My friends often bring me speakers in need of repair in spite of my protestations of relative ignorance of the subject.
The attached photo is of a 12 woofer minus a big ring that came unglued. I'm guessing the ring is to add mass to the cone but I'd like to know more about that if someone can take a moment to enlighten me.
I'm planning to reglue it with contact cement unless there are better options. It gets hot here in Phoenix at times and I find adhesives don't always live up to their promise here.
The attached photo is of a 12 woofer minus a big ring that came unglued. I'm guessing the ring is to add mass to the cone but I'd like to know more about that if someone can take a moment to enlighten me.
I'm planning to reglue it with contact cement unless there are better options. It gets hot here in Phoenix at times and I find adhesives don't always live up to their promise here.
Attachments
It is probably just a simple tweak to tune a cab adding mass, but remembers me too shorted turn to give some braking effect and some over-excursion limiter.
For references :
Seas :
"The "33F" was made in a number of versions: 33F-WB, 33F-WK, 33F-WKA and 33F-ZBX and some of these with "DD", dynamic damping:.The "DD" refers to "two high conducting rings placed at each end of the motor coil. These act as eddy current brakes, firmly halting additional cone excursion as the rings enter the magnetic field". Thanks to Martin Colloms/High Performance Loudspeakers, page 79, 6th edition."
From :
SEAS Kit 503
And in JBL dual coil :
https://www.jblpro.com/pub/technote/JBL_TN 1-33 rev3.pdf
For references :
Seas :
"The "33F" was made in a number of versions: 33F-WB, 33F-WK, 33F-WKA and 33F-ZBX and some of these with "DD", dynamic damping:.The "DD" refers to "two high conducting rings placed at each end of the motor coil. These act as eddy current brakes, firmly halting additional cone excursion as the rings enter the magnetic field". Thanks to Martin Colloms/High Performance Loudspeakers, page 79, 6th edition."
From :
SEAS Kit 503
And in JBL dual coil :
https://www.jblpro.com/pub/technote/JBL_TN 1-33 rev3.pdf
"Contact adhesive, is a neoprene rubber adhesive that creates a fast, flexible, permanent bond."
Sounds like it's just the job to me! I would embed the ring in the adhesive.
OK- second post here, so takes this with a grain of salt.
I suspect it was a multi-purpose component. As others have already stated: added mass to lower Fs, looks like brass which is a little strange because copper is the metal of choice for inductive "shorting rings". Looks like it may have been directly attached to the top of the VC Former? If so, that's a high-heat interface. I would only recommend hi-temp epoxies for that application. In a pinch, JBWeld could work. Just be very attentive not to coat the coils, as I believe it has particulate aluminum fillers in it (I could be wrong about that though) check the MSDS.
Good luck on the driver rebuild!
I suspect it was a multi-purpose component. As others have already stated: added mass to lower Fs, looks like brass which is a little strange because copper is the metal of choice for inductive "shorting rings". Looks like it may have been directly attached to the top of the VC Former? If so, that's a high-heat interface. I would only recommend hi-temp epoxies for that application. In a pinch, JBWeld could work. Just be very attentive not to coat the coils, as I believe it has particulate aluminum fillers in it (I could be wrong about that though) check the MSDS.
Good luck on the driver rebuild!
Yes, I think that's right. And this ring is brass. This ring is "above" the cone, just under the dustcap.
Yes, I believe so.
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Sublimacon, it is indeed installed above and outside the VC former. Given your remark about heat, the failure isn’t too remarkable, however it’s apparent that it wasn’t bedded well the first time. Orange silicone would have been an excellent choice for adhesive. Unfortunