Project "Groove Scribe"- A DYI stereo 45/45 head.

[EpicenterBryan]

hey .. bryan ... wanted to ask, what have you achieved resonant frequency of the driver with this configuration! diafragm with carbon membrane? Have you ever taken a test? how thick is diafragm?

I haven't set up to do a transfer function yet, but I have taken some initial readings on the feedback to see what kind of level I could get. But in the process, I did find the peak output which is the new resonant frequency. Here is what I got:

Coil: 6 layers, 30 turns per layer (180 coils) 8 ohm resistance.

@1Khz:
0.5A drive current
Feedback output 4.89mv

@2.22Khz (highest feedback output)
0.378A drive current
Feedback output 23.28mv

As far as the thickness of the diaphragm goes: It's 2mm thick, with a 1mm counter sink for the 1mm carbon fiber disc to be glued into.


I would have thought to see the resonant frequency drop more but it is quite a bit lower than the last 2 nylon 100% infill diaphragms.

Hopefully I'll have a transfer function with phase relationship tonight.

Bryan

[EpicenterBryan]

Here is the response of the latest driver, using the feedback coil noted above. I have intentionally removed the phase plot so as not to confuse discussion too much in this post. It's not good at all...

IMG_0025.JPG

I believe there are two things going on here. One is the recent change of the diaphragm material from Nylon to NinjaFlex (SemiFlex). With this change, the Glue had to change which had other implications I'll go into. The 2nd big thing is the mass went up with the aluminum push rod segment rather than the carbon fiber push-rod.

Yes, the magnet structure for feedback changed which increased the signal even beyond test case #6 which I was happy about. And using the NinjaFlex rather than the Nylon dropped the main resonant frequency down (even with the full diaphragm vs the minimalist version).

There is one common denominator in everything I have done trying to modify this driver. And that is to have a flat material to mate with the push / pull coil force, and a push rod at the center of a transitional material - being either a disc with an integral spring or with a connection point in the center for a push rod. That is the root of the problem.

To quote Albert Einstein:

Insanity: doing the same thing over and over again and expecting different results.

This will not work. I guess I should now concede to Todd on the Einstein references...

Many of you guys have had success using cone shaped structures attached to the voice coils. Now I understand why and I'll quickly explain... What you are really doing whether you are Fella making paper cones and dipping them it lacquer, or what Mark, or Ciuens or any number of other brave soles experimenting with things is that you have created the most stable (and light) stricture we know. A triangle, rotated on a central axis into the ultimate structural shape - a cone.

This is the most efficient way to take a force generated at the coil (at a larger diameter), and transfer it to a different location in this case at a smaller diameter where the push rod is located. When I first saw this I thought focus the sound to the torque tube. That's silly. I'm just trying to move stuff not focus sound. It's not like that at all. Now I understand it's not about the sound, it's about eliminating an intermediate material with it's own flex and such - the diameter adapting centrally located disc has to go away in future designs.

Get it? That disc in each variation I have played with has it's own flex, it's own transfer function, it's own resonance. The driver pushes, the mass resists, the carbon fiber flexes until it moves, that moves the push rod and coil. Time delay results. More noticeable at higher frequencies which results in phase shift in the measurement. But like Todd noted that is not possible - unless you ignore the intermediate material between the driving force and the measurement device mounted on a mass that is not being accelerated at the same rate due to a transnational material in between the stimulus and response.

So yes, Todd was right. I did not understand the problem.

Is there a quick fix that is light, easy to replicate and build?
Yes and no. It kind of messes up my whole design for Feedback, but here is what I'm thinking about right now.

There are light weight Carbon Fiber cones like this for model airplanes. There are also carbon fiber nose cones for model rockets that might also be an option. I'm sure they would all need to be trimmed to line up with the diameter of the coil on these drivers. But let me say that I'm not married to these drivers. I'm passing on this idea so someone can experiment with this now with some reason why it might work.

4857.jpg

[EpicenterBryan]

I was near the "I give up" point last night.
But I have 2 new ideas I'm going to try this week before throwing in the towel.

Our young Canadian brother (Bennett) came up with that awesome idea for spinning aluminum. That got me thinking about using beer cans (I usually have some empties around ) and I went back and read one of Ciuens posts on his ZEZ Cutter One.

