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Author Topic: liquid cooled subs? alternative?  (Read 6349 times)

Christian Effendy

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liquid cooled subs? alternative?
« on: September 19, 2006, 12:32:21 pm »

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?
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John Roberts {JR}

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Re: liquid cooled subs?
« Reply #1 on: September 19, 2006, 12:55:24 pm »

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
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Mac Kerr

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Re: LOX cooled subs?
« Reply #2 on: September 19, 2006, 02:04:52 pm »

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

Mac
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John Roberts {JR}

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Re: LOX cooled subs?
« Reply #3 on: September 19, 2006, 02:26:18 pm »

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  Laughing

JR
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Wayne Parham

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Re: liquid cooled subs? alternative?
« Reply #4 on: September 19, 2006, 05:57:16 pm »


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.
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Evan Kirkendall

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Re: liquid cooled subs? alternative?
« Reply #5 on: September 19, 2006, 06:18:39 pm »

Why not use your cooling plug Wayne? Very Happy




Evan
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Iain_Macdonald

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Re: liquid cooled subs? alternative?
« Reply #6 on: September 20, 2006, 01:53:54 pm »

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.
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Christian Effendy

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liquid cooled subs? alternative? heatsink?
« Reply #7 on: September 29, 2006, 12:07:58 pm »

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.
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Iain_Macdonald

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Re: liquid cooled subs? alternative? heatsink?
« Reply #8 on: September 29, 2006, 03:59:07 pm »

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.
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Christian Effendy

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Re: liquid cooled subs? alternative? heat sink?
« Reply #9 on: October 01, 2006, 03:29:50 pm »

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
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John Roberts {JR}

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Re: liquid cooled subs? alternative? heat sink?
« Reply #10 on: October 01, 2006, 04:09:03 pm »

Christian Effendy wrote on Sun, 01 October 2006 14:29

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


http://www.ferrotec.com/products/ferrofluid/audio/

They offer two series of ferro fluid ("0" and "S")  presumably for woofers or full range use. I can't say that I've ever seen it used in such applications but I'm no speaker guy.

There was also a mention about it degrading from extended use above 125'C while it will tolerate 225'C transients, so good luck.

JR
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Wayne Parham

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Re: liquid cooled subs? alternative?
« Reply #11 on: October 02, 2006, 02:48:46 pm »


Quote:

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.


That's right, exactly.  The point I was making is that some mechanism needs to be employed to deal with splash, especially in a subwoofer application.  You have to seal it some way or the fluid will separate and leak away.  Splash guards, alternate venting, something - The large gap and long excursion of a subwoofer make ferrofluid leakage a problem.

I imagine leakage is why there are more hifi tweeters and mids with ferrofluid than there are high-power subs that use ferrofluid.  It seems like a good solution to me, but the leakage problem is probably the hardest one to solve.  Eminence told me that's why they don't use ferrofluid - Too much leakage.  I forget if I heard that from Jerry McNutt or Chris Rose, but I do recall talking to them about it in the context of an upgraded LAB12 driver I was looking at having them make for me a couple years back.

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Paul Gariepy

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Re: liquid cooled subs? alternative? heat sink?
« Reply #12 on: October 09, 2006, 03:31:57 pm »

heres an idea:

have vents on side of spider and a big pc fan on back of magnet. instant active and continus cooling.

maby even vent the hot exhaust out the ports?

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Wayne Parham

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Re: liquid cooled subs? alternative? heat sink?
« Reply #13 on: October 10, 2006, 01:07:21 pm »


Paul Gariepy wrote on Mon, 09 October 2006 14:31

maby even vent the hot exhaust out the ports?


