The other thing about reversing the valve body to suck air from the back of the box into the magnet is that you can mount any type of filter material into the terminal cup to ensure no debris gets into the coil. Only thing about that orientation is that you have to silicone the central nub of the flat disc to the valve mounting hole so it doesnt get sucked into the woofer.
Good thing about the original setup is you will smell a burning coil alot sooner and see any smoke pouring out the terminal cup right away.
Cheers!
Good thing about the original setup is you will smell a burning coil alot sooner and see any smoke pouring out the terminal cup right away.
Cheers!
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would a simple piece of copper plumbing pipe poked down the magnet vent an with soldered fins do enough good to be worthwhile with no external heat exchamger? I think the pipe might have holes like a "muzzle brake"
Instead of pipe you could easily stuff in an interference fitted "internal" custom heatsink extrusion. But the problem is still that the pole piece isn't what makes the heat. Ideally you directly cool the coil. In the case of the 15N850 the closest stock option you have is to apply a vacuum (or presssure) to the array of coil vent holes. Unfortunately, in any forced flow situation, there is no out without an in, or vice versa. An array of vent slots in the magnetic gap are required, as in the JBL I mentioned. Without that the only flow has to make it through the magnetic gap, thousandths of an inch. If additional slots were only on the top plate then air could be let in through the spider. Alternatively a sealed spider could have vent holes. A point to mention is that thermal resistance along the coil coaxially is very high compared to radially. So you do not need flow around the entire circumference of the coil, but several spots that flow across the entire coil length could be sufficient. In case of the JBL, there are only three, which probably isn't optimal on a 4" coil with forced air.
Thanks - see the limitations as the small mass of the coil can heat very quickly. I've accidentally smoked a 3" coil that was pretty long in less than a minute with a 100 watt amp (LF sine and not much cone movement) - It would be interesting if manufacturers would implement air cooling features into some products.
Could the magnet of the driver be mounted outside the rear of a shallow cabinet through a closely fitting large hole which could be sealed all around . Allowing cool air to be sucked in and out of the voice coil with the rest of the driver still inside the cabinet ? The you could just point a fan at the voice coil if you still needed to
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RC1 sound system used "active cooling" in their subs:
6- RC1 Technical Information – RC1 Sound System
6- RC1 Technical Information – RC1 Sound System
JCCART. Yes but unless you're using weather strip foam it may be difficult to remove the driver. Eg silicone.
Maybe try 3-4" abs pipe from the back of the magnet sealed with foam tape and put it right thru the rear wall like a regular port. That size pipe should give enough air mass for good heat exchange. This configuration will also brace the rear wall against the woofer.
Maybe try 3-4" abs pipe from the back of the magnet sealed with foam tape and put it right thru the rear wall like a regular port. That size pipe should give enough air mass for good heat exchange. This configuration will also brace the rear wall against the woofer.
Thanks that's a good idea . How much of an issue would this compression be if using in the home I'm hoping to make some big subs soon ?
If big means a couple 15's or 18's in an average livingroom, then no, it won't be an issue at all. The room will be your biggest problem.
ferro-fluid injection?
Edit: Strike that.. It seems unreasonable with a woofers movement. Even though it's not only done to tweeters. I will leave the idea up though.
Edit: Strike that.. It seems unreasonable with a woofers movement. Even though it's not only done to tweeters. I will leave the idea up though.
It has been done. But it adds mechanical friction losses and reduces Qms, often to values of less than 1. I’ve only seen it done in car subs - and yes they came that way.
Yes, this. Mount a large metal plate / heat sink in the back of the speaker. Thermally connect that to the speaker motor.
How to do the connection?
A high tech and cheap method: use a heat pipe from an old laptop. They are designed for exactly this purpose, to pump heat from the CPU to a (relatively) large heat sink.
Or something like this:
Products
Too late for one of my drivers. Was noodling around on my bass guitar at a decent volume but nothing crazy. Bass cut out and I see that the woofer jumped the gap. Seems that the adhesives at the spider/former joint became brittle with the excessive heat. Simply broke free from the spider. Other joints and the coil seem fine.
I'm a bit leery about pushing the limits at this point. This is the second expensive driver I've damaged in development of this project. First was a high xmax tweeter and then this high xmax woofer. Too rich for me. Think I might just go for a more conservative high SD/lower excursion approach. I have another 15N850 that hasn't gone through high power testing. Not sure what do with it at this point.
I'm a bit leery about pushing the limits at this point. This is the second expensive driver I've damaged in development of this project. First was a high xmax tweeter and then this high xmax woofer. Too rich for me. Think I might just go for a more conservative high SD/lower excursion approach. I have another 15N850 that hasn't gone through high power testing. Not sure what do with it at this point.
Always use a highpass filter 😉
I folded the cone on a Beyma 15P1200Nd using high-power VLF sine waves. Stupid mistake, but I feel your pain.
You'll certainly be able to get it reconed, or even DIY it. After that, they'll probably sell on quite easily. Alternatively, integrate into the home HiFi!
Chris
al the solutions above wil help cooling the magnet,but not the coil,
that's were the problem ocurs.
the problems are redused with the tetra coil drivers from eigtheensound
(eighteensound even state the powercompression figures),
and eliminated with the m-drive/m-force from powersoft
expensive stuf!
if the vc leaves the gap ,the maybe a hpf is needed.
what amp are u using?
that's were the problem ocurs.
the problems are redused with the tetra coil drivers from eigtheensound
(eighteensound even state the powercompression figures),
and eliminated with the m-drive/m-force from powersoft
expensive stuf!
lower excursion give's even less cooling to the vc.
if the vc leaves the gap ,the maybe a hpf is needed.
what amp are u using?
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I'll have to check prices on a recone. I'm usually pretty cautious with regards to excursion limits. I didn't think it would jump the gap with the power I was running at (1200w, 2500w peak) and program material mainly above 60hz. I still think I cooked the adhesive joining the spider to the collar. I've used(and abused) 3015LF's for years in the same box. They let you know when you're at the limit though. Will adjust my highpass if I end up keeping them.
They would kill in a home enviroment...
I cut out the cone and had a look inside. It seems like pulling out air through the rear motor vents would be a good potential solution of getting air moved passed the voicecoil. The Noctua fan performs well with static pressure with low noise and good air flow.
The M-Force stuff is incredible for sure. Would like to see it scaled down to traditional driver sizes.
Lower excursion, more sd, bigger box, much less power, optimized for 60hz and up. Much like a traditional musical instrument box. It's tried and true but boring for diy.
Using two channels of a QSC PLD4.5 bridged.
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Anybody thought of re-cycling magnets from MRI machines? Do super-conductors get hot? Or does running them in liquid nitrogen keep them cool?
(Kidding, I think)
B.
(Kidding, I think)
B.
Unprocessed bass guitar has a lot of <1Hz signal from finger plucks etc. Try plugging straight into a soundcard, record a section and run a spectrum analysis.
I often see/hear cheaper bass amps struggling with this - you can watch the cone(s) jump as each note is plucked.
Chris
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