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Refrigerated Rear compartment of Speakers?? Problems??

190.56.56.102
Posted on February 15, 2015 at 05:35:01
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
 Drivers Power tolerance ratings are notoriously overrated. Actually at about 25% of that rating the VC resistance rises and distortion etc occurs. Manufacturers of drivers design air cooling methods utilizing the moving action of the cone to shuffle air causing heat removal out of the VC and nearby structures. But air is actually an excellent heat insulator and this heat removal method is inefficient. It seems obvious that refrigeration cooling of the rear compartment of speakers would cause a much greater differential between the VC ,nearby hot stuctures and surrounding air and improve the heat transfer out of drivers.

Anybody seen this method used?? Any problems?? Actually my main concern would be condensation of the humidity in air causing water drops and dripping internally. We all know that water and electricity ( in the form of AC to speakers ) donīt mix. But actually cooling dries the air and if cooling is started some time before speaker power is applied this may not be a problem as water and humidity is removed??

Actual refrigeration of the rear compartment can be very easy. Just remove the door out of an old small frig and bolt the frig box to the driver board so that it acts as the speaker rear enclosure itself. It would be nice to be able to use a driver close to its overrated power rating for a change. In PA work some efficient horn designs using a single refrigerated driver may do the job instead of many direct radiation boxes. For example 2x18" boxes with drivers rated at 600 Watt really put out less than 5% of 1/4 of its power rating. So less than 15 Watts of acoustic power is really put out per box. Yet a 300 watt rated driver operating close to full power in a refrigerated 50% efficient horn would put out 150 Watts of acoustic power equalling TEN 2x18" cabs!!

Anyone seen any use of refrigerated speakers....any problems etc. Opinions advice welcomed.


Thanks
Rafaro

 

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Wooden enclosures, posted on February 15, 2015 at 06:11:45
genungo
 Wooden enclosures and refrigeration sometimes don't mix very well. I recommend moving your speakers into an igloo if you can afford it.

 

RE: Wooden enclosures, posted on February 15, 2015 at 09:03:48
adam@denderapartners.com
Audiophile

Posts: 282
Location: So. Oregon, State of Jefferson
Joined: October 1, 2007
 I'm having a vision of a great video of what happens to the igloo when the OP is making use of that massive power efficiency and the drummer gives the bass drum a good thwack!

Holy flying ice blocks, Batman!

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 15, 2015 at 09:10:09
Serge_S
Audiophile

Posts: 112
Location: NYS
Joined: March 13, 2012
 .

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 15, 2015 at 09:53:31
zako
Audiophile

Posts: 935
Location: Mo.
Joined: March 29, 2004
 the newer voicecoil bobbins are designed to take the heat and dissipate it,,,I wouldn't be obssesive about...

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 15, 2015 at 11:14:16
Alpha Al
Industry Professional

Posts: 2958
Location: N. Carolina
Joined: February 16, 2004
Contributor
  Since: December 3, 2015
 Some PA and guitar speakers (EV primarily) have heat dissipating fins on the rear of the magnet. I've never seen any get the slightest bit warm. Never!

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 15, 2015 at 13:32:01
tomservo
Manufacturer

Posts: 8215
Joined: July 4, 2002
 The voice coil is the thing that gets hot, the temperature is what makes the resistance rise and causes the output to go down and T&S parameters to change with increasing temperature.

It is the wire that needs to be cooled off and the easy way is to pass air across the wire. In the 80's and 90's i worked at a NASA contractor and was allowed to pursue a loudspeaker based on a rotary servomotor and which used air cooling. The air was blown through the motor, across the conductors and the hot air ejected.

These were not for home use but were used on a number of large concert tours like Def Leopard, Garth Brooks and Micheal Jackson.
If you Google "Servodrive BT-7" and look at the images, you will notice a vacuum cleaner style motor used for cooling air.
This can be applied to "normal driver as well...

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 15, 2015 at 14:46:30
zako
Audiophile

Posts: 935
Location: Mo.
Joined: March 29, 2004
 JBL Just used a series of holes in the bobbin of the voicecoil to pump air around the VC wires,, It was enough to keep the down the temperature of the voicecoil..Refridgment or fans were not used..