Surprisingly, the air coming from the vents isn't hot, not even warm.  Voice coil temperature can be 450
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John Roberts {JR}

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Re: liquid cooled subs? alternative? heat sink?
« Reply #14 on: October 10, 2006, 01:43:48 pm »

Wayne Parham wrote on Tue, 10 October 2006 12:07


Paul Gariepy wrote on Mon, 09 October 2006 14:31]maby even vent the hot exhaust out the ports?
==============

Surprisingly, the air coming from the vents isn't hot, not even warm.  Voice coil temperature can be 450
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Wayne Parham

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Re: liquid cooled subs? alternative? heat sink?
« Reply #15 on: October 10, 2006, 04:18:46 pm »


There's no question that loudspeaker venting is a good idea.  But as to how much heat is actually transferred from a loudspeaker voice coil into the cooling vent air, I suggest a simple test.  Connect a loudspeaker to an amplifier and run it at high power levels.  Check the temperature of the air coming from the vent.  You might be surprised.
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Christian Effendy

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Re: liquid cooled subs? alternative? heat sink?
« Reply #16 on: October 11, 2006, 02:51:56 pm »

Yeah, and with what you gonna measure the temperature of that air? Your body thermometer needs few minutes to do so Smile Most thermometer won't be fast enough to measure the temperature of air moving as fast as that.
Maybe the different is just few degrees and can't be felt by your hand. And the air moving back and fort in very rapid succession, as fast as the cone moving right? Your skin will be very confused to noticed the difference
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Mac Kerr

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Re: liquid cooled subs? alternative? heat sink?
« Reply #17 on: October 11, 2006, 03:03:27 pm »

Christian Effendy wrote on Wed, 11 October 2006 14:51

Yeah, and with what you gonna measure the temperature of that air? Your body thermometer needs few minutes to do so Smile Most thermometer won't be fast enough to measure the temperature of air moving as fast as that.
Try this.

Mac
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Paul Gariepy

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Re: liquid cooled subs? alternative? heat sink?
« Reply #18 on: October 12, 2006, 12:25:56 pm »

ok this calls for an experiment....

I have a digital temp meter and a laser temp meter and a bunch of pc fans, now i need to choose a speaker to "cook" and see if i can get some results. I'll keep you posted.


i just saw this... Tom beat me to it (and then some)! lol

http://www.freepatentsonline.com/4757547.pdf
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Mark "Bass Pig" Weiss

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Re: liquid cooled subs? alternative?
« Reply #19 on: October 15, 2006, 04:00:27 am »

Another very sticky issue is certain weak points in the voice coil assembly. One area that I have seen prone to failure in commercially produced woofers and lead drivers is the portion of the voice coil winding that turns 90

Kerry Stansbury

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Re: liquid cooled subs? alternative? heat sink?
« Reply #20 on: October 15, 2006, 08:52:18 pm »

Just because you can't feel a warmer temperature of the air passing through the vents doesn't mean it's not removing heat. If you move a large volume of air fast enough you won't feel any temperature difference, even though it's removing heat. Take a frying pan and heat it up on the stove, shut the stove off and have a 22" box fan blow on it. The air that has already passed by the pan will not even feel warm, but the pan will be cooled off in a minute or so. If the air does feel hot, you're not moving enough air to cool at a maximum rate.
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Wayne Parham

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Re: liquid cooled subs? alternative? heat sink?
« Reply #21 on: October 17, 2006, 03:35:18 pm »



Kerry Stansbury wrote on Sun, 15 October 2006 19:52

Just because you can't feel a warmer temperature of the air passing through the vents doesn't mean it's not removing heat. If you move a large volume of air fast enough you won't feel any temperature difference, even though it's removing heat. Take a frying pan and heat it up on the stove, shut the stove off and have a 22" box fan blow on it. The air that has already passed by the pan will not even feel warm, but the pan will be cooled off in a minute or so. If the air does feel hot, you're not moving enough air to cool at a maximum rate.


There are a lot of things in play.  First, if the pan is hot at all, it will be radiating heat that you can feel.  Even at just a couple hundred degrees Fahrenheit, it radiates enough to feel.  By 400 degrees, it radiates a lot of heat, even though it is nowhere near luminous.

The air passing over the pan will also carry some heat away, some by convection and if there is liquid in the pan, some by evaporation.  Air rising makes convection, and air blowing over the pan makes forced air convection.  Evaporation of any liquid in the pan removes heat too.

The amount of heat carried by the air can be measured, and if it's a lot, it can be felt.  Stand near a car engine, for example.  You'll feel a lot of heat radiating from the engine.  Put your hand behind the radiator and you'll feel the air carrying a lot of heat too.

I agree with you that not being able to feel heat in the air does not necessarily mean it isn't carrying heat away.  But it is something of an indicator of how much heat is getting carried away.
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