Project Ryu - DIY Field Coil Loudspeaker

[Hentai]

Looking good,

Im sure next round will turn out great. Keep up the good work.

[Dave Zan]

Originally Posted by Hentai

David saw your post and i took some pictures of the PUMA 400
Would love to see a pic of your Valliere when its all setup.

Finally, a phone photo.

http://www.diyaudio.com/forums/attac...1&d=1363595516

Best wishes
David

Altered oversize picture to a link to save a download for the uninterested.

[Hentai]

hmm not working for me David,
i get "Invalid Attachment specified."

[Dave Zan]

Originally Posted by Hentai

hmm not working for me David,
i get "Invalid Attachment specified."

This better?


Best wishes
David

[Hentai]

Still can't see it, any other guys having troubles or is it just me?

[hajj]

Same here, can't see it.

[Hentai]

Hello,

Happing Easter for those celebrating, hope the small vacation meant time for building things audio.

I have been busy building a pair of field coil motors for our colleague Frank.
He is pursuing his fiberglass cone development, and i hope he will write more about it as it is very interesting and helpful for DIY community.

Motors will be for a 6.5" unit so diameter is 124mm. Here are some pictures of field coil, pole pieces and phase plugs. Frank had an interesting idea about phase plugs, maybe he will share if he wants to.











The above picture is the top plate, designed to nicely saturate just the gap so that it will be less prone to modulation.



Will be complete soon and then Frank can compare magnets vs field coils


On another side, I've basically finished TEA, temperature effect analysis tool. Just needs a minor calibration. It can measure field coil resistance over time, voice coil resistance over time, system temp and calculates temp coef for voice coil to be then used to determine power compression and the like. Data can be exported as image or csv file for archiving or further processing.

Here is a 30 min run on the field coil for the 12 incher and some shots of the tool and such.








So busy days here, but i will get back on the 12 incher soon. I have prepared for a test session which i expect to reveal some important technical aspects.

[misok]

beautiful. just keep posting ;

[Frank40]

Hi all

Fist I will like to say....I am relay looking forward to receive my new motors, you have done an excellent job Hentai.

I have done some experiments on cone material and I found two that I like very much. The first one is fibre glass it is very stiff and light and has a good energy conductivity at high frequency, perfect for wizzer's. The second one is viscose cloth treated with resin/epoxy, it is not as stiff as fibre glass but is has a high degree of self damping and I use it as the main cone for now.

I need to make a new experiment with a wizzer that is made of both fibre glass and viscose cloth, to see how the wizzer works with a higher degree of damping.

The idea for the phase plug the Hentai mention, is to minimize the air tubules and resonances between the coil form and the phase plug it self. The solution is simple, the phase plug is designed so there is room for some damping material. See pic.

I did some funny math to see what it is we like our speaker to do, and to say the lest I was surprised. I was looking to how small movements the speaker is requite to do... If you stayed a cone is moving +/- 1mm at 20Hz the movement is just 1 micro meter at 20KHz and given you have a dynamic range of 90-100 dB you can see the movement is less that most light waves!!!!!!!
This gives a good indication that all flexing in the material and glues we use, must be taken to account.

I have posted some pic's of some of my work, please fell free to comment.

Take care
Frank

[Johno]

Quote; "If you stayed a cone is moving +/- 1mm at 20Hz the movement is just 1 micro meter at 20KHz and given you have a dynamic range of 90-100 dB you can see the movement is less that most light waves"

One way to see the standing waves on the cone material is to use Moire diffraction where white light is differentially diffracted into component colours (wave lengths) in proportion to the vertical height of the cone perturbation. Longer wave lengths indicating greater perturbation height (or is it the other way around?).
Focus is achieved by varying the distance between the Moire grid and observation point (camera or naked eye).
A Moire grid can be easily made by printing black stripes on clear film using your laser printer. The challenge is to determine the grid dimensions for the subject size and perturbation height (see any physics 201 text because I do not remember).

And many thanks for a very stimulating and interesting thread, I really admire the art and engineering that you and Hentai and others are putting into this. Please do not stop sharing your journey.

John