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| Re: Heat sink, Heat exchange for driver/cabinet [message #78159 is a reply to message #78156] |
Mon, 21 October 2013 08:45   |
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Wayne Parham
Messages: 18793
Registered: January 2001
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Illuminati (33rd Degree) |
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In Eminence drivers, the mesh is just pressed in, and can be easily pried out.
Check to see that the ID of the center pole has constant diameter throughout. Sometimes, when the back plate is pressed on, it compresses the center pole piece and makes it out of round. You want a constant diameter to maximize the area of contact between cooling plug and center pole. If it is not round and uniform, machine it to make it so.
You can use a hone, but even a drill press will suffice. Naturally, this step is easiest before assembly (or during a recone) because the magnet will capture the debris. That's OK unless if it doesn't get into the gap. If debris does get into the gap, it is easy to clean if the voice coil isn't there, but practically impossible if it is.
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| Re: Heat sink, Heat exchange for driver/cabinet [message #78224 is a reply to message #78223] |
Tue, 29 October 2013 10:56 |
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Wayne Parham
Messages: 18793
Registered: January 2001
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Illuminati (33rd Degree) |
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The vent through the center pole has to have consistent diameter for best contact with the cooling plug. The only way to know is to measure it. But if the center pole hasn't been machined - and most aren't - you can assume that the diameter isn't consistent. How much inconsistency is there is really the question, and whether or not it is good enough to make an adequate thermal interface. Still, the best approach is to machine the pole piece to make it true.
The depth of the cooling plug should be the same as the depth of the center pole. It doesn't have to be precisely the same length though. In fact, my loudspeaker designs allow the cooling plug to "float", in that the position of the cooling plug can change depending on the position of the dissipation plate it is attached to. This is because the plate serves double purpose as an access plate. I allow 1/8" movement in or out in the design of my cooling plugs to allow for changes in access plate gasket thickness (squish) and other loudspeaker assembly tolerances.
The goal is to have as much surface area between cooling plug and center pole as possible. So it is desirable that the plug be as long as required to extend all the way into the vent. It can even extend beyond the pole piece, into the cavity behind the dust cap. However, be careful not to extend so far that the center cap might strike the cooling plug at full excursion.
As for the magnetic effects, the cooling plug acts weakly as a shorting ring. It does have an affect, similar to the ones used to counter flux modulation. But it isn't a strong electro-magnetic modifier because of its position in the motor, and in my experience, I haven't see any measureable changes other than those due to thermal effects.
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