . We also made with glass fiber for both sides. We have plan to make with carbon fiber too but for now we don't find cheep supplier for ~65gm/m2 :coffee:If you want to laminate rohacell for FR cone you must find material with specific mass ( mass of materials + mass of laminating resine) less then 40 gm /m2 How to send rohacell samples to you ?