Hi gomper,
First, I'm happy to see your work. Your cone looks amazing, very nice work. I don't remember what diameter you go for, 8"? Weight is important, at 7g it should be good but you can experiment with as many cones as you can to get to your desired outcome. If you make it lighter you need to balance your spider and surround too, make them softer.
I am making a little piece of software to help design voice coils but not sure when I will finish it. I will do my best so that it doesnt take too long. You can see a pic of how it looks like. I will release it when it closer to finish.
The holes are for cooling, coupling the field coil with the exterior air will vent some of the heat outside.
First, I'm happy to see your work. Your cone looks amazing, very nice work. I don't remember what diameter you go for, 8"? Weight is important, at 7g it should be good but you can experiment with as many cones as you can to get to your desired outcome. If you make it lighter you need to balance your spider and surround too, make them softer.
I am making a little piece of software to help design voice coils but not sure when I will finish it. I will do my best so that it doesnt take too long. You can see a pic of how it looks like. I will release it when it closer to finish.
The holes are for cooling, coupling the field coil with the exterior air will vent some of the heat outside.
Attachments
Cooling, of course... That's a great idea, just opening up the casing. I've had heat as a concern in the back of my mind for some time, since my first time running the motors at 2.4A / 18V. My plan is to try a large heat sync (perhaps with a silent fan attached?) to the bottom plate with thermal paste. If it works well to cool the CPU in a gaming computer, it seems like it should work equally well for these motors to keep them cool.
Thanks so much for the kind words and feedback Hentai - I'll post a few pics of the second-attempt cones this week, and will plan to make several versions with different thicknesses and papers.
My intent has been a 10" driver, but I'm not clear on what informs the diameter of a driver as it is described. The Tang Band W8-1772 is an 8" driver I am fond of, and it measures just 5.5" across the cone. These cones I'm making currently are 7.5 inches in diameter when measured simply across the center. Is the nominal diameter determined by a measurement of the diameter against the actual surface of the cone? Or does it simply include the surround? Of course nobody need feel compelled to educate me on the topic, it's just a curiosity.
More soon.
Thanks so much for the kind words and feedback Hentai - I'll post a few pics of the second-attempt cones this week, and will plan to make several versions with different thicknesses and papers.
My intent has been a 10" driver, but I'm not clear on what informs the diameter of a driver as it is described. The Tang Band W8-1772 is an 8" driver I am fond of, and it measures just 5.5" across the cone. These cones I'm making currently are 7.5 inches in diameter when measured simply across the center. Is the nominal diameter determined by a measurement of the diameter against the actual surface of the cone? Or does it simply include the surround? Of course nobody need feel compelled to educate me on the topic, it's just a curiosity.
More soon.
Hentai, I'd like to congratulate you on your field coil speaker build. That is one of the finest DIY projects that I have ever seen. As a machinist I appreciate the skill and labor that went into these but it's the engineering and testing that really makes your project stand out.
I'm a big fan of Altec speakers and would love to build some field coil drivers for my horns. My problem is that I don't have the engineering background that you have and any attempts to modify a set of crusty 808 drivers that I have will be nothing but a shot in the dark, lucky for a near miss but probably miss by a mile. LOL
I can do the machining, have a nice Monarch tool room lathe and Bridgeport mill. It's the engineering of the magnetic structure that holds me back.
There is more than a few Altec enthusiast that would love to experiment with field coil drivers. Any chance that you would like to use your considerable skills to design something for us?
Thanks
BillWojo
I'm a big fan of Altec speakers and would love to build some field coil drivers for my horns. My problem is that I don't have the engineering background that you have and any attempts to modify a set of crusty 808 drivers that I have will be nothing but a shot in the dark, lucky for a near miss but probably miss by a mile. LOL
I can do the machining, have a nice Monarch tool room lathe and Bridgeport mill. It's the engineering of the magnetic structure that holds me back.
There is more than a few Altec enthusiast that would love to experiment with field coil drivers. Any chance that you would like to use your considerable skills to design something for us?
Thanks
BillWojo
That's awesome, FielCoil Adventure. Very nice finish and I like the SMART field coil concept! Please show us more.
BillWojo,
Thank you for your kind words and interest in fieldcoils.
