ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  
Pages: [1] 2 3 ... 5   Go Down

Author Topic: Cooling fan (Patent 4757547)  (Read 10691 times)

Grant Rider

  • Newbie
  • *
  • Offline Offline
  • Posts: 34
Cooling fan (Patent 4757547)
« on: September 11, 2006, 09:38:36 pm »

I tried Tom Danley's cooling idea from the patent at http://www.freepatentsonline.com/4757547.pdf. I have some questions. I got cooling plugs and they work great. Now I want to try Danley's idea too. The cooling plug is threaded at one end so it makes it easy to add a pipe fitting for fan air.

I did a experiment and hooked up a fan to give a blast of air. I took Wayne Parham's sugestion to use the cooling plug as a fitting for the fan. The fan is in a funnel with caulk all around so it makes a blast of air out the small end. I hooked that to a tube and used a pipe fiting on my cooling plug.

The air rushing out of the magnet hole blasts with woofer movement even if the fan isn't connected. The air blasts are enough to move my pants leg! It turns the fan just from woofer air blasts!

The fan moves the woofer cone forward. How bad is that? Parham said it makes the speaker suspension stiffer in one direction and looser in the other. How much is too much? I know it makes more distortion and less xmax by shifting offset, but Danley must have figured something out. What can I do about the offset besides taking off the fan?

Does it only work with a specially designed woofer that has a cone that can move further out than in to make up the difference? Maybe a special speaker is a requirement for this to work? If there are exit holes maybe that will help. I think the problem is the restriction at the voice coil gap so the fan air will still push on the back cap a lot but not on front of the cone. That is my dilemma.

Here is what I tried. If I don't use much fan power, the woofer moving air blasts spin the fan by itself, so it isn't much use. If I use more fan power, the fan spins normally but the cone moves out further, sometimes almost as far as it can go. I can change fan speed in between, and that works sort of. The Danley patent uses power from the signal so it won't make the fan go unless power is high. I think the woofer will be pushed forward a lot by the fan when power is high though. That seems like it would still be a problem. Even if power is high, I don't think the cone should be shoved forward. Thoughts anyone?

Logged

Antone Atmarama Bajor

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 851
    • http://www.geocities.com/somesoundgreat
Re: Cooling fan (Patent 4757547)
« Reply #1 on: September 12, 2006, 04:46:51 pm »

     I'm not familiar with the particular patent that you are talking about but the cooling fan used in the BT7 does not blow air through a drivers pole piece but through a servomotor, and is vented back out of the box which never interacts with the diaphragm of the driver nor enters the horn chamber.  It runs in parallel with the motor using a rectifier and I think a filter to give DC signal proportional to the audio input.  

Antone-
Logged

Grant Rider

  • Newbie
  • *
  • Offline Offline
  • Posts: 34
Re: Cooling fan (Patent 4757547)
« Reply #2 on: September 12, 2006, 07:56:25 pm »

I can see blowing air through round dc motors with a fan. Open the can and run air through it. It can cool the brushes and windings and doesn't blow the cone forward or backward. What I don't see how to do is use a fan on a regular speaker without pushing the cone with fan air pressure. Wayne Parham said air cooling was a good idea but the problem was how to do without making a pressure differential between the front and back of the cone.

http://www.audioroundtable.com/ProSpeakers/messages/350.html

Tom Danley must have some idea because it is shown in his patent.

http://www.freepatentsonline.com/4757547.pdf.

I want to know how this can work.
Logged

John Roberts {JR}

  • Newbie
  • *
  • Offline Offline
  • Posts: 0
Re: Cooling fan (Patent 4757547)
« Reply #3 on: September 12, 2006, 08:24:51 pm »

Grant Rider wrote on Tue, 12 September 2006 18:56



I want to know how this can work.


I suspect a great deal of benefit could be realized with only modest air flow. Just removing the hot air from inside the box at a regular interval helps so you don't need much pressure. If you know in advance that you will have a pressurized box you can provide an asymmetrical bias in the surround (easier to say than do).

Now just off the top of my pointy head how about using two fans with one fan blowing in while another fan is sucking out. In principle if their flow rates are matched there would be no net pressurization of the chamber.  Very Happy

I suspect the fans will also look like a lossy port so that would need to be factored in for box tuning.

