Magnet Question

[audioholic 5,000+ posts]

My first post stated that it's worth noting that a motor acts as a heat sink... you and helotaxi seem to think otherwise or you wouldn't have posted...

I wouldn't consider the size of the motor as any realisitic difference in heat dissipation, unless a method is used like on the GTi subs that actually have cooling fins built into the motor structure.
Yes the motor gets hot. But will the relatively small difference in surface over a 'medium' motor and a 'large' motor make a significant difference in cooling the voice coil? No.

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I disagree about the channels in a motor.. they are there primarilly to increase the cooling of the motor itself.. not the coil..

The DD example you cited has holes drilled for 'direct cooling' of the coils, iirc. This allows cool air to be more easily dispersed across the coil and through the motor...

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As far as the JBL.. a motor dosen't have to have fins per say to act as a heatsink... JBL just capitilized and improved on the fact that a motor acts as heatsink...

I wouldn't consider the size of the motor as any realisitic difference in heat dissipation, unless a method is used like on the GTi subs that actually have cooling fins built into the motor structure.

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I really don't want to get into a clown match with anyone over something I already know about.. To state the obvious, again.. a motor does infact act as a heatsink... and like any heatsink increasing it's surface area increases it's ability to disapate heat.. and increasing it's mass increases it's heat capacity..

Are you planning making a point someone has contradicted?

 

[1ndatrunk 10+ year member]

Wow. This is getting good!//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif Can one of you gentlemen take a breather and give me some extra info, please

 

[Haunz 10+ year member]

Are you planning making a point someone has contradicted?

wow, you are being a real tool... with no use

And I really like the way you put quotes together to misconstue the thread...

Incase you missed it 3 pages ago I am contradicting the comments that a motor has no affect on the dissipation of heat from a voice coil when it clearly does...

 

[helotaxi 5,000+ posts]

The outside air temperature has some effect, too. I never said nor implied that it had no effect. It still isn't that efficient which is probably why so many companies have designed forced air cooling for the coil. Heating the pole and the steel of the motor (which isn't the same as the magnet which has almost NO effect on coil cooing) only does so much for you. You're not really getting rid of the heat very effectively if you're just moving it in one of the least efficient manners (convective transfer x2) to a material that is a very poor radiating material. Aren't the fins on the GTi drivers aluminum? You know, a material that actually does a good job of transferring heat. Also quite possible that those fins are purely cosmetic...

 

[squeak9798 5,000+ posts]

Read my first post.. then go from there..



And for the record... a motor dosen't just sink 'some' heat... it sinks a lot...

So you're playing a game of semantics.

Define "a lot".

Define "some".

They've both acknowledged that the motor does indeed act as a heat sink. Presently you're just hellbent on proving that you're more right than they are by replacing their ambiguous term with an equally ambiguous term.

Petty. There's another ambiguous term to throw into the mix //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[James Bang 5,000+ posts]

Petty. There's another ambiguous term to throw into the mix //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

No, it's very petty

//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[audioholic 5,000+ posts]

Incase you missed it 3 pages ago I am contradicting the comments that a motor has no affect on the dissipation of heat from a voice coil when it clearly does...

I guess that is where the problem lies, then. Yes, I obviously missed it, please tell me exactly where helo or I said the motor has no affect on heat dissipation. //content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif I think squeak summed up this argument pretty well. I could say more, but I wont.

 

[fast85_gt]

i say go for it you have $2000 dollar woofer motor that can take a 20k bump so do a 12 or 15" fi recone give it 2000wrms dailey and im sure it will be fine you have a beast of a motor there have fun with it let us know how it works out i did the same thing same motor not fi thow i ran 1400wrms daily did good had no heat probs. did not overheat the voice coils or any thing just play with it and have fun my recone was 160 with ship and did it myself and still sold the sub with box for 400

 

[Haunz 10+ year member]

I guess that is where the problem lies, then. Yes, I obviously missed it, please tell me exactly where helo or I said the motor has no affect on heat dissipation. //content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif I think squeak summed up this argument pretty well. I could say more, but I wont.