The first idea is to see if I could press a piece of beer can in some home made die. The beer can is 0.1mm thick. I don't think I need anything too special but a hydraulic press (which I have). I have made DIY dies cast in concrete before for thin steel. It worked fine, but I think this beer can material might be easy enough to shape, I'm going to try a die printed in plastic. The result doesn't need to be exact - I just need two the same cone shape. These two parts will take most of a day to print on my printer... They may only be good for one use. Here is what I'll try:

die.jpg

I'll put a circle of material in there and apply pressure - let's see if I get the general shape, and an indentation at the rim where I can trim the result.

The next idea really came from everyone who has shared their DIY that has a cone. I wondered how that was made. Some looked really hand made and not so symmetrical. Some looked great.

I found a website that has a cone calculator. You enter the base size, the top size and the height and it does the calculations and provides a PDF with a printable template you can cut out and also shows other details you need to know to cut the pattern out.

http://www.wegmuller.org/cones/

Here is the printout for a cone I wanted to try:
Base diameter: 28mm
Top diameter: 3mm
Height: 10mm

I printed the image and applied it to the flattened beer can. Then drilled the hole and cut the perimeter with a pair of scissors. I'll need to make a cutting jig to make this more precise if I end up going this route. But it worked. Just bent the ends together and applied tape for now to see if it fit. I'll also have to play around with what to use to bond the ends together, but it's stable like crazy. Just like Bennett mentioned with his spun part.

IMG_4323.JPG

Shown here is one of the coils that had epoxy and a carbon fiber disc. I was able to get the nylon off, but no way I will be able to get the disc off.

IMG_4324.JPG

As far as the other two coils / carbon fiber discs and NinjaFlex diaphragms go, It may be possible to salvage one or both of them but it may be easier to start over with 2 new drivers. What could be done easily would be to pull out the push rod, leave a carbon fiber disk installed as is, just put this cone on top and a new pushrod / coil glued to the cone only just to see if this fixes the phase issues...

I'll have to think about that and see if I can take things apart yet again.

That's the update for now. I'm down - but not quite out yet.
More fun to come with beer cans like I need an excuse!

Bryan

[Snug Music]

Hey, bryan .. ...
yes .. that the cone was a good idea of Ciuens.
I also made this cone and have noticed how the ups have prevailed.
My problem was that the membrane was too thin. Also to soft material I have used. The result was that I had to large deflections.
and now, .. these have now built like your diaphragm.
let's see how it works now ...

hope you get it out ..
We believe so strongly in you

greetings Scotty

[juba bc]

Bryan, you think to wear half ball instead of the cone would be effective too?

[dimi751]

Hi Bryan

I hope your doing well happy new year to you and family.

I have not tried metal from a can, but I tried paper dipped in lacquer and that seemed to have worked really well.( thanks mark rob )

It will be interesting to hear what it sounds like using your material, buy the way your posts are very interesting as always your doing a great job.

Rgds
Dimi

[EpicenterBryan]

Bryan, you think to wear half ball instead of the cone would be effective too?

I would think it will work much better than a disc, not as well as a cone though. A cone has a more direct path to move forces from the large diameter to the small diameter. But if you can find something like that off the shelf it's worth trying out.

Bryan

[EpicenterBryan]

Well, that was fun to try.
The one on the right is the beer can, the one on the left is just aluminum foil to see if it also ripped.

IMG_4325.JPG

I may try eliminating the ridge on the female part. It's possible that is pinching and causing the terminal rip on the last part of the forming.
But I'm also going to try annealing the aluminum can material, and then hardening the final result if it stays intact.
If that doesn't work, I'm going to try softening some plastic discs that has a lower melting temperature than the plastic mold and see if that works. I don't think I want to use plastic cones though.

Right now it's looking like the Spin method (Bennett mentioned) or the cone made from a cut circle are the two possibilities.

Bryan

[Snug Music]

Well, that was fun to try.
The one on the right is the beer can, the one on the left is just aluminum foil to see if it also ripped.

IMG_4325.JPG

I may try eliminating the ridge on the female part. It's possible that is pinching and causing the terminal rip on the last part of the forming.
But I'm also going to try annealing the aluminum can material, and then hardening the final result if it stays intact.
If that doesn't work, I'm going to try softening some plastic discs that has a lower melting temperature than the plastic mold and see if that works. I don't think I want to use plastic cones though.

Right now it's looking like the Spin method (Bennett mentioned) or the cone made from a cut circle are the two possibilities.