JR


Logged
 https://www.resotune.com/


Tune it, or don't play it...
-----

Grant Rider

  • Newbie
  • *
  • Offline Offline
  • Posts: 34
Re: Cooling fan (Patent 4757547)
« Reply #4 on: September 12, 2006, 11:52:13 pm »

Maybe so. Sounds tricky.  If the fan sucking is very strong it can balance the one that blows. I think it would be hard to balance because the one that blows has a lot of cone area to push against and the one that sucks only pulls on the small area through the voice coil gap. That's a good idea but I think it must be tricky to get right. Fan speed is probably critical too.

Maybe Tom Danley has other ideas we aren't thinking about. Otherwise I guess it needs a tricky balance. I guess I can't do it with a normal driver. A special one has to be made with extra ports or asymmetrical bias in the surround. Darn!


Logged

Grant Rider

  • Newbie
  • *
  • Offline Offline
  • Posts: 34
Re: Cooling fan (Patent 4757547)
« Reply #5 on: September 13, 2006, 09:41:34 pm »

Something I thought about all day keeps bothering me:

John Roberts  {JR} wrote on Wed, 13 September 2006 01:24

I suspect a great deal of benefit could be realized with only modest air flow.


The air rushing out of the magnet hole blasts with woofer movement already. The air blasts are enough to move my pants leg! I think it must do a lot by itself. How can the fan do more with "only modest air flow"?
Logged

John Roberts {JR}

  • Newbie
  • *
  • Offline Offline
  • Posts: 0
Re: Cooling fan (Patent 4757547)
« Reply #6 on: September 13, 2006, 11:04:54 pm »

Grant Rider wrote on Wed, 13 September 2006 20:41

Something I thought about all day keeps bothering me:

=John Roberts  {JR} wrote on Wed, 13 September 2006 01:24 I suspect a great deal of benefit could be realized with only modest air flow.

The air rushing out of the magnet hole blasts with woofer movement already. The air blasts are enough to move my pants leg! I think it must do a lot by itself. How can the fan do more with "only modest air flow"?


At issue is whether it's the same hot air moving back and forth vigorously or new cool air replacing the old hot air.

JR
Logged
 https://www.resotune.com/


Tune it, or don't play it...
-----

Grant Rider

  • Newbie
  • *
  • Offline Offline
  • Posts: 34
Re: Cooling fan (Patent 4757547)
« Reply #7 on: September 14, 2006, 12:18:28 am »

John Roberts  {JR} wrote on Thu, 14 September 2006 04:04

At issue is whether it's the same hot air moving back and forth vigorously or new cool air replacing the old hot air.


I think you are right there. The air must be cool.

The fan isn't needed because the air blasts from the cone are strong. Using the cone as the pump makes the fan not needed. There is no pressure differential offset problem that way either.
Logged

Al Limberg

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1482
Re: Cooling fan (Patent 4757547)
« Reply #8 on: September 14, 2006, 12:29:11 am »

You might contact the good folks at Community and see if they can provide you with any of their papers concerning their 'Air Force' concert system which used forced air cooling on traditional voice coil drivers.

Al
Logged
If the automobile had followed the same development cycle as the computer, a Rolls-Royce would today cost $100, get one million miles to the gallon, and explode once a year killing everyone inside - Robert X. Cringely

Grant Rider

  • Newbie
  • *
  • Offline Offline
  • Posts: 34
Re: Cooling fan (Patent 6837333)
« Reply #9 on: September 14, 2006, 01:32:11 am »

Thanks for the tip!  I found the patent:

http://www.freepatentsonline.com/6837333.pdf

This answers my questions. The Community Light and Sound patent references Danley's patent but says his invention resulted in too much noise and distortion as a result of the air pressure through the gap. That is what I thought was happening too.

I have disconected the fan. Danley's idea was worth a try though!

Do you know if Community still sells Air Force speakers?  I don't see them on their website. Have they been discontinued?
Logged
Pages: [1] 2 3 ... 5   Go Up
 

Page created in 0.051 seconds with 18 queries.