Hello,
A larger voice coil will provide you with an overall stronger motor/cone assembly. There will be more surface are to glue the cone & spider & former together.
A larger voice coil will also help in keeping hte voice coil cool. It will dissipate heat better.
The size will not effect the impedence, the windings do that.
Inductance, not sure. I am sure others will.
Regards
KevinLee🙂
A larger voice coil will provide you with an overall stronger motor/cone assembly. There will be more surface are to glue the cone & spider & former together.
A larger voice coil will also help in keeping hte voice coil cool. It will dissipate heat better.
The size will not effect the impedence, the windings do that.
Inductance, not sure. I am sure others will.
Regards
KevinLee🙂
Below saturation, the geometry of the voice coil will subtly affect the Le, inasmuch as the ratios of winding width, thickness, and diameter affect the performance of an air-core choke.
I like large-diameter VCs for many apps. For example, I believe the dome mid-bass is a fertile direction for exploration. How about a 10" voice coil? 😎 An underhung topology wouldn't need a very thick top plate, and the inherent heat sinking would be awesome--power compression would be a thing of the past...
I like large-diameter VCs for many apps. For example, I believe the dome mid-bass is a fertile direction for exploration. How about a 10" voice coil? 😎 An underhung topology wouldn't need a very thick top plate, and the inherent heat sinking would be awesome--power compression would be a thing of the past...
An underhung voice coil must fit inside the top plate...
Besides, aren't dome mid-range units hard to do? The few on the market aren't comparable to the better cone midrange units, I've heard.
Besides, aren't dome mid-range units hard to do? The few on the market aren't comparable to the better cone midrange units, I've heard.
Some say that a larger voice coil adds more moving mass, which may have a grain of truth to it, but the JBL E145 combines a moving mass of 55 grams (very light) with a 4" vc and still manages to handle 300 watts music power.
Exactly. So if you take a given 3" VC, unwind it from its former, and rewind it on a 10" former with the same number of layers, the winding height will be 0.3x the original height. Thinner top plate for same Xmax. And the heat sinking would be multiplied.
There shouldn't be much of a weight penalty if any. Since the dome VC it attached around the perimeter (more attachment area), you'd have the makings of a stiffer system without having to increase diaphragm thickness.
It probably wouldn't be cheaper to produce, and there may be other downsides I'm not thinking of, but I think it could be a really great performer.
A 10" VC on what size cone?
If driving a 10" cone then all the force is at the perimeter which just wouldnt work as there would be nothing to hold the apex of the cone.
I think 3" is about the limit, on a 6" cone this puts the 'driving force' iin the middle, any further and I would imagine cone flexure to start creeping in.
If driving a 10" cone then all the force is at the perimeter which just wouldnt work as there would be nothing to hold the apex of the cone.
I think 3" is about the limit, on a 6" cone this puts the 'driving force' iin the middle, any further and I would imagine cone flexure to start creeping in.
Cones flex anyway.
Goodmans designed the cones in their loudspeakers specifically to flex in order to produce the desired frequency response.
I mean, if the cone folds up, you have a problem, but I think it could be made to work. Cones can be made very tough these days, with just whatever properties we want in many cases.
Goodmans designed the cones in their loudspeakers specifically to flex in order to produce the desired frequency response.
I mean, if the cone folds up, you have a problem, but I think it could be made to work. Cones can be made very tough these days, with just whatever properties we want in many cases.
Bill has mentioned cost but I think it needs a little more weight. The quantity of steel required to make a >10" motor and the extra magnets required would make this very expensive indeed (relatively speaking), and thus probably only practical in the DIY realm.Bill F. said:
Off course the benefits mentioned sounds very appealing 😉
I'm thinking dome, so VC dia.=diaphragm dia.
If you're worried about rocking modes, using a spaced pair of surrounds/spiders would take care of that.
If you're talking about deflection under load, IMO, one of the big advantages of a perimeter-driven dome is that as the cantilever distance increases (from the driven edge toward the unsupported center), decreasing amounts of mass are added. This is an improvement over an apex-driven cone where most of the mass is located at the end of the cantilever farthest from the VC, putting greater deflection loads on less material.
Ok, so maybe I soft-peddled the expense just a bit... You're right--it would indeed take a lot of magnet to make this motor. But if you want to push the performance envelope, you gotta be ready to shell out. You oughtta see all my pet transducer designs--not a frugally specd one among 'em. I'm talking pounds of neodymium! 😀
You should be banned from this forum Bill. Everytime I start reading your posts I start thinking about motor designs - and my work suffers... 😀
Have you implemented any of you monster motor designs. Would be great to see them...
Thanks! If I am ever banned, I guess I will take it as flattery.
Lots of designs, but none prototyped just yet. It's so darned expensive to have custom machine work done, and I'm always refining my designs...
Actually, I recently picked up four Aura 1808 NRT motors for cheap that I'll be turning into something functional soon. These things are monsters--4" dia. x 2" tall gaps lined with NdFeB. Their poles are fully copper sheathed, and they each weigh probably 25 lbs.
My first idea was to make 4" dome midranges out of them with EM/ferrofluid suspension--I think you know what I mean. 😉 It would kind of be an ATC-type dome on steroids. I'd potentially have 20+mm of one-way underhung excursion on tap, but I'll never use half of that.