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 16, 2015 at 10:36:27
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Short of PA applications, it seems unlikely that most folks will ever throw enough power at their drivers to run into this issue. Look at L-pad resistor dividers in your average crossover, you may find an 8 Ohm 10W resistor in series with a driver, and they hold up OK.

My vote for cooling would be to have a large threaded hole in the pole piece, then thread in a water cooling block. A simple pump/radiator intended for cooling a computer's CPU could sit behind the speaker. Now that would be fun!

It is also worth noting that field coil drivers run insanely hot, so you can design for such things in the first place.

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 16, 2015 at 20:44:04
Steve Schell
Manufacturer

Posts: 1440
Location: So. California
Joined: December 16, 2001
 Despite endless hours of play at live + levels, the only voice coil failure we've ever experienced with our Cogent horn drivers was the time a customer tried some strange, supposedly great solid state amps on his bass horn drivers, one of which malfunctioned and presented a large DC offset. The portion of the voice coil forced out of the gap, thus bereft of heat transfer, showed all sorts of weird colors and unraveled from the former due to the insane heat. Some refrigeration might have helped here!

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 17, 2015 at 03:41:35
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
 Hello Tom.

Yes itīs the VC wire that gets hot. The nearby magnet front and rear plate receive some of the radiated heat from the VC and help in shunting heat away from the VC. It seems reasonable since manufacturers have already designed air cooling as the main method to help cool the VC wire to go further and reduce the temp of the surrounding air. The greater temp difference between the VC wire and air should help and make up for the insulating nature of air. As you know the main failure mechanism of drivers especially in PA work is overheating of the VC wire. This also limits actual performance! In efficient horn designs this is less because of the greater electric to acoustic conversion. Nevertheless it also means that increasing the heat tolerance of drivers results in much greater benefit as my example pointed out.

My respects for your designs and mission statement!


Rafaro

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on February 17, 2015 at 04:07:02
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
 Hello Steve and Caucasian:

Yes horn drivers experience less thermal stress because of the greater electric to acoustic efficiency but imagine the output being able to push them 50% more!!!

Liquid cooling has already been done along with other methods of reducing VC overheating by conduction. These work better than air cooling as air is actually an excellent insulator and just removes radiated heat and poorly at that. Refrigeration is easy to do applies to all drivers no specific yoke etc needs to be designed to each driver.


Rafaro

 

Why don't you construct prototypes?, posted on February 17, 2015 at 12:53:39
Craiger56
Audiophile

Posts: 5574
Location: San Jose CA
Joined: April 3, 2002
Contributor
  Since: December 29, 2003
 You don't seem to understand the great advise given so far.

If you construct working models and live with them for a month or two then you can see for yourself how valuable your idea is.

Craig

 

RE: Why don't you construct prototypes?, posted on February 17, 2015 at 21:38:58
Rafaro
Audiophile

Posts: 158
Joined: July 30, 2005
 Right....I always pass new sometimes crazy ideas by the forum as a filter. I was hoping someone had seen, heard of or had tried this but even in this very knowledgeable group with many Pros it seems it has not been done. I think it has potential I will proceed with prototypes.

thanks


Rafaro

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on March 6, 2015 at 02:15:36
hollowboy
Audiophile

Posts: 263
Location: Melbourne
Joined: June 26, 2007
 1) Make the rear wall of the cabinet a heat sink (a thick, ribbed sheet of metal).

Use heat pipes to link the magnet to it.

= much less trouble "The significant feature of a thermosyphon is that it is passive and does not require any external power to operate"

...but still more effort than I'd ever go to

2) Adapt a CPU cooler / oil pump. Put the oil reservoir in the fridge, rather than putting the speaker in the fridge.

 

RE: Refrigerated Rear compartment of Speakers?? Problems??, posted on March 6, 2015 at 09:54:16
zako
Audiophile

Posts: 935
Location: Mo.
Joined: March 29, 2004
 YEH,,,GO ahead and invent a cooling system that's not more expensive than the speaker

 

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