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[Christian Effendy]

I've read some exciting discussion in cooling fan topic.
Yes, the heat is big problem in long term high level operations.
That give me and idea, how about liquid cooling, you know like your car's radiator. It's been proved to be very effective.
I've seen a car sub employing this method, from Bazooka, I think.
And I've also seen few alternative method like the cooling plugs from Eminence's Kilomax and a sub (I forget the brand) even use it's one piece VC former / cone made entirely of aluminium as a heatsink.
Any idea guys?

[John Roberts {JR}]

Christian Effendy wrote on Tue, 19 September 2006 11:32

I've read some exciting discussion in cooling fan topic. Yes, the heat is big problem in long term high level operations. That give me and idea, how about liquid cooling, you know like your car's radiator. It's been proved to be very effective. I've seen a car sub employing this method, from Bazooka, I think. Any idea guys?

Yup, forget water cooling. There's probably a room in the Patent office dedicated to all the inventions responding to this problem.

IMO the main problem with water cooling or the perhaps more practical sealed heat pipe approach is that the heat is localized in the voice coil which is part of the moving mass of the loudspeaker so you can't rely upon direct conduction for getting the heat out of that VC.

As TD has already offered, even modest clear air flow will generate significant cooling without mechanical contact. There are probably multiple patents along the lines of harnessing cone motion or sound energy to pump air with varying success and considerations.  

JR

[Mac Kerr]

Yeah...Yeah...that's the ticket...liguid oxygen cooling!

Mac

[John Roberts {JR}]

Mac Kerr wrote on Tue, 19 September 2006 13:04

Yeah...Yeah...that's the ticket...liguid oxygen cooling! Mac

c'mon everybody knows that's impractical, and LOX is a fire hazard to boot. Now a well timed dose from a CO2 fire extinguisher is another story  

JR

[Wayne Parham]

Ferrofluid is used for liquid cooling, among other things.  It's a good idea, but naturally requires that the gap be sealed.  It has its own sets of problems but it does provide a good heat conduction path from voice coil to pole piece.

There are several good ways to cool the motor.  Cooling vents and fans work by forced air convection, ferrofluid filled gaps work by direct conduction and cooling plugs work by radiation.  

Any of these methods will work to remove heat from the motor, and the effectiveness of any of them is a result of the particulars involved.  Forced air works best if airflow is high, temperature of the air is low and surface area is large.  Radiation works best if the area between surfaces is large, the distance between them is small and the temperature difference is high.  Conduction works best if the surface area is large, the temperature difference across the conductor is high and the conductive properties of the material are good.

Seems to me that the best solutions are those that are simple and effective.  No harm in using more than one type of cooling method either.

[Evan Kirkendall]

Why not use your cooling plug Wayne?




Evan

[Iain_Macdonald]

Wayne Parham wrote on Tue, 19 September 2006 22:57

Ferrofluid is used for liquid cooling, among other things.  It's a good idea, but naturally requires that the gap be sealed.  It has its own sets of problems but it does provide a good heat conduction path from voice coil to pole piece.

Wrong !!!!

1) Ferrofluid does not need a "sealed gap". It is held in place by the magnetic field in the gap. Venting is sometimes/almost always needed with woofers. Because the air displacement can blow a significant amount of the fluid out of the gap during high excursions.

2) It also provides conduction to the magnet and back plate assembly. Not just the pole piece! Why? Because it is disposed about both sides of the voice coil assembly, and towards the back plate.

Iain.

[Christian Effendy]

I'm agree about the ferro fluid, it will work perfectly with tweeters because the gap is very narrow and the coil doesn't move too much. For woofers, I think the excursion and wide gap will spill the fluid over. Maybe if someone can come with some way to sealed the gap or make the ferro fluid with different viscosity to fit every driver, you know, like automotive lubricants.

If radiation method don't work, why the many manufacturers nowadays use heat sink. Most neodymium use them. The aluminium panel you used for the LAB subs is there for radiating the heat, right?

The heat sink design appeared for car audio subs long ago. At first I think it's just for cosmetics show off. But when I touched my sub's backplate after just few minutes blast , I understand that it's not. The magnet and backplate structure was too hot to touch.
For pro sound woofers that work for hours, it will make even bigger difference.

[Iain_Macdonald]

Christian Effendy wrote on Fri, 29 September 2006 17:07

"For woofers, I think the excursion and wide gap will spill the fluid over. Maybe if someone can come with some way to sealed the gap"

No, quite the opposite you need a vented gap in a loudspeaker.

Christian Effendy wrote on Fri, 29 September 2006 17:07

"Maybe if someone can come with some way to sealed the gap or make the ferro fluid with different viscosity to fit every driver, you know, like automotive lubricants.

This will surprise you !!! There are dozens of standard viscosity grades of ferrofluid and hundreds of custom variations. That's from just one company. DON'T think of it like an Automotive lubricant. That isn't how it works. It's a magnetic colloid. In other words the magnetic particles are in suspension. The FF is held in the gap by the magnetic field in the gap. Using ferrofluid is much more than just taking a syringe and injecting it in to the gap. Knowledge of the gap geometry and preferably a FEA of the magnetic circuit is important.

I should add, that the principle of magnetic colloids in lubricants, is used in some specialist aerospace bearings. Mostly where extreme pressure or lack of gravity occurs.

Iain.

[Christian Effendy]

Wow, I didn't know that. Can you give me recommendation on where can I get those kind of FF? I think I need them, most problem I've found here are burned-up voice coils.
For tweeters, I've found that FF also smooth the freq. response. Will the same thing applied for woofers?

Thanks
Christian