Voice coil cooling

[Moondog55]

Just a short query and conjecture.
i've just read through the Pi Speakers article on cooling high power woofers.
When testing my current project, (OB with cheapo woofers and old japanese 8inch midrange ), the backplate on the mid was getting very hot.
I moved the crossover frequency up a bit and changed the slope a bit and that helped but midrange was still getting much hotter than the bass units.
I am considering a quick fix using silver epoxy and a couple of old heatsinks from computer chipsets.
These old Coral 8inchers sound too good to destroy, has any-one tried this?? and if so what difference did it make??
I will of course make my personal findings known but they will be subjective as I don't hav a sensor that I can fit to the back plate easily.

regards
ted

[Cal Weldon]

It can't hurt can it? The only thing I've seen (diy? I'm not sure) was a heatsink stuck to the back of a TB neo tweeter.

This one:
http://www.partsexpress.com/pe/showd...number=264-804

Sammi did this to their 12" coax

[Moondog55]

I got the idea from the Vifa neo tweeter, I'm going to see how this silver / epoxy from "Arctic Silver" works

[breez]

A while back I had an idea of voice coil cooling by heat pipes. A heat pipe would go into a vented pole piece and transfer heat effectively to a large heat sink in the back panel.

I also found an old japanese AES paper on the subject, only that they had the radiator in the port of a ported box (for airflow = cooling). They could double the continuous power handling by using the method.

However, it doesn't look like it would be easy to pull off as DIY. One would need a heat pipe manufactured to fit the dimensions of an existing woofers pole piece. This would be more suited to commercial loudspeaker manufacturers who could manufacture all parts to specification themselves.

One possible DIY option would be a screw threaded woofer vent with the possibility to stick whatever length and shape of heat pipe provided it has a matching screw thread on one end.

[Moondog55]

Hi breez, thats how Pi did them but with a large passive plate as the heat exchange inside the box.
As I can't abide throwing anything away ( Hey!! It may come in useful iff'n I keep it long enuf ) I have rather a large collection of used heatsinks here.
West Systems epoxy may also be used here i would say but I haven't been able to find any data on the thermal resistance of aluminium filled epoxy.

[BlueWizard]

This is an open baffle cabinet...right?

You may not be aware of this, but those who push there computers to the limit, and those who don't like fan noise, use water cooling in place of fan cooling on their processors.

An aluminum plate is attached to the processor with tubes running to a radiator, and the fluid (it's actually not water) is pumped through the system.

These are very effective cooling devices, so effective that one of the problems is occasion condensation of water on the tubing.

Just a thought.

Steve/bluewizard

[Moondog55]

Yes Steve in this instance it's an open baffle, but in principal you could apply this sort of cooling to any speaker.
Even if the voice coil is centre vented I have seen heatsinks that could be drilled out, leaving the hole uncovered but still enough contact around the edges.
I have a son who is into computers in a big way and I've seen those water cooled radiators, some of the new computer chips run "HOT" but that is going too far for speakers, think of the pump noise raising the floort hreshold by 12dB

[Brett]

Originally posted by Moondog55
i've just read through the Pi Speakers article on cooling high power woofers.

I read that a while ago, not long after I finished my LABhorns from memory. Whilst it seemed to be an issue in Pro use, mine certainly never even got warm. As I'm going to be using the second NOS set for some PR subs, I may mount them magnet out to keep them cooler.

Can't see why it would make much difference OB, but as it's free, try it and tell us your results.

I also like the idea of some external cooling system, but I'll keep that experiment for later with my bass guitar cabs.

[Moondog55]

Hi Brett!
I was surprised at how hot the Corals were getting when I started to put more than a couple of watts thru them.
These are an older driver and the dust caps are sealed so no ventilation ( these drivers may have been modified by the last owner to improve HF radiation ) but they were HOT to touch 88 +, and as I have all the stuff here why not??

Moving the X-over up a touch and making the slope a little steeper so less movement in the driver probably means more.
As this is experimental I wanted to use what I had on the shelf, so cross-overs were determined not by driver performance but by what inductor I had in my tool box ( in this case the cheap laminate cored unit from Jaycar 9.**mH )
I can actually see a time in the future when watercooling PRO gear makes sense, the cost of the required hardware is going down faster and faster.
It must make some difference as the little Vifa neo I have had them designed in from the get-go.

[Moondog55]

Just a little OT but if you wanted to make a good low mid driver , what is better fot the high frequencies?? a whizzer cone or a big dome, looking at this driver I think the woven vent cap was replaced as these are big and heavily textured soft paper.