My appologies if it appears that I am attempting to argue semantics... My first post simply stated that it's worth noting that a motor acts as a heat sink for the coil.. then Helo had to chime in with "the transfer of heat from the coil to the motor is horrible inefficient" and "The magnet itself is a terrible heatsink material"

The fact is that the motor structure of a moofa plays a large roll in keeping the coil cool by sinking heat away from it.. and I do not think this fact should be down played..

 

[Haunz 10+ year member]

Heating the pole and the steel of the motor (which isn't the same as the magnet which has almost NO effect on coil cooing) only does so much for you. You're not really getting rid of the heat very effectively if you're just moving it in one of the least efficient manners (convective transfer x2) to a material that is a very poor radiating material. Aren't the fins on the GTi drivers aluminum? You know, a material that actually does a good job of transferring heat. Also quite possible that those fins are purely cosmetic...

The OP was asking about motors as a whole.. not just the magnet.. but FYI, both the magnet and the steel in the motor are primarilly made up of ferrite.. that should tell you that they will have some similar properties; and while the magnet will have a lower thermal conductivity then the steel in the pole & plates it's not exactly an insulator either... //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

If you are going to add sink material to a motor it makes sense to use copper or aluminum, hence the fins on the JBL.. that still dosen't change the fact that the motor alone sinks heat away from a coil and disipates it into the air around the sub...

I recall this being discussed by some industry memebers over on carsound back in the day.. including a rep from JBL..

 

[audioholic 5,000+ posts]

My appologies if it appears that I am attempting to argue semantics... My first post simply stated that it's worth noting that a motor acts as a heat sink for the coil.. then Helo had to chime in with "the transfer of heat from the coil to the motor is horrible inefficient" and "The magnet itself is a terrible heatsink material"
The fact is that the motor structure of a moofa plays a large roll in keeping the coil cool by sinking heat away from it.. and I do not think this fact should be down played..

Clearly our difference of opinion here comes down to how much we feel the motor size plays a role in cooling.

 

[helotaxi 5,000+ posts]

Big difference between ferrite (ceramic) and steel. I would hope you know that...I've never seen steel made fron ferrite. Ive seen it made of a ferrous material because it is by definition, but iron and ferrite are hardly the same thing.

Without being designed specifically as a sink, the motor makes a poor one. It will draw some heat into itself but as you said yourself steel is a poor thermal conductor. It is slow to heat up (so slow to draw heat from the coil) and slow to cool off (so slow to shed the heat that is has absorbed). If designers were counting on the motor to act as a significant heatsink, they would actually address making it more efficient.

 

[1ndatrunk 10+ year member]

Lets just be friends guys I thank you all for this valuable information. I feel smarter already:veryhapp:

 

[Haunz 10+ year member]

I've never seen steel made fron ferrite. Ive seen it made of a ferrous material because it is by definition, but iron and ferrite are hardly the same thing.

You are in way over your head....

Clearly our difference of opinion here comes down to how much we feel the motor size plays a role in cooling.

Fair enough.. and it's debatable.. but the more I think about it the more it's clear that the motor is integral to taking heat away from the coil..

Did you happen to catch the white paper that was being discussed on here a few months back which showed how ineffectual pole vents are at getting air to the voice coil and the top of the motor ?

How many drivers only have pole vents, or no venting at all ? The question then is, where does the heat go ????

I am very confident in saying that if you took the same coil with the same amount of power it's going to run cooler and longer in a 100lb motor then it is going to in a 30lb motor..

Of course a 100lb motor is not always going to be practical or even necessary; and much depends on the application... As with any other aspect of a driver the sheer size of the motor is only one part of the overall equation... but it is certainly a part of that equation nonetheless...

 

[helotaxi 5,000+ posts]

You are in way over your head....

Well then since you seem to know all why don't you explain how ferrite (a ceramic made from iron dust in the case of this discussion) is made into steel? Going to mince words I imagine. Containing the one of the same basic materials, doesn't make it the same material or have even similar properties, you should know that.

Your really have a way of coming across like a know-it-all smug ***, you know?