Project Ryu - DIY Field Coil Loudspeaker

[Frank40]

Hi,

I just found this thread. First let my say you guy's are doing a awesome job, and you got some great skill's to. I am all so trying to make my own unit, it will be a small 6" unit... hope it will end up to be a full range. But I have a long way to go....

Anyway, you should try looking at depron as a membrane material, I made a vacuum for mine and it wight only 0.9gr for a 6" membrane.. not to bad. And the material has a high damping as well.

[Hentai]

Originally Posted by wolf_teeth

You could always do a bolt/sleeve/slab construction like the Dynavox woofers are assembled. That wouldn't take much thought at all.

Later,
Wolf

Well i have found some aluminum bars to do the arms, now i need to find 15mm thick aluminum plates. Soon...

Originally Posted by Frank40

Hi,

I just found this thread. First let my say you guy's are doing a awesome job, and you got some great skill's to. I am all so trying to make my own unit, it will be a small 6" unit... hope it will end up to be a full range. But I have a long way to go....

Anyway, you should try looking at depron as a membrane material, I made a vacuum for mine and it wight only 0.9gr for a 6" membrane.. not to bad. And the material has a high damping as well.

Thank you Frank,

I am interested in learning more about depron and your project if you want to share.

[Frank40]

Hi Hentai

Sorry for the late replay.....I made a vacuum form of plaster and made a little jig for suction, for suction I used a vacuum cleaner. The Depron (3mm) was taped over the jig and the Depron was heated up with a hot air blower, when the Depron is getting bendy (Just a bit soft) the vacuum is set on in a slow manner.

You have to bee very careful when using the hot air blower, Depron is a very good insulator so on side can be hot and the other side cold.. So I think it will be easer to work with if it is heated up with radiated heat, or even better if the hole thing is heated up and vacuum-ed in a oven in one process.

My project:

My project is in a early stage, it should end up with a 6.5” full range unit. It will be using faraday ring's and it will be a double voice coil. The reason for the double voice coil is, for two reasons. First it can be used to ad some extra energy to the coil at higher frequency if needed or it can be used as an extra faraday ring, to lower the induction in the coil.

I will be using magnets not a field coil, I am trying to figure how to make sure that the pol are magnetic saturated with a good margin so it dose not get unsaturated regardless of how much flux is generated in the coil.

[Hentai]

Hello Frank,
Thank you for reply, it is very interesting to read about it, a very nice jig. I'm not sure how the mold is, but would it be possible to make it from metal (either aluminum or steel) and heat its surface?
How are the acoustic properties of depron compared to paper?

The second voicecoil if shorted im not sure if it will lower inductance but my guess is it will have an impact on Qms as it will seem the former as having a higher conductance. Ofc it will also impact Qes. I hope you can experiment soon and share the results. I am also fighting inductance.

[Frank40]

Hi Hentai

As I see it the faraday ring act's like a secondary coil on a transformer. So when using a faraday ring you have a transformer and not just a single coil, this means that the impedens from the sec. winding will load the primer side by N/N. I found this nice dok. http://www.diy-audio.narod.ru/litr/F...lImpedance.pdf

Please correct me if I am wrong.

You can make the form from any material realy as long it will hold to about 140 degree C. Paper vs. Depron.. It is to early to tell, but depron has a very high degree of damping and it is ultra light... but time will tell.

[Hentai]

Hi Frank, i am familiar with Ahmet Feyz Pirimoglu's paper. We had a few conversations on facebook, i wish he could join this discussion as well.

The reason why i don't believe it will have a big effect on inductance is because it will have a high resistance. Unless you can short all the turns in the second voice coil the resistance even if in shortcircuit will be that of voice coils Re. In my initial tests i made the model Ahmet suggested in spice also thinking the field coil if fed by extremly low impedance power supply will have an influence on inductance. It didnt because it had high Re (Rdc). I found that for a shorting ring to be effective, for that coupling to be of high value the resistance of the shorting turn must be very very small. 0.1 ohms and less. The lower it went below 0.1 ohms the higher the effect it had on inductance.

Granted tho it will lower Qes and i guess that you should verify if that will compensate for the higher voice coil mass. Since your cone is much lighter than your voice coil i believe that it would be advantageous to try to lower voice coil mass as much as possible. In a graph i posted here i tried to see how much of a difference was in overall efficiency between higher vc mass and lower Re. I found that for cone mass close or lower in value than vc mass, this mass has a bigger influence on efficiency and for cone mass higher than vc mass, Re has a bigger influence on efficiency.

I also made dual coils 32 ohms each to work in parallel. I will try in the following days to use one in short and see what happens.
Keep us posted with your project and findings, to check out saturation levels for your magnetic structure you can use FEMM.

[454Casull]

I am sorry if you have already done this but have you measured distortion against field coil current? The excess current may help reduce local hysteresis of B vs voice coil current.

[Hentai]

Yes i measured it and indeed distortion drops with increased field coil current. I haven't posted the graphs yet because i plan to do these measurements in a more quiet and controlled environment.
While i could get away with outside measurements for frequency response for distortion i need a better place to lower noise floor for useful results.

[Frank40]

Can some one tell me if the Faraday ring should have electric contact to the pol or not, I can't figure out what is best.

Also.. Do you know what kind of glue to use for holding the wire on the voice coil base.

Hentai, Looking forward to hear what happens when you short one of your wingding on your voice coil.
Is the FEMM a free softweare, and if so where can I find it.

[Marcos_SuperSom]

Hi to all.

Beautifull work Hentai. Congrats.

Hentai I have a question. What glue you use for fix the wire in the former of voice coil (winding)?

Thanks.