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Old 30th May 2004, 04:10 AM   #1
Wizard of Kelts
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Default Weight Of Voice Coil, (As Opposed To Mms)?

Trying to get a handle on what would be the weight of a voice coil, former and wire alone, unattached to the cone.

I am mostly interested, for now, in an average weight of a five inch midbass speaker. Just a ballpark figure.

These speakers from Australia have a 6 inch midbass with a voice coil weight of 1.4 grams and a total moving mass of 10.6 grams.
http://www.osbornloudspeakers.com.au.../epitspec.html

Is that typical? Are the former and wire of voice coil usually such a small percentage of the total moving mass? Or is the Osborn company pointing out this stat because it is so unusual?

Any help would be appreciated here.
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Old 30th May 2004, 04:37 AM   #2
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What would you do, even if you got your answer?
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Old 30th May 2004, 05:25 AM   #3
Wizard of Kelts
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Quote:
Originally posted by 454Casull
What would you do, even if you got your answer?
A) Curiosity. We see the Mms parameter so often, might as well find out what is the voice coil and what is the diaphragm.

B) Thinking of taking a cheap midbass, eliminating the cone, and making a solid, flat-faced cone composed of wafers of expanded material encased in metal foil, electroplated or perhaps dipped in some hard material. Then glued together.
http://www.diyaudio.com/forums/showt...091#post400091

Have seen Mms ratings of 5.7 and 7 grams for five inch midbasses, (4 inch cone diameter). Need to find out how much of that is the voice coil itself in order to know what total weight the wafers should add up to.
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Old 30th May 2004, 08:18 AM   #4
Svante is offline Svante  Sweden
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You should be able to calculate the amount of copper in the gap from BL and B (which would give you the length of the wire in the gap), then compensate for the "overhang". The factor would be <voice coil length>/<height of the gap>. Then as you know the total length of wire, and its DC resistance, you should be able to calculate the cross-sectional area from the resistivity of copper. This, multiplied with length and density of copper should give you the mass.

Added to this would be the material that the coil is winded on (what's the name of that?) and glue, but that is probably a small part of the total mass.

Easy...
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Old 30th May 2004, 11:13 AM   #5
sreten is offline sreten  United Kingdom
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To a first approximation the weight of the voice coil determines
the high frequency cut off of the driver. So for a bass only unit
the %tage of Mms that is the voice coil is not relevant.

For bass/ mids and "fullrange" drivers the %tage is very
important, ~ the lower it is the higher the driver will go.

Aluminium is used for the voice coil wire whenever
voice coil mass is a major issue (instead of copper).

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Old 30th May 2004, 11:18 AM   #6
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by Svante

Added to this would be the material that the coil is winded on (what's the name of that?)
Commonly referred to as the voice coil former.

Note that you can have formerless voice coils.

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Old 30th May 2004, 11:33 AM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by kelticwizard

B) Thinking of taking a cheap midbass, eliminating the cone, and making a solid, flat-faced cone composed of wafers of expanded material encased in metal foil, electroplated or perhaps dipped in some hard material. Then glued together.
http://www.diyaudio.com/forums/showt...091#post400091
Nearly all "flat" bass / mid drivers in the days when they were
popular used a cone from the voicecoil to drive the diaphragm
over a much larger radius - typically this was determined by
the first nodal resonant points of the flat diaphragm.

Possibly your best bet is using a small 3" voice driver e.g. :
http://www.partsexpress.com/pe/showd...number=295-605

Balsa wood and alumimium foil work well apparently, I remember
a design using a 2" x 6" diaphragm with an elongated parallel coil.

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