Although you are overestimating my abilities, sure I can help with that. I remember I have seen at least one conversion of 808s to fieldcoil. I will look for detailed dimensions of the driver (if you have them or can help with that would be great) and see what we can do.
BillWojo,
Thank you for your kind words and interest in fieldcoils.
Although you are overestimating my abilities, sure I can help with that. I remember I have seen at least one conversion of 808s to fieldcoil. I will look for detailed dimensions of the driver (if you have them or can help with that would be great) and see what we can do.
Wow, thanks for the quick response. I pulled out my two 808's that I have, one is an early unit with the cast pot and one is the latter style with the machined pot. Any preference as to type? I'll pick up another along the way so I have a matching set.
Here is a link to a set just ready to sell on Ebay. Looks to have the machined pot.
Altec Lansing 802D Field Coil | eBay
I'll check with the fellows on the Altec board and see if they have any links to other pictures as well.
Thanks again.
BillWojo
Here is a link to a set just ready to sell on Ebay. Looks to have the machined pot.
Altec Lansing 802D Field Coil | eBay
I'll check with the fellows on the Altec board and see if they have any links to other pictures as well.
Thanks again.
BillWojo
Some information regarding the Altec field coil conversion. - http://www.diyaudio.com/forums/multi-way/203185-field-coil-conversion-jbl-altec-western.html
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Pictures of 802 drivers as found on the internet, sames as 808 but uses different material diaphragm. I'm guessing the pot on the right is the cast one. Has heavier wall and looks like a cast in ring at the bottom to center the magnet.
I have asked the guys on the Altec host board to help gather any information that may be of use to you.
My guess is that the cast pot will have a better magnetic circuit?
BillWojo
Hi,
what i will need are dimensions of the phaseplug, pot, top plate and voice coil. I will look for a cut-through image and mark dimensions i need. If you can measure those for me then we should be able to make a conversion.
The cast pot might be better, if the machined one was not treated but i doubt that. As I recall Altec, JBL used 1008 steel. Can anyone confirm that?
what i will need are dimensions of the phaseplug, pot, top plate and voice coil. I will look for a cut-through image and mark dimensions i need. If you can measure those for me then we should be able to make a conversion.
The cast pot might be better, if the machined one was not treated but i doubt that. As I recall Altec, JBL used 1008 steel. Can anyone confirm that?
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Hentai, not sure what you mean by the steel pot being treated.
For some reason I'm thinking that the steel pot is a welded structure, that it was not a solid that was machined out. I could very well be wrong on that point though. I should have more answers tomorrow when the folks on the Altec host board awaken to hear the good news.
I'll ask over there about the alloy used as well.
You should stop by and join us. It takes a few post before you can post freely as the moderator needs to make sure your not a bot. I just made a few post on different subjects on the forum and in a few days I was in.
It's past midnight here, need to get some sleep.
I'll check in in the morning.
Thanks
BillWojo
For some reason I'm thinking that the steel pot is a welded structure, that it was not a solid that was machined out. I could very well be wrong on that point though. I should have more answers tomorrow when the folks on the Altec host board awaken to hear the good news.
I'll ask over there about the alloy used as well.
You should stop by and join us. It takes a few post before you can post freely as the moderator needs to make sure your not a bot. I just made a few post on different subjects on the forum and in a few days I was in.
It's past midnight here, need to get some sleep.
I'll check in in the morning.
Thanks
BillWojo
Dear 454Casull,
The voice coil in the project 18" fieldcoil is 2.5" and the width of voice coil gap is 1.65mm (measured by millimeter)
Dear Gromper, Hentai,
Thank you for replied on my post soon, I will have more on next some day.
Best Regards,
FieldCoil Adventure.
Since I have two different drivers here and would like to get some measurements to you I would like to know what driver I should take apart. Since taking the plate off of the structure kills the alnico magnet, I'm not excited to do both units. I haven't had a reply yet as to the steel alloy but in general would steel or cast pot be better? I'll do a spark test on the cast one if I can today. That should tell me if it's cast iron or cast steel.
