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Old 24th May 2012, 08:52 PM   #21
tvrgeek is offline tvrgeek  United States
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Have to pass on the props. I have seen many a post on magnet sims, but never someone actually build what they were talking about.
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Old 27th May 2012, 07:13 PM   #22
Hentai is offline Hentai  Romania
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Hello and thank you for your comments.

I have returned with more details. I was in hurry and i missed a few questions from LineSource.

I see no major problems with using this type of unit as a mid-bass like in the Daniel Hertz loudspeaker. A heavier cone would be more advantageous i guess in such application and one can do that by adding a mass ring right at the base of the cone. Or one can just lower the current through the field coil. (one of the greatest feature of these kind of units).

As LineSource pointed out for 12 inchers 1khz is about the 90 deg point. Once the whizzer cone is added, things change. From low high frequencies (1-3Khz) , depending on size ( mostly voice coil diameter as i have noticed) up to about 5-7kHz both cones work together and after that the whizzer cone has the significant role in output. Therefore the directivity pattern is pretty different from a normal mid-bass unit. A 2" voice coil makes life hard in this matter tho.

Below is an AxiDriver simulation of a whizzer cone i want to try out. This is just the whizzer without cone. Reality will be different because there is no way to tell how it will interact with the main cone and the simulation has the whizzer connected to chassis through wide surround.

Click the image to open in full size.

There is much work i need to do to determine whizzer cone parameters. I have simulated various shapes, diameters and heights. Haven't done much regarding a possible phaseplug.

This weekend i started to test some cone shaping. So far i tried straight cones from a single plain sheet and petal cones. These are just try-outs but here are some pics:

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

To stiffen the cone i layered the paper like a sandwich putting a higher density one in the middle. Should try the opposite too.

Click the image to open in full size.
Attached Images
File Type: jpg whizzer03.jpg (15.3 KB, 1467 views)
File Type: jpg DSC02874.JPG (666.2 KB, 50 views)
File Type: jpg DSC02875.JPG (537.4 KB, 58 views)
File Type: jpg DSC02880.JPG (295.2 KB, 70 views)
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Old 28th May 2012, 04:25 PM   #23
Hentai is offline Hentai  Romania
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Things are progressing.

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.

Here's the assembled structure w/out fieldcoil on a vintage 12" Al frame:

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

I will use nicer screws in the end, these are what i had on hand.
Attached Images
File Type: jpg DSC02884.JPG (220.2 KB, 61 views)
File Type: jpg DSC02885.JPG (320.3 KB, 37 views)
File Type: jpg DSC02886.JPG (249.6 KB, 33 views)
File Type: jpg DSC02888.JPG (300.0 KB, 58 views)
File Type: jpg DSC02891.JPG (541.3 KB, 70 views)
File Type: jpg DSC02892.JPG (622.1 KB, 89 views)
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Old 28th May 2012, 09:06 PM   #24
kevinkr is offline kevinkr  United States
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Wow, that motor structure looks great. Do you have drawings of the various machined parts you could post in the event that others might want to copy your efforts?
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Old 28th May 2012, 09:23 PM   #25
Hentai is offline Hentai  Romania
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Hello Kevin, yes, after some testing of the motor and if no major adjustments are needed to current design i will post the full schematics.
Pretty soon i hope
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Old 2nd July 2012, 09:30 AM   #26
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great project! just waiting for further information
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Old 2nd July 2012, 06:46 PM   #27
Hentai is offline Hentai  Romania
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more info will come, pretty busy month but will resume the project soon.

But here is a little teaser. A friend and countryman helped me and manufactured a couple of mullbery paper cones. Here are some shots:

Click the image to open in full size.
Click the image to open in full size.
Attached Images
File Type: jpg DSC00045.JPG (53.9 KB, 60 views)
File Type: jpg DSC00046.JPG (98.7 KB, 53 views)

Last edited by Hentai; 2nd July 2012 at 06:56 PM.
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Old 2nd July 2012, 07:43 PM   #28
Zen Mod is offline Zen Mod  Serbia
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will you leave them flat , or you intend some curvature ?
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Old 2nd July 2012, 08:40 PM   #29
Hentai is offline Hentai  Romania
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I'm also making exponential curved cones, from 12 petals, washi paper. I'm still experimenting with stiffening the washi.

Click the image to open in full size.

I will test everything i can. Straight and exponential and maybe hyperbolic but i fear the curvature will be too great.

So far mass is well within my goal. I will perform as much tests and measurements as i can and my equipment allows on all cones and whizzer types. Hopefully phase plug variations too.
Attached Images
File Type: jpg DSC02933.jpg (943.2 KB, 46 views)

Last edited by Hentai; 2nd July 2012 at 08:41 PM. Reason: grammar
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Old 2nd July 2012, 11:19 PM   #30
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All this is really really great.

I would risk two noobish questions :

1. Nowhere I read a reference about the voice coil inductance. Isn't it BTW the limiting factor in bandwidth extension ? Then, isn't a smaller VC more adaptated for this issue ?


2. For the cone and the whizzer, with the skills you have, aren't you considering to make a one piece molded one, from your own paper mix over a machined shape ? I guess you could even make a press for exponential parts.
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