Voice Coil Formers... Kapton vs Nomex vs Aluminum vs GF/TIL - diyAudio
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Old 1st June 2007, 12:43 AM   #1
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Default Voice Coil Formers... Kapton vs Nomex vs Aluminum vs GF/TIL

OK a sequence of events has got me thinking and I can't make up my mind... So I figure I'll ask what everyone else thinks on the topic and make sure I'm not overlooking anything crucial.

OK!
Kapton, Nomex, and GF voice coil formers are all non-conductive. This means that the QMS value will be higher (1.5-2.5x the value depending on the thickness), the BL will be higher (slightly) and well you can do the math on the mms, many of these are very light, but less structurally sound so need to be thicker so it evens out more or less.

Aluminum is conductive (thermally and electrically) so therefore in reality power handling should go up at least a bit if the thickness of the aluminum is substantial enough to matter. For example some subwoofers I'm playing with have .2mm thick Black anodized aluminum formers wrapped in some .13mm thick nomex reinforcing paper for the collar... Granted if the voice coil is wound on the inside and the outside of the former (more $$$) it won't matter too much if you use a thermally conductive former or not.
Aluminum vs kapton coils as noted in another thread:
http://www.tymphany.com/datasheet/printview.php?id=90
http://www.tymphany.com/datasheet/printview.php?id=91

Does anyone have any input/preferences/observations I missed?

Oh they are all good until about 220-250C... With the right reinforcement you can push BASV to 280C though… Really higher but that’s starting to get risky for other reasons.

Thanks
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Old 1st June 2007, 01:43 AM   #2
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Aluminium ones usually have a thin slot cut along the side so that they don't form an electrically closed loop. Otherwise Qms would drop below the level of Qes, which would be worse than trying to use a dual-VC speaker with one of the voice coils short-circuited.
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Old 1st June 2007, 02:44 AM   #3
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Quote:
Originally posted by CeramicMan
Aluminium ones usually have a thin slot cut along the side so that they don't form an electrically closed loop. Otherwise Qms would drop below the level of Qes, which would be worse than trying to use a dual-VC speaker with one of the voice coils short-circuited.

that would be fun!

Against my better judgment I have some up close and personal pictures to go with the theme...

Black anodized aluminum with black nomex, 220C minimum, 250C rated wire with high emissivity... 2" Dia coil for an ultra budget unit.
Click the image to open in full size.

Black anodized aluminum... I forgot what paper and 180C wire... WRONG! I'm waiting for the right one That coil is 3" dia. if it gives you any idea about how crazy I am... Yes the motor structure is huge, and if I don't get full saturation of that pole like my calculations say, I'll be getting an even bigger structure... I really don’t want to take off winds if I can help it.

Click the image to open in full size.

hopefully there isn't too much flame for such a monstrosity...

Edit:
Well if it is 20% lower BL the 15" actually would be rather nice.... but limited to the cult of the infinitely baffled and insane SPL competitions... Oh and people that don't mind *really* large (8cuft+) boxes @home... Limited to about 84-86dB/w...
Granted the normal BL is still happiest in 8cuft+ it can handle a bit smaller and into 87-89dB/w.
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Old 1st June 2007, 03:27 AM   #4
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Meh... If I were you I'd chuck out the old-fashioned ceramics and build myself a beefy electromagnet! ...Just like the ones they use in movies to pick up cars with helicopters.
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