Project Ryu - DIY Field Coil Loudspeaker - Page 17 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 18th February 2013, 03:54 PM   #161
Hentai is offline Hentai  Romania
diyAudio Member
 
Join Date: Nov 2006
Cool work,

Frank you should try a triple roll cloth surround as well. I like it more than the single roll foam one.
  Reply With Quote
Old 19th February 2013, 06:48 PM   #162
Frank40 is offline Frank40  Denmark
diyAudio Member
 
Frank40's Avatar
 
Join Date: May 2004
Location: My workshop :-)
Quote:
Originally Posted by Hentai View Post
Cool work,

Frank you should try a triple roll cloth surround as well. I like it more than the single roll foam one.
Hi Hentai

I am trying to figure out how to make a cloth surrounding, the foam one weighs almost double of the cone and wizzer together Do you know of any ease way.....

Take care
  Reply With Quote
Old 20th February 2013, 05:28 AM   #163
diyAudio Member
 
Join Date: Feb 2013
Quote:
Originally Posted by Hentai View Post
Thank you for your words.
My impressions, hmm i stayed away from that as i tried to keep it things objective as ofc i cannot show how it sounds on a forum but since you asked...
The best thing this speaker does is dynamics and is something i always crave for in sound.
Wow, what an incredible thread. And so much of it is over my head, but I keep on reading, mesmerized.

This is my favorite post. I know you want objective, but I have been craving for pages to get to this. A few years ago I had the pleasure of hearing a Field Coil system at a trade show. By far and away the best speaker I have heard. And the dynamics were what stood out for me.

About page 8 or 9 someone asked you why Field Coil. It is my impression that Field Coil has a much more stable flux density than magnets. That the tesla factor does not vary as the power band changes. (and that to a certain extent alnico magnets are more like this than other magnets, and that is why they sound better.)

I think the best comparison is microphones, and that condensor mics compare to field coil speakers, with better dynamics than their magnet counterparts.

Now back to more reading for me.
  Reply With Quote
Old 20th February 2013, 12:14 PM   #164
Hentai is offline Hentai  Romania
diyAudio Member
 
Join Date: Nov 2006
Hello Frank, you will need to machine a form with grooves corresponding to your rolls ofc you will need positive and negative.
For cloth surround tho you can find good options off the shelf and treat it to reach the mechanical properties that you need in order to terminate the cone properly.
However it will contribute less mass than a foam one.


Hello Jack, thank you so much for reading and confirming the search for improved dynamics.
Yes Flux density is more stable, but there are also some interesting interactions within the system that i am studying. Keep on reading as soon i will return with a informative update.
  Reply With Quote
Old 24th February 2013, 08:28 AM   #165
diyAudio Member
 
Join Date: Jun 2006
Quote:
Originally Posted by Hentai View Post
Hello,

***First i want to say I'm not sure if i should post this under Fullrange or Multiway. Since at this point, there is a high posibility of the need for a supertweeter i chose Multiway forums. I won't mind tho if moderators think it's more suited for Fullrange forums.

About 6 months ago, i started thinking about a DIY fieldcoil speaker. I know opinions vary quite a lot on this matter and so i will do my best to offer as much data as possible for things to be judged objectively. Since that time I have been talking with some fellow countrymen and audio enthusiasts about this project and these conversations helped me in making some of the design decisions. The work is still in progress and i hope your opinions and comments can help tune it to higher performance.

To begin, here are the basic aspects about this project:

- field coil underhung motor structure
- 12" diameter
- Wide range (up to 10kHz), hopefully fullrange (up to 20kHz)
- high efficiency
- to be used in BLH

My personal taste in sound is that i like it when it comes out of large radiating surfaces. Large SD, large horn mouths etc. I think it's a necesity when one tries to reach real, live music levels and at the same time keep a good response to instruments' attack, sustain and decay. This is the reason i chose 12 inch diameter. I would've liked 15" better but it would've been too difficult to make it wide range. Perphaps a future project.