Bryan

hey...

Bryan nice ... I .. did my cone from the aluminum of tea lights! hehee..die are thin and very light!

bryan .. a question to the membrane:
if it is glued and fitted together, how elastic or hard is it?
I have a feeling they will be able to move any more. is that right ??
or it must be possible to press down slightly? I'm just overwhelmed a bit. smile

regards Scotty

[EpicenterBryan]

Progress!
It looks like the "press method" issue relates to the female die tolerances.

In this round, I had to drink more beer for science. I prepped and flattened the cans. This time, I heated the can discs to anneal them (soften them) until the silkscreen darkened. Then I tried 3 tests.

IMG_4329.JPG

IMG_4330.JPG

The first test was a quick one without cleaning the disc . I used my plastic die and my little 6 ton press. I didn't really force it, just applied pressure until it bottomed and checked it. It worked!

The second test (in the center) was after I used 00 steel wool to clean it and applied pressure until I really felt the press holding back when being pumped. That one resulted in the split I have see in other tests.

The final one was after I trimmed some plastic with a razor blade to open up the female die near the final position. I didn't spend much time, but you can see the die is a bit wider in that area. Then I applied pressure like in test 2. The result was also a split but much smaller. So I think I need to make a new Female die with slightly wider tolerances for the final 2mm. Then I need to learn how to harden what I get in the final press - it looks doable, but is a lot of messing around.

I still like the spin method. I also have some glue drying for the "cut circle" method as well. The first glue round failed. I had tape on one side to hold the shape, and applied the black stuff on the other side. The acetone based black stuff melted the tape on the other side and the gap widened before the glue dried. I'm trying other ideas. I'll see how that goes in the next few days.

But what I really want to try someday is something like this. It's similar to what a Lab I did some work for about 20 years ago was playing with. Their application was aircraft related - oddly enough - torque tubes. They had thousands of volts and massive capacitor banks to play with. Results were amazing and instantaneous.

Check out this video for a different application and you will see how easy it would be to make cones or coil former's if someone had something like this - or built one.... Hummmm. Let me think about this.... I hate high voltage and high current though. It's easy to die with that stuff if you mess up. But think about the possibilities.

Bryan

[EpicenterBryan]

They don't allow embedded videos, so here is the link. Copy and paste it...

https://www.youtube.com/watch?v=Y1Yw7jYcdZg

Bryan

[Snug Music]

Yeahh,..great tunes
I have a good friend by airbus-bremen they can do this!
Heheee...cool...

[EpicenterBryan]

I also love the "Explosive forming" idea shown in this video.
Guns, ammo, and explosive forming charges - Oh my....

Bryan

[Snug Music]

I also love the "Explosive forming" idea shown in this video.
Guns, ammo, and explosive forming charges - Oh my....

Bryan

Booooommmmmm,...chacka...heheee...thats realy cool...

[Snug Music]

Ok,..i take a little bomb in my workbank...wait 5 sec. and wwoooommmmmm,
And now...i have al brand new cutting-lathe....smile

Greetings Scotty

Great id

[Bahndahn]

Hey Bryan, I've been following your updates, very exciting!

The spin method has been really fun to play with. I'm still working on those tools but have been getting good results with the beverage can aluminium regardless of trying a number of different gauges of aluminium. It's quite easy to tear them even when spinning them, but when spinning it's possible to 'roll some aluminium back' towards the apex of the cone [away from the outer diameter of the cone] – this seems to ease the stress by providing more material to the stretched area.

Here's a little collection of cones in a few different gauges, the front ones being beverage can.

Cones.JPG

I think it wouldn't be to hard to set up a little spinning apparatus vertically using a drill press or your mill. I think it would be worth the setup!

[Bahndahn]

I also would totally spin you some and send them to you if you send me a drawing! I'd be happy to return a favor.

[Fela Borbone]

Hi Bryan,do you spray some oil on moulds or sheet?

[EpicenterBryan]

I also would totally spin you some and send them to you if you send me a drawing! I'd be happy to return a favor.

Thanks Bennett! I might take you up on that. Let's see how things go this weekend. I don't want to squander an awesome offer like that.

Bryan

[EpicenterBryan]

Hi Bryan,do you spray some oil on moulds or sheet?

No, I didn't and that's a great idea. I'll give that a quick try this weekend.

Bryan