OK the speakers I'm working with at the moment don't qualify as rare or expensive, so, I'll probably stop with the heat sink as being easy and cost effective.
That said the idea of drilling and tapping the centre pole would allow me to use something with good thermal character such as a solid brass bolt, if it was long enough it would be easy to add radiation area in the form of a disk of aluminium or copper or just a commercial heat sink with the properties needed.
Good stuff😀 😀
That said the idea of drilling and tapping the centre pole would allow me to use something with good thermal character such as a solid brass bolt, if it was long enough it would be easy to add radiation area in the form of a disk of aluminium or copper or just a commercial heat sink with the properties needed.
Good stuff😀 😀
A fairly easy mod would be to drill a small (~1/4") hole into the center of the [solid] backplate, insert a copper heat pipe with an aluminum heat sink on the end, and solder it in. The heat required for a eutectic solder is lower than the Curie point of a ceramic magnet... however, with the heat pipe in place, you will need to dump tons of heat into the backplate. Not sure how the voice coil or former would fare.
A little goes a long way
OK after waiting a while for the aluminium powder to arrive I did some work with epoxy today.
West Sytems resin with slow hardener as thats what I had.
Added an equal amount of aluminium powder by volume to give somethinf with the consistecy of cold treacle.
I started on the drivers I thought needed a little help
http://www.flickr.com/photos/25510659@N07/2920978628/
http://www.flickr.com/photos/25510659@N07/2920133519/in/photostream/
http://www.flickr.com/photos/25510659@N07/2920977134/in/photostream/
http://www.flickr.com/photos/25510659@N07/2920976960/in/photostream/
The Kaltro driver got a bigger heat sink as I'll probably be pushing it a little harder but the black triple rb heatsink was for dual 100 watt TO3's so should move quite a bit of heat, the smaller Coral/Foster midbass has a mesh vented cap so the smaller heatsink ( from P3 cut in half ) should be enough.
Easy stuff to work with I'll give them 48 hours to cure and give a report
OK after waiting a while for the aluminium powder to arrive I did some work with epoxy today.
West Sytems resin with slow hardener as thats what I had.
Added an equal amount of aluminium powder by volume to give somethinf with the consistecy of cold treacle.
I started on the drivers I thought needed a little help
http://www.flickr.com/photos/25510659@N07/2920978628/
http://www.flickr.com/photos/25510659@N07/2920133519/in/photostream/
http://www.flickr.com/photos/25510659@N07/2920977134/in/photostream/
http://www.flickr.com/photos/25510659@N07/2920976960/in/photostream/
The Kaltro driver got a bigger heat sink as I'll probably be pushing it a little harder but the black triple rb heatsink was for dual 100 watt TO3's so should move quite a bit of heat, the smaller Coral/Foster midbass has a mesh vented cap so the smaller heatsink ( from P3 cut in half ) should be enough.
Easy stuff to work with I'll give them 48 hours to cure and give a report
I have been pumping music thru these drivers all morning, same crossover as before 33uF in series and 9mH in parallel.
3 hours now and the heatsink is not even warm, higher than ambient but much lower than last time.
I don't know how many watts are going to the driver but the amp is capable of 100 all day and the SPL is average 90 with peaks of 106dB, mind you it is a really cheap meter, but so far I'd say it works and works quite well.
The West Systems mix of epoxy and aluminium is easy to work with ans is high temperature rated ( above 88 degrees Celcius ) and has set smoothly and hard.
Obviously Waynes plug and radiating plate is much better but I think this is going to be a very cost effective solution to overheating of the cheaper sort of driver, when combined with sensible cross-over design that is.
So far I'm happy with the experiment, thanx to Wayne for his insight and Cal for his encouragement
3 hours now and the heatsink is not even warm, higher than ambient but much lower than last time.
I don't know how many watts are going to the driver but the amp is capable of 100 all day and the SPL is average 90 with peaks of 106dB, mind you it is a really cheap meter, but so far I'd say it works and works quite well.
The West Systems mix of epoxy and aluminium is easy to work with ans is high temperature rated ( above 88 degrees Celcius ) and has set smoothly and hard.
Obviously Waynes plug and radiating plate is much better but I think this is going to be a very cost effective solution to overheating of the cheaper sort of driver, when combined with sensible cross-over design that is.
So far I'm happy with the experiment, thanx to Wayne for his insight and Cal for his encouragement
Wow!
The meter on the amp has been reading at the top of the scale on peaks for over 3 hours now ( 100 Watt ) so I guess average of about 30 watts has been going to the drivers, split that in half given the low C/C point and the mid isn't even warm, BUT the low pass coil is almost too hot to touch, I could smell hot insuation.
I have of course turned the music way down.
I knew that the coil was bordrer-line being almost 1R0 DCR.
I need coils with bigger wire ( Damn!! I need more expense like I need a hole in the head It's going to take a lot of persuasion with the missus for those )
Regards
Ted
The meter on the amp has been reading at the top of the scale on peaks for over 3 hours now ( 100 Watt ) so I guess average of about 30 watts has been going to the drivers, split that in half given the low C/C point and the mid isn't even warm, BUT the low pass coil is almost too hot to touch, I could smell hot insuation.
I have of course turned the music way down.
I knew that the coil was bordrer-line being almost 1R0 DCR.
