Has anyone tried to convert a woofer into a passive radiator? I want a very high excursion 5'' passive radiator, and the Peerless 5.25'' just won't do it.
The Tang Band W5-1138SMF looks like a driver that can do over an inch of excursion, which is what I need. It has around 3-4 times higher Mms than a typical 5'' woofer at 29g, which means the suspension should be capable of handling the 40-50g of additional mass I want to put on.
Good idea? Anything I should watch out for? If it is, any tips on how to do this? The first question would be finding a way to remove the magnet.
Thanks
The Tang Band W5-1138SMF looks like a driver that can do over an inch of excursion, which is what I need. It has around 3-4 times higher Mms than a typical 5'' woofer at 29g, which means the suspension should be capable of handling the 40-50g of additional mass I want to put on.
Good idea? Anything I should watch out for? If it is, any tips on how to do this? The first question would be finding a way to remove the magnet.
Thanks
Safest way would be to cut through the basket below the spider. Don't try prying it off as the basket will likely bend, and there are possibly screws, rivets, etc. in addition to the glue.
Still not sure that it'd solve the problem, as while they have tremendous xmax capability for their size, the little spiders can only handle so much and seem to be the limiting factor.
What are you planning on using it with?
Still not sure that it'd solve the problem, as while they have tremendous xmax capability for their size, the little spiders can only handle so much and seem to be the limiting factor.
What are you planning on using it with?
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Well, the best idea is to use a PR that is "two sizes up" from the main driver.
So, for a 5.5" driver that would be an 8" PR. This makes the requirements for excursion lower, and so a standard suspension works way better in this application.
"Killing" a good high excursion driver to get the PR parts is likely a waste of money. Best to try to find some burnt up drivers from a recone shop and then remove the magnets.
Most magnets are only glued in place. Since you don't want the driver to work, only the suspension & cone you can get 'brutal' in the removal. The way to do this is to first detach the rear pole piece from the magnet, then the magnet from the front pole piece, then drill out or if not riveted, remove that part by impact. All of the parts will come off with a proper transfer of force.
The easiest way to do it is to support the magnet edge OR the basket in an immovable support... perhaps a bunch of stacked up wood with a hole precisely fit to just slide the magnet into. Remove the dust cap and with a bit of wood, or better still a brass rod or aluminum rod, WACK the pole piece (via the rod) with a 5lb hammer... should blow right off the back end.
The alternative is to wack the rear pole piece solidly sideways while the magnet is supported - you want to break the glue bond. Then the same for the magnet, which may or may not break. WEAR EYE PROTECTION!!!
This may not be sufficient, since the back of the assembly may still wack the rear of the basket... in which case a hole saw and drill press will be able to cut at wide circle out of the rear...
So, for a 5.5" driver that would be an 8" PR. This makes the requirements for excursion lower, and so a standard suspension works way better in this application.
"Killing" a good high excursion driver to get the PR parts is likely a waste of money. Best to try to find some burnt up drivers from a recone shop and then remove the magnets.
Most magnets are only glued in place. Since you don't want the driver to work, only the suspension & cone you can get 'brutal' in the removal. The way to do this is to first detach the rear pole piece from the magnet, then the magnet from the front pole piece, then drill out or if not riveted, remove that part by impact. All of the parts will come off with a proper transfer of force.
The easiest way to do it is to support the magnet edge OR the basket in an immovable support... perhaps a bunch of stacked up wood with a hole precisely fit to just slide the magnet into. Remove the dust cap and with a bit of wood, or better still a brass rod or aluminum rod, WACK the pole piece (via the rod) with a 5lb hammer... should blow right off the back end.
The alternative is to wack the rear pole piece solidly sideways while the magnet is supported - you want to break the glue bond. Then the same for the magnet, which may or may not break. WEAR EYE PROTECTION!!!
This may not be sufficient, since the back of the assembly may still wack the rear of the basket... in which case a hole saw and drill press will be able to cut at wide circle out of the rear...
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I'll go along with the other suggestions to use available PRs, but if you find yourself in a situation where you have to remove a magnet; I've had a lot of luck supporting the ceramic with the anvil of a vise (or an actual anvil) and sharply smacking the magnet itself with a tack hammer. It usually shatters radially but doesn't move much if you are careful, which comes to the aid of non-destruction of the coil, which you probably don't care too much about here. Once the magnet is shattered you can pull the T pole out and chisel away remaining ceramic off the top plate until you expose the mounting screws or rivets, which can then be drilled. Happy basket assembly extraction...
Do not hit the ferrite magnet with a hammer... be sure to wear EYE PROTECTION, the magnets will shatter and can send shards at high velocity...
Best to not hit magnets with steel or cast iron, at least not directly - interposing a rod or other metal object will transfer the energy
without the impact effect, so not directly hit, if it can be avoided.
Not usually required to remove magnets, although some are stubborn... also the epoxy used is going to give up with heat, although the same heat will not do well for the moving parts... 🙁
But magnets can be broken up by impact... best to try other means first. imo.
Best to not hit magnets with steel or cast iron, at least not directly - interposing a rod or other metal object will transfer the energy
without the impact effect, so not directly hit, if it can be avoided.
Not usually required to remove magnets, although some are stubborn... also the epoxy used is going to give up with heat, although the same heat will not do well for the moving parts... 🙁
But magnets can be broken up by impact... best to try other means first. imo.
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I always seriously respect concerns about safety, but it usually takes more than one whack to ramp up the amount of shock needed to fracture the ceramic slug. I always wear eye protection when doing something like this. The tiny iron/steel hammer is best applied as it isn't really a large amount of energy required but simply shock. Usually the attractive forces of the magnet material is more than enough to keep anything from flying. It's usually not very eventful. You just get the needed crack. It's also helpful to look through the spider with a strong flashlight to see where the fasteners are. Otherwise you are faced with removing very hard ceramic material for no expedient gain in removing the entire magnet structure.
Sure, but I'd not advise anyone who has to ask how to do this to hit the magnet directly unless they are being supervised by someone who knows where the threshold of danger may lie... your "tack hammer" might be someone else's Hammer of Thor!! 😛
Hi Y'all,
Here is a little video from youtube, "making a 6.5 inch passive radiator":
https://www.youtube.com/watch?v=eF_p0o2I3JE
And don't forget EYEPROTECTION and gloves! That method should apply to smaller speakers too.
PE has a 6.5" PR.
Regards.
Here is a little video from youtube, "making a 6.5 inch passive radiator":
https://www.youtube.com/watch?v=eF_p0o2I3JE
And don't forget EYEPROTECTION and gloves! That method should apply to smaller speakers too.
PE has a 6.5" PR.
Regards.
Hi,
This all sounds like a very bad idea. What driver will be used with a 5"
driver of allegedly 1" excursion ? and what a waste of a good 5" sub.
The Peerless 830880 has pretty much flawlessly sensible specifications.
Two of them will give you the 1" excursion needed, and at 48g Mms
they will take extra mass if lower tuning is needed.
Generally if using drivers as PR's : Don't more than double cone mass.
They should be bigger than the active driver. They should have good
Xmax electrical, not just mechanical, because by keeping the magnet
you can wire a resistor across the coil to adjust the bass damping.
rgds, sreten.
This all sounds like a very bad idea. What driver will be used with a 5"
driver of allegedly 1" excursion ? and what a waste of a good 5" sub.
The Peerless 830880 has pretty much flawlessly sensible specifications.
Two of them will give you the 1" excursion needed, and at 48g Mms
they will take extra mass if lower tuning is needed.
Generally if using drivers as PR's : Don't more than double cone mass.
They should be bigger than the active driver. They should have good
Xmax electrical, not just mechanical, because by keeping the magnet
you can wire a resistor across the coil to adjust the bass damping.
rgds, sreten.
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Ceramic is very brittle, and chips very easily. If it doesn't fracture it'll at least chip.
Those Tang Bands have venting below the spider, so the job of cutting the magnet off is already half done for you.
There will still be a better way than butchering a speaker. Tang Band does actually have passive radiators to match their various woofers on their site. However they are only sold with the woofers, and most likely in rather large quantities.
Those Tang Bands have venting below the spider, so the job of cutting the magnet off is already half done for you.
There will still be a better way than butchering a speaker. Tang Band does actually have passive radiators to match their various woofers on their site. However they are only sold with the woofers, and most likely in rather large quantities.
Re-read - he was looking at butchering a high excursion Tangbang to get a high Xmax PR...
Didn't realize so much activity happened after 2 weeks of no responses.