The other idea is an open-baffle woofer using some of the thinking I put into that DIY Parthenon thread that seems to have fizzled. Either one or two Aura motors would drive either 2'x2' or 2'x3' expanded polystyrene diaphragms suspended by a novel means I've developed. The single-motor app. would have ~20mm of one-way xmax, and the push-pull two-motor app. would have a little more than twice that. App. one would be excursion limited, and app. two would be thermally limited down to the teens.
Lots of designs, but none prototyped just yet. It's so darned expensive to have custom machine work done, and I'm always refining my designs...
Actually, I recently picked up four Aura 1808 NRT motors for cheap that I'll be turning into something functional soon. These things are monsters--4" dia. x 2" tall gaps lined with NdFeB. Their poles are fully copper sheathed, and they each weigh probably 25 lbs.
My first idea was to make 4" dome midranges out of them with EM/ferrofluid suspension--I think you know what I mean. 😉 It would kind of be an ATC-type dome on steroids. I'd potentially have 20+mm of one-way underhung excursion on tap, but I'll never use half of that.
The other idea is an open-baffle woofer using some of the thinking I put into that DIY Parthenon thread that seems to have fizzled. Either one or two Aura motors would drive either 2'x2' or 2'x3' expanded polystyrene diaphragms suspended by a novel means I've developed. The single-motor app. would have ~20mm of one-way xmax, and the push-pull two-motor app. would have a little more than twice that. App. one would be excursion limited, and app. two would be thermally limited down to the teens.
This is heading somewhat off topic.
Take a 6.5" / 8" unit with a 1" voice coil.
A bigger voice coil (1.25"/1.5") alows a higher sensistivity
alignment and more power handling at a minor cost of
top end extension.
Once you get past say ~ 2" voicecoils the magnet gap
is not run at full strength (Q would be too low) and its
really a philosophical design issue, the Dynaudio and
Morel drivers are examples of this using a 3" coil.
Here the design purpose is to keep all parts of the cone
a short distance from the voice coil and it seems to work.
IMO a coil bigger than 3" for an 8" unit is fairly pointless.
And motor strength, inductance etc cannot be compared
because large voice coils are not run at saturation levels
like much smaller voice coils.
🙂 sreten.
Take a 6.5" / 8" unit with a 1" voice coil.
A bigger voice coil (1.25"/1.5") alows a higher sensistivity
alignment and more power handling at a minor cost of
top end extension.
Once you get past say ~ 2" voicecoils the magnet gap
is not run at full strength (Q would be too low) and its
really a philosophical design issue, the Dynaudio and
Morel drivers are examples of this using a 3" coil.
Here the design purpose is to keep all parts of the cone
a short distance from the voice coil and it seems to work.
IMO a coil bigger than 3" for an 8" unit is fairly pointless.
And motor strength, inductance etc cannot be compared
because large voice coils are not run at saturation levels
like much smaller voice coils.
🙂 sreten.
rumours says that ATC's allready done that - perhaps billy woodman has a "grand design" up his sleeves........😉
That agrees with my WAG 'rule of thumb' for voice coil diameter optimization🙂
approx 3" vc for 8" driver
3-4" for 10" driver
4-5" for 12" driver
6" for 15" driver
Really huge voice coils sometimes tend to require more pole piece material, but designs like Dynaudio's and Morel's do an excellent job of keeping the total magnetic assembly reasonably sized even with the largest practical voice coils for their drivers, and they are self shielded, electrically rugged drivers to boot.
I'd really like to see some one put on the market a 8/16 ohm 15" woof with a 6" underhung vc, doped fabric surround, shielded neodymium magnet assembly, Mms of, say 60 grams, 100db/w/m efficiency, Fs of, say 32 hz, Qts of, say 0.25 and a linear one way Xmax of 10mm. The closest I've seen so far are the JBL E145 and Oris BD15 woofer, but they fall short of having the full bill of goods in several areas.
Who'll be first to step up to the plate on this one?🙂
🙂att'n: Going further OT
)
I just picked up a driver from some guy for a hundred clams that you might like--it's a Seismic 8196.
It's 18", not 15", and it's got a 4" VC instead of a 6", but it doubles your excursion goal...
fs: 31 to 35 Hz
Qts: 0.22 to 0.28
Qes: 0.23 to 0.33
Qms: 3.609
Vas: 311 liters
Sensitivity: 99dB
Linear (underhung) throw: 40mm p-p
Max throw: 54mm p-p
Any ideas on what I should do with it?
)I just picked up a driver from some guy for a hundred clams that you might like--it's a Seismic 8196.
It's 18", not 15", and it's got a 4" VC instead of a 6", but it doubles your excursion goal...
fs: 31 to 35 Hz
Qts: 0.22 to 0.28
Qes: 0.23 to 0.33
Qms: 3.609
Vas: 311 liters
Sensitivity: 99dB
Linear (underhung) throw: 40mm p-p
Max throw: 54mm p-p
Any ideas on what I should do with it?
That Seismic is really an Aurasound 1808. You got a great deal as the Aura unit is over $1000....
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