Field Coil Motor Structure:

I have spent a lot of time looking for other field coil projects, for any information on FC design or about available products and i have to say there isn't

much out there. From the pictures of opened FC units i could see a basic shape of the pole pieces. I have to say this is amongst the first design issues i encountered, there isn't much freedom to design these pole pieces, not like the case with permanent magnets anyway.
The next thing one can notice is that the new FCs are low impedance type and this is easily understandable. I have decided that my field coil will also work with 12-15V supply.
Underhung design means thick top plate. Of course this will cause a drop in flux density in the gap. The compromise here i found to be between flux density value [B] and voice coil excursion. Since this speaker will mostly be used horn loaded i sacrificied Xmax to make a thinner top plate. I use standard 1010 steel with a maximum of 0.13% carbon, the best i could get my hands on.
I ran simmulations in FEMM for different values of top plate thickness, FC's number of turns, dimension, wire diameter etc. Here are the results i stopped at:

- magnetic gap height: 12mm
- magnetic gap width: 1-1.5mm
- 5.3 ohm FC 1400 turns of 1.25mm copper wire

Below you can find a rather crude sketch of motor structure:

Click the image to open in full size.

Here are some results from FEMM analysis:

I ran simmulations with 1010 steel as well as 416 steel (has slightly more carbon typical 0.15%) to see the differences.

Click the image to open in full size.
Click the image to open in full size.

1010 Steel [B] Curve over 20mm and 12mm:

Click the image to open in full size.
Click the image to open in full size.

416 Steel [B] Curve over 20mm and 12mm: (actually the curves are smoother had to lower resolution a bit because of my computer)

Click the image to open in full size.
Click the image to open in full size.

Magnetic gap:

Click the image to open in full size.

AS it is, at 2.2 Amps we have 25W for the FC. I don't expect to have too much trouble with heat at this power. Test will tell tho, depending on how well the metal does the job of sinking the heat. The [B] value predicted by FEMM lies around 1.6 Tesla. In reality i believe this value will be smaller 1.4-1.5 T. In tests i will drive the FC with 3 amps and see how much it heats up.

In this design the gap width is 1.5mm. Somewhat large, I'm thinking to add a 0.5mm thick copper ring right in the gap (yellow part from picture below). Now
it's true i have never seen a picture with a FC unit having a faraday ring and I'm not sure if it's necesary. I guess the FC itself has a role in that too.

Click the image to open in full size.

I'm also making a 1mm gap variant (without copper ring) in hopes to get more flux density. The FEMM simmulation shows:

Click the image to open in full size.
Click the image to open in full size.

Here are some parts of the magnetic structure after machining:

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.



se me lo consenti vorrei farti alcune domande perch piacerebbe anche a me imparare ad fare i field coil ma non s alcune cose.

che temperatura raggiunge il solenoide dopo mezz'ora di funzionamento continuo e quanto diminuisce la resistenza e di conseguenza amperaggio e campo magnetico ?
quanto aumenta il voltaggio tra la prima serie di spire e la seconda e tra la seconda e la terza ?
con che formula hai calcolato, dato il diametro del nucleo, larghezza e altezza del solenoide ?
cos' questa formula ?
Click the image to open in full size.

nei tuoi solenoidi il numero di spire per ogni strato sempre uguale o cambia?
cos' un'elettrocalamita a doppio nucleo nudo?

Last edited by audiofilofine; 24th February 2013 at 08:52 AM.
  Reply With Quote
Old 24th February 2013, 08:48 AM   #166
Hentai is offline Hentai  Romania
diyAudio Member
 
Join Date: Nov 2006
Hello audiofilofine,

I'm sorry but i don't understand the language, can you use english please?
I can tell it's about temperature. On page 5 you can find these graph:
Click the image to open in full size.
Click the image to open in full size.

Im not sure what formula you are referring to, all i see is a calculation.
  Reply With Quote
Old 24th February 2013, 09:03 AM   #167
Frank40 is offline Frank40  Denmark
diyAudio Member
 
Frank40's Avatar
 
Join Date: May 2004
Location: My workshop :-)
Hi

Here is a update on the full range project. I would like to back up my impression on the unit so I decided to use my Room correction unit, to make some measurements.... And it confirmed what I was hearing.......But I still have some doubt can this relay be true? it's almost to perfect, sense the unit is not in a box I cut it at 300Hz.