Thanks
BillWojo
Thanks
BillWojo
Well, I didn't get to my bench grinder today but sometime this week I should be in a shop that has a portable XRF metal analyzer gun. I'll scrape the paint off of both units on the mounting surface and see if they can scan them for me. This will give us a detailed report of the composition of the metal. I'm not making promises but I'm sure going to try to get this info.
Hentai, if I need to open up both drivers to find the best one to build upon, than that's what I'll do. It can always be reassembled and sent to GPA for remagnetizing. From what I understand, he remagnitizes any alnico driver that comes in for service anyway.
From the picture I put up it looks like the cast pot has a lot more material in the walls than the steel pot. Could be from several factors.
A) The cast pot is not as good a conductor of magnetic flux due to the material.
B) It was just easier to cast a little thicker wall pot than a thinner wall pot.
C) Some factor that I'm unaware of.
As soon as I have more info I'll post back.
BillWojo
Hentai, if I need to open up both drivers to find the best one to build upon, than that's what I'll do. It can always be reassembled and sent to GPA for remagnetizing. From what I understand, he remagnitizes any alnico driver that comes in for service anyway.
From the picture I put up it looks like the cast pot has a lot more material in the walls than the steel pot. Could be from several factors.
A) The cast pot is not as good a conductor of magnetic flux due to the material.
B) It was just easier to cast a little thicker wall pot than a thinner wall pot.
C) Some factor that I'm unaware of.
As soon as I have more info I'll post back.
BillWojo
Had a busy day today and got to the steel distributor late in the afternoon. In preparation of getting the pots analyzed I had scrapped off some paint on the mounting faces of both drivers and polished the surface with Scotchbrite, a fine abrasive.
I arrived as the first shift foreman was cleaning up for the day and asked him to "shoot" a few parts for me. No problem and he goes and gets the XRF gun. Cast pot comes up as no match and he reads off the major elements as I scribble them down. Same thing for the steel pot, no match. Hmmmm, this doesn't make sense.
Later as I'm done my repairs I pull out the slip of paper I wrote my notes on. It was than I realized that I needed to lightly grind the surface and scan them again. I did learn that the cast pot was cadmium plated and the steel pot was zinc plated. LOL
So after taking a light grind on the surface using a fresh belt with the air powered mini belt sander, (fresh belt so I would not cross contaminate with Cr and Ni from the stainless they were deburring) I had the night foreman reshoot both parts. He was very busy so I just wrote down the % of iron and the match.
Cast pot 97.31% iron and matched with 1215 steel (must be a steel casting)
Steel pot 98.23% iron, no match.
Hentai, looks like the steel pot has 0.92% more iron in the mix. Do you think that the thicker walls of the cast pot would offset that?
I'm thinking of just taking both apart for full measurements at this point in the interest of documenting the differences. After I get full measurements your simulations should allow us to pick the best one to modify.
Unfortunately, we have a blizzard moving in tonight, don't know when I'll get to the shop where my tools are.
As I gather more information I'll post it.
BillWojo
I arrived as the first shift foreman was cleaning up for the day and asked him to "shoot" a few parts for me. No problem and he goes and gets the XRF gun. Cast pot comes up as no match and he reads off the major elements as I scribble them down. Same thing for the steel pot, no match. Hmmmm, this doesn't make sense.
Later as I'm done my repairs I pull out the slip of paper I wrote my notes on. It was than I realized that I needed to lightly grind the surface and scan them again. I did learn that the cast pot was cadmium plated and the steel pot was zinc plated. LOL
So after taking a light grind on the surface using a fresh belt with the air powered mini belt sander, (fresh belt so I would not cross contaminate with Cr and Ni from the stainless they were deburring) I had the night foreman reshoot both parts. He was very busy so I just wrote down the % of iron and the match.
Cast pot 97.31% iron and matched with 1215 steel (must be a steel casting)
Steel pot 98.23% iron, no match.
Hentai, looks like the steel pot has 0.92% more iron in the mix. Do you think that the thicker walls of the cast pot would offset that?
I'm thinking of just taking both apart for full measurements at this point in the interest of documenting the differences. After I get full measurements your simulations should allow us to pick the best one to modify.
Unfortunately, we have a blizzard moving in tonight, don't know when I'll get to the shop where my tools are.
As I gather more information I'll post it.
BillWojo