I need coils with bigger wire ( Damn!! I need more expense like I need a hole in the head It's going to take a lot of persuasion with the missus for those )
Regards
Ted
Moondog55 said:
How about some wacky idea like using aluminum filled west system epoxy to bond the coils to some kinda heat sink??
Nah....that'd be just silly...😉
Cheers, John
I thought of that and then remembered a post linking to some experiments where that had been done ( sort of ) it does strange things to value of inductance.
I just need to use higher quality coils.
This coil was from "Jaycar" a local supplier and rated at 100 watts, but when it gets hot it must be dropping SPL a few dB as the copper gets hot and resistance increases.
Isn't the basic "rule of thumb" to try and keep DCR of inductors below 10% of the nominal impedance of the drivers?? What can I expect when I break that rule
I just need to use higher quality coils.
This coil was from "Jaycar" a local supplier and rated at 100 watts, but when it gets hot it must be dropping SPL a few dB as the copper gets hot and resistance increases.
Isn't the basic "rule of thumb" to try and keep DCR of inductors below 10% of the nominal impedance of the drivers?? What can I expect when I break that rule
If you put a conductive material within the flux lines in such a was as to create eddy currents within the conductor, then the inductance of the coil will be reduced as a result, and the entire structure will dissipate more.
Just bond aluminum fins so that they don't allow flux lines to pass normal to the material..
Simple..
Cheers, John
ps..here's a link. Yah, it's not an inductor, but the geometry of the heatsink is correct for use as a heatsink for an inductor. If you think of the magnetic field of the inductor as a toroidal set of field lines, you can see that the bulk of the field lines will travel parallel to the fins of the heatsink assembly I show. So it'll not change the inductance of the coil, but will allow cooling.
http://www.cpii.com/docs/datasheets/78/3CX1500A7-8877.pdf
Just bond aluminum fins so that they don't allow flux lines to pass normal to the material..
Simple..
Cheers, John
ps..here's a link. Yah, it's not an inductor, but the geometry of the heatsink is correct for use as a heatsink for an inductor. If you think of the magnetic field of the inductor as a toroidal set of field lines, you can see that the bulk of the field lines will travel parallel to the fins of the heatsink assembly I show. So it'll not change the inductance of the coil, but will allow cooling.
http://www.cpii.com/docs/datasheets/78/3CX1500A7-8877.pdf
..... I wonder why nobody took resort to taking a bigger tube of aluminium (in diameter, that is) of and cutting (deep) threads both on the outside and inside to increase the surface of the cooling tube.(Choice of rectanglar, trapeze and ordinary v-shaped threads there is. Rounded threads do not fit the bill here. )
No bolted connections needed there.
Since I unfortunately do not have access to a turning lathe anymore I can't serve with samples here.
Using cutting tools with "not-so-sharp" tips/cutting area would increase the surface even further.
One could achieve a tight fight by turning the area of contact with the loudspeaker magnet/pole-piece slightly larger than the inner diameter of the pole-piece vent, cooling/freezing the tube a bit down to shrink it and slip it into the pole-piece vent.
(O.K. let's be very careful there, to my exoerience , and probably to the experiences of others, ferrite magnet structure are not very "resistive" to magnetic stress.)
Greez
SigFire
No bolted connections needed there.
Since I unfortunately do not have access to a turning lathe anymore I can't serve with samples here.
Using cutting tools with "not-so-sharp" tips/cutting area would increase the surface even further.
One could achieve a tight fight by turning the area of contact with the loudspeaker magnet/pole-piece slightly larger than the inner diameter of the pole-piece vent, cooling/freezing the tube a bit down to shrink it and slip it into the pole-piece vent.
(O.K. let's be very careful there, to my exoerience , and probably to the experiences of others, ferrite magnet structure are not very "resistive" to magnetic stress.)
Greez
SigFire
Probably because most voice coils dont have that much metal avaliable to allow for the depth of the thread, but I did think of that see previous posts.
Most of us don't have lathes avaliable and hand tapping half inch coarse threads in mild steel is quite hard, not to mention the cost of buying the tap and die set.
However if you already owned a tap set and could do it I think it is possibly one option in a solid pole piece. The extra surface area of the thread does allow more heat to escape; common solution on machine gun barrels
Most of us don't have lathes avaliable and hand tapping half inch coarse threads in mild steel is quite hard, not to mention the cost of buying the tap and die set.
However if you already owned a tap set and could do it I think it is possibly one option in a solid pole piece. The extra surface area of the thread does allow more heat to escape; common solution on machine gun barrels
....ooopps , I never thought that my english was THAT bad.
I didn't think of threading the speaker and the tube to fit.
I thought of cutting grooves into the part of the tube that stays outside the speaker. The tube would have to be, well, fit by "due expansion" after freezing. ( not quite "press-fitting", that would be) No threads THERE. You just got to see that the (thermal) expansion of the cooling tube when "in full function", is not so much as to burst the speakers magnet structure or pole-piece.
Greez
SigFire
I didn't think of threading the speaker and the tube to fit.
I thought of cutting grooves into the part of the tube that stays outside the speaker. The tube would have to be, well, fit by "due expansion" after freezing. ( not quite "press-fitting", that would be) No threads THERE. You just got to see that the (thermal) expansion of the cooling tube when "in full function", is not so much as to burst the speakers magnet structure or pole-piece.
Greez
SigFire
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