Here is a pic one how I measured it and the result.

Take care
Attached Images
File Type: jpg Capture_374.jpg (580.8 KB, 154 views)
File Type: jpg Capture_373.jpg (114.3 KB, 231 views)

Last edited by Frank40; 24th February 2013 at 09:05 AM.
  Reply With Quote
Old 24th February 2013, 09:39 AM   #168
Hentai is offline Hentai  Romania
diyAudio Member
 
Join Date: Nov 2006
Hi Frank,

Is the mic going to line in of your soundcard? if so you can use HOLMImpulse for measurements. I think it will have a better display.

Also try to put the driver as far as you can from boundries, walls, floor, ceilling.

Keep up the good work.
  Reply With Quote
Old 24th February 2013, 09:47 AM   #169
diyAudio Member
 
Join Date: Jun 2006
Quote:
Originally Posted by Hentai View Post
Hello audiofilofine,

I'm sorry but i don't understand the language, can you use english please?
I can tell it's about temperature. On page 5 you can find these graph:
Click the image to open in full size.
Click the image to open in full size.

Im not sure what formula you are referring to, all i see is a calculation.
If you would allow me some questions why'd I learn to do the field coil but I do not know a few things.
that temperature reaches the solenoid after half an hour of continuous operation and how much resistance decreases and consequently amperage and magnetic field?
as the voltage increases between the first set of loops and second and between the second and third?
with that formula you calculated, given the core diameter, width and height of the solenoid?
What is this formula?




in your solenoids the number of turns for each layer is always the same or change?
What is a dual core electromagnet naked?

Last edited by audiofilofine; 24th February 2013 at 09:55 AM.
  Reply With Quote
Old 24th February 2013, 02:35 PM   #170
Hentai is offline Hentai  Romania
diyAudio Member
 
Join Date: Nov 2006
Hello audiofilofine,

Temperature of the whole system depends on a few factors. Fieldcoil power disipation being perhaps the most important one. The amount of steel and geometry plays a role also.

The drop in current with increased field coil resistance due to rising temp i found to be around 0.1-0.3A depending on the driving current with the same number of turns on each layer.

About formulas, there is no general formula for what you are asking. Giving inside and outside dimensions all you need to calculate is a coil that will a specific DC resistance in order to meet your power requirements.

In my design proccess i started from the voice coil actually, chose diameter, underhung topology, voice coil height, plate thickness and then moving down to fieldcoil. Core diameter is in close relationship to voicecoil diameter about 150-200% so that you dont saturate plates too soon.
So designing the field coil i did knowing what i want to get in the gap and the structure around the gap.

Since you brought up the temperature subject, i am developing a tool for this kind of analysis. It is almost done and will allow monitoring of fieldcoil resisntace increase and voice coil resistance increase in time. A temp probe can be placed on the center pole piece near the voice coil to calculate a temp coef. This can help in determining large signal parameters and create a more precise model.
The tool is based on PIC18F4550 and connects to the PC via USB for data logging and visualization. It can export data for archiving.
Will show you what it can do once it is completly done but here are some teasers with a test unit, i heated up the temp senzor with a lighter thats why it goes up. Im designing a PCB now hope by next weekend to be done.

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

PS. Not sure what you refer to as dual core electromagnet naked
Attached Images
File Type: jpg DSC03384.jpg (487.9 KB, 13 views)
File Type: jpg export.jpg (187.3 KB, 13 views)
File Type: png screenshot.png (339.9 KB, 14 views)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
First DIY loudspeaker project for LM3886 kiske1 Full Range 68 26th April 2012 03:27 PM
Open baffle field coil project jonjin Multi-Way 1 6th December 2010 11:19 AM
Has anyone DIY a Field coil? OzMikeH Full Range 18 16th November 2010 01:56 PM
field coil? otto88 Markaudio 0 2nd October 2010 03:33 AM
What's a Field Coil Amplifier? krzanik Tubes / Valves 9 14th May 2005 03:22 PM


New To Site? Need Help?

All times are GMT. The time now is 04:26 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2