Project Ryu - DIY Field Coil Loudspeaker

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my, those surrounds looks a bit on the heavy side for such a light cone

I once thought the best surround would be S-shaped
would have said 'ideal'
but since ideal would mean flawless, I guess that will never happen

same goes for the spider...less is more

I was planning to try with felt surround for my own driver project

very impressive project btw
 
An idea just popped in => ferro fluid for the surround.

It is complicated and not cheap but i think it has some great advantages.
A little extra mass and good damping characteristics (you can choose in different viscosity samples) + totally air blocked.
No surround resonances in the well known important freq. range.

ferro surround.JPG


Thx for the info. Hentai, the use of Alu wire is maybe in my case an option because in parallel the Re value is within the 6ohm range and Mms will be much lower (a lot of windings). I'm going to try that within a few weeks.

Silk oke sound good is there some info on how to make the resin in different hardnesses?
 
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Hello all.
Just a thought: has a surround of cloth been given serious consideration? The characteristics of behavior in a cloth surround could be easily adjusted to suit the application by the implementation of various treatments of whatever impregnations or surface coatings (on the one hand). In the other hand, there are the endless options of fibers to choose from, both natural and manufactured. If I dare give a specific recommendation for your consideration regarding the choice of fiber, it would be silk: thin, lightweight, incredibly strong, incredibly fatigue resistant, easy enough to impregnate to suit whatever desired damping characteristics (and would still be light), and also would exhibit a low friction through excursion.
Regards - Aubrey


Cloth is basically what, personally, am set on.

The whole thing with the surround is this. I can see an advantage of no surround for a woofer because thats only on low frequency you will get the effects of Kms(x) non-linearity, and in any electrical model of a loudspeaker surround compliance only has a say in lower region.
For higher frequencies i would like a surround, something to properly terminate that cone, to absorb any waves traveling trough the cone from voicecoil.
In this regard tinitus might have something using felt as surround.
 
Jef it could work but even if you say no extra mass you do add a shorted ring there in the upper rim? depending on diameter that could be alot more than surround material. Also you need steel and magnet structure with high diameters which are very costly as you know.

In the mean time i changed it to little extra mass ;-) You are right on this.
For production too expensive, for one of a kind do-able i think
 
Another thing to consider is that more often than not it is the spider that has the biggest influence on compliance and the one with the bigger linearity problems.

In this regard, I like GOTO philosophy. I had the chance to meet Tanaka-san from Audio Laboratory Tanaka and he revealed the importance of strong motors and soft suspension system. It is a quite natural way for a very detailed sound.
After that i did test this replacing Ti suspensions in compresion drivers with mylar much softer and alot more revealing in the midrange at least.
 
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Hi to all

Hentai,
Is that my new motor? It looks awesome, what is the final weight? I am a bit concerned don't think the basket I am using now is strong enough to hold it. Well time will tell. You mentioned that the surrounding will absorb some of the energy from the cone.....I never thought of that, you may have a good point there.

Jef,
I relay like your idea, I have been thinking along those lines. But the thing I wasn't sure of was if the suspension coil will fix the voice coil in both directions X and Y.

I did some experiments with different materials for cones also silk, I found that silk is to soft compared for a given weight. I did one cone of silk that weight 5,2g and it was way softer than a 2,4g Viscose/resin cone.

For different stiffens you can you different resin/epoxy, I use one that is approved for F16 fighter jet, it has a nice weight to stiffens ration. If you ad micro balloons to the resin you can increase the stiffens.

I have a idea for a spider with a suspension that varies with frequency, I will make a drawing and get back.

Take care
Frank
 
Hi Frank, yep that is your motor.

Spider has a mass component as well. So if you think using 2 spiders and no outer suspension will yield lower mass, you have to calculate spider mass as well.

tinitus has a a point. Think of guitar louspeakers. These extend well in the upper midrange section, one can think of them as wide range speakers. But what we need to think about is wide range and low distortion, something a small spider can't provide.
 
Hi to all

Jef,
I relay like your idea, I have been thinking along those lines. But the thing I wasn't sure of was if the suspension coil will fix the voice coil in both directions X and Y.

Take care
Frank

Radial centering is possible with ferrofluid. between the inner voicecoil and the polepiece. That is the main reason why the motor has two airgaps to hold the whole cone with ferrofluid stable as there is no surround. After simulating this structure i found out that the double airgap brings a lot more flux density to the bottom airgap. (two magnets opposite to eachother, they wil attract eachother because of the iron between them) Axial centering is also possible due the use of a second underlying coil. => the main advantage is that you can soften or harden the suspension like disired. But the main advantage is that the suspension has the same force reduction as X increases like the voicecoil (see curve i posted). So X-I curve is full lineair. i think is almost impossible with a normal spider. The first type is already made and working but the parameters were the worst ever (nothing was calculated) now with the new motor system everything looks good on paper. Within a few weeks it must be ready to test.
It is possible to drive the suspensioncoil with a current driven source this eleminates the fluctuating inductance till 20Khz
It is also possible to drive the suspension with a voltage driven source the inductance wil fluctuate in the same way as the voicecoil so this effect on both the suspension and voicecoil will compansate eachother.
So X is more lineair but Q will fluctuate in this case. With a total BL of 20NA I think this is less or even not noticable.

For the cone still searching for the ideal solution but you guys already helped a lot. gonna research some suggestions. start with glassfibre...

Thx.
 
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what is the final weight? I am a bit concerned don't think the basket I am using now is strong enough to hold it.

Haven't weighted them yet but i would expect around 15kg. It will definately not hold with just the holes in the frame. You need to make a holder for the motor inside the speaker so that the motor rests on something solid.

Jeff for cones it all depends if you want it conical or curved.
 
i don't know if that would be helpfull for You ( haven't seen anything on that in this thread ) but you can actually try to make paper pulp of some kind and apply it on the surface of the mould ( previously coated with something non sticky ) - or just try to make positive mould out of negative mould the same way and use it as a press for making cones - also when it comes to fiberglass maybe if it's so lightweight it's better to try to make sandwich of some kind out of it instead of multi layered cones ( the fact is that this kind of structure should be way more rigid ) - this way You could even create cone that would be fiberglass on the inside of speaker and paper on the outside ( and I didn't figured out what could be in between as of yet :) but eton springs to mind with theirs honeycomb of some kind )

great work - I'm highly impressed
 
Hi piotr z

I did try making a cone from paper pulp but it did not work out for me, it wasn't as easy as I thought. Making a composite with fibre glass is definitely a possibility, but it will ad to the mass.
But in the end it is all about finding the sweet point between weight, stiffness and damping of the cone.

I did managed to make a spider and a cloth surrounding, still waiting for the epoxy to cure fully.
 

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Hi piotr z

I did try making a cone from paper pulp but it did not work out for me, it wasn't as easy as I thought. Making a composite with fibre glass is definitely a possibility, but it will ad to the mass.
But in the end it is all about finding the sweet point between weight, stiffness and damping of the cone.

I did managed to make a spider and a cloth surrounding, still waiting for the epoxy to cure fully.

wow surround looks awesome. Good work!