Surround less, spider less, mid bass driver - diyAudio
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Old 1st July 2014, 08:55 PM   #1
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Default Surround less, spider less, mid bass driver

Hi,

Some people may know me from this forum as in Hentai's thread about field coil full range drivers. The people there (and information) were very helpful to me. That said, I waited to start my own thread until the driver i'm working on is as good as i want. It is not at the final stage, especially cosmethic, but the fundamental part is ready (after 2 years). A few days ago I tested the latest design and must say the sound was incredible. Oke it is hard to judge your own design especially when there is so much effort is involved. That is the reason I contacted a friend of mine, he has the Gamut L5 for reference. The simple setup I use for now (active crossover) simple bass reflex case tuned to 45Hz give some incredible results. The clearness, imaging, and refinement where beyond the gamuts. So easy to listen to, clear but not harsh or thin.
Over the past months I read tons of documents, artikels, even commercial sales talk to get as close as it gets to come to the point of what is really important for the best sounding speaker/driver as possible.
The main goal for me was to create a driver that has as little distortion as it could be. In my opinion there were some general driver characteristics that could be improved. The most important task of a driver is the conversion of an electrical signal into the correct corresponding sound wave. This is only possible if you can maintain a high level of linearity on different aspects. For example, a spider is never full lineair because of the changing angle between the spider and the former. This is where manufacturers have to find a compromis between linearity (large spider) and mass,resonant and back wave distortion.
Also the surround is for me a eyesore, the most surrounds add non linearity to the excursion and not to forget it moves as fast as the cone, producing sound from soft bending rubber. Also the weight and compliance of the surround results in more internal forces on the cone this results in flexing and bending.

Personally I belief in dome setups, the despertion is not as great as some would consider but it will give a wider sweet spot and cleaner sound (this is not coming from calculations but only from real world testing).

These above findings resulted in a speaker that has almost none of those irregularities.



Some advantages:
- Full lineair excursion till X-max p-p 8mm. It compensate the reduced force of the voicecoil at high excursion due to lower springforce on this position, just in the same way)
- Small neo magnet so the motor is small (60mm) and has no basket (it is extended by a pipe and mounted on the back of the cabinet)
- No spider => thus no backwave distortion on the spider and resonances
- Suspension is changable from zero till very stiff
- No surround => no counterforce on the edge of the cone => this greatly reduces flex of the cone and retain the linearity of the suspension.
- 10mm 0.2mm thick Alu ring on the outside of the cone (also greatly reduce flex of the cone) + very stiff and light carbon/kevlar cone treated with some damping layer resulted in a very stiff and refined cone/dome.
- Very good airtightness. The alu ring on the cone is placed between two other rings to avoid wind noise.

The principle of this driver is made possible by electromagnetic force for the suspension.

My question:
- I like to know the comments and maybe improvements of other members. My primary goal is not only to sell these speakers (you never know offcourse) but make the best drivers in the world with no compromises. Oke this might too much but you have to aim high if you want to make a good product.

- I will consider to manufacture these drivers but only if there is alot of interest in it. You don't have to beleive what i'm saying now but if this driver is as good as i say what is the response to this?

Picture of 3th generation driver. The last one (4th) is with damping material and the phaseplug is almost flat made of aluminium.
For who is interested i can give impedance plot and small thiel parameters.


Take care,

Jef N.
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Old 3rd July 2014, 12:03 AM   #2
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Measurements?
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 3rd July 2014, 02:30 AM   #3
CLS is offline CLS  Taiwan
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Seems very interesting, but, er, please excuse my ignorance, by the description and photo, I still can't figure out how it works.

Is it possible to have some cut-away drawing or the likes?
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Old 3rd July 2014, 04:33 AM   #4
sreten is offline sreten  United Kingdom
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Hi,

Making some coherent sense would help a lot.
Like how a spiderless / surroundless driver has
an easily adjusted suspension that is neither.

rgds, sreten.

And no, TS parameters and an impedance plot are not useful.
I suspect this is going to turn out to be a clueless wind up.
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Last edited by sreten; 3rd July 2014 at 04:46 AM.
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Old 3rd July 2014, 09:09 AM   #5
pos is offline pos  Europe
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Nice!
What is the mechanical resistance (Rms T/S) of such a driver?
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Old 3rd July 2014, 02:39 PM   #6
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Quote:
Originally Posted by pos View Post
Nice!
What is the mechanical resistance (Rms T/S) of such a driver?
Hi,

Rms= 8.0044 N*s/M with 0.4A through the suspenion coil (can go to 1A)
Re= 4 Ohm
Bl= 8.9NA this wil be lower in the next version (around 6.5NA)
Qts= 0.3
Le= 0.1316mA
Mms= 15.1g
Sens. 92db @ 1W
Fs. from 21.9 to 35Hz

The values will change a little going to plan to drop Bl to get a more flat response curve. Re will be 5.5Ohm in the next version.

You can clearly see on the back (this was cone setup with surround) that there is no spider. The latest version don't have a surround.

The problem is that i have no patent on this so I can't give al the info on how it is made but believe me it works very good. I understand this is not pleasant but I hope you guy's will understand me. I can give some info...

the radial centering is with ferrofluid and there are two airgaps inside.
It needs a Dc current for the suspensioncoil. There are DIY project on the net that tries the same with a coil above and below the airgap in opposite direction but this is not lineair around the zero point. But you get the idea:-)

You can see the magnetic flux density in the gap is also as flat as possible (overhung system)

The final driver is not ready yet but further development will become quite expensive. So that is the reason that I post this thread to see if the extra money is well spend.

Take Care
Attached Images
File Type: jpg IMG_9633.jpg (754.0 KB, 695 views)
File Type: jpg impedance dome kevlar.JPG (70.7 KB, 660 views)
File Type: jpg Plot x-y.JPG (35.6 KB, 624 views)
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Old 3rd July 2014, 02:53 PM   #7
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Quote:
Originally Posted by sreten View Post
Hi,

Making some coherent sense would help a lot.
Like how a spiderless / surroundless driver has
an easily adjusted suspension that is neither.

.
"The principle of this driver is made possible by electromagnetic force for the suspension" => extra coil with dc current.... so no there is no spider and surround and yes there is a suspension.
https://www.youtube.com/watch?v=wSkL0osNzWY

No not a windup if you like, on youtube, is a video of the earlier version (version 2) in action.

Kind regards,
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Old 3rd July 2014, 03:02 PM   #8
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Wink Worth protecting!

Hi Jeff,

I like this concept and I would encourage you to submit a patent application before you give away any more information...Lots of commercial designers steal ideas from DIY guys and then claim its their own!

I have some ideas but I would not want to discuss them in public as this would compromise any future IP claim you might wich to make.
Happy to PM then email from there.

Good luck....!
PS Ignore the ignorant old guys who have had 50 years of passive crossovers & " them there Scanspeak cones and domes " ....They just cant understand anything else!!
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Old 3rd July 2014, 08:16 PM   #9
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Looks interesting even if i don't get it!
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Old 4th July 2014, 01:53 AM   #10
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Why not simply make it as a kind of a voice coil at the cone perimeter, as well as elsewhere if desired? Then you can tune suspension damping if desired with a version of the actual signal to be reproduced.
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Last edited by thoriated; 4th July 2014 at 01:58 AM.
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