Thank you everyone for the very detailed explanation. To the people that says it is wasteful to do this, the other way to think about this is a 6.5'' SEAS passive radiator is $65, more than double the price of the nice Tang Band 5'' woofer. Even if we compare to the $13 Peerless 5'' PR, the TB woofer is capable of twice the excursion, which is equivalent of 2 of those Peerless PR's. $26 vs $30 isn't a big difference, and the TB has the advantage of being just one PR, saving space and significantly reducing weight requirements for tuning.
In my case, I can't fit more than one 5'' PR, so the high excursion capability is extremely valuable, so $30, to me, is quite a steal.
Thank you everyone for the very detailed explanation. To the people that says it is wasteful to do this, the other way to think about this is a 6.5'' SEAS passive radiator is $65, more than double the price of the nice Tang Band 5'' woofer. Even if we compare to the $13 Peerless 5'' PR, the TB woofer is capable of twice the excursion, which is equivalent of 2 of those Peerless PR's. $26 vs $30 isn't a big difference, and the TB has the advantage of being just one PR, saving space and significantly reducing weight requirements for tuning.
In my case, I can't fit more than one 5'' PR, so the high excursion capability is extremely valuable, so $30, to me, is quite a steal.
Hi bcodemz,
One source for speaker repair parts (suround, spider, etc.) is ebay, here are some typical auctions:
4 5 in Speaker Surrounds Inverted Roll Special Quality Repair Foam New | eBay
2 Pcs Best Subwoofer Bass Speaker Repair Spider 78mm 25 5mm 10mm Z668 ZY | eBay
Regards,
One source for speaker repair parts (suround, spider, etc.) is ebay, here are some typical auctions:
4 5 in Speaker Surrounds Inverted Roll Special Quality Repair Foam New | eBay
2 Pcs Best Subwoofer Bass Speaker Repair Spider 78mm 25 5mm 10mm Z668 ZY | eBay
Regards,
Is there value in the degenerative feedback that arises from shorting the voice coil on the passive radiator?
Is the magnetic circuit more linear or less linear than the behaviour of the cone surround and the spider?
Ben
Is the magnetic circuit more linear or less linear than the behaviour of the cone surround and the spider?
Ben
Picowallspeaker is close, but you´ll need more than a suspension.
You might just buy a spare cone , any size you like, and a cardboard dustcap to seal the voice coil , cut a hole in your cabinet and actually glue the cone edge to the wood, no gasket needed and of course no frame either , which is only needed to hold magnetic system and keep voice coil concentric; you have no use for either of these-
Then measure cone resonance (you sweep the active speaker and take note of the impedance notch) and add weight as needed (gluing solder rings to cone is one possibility, other is gluing metal "coins" sealing the voice coil hole in the process).
A couple examples:
this 10" foam edge woofer cone costs all of $7.95 including free international shipping:
these 8" cones are 2 for U$16, again free shipping:
Before somebody worries about that: not using a spider will lower natural resonant frequency somewhat because you reduce stiffness opposing cone movement, but on the other side, you rise resonance because you also removed a relatively heavy voice coil, in any case you will tune final resonance to what the active speaker needs by adding weights so end result lies in your hands.
Keep searching if 8" or 10" are too large 🙂
You might just buy a spare cone , any size you like, and a cardboard dustcap to seal the voice coil , cut a hole in your cabinet and actually glue the cone edge to the wood, no gasket needed and of course no frame either , which is only needed to hold magnetic system and keep voice coil concentric; you have no use for either of these-
Then measure cone resonance (you sweep the active speaker and take note of the impedance notch) and add weight as needed (gluing solder rings to cone is one possibility, other is gluing metal "coins" sealing the voice coil hole in the process).
A couple examples:
this 10" foam edge woofer cone costs all of $7.95 including free international shipping:
these 8" cones are 2 for U$16, again free shipping:
Before somebody worries about that: not using a spider will lower natural resonant frequency somewhat because you reduce stiffness opposing cone movement, but on the other side, you rise resonance because you also removed a relatively heavy voice coil, in any case you will tune final resonance to what the active speaker needs by adding weights so end result lies in your hands.
Keep searching if 8" or 10" are too large 🙂
Hi JMHahey,
It would not surprise me if 'somebody' worries about leaving the spider out is equal to destabilizing the cone and equal to removing the 'constant factor' of the centre of mass... ;-)
Cheers,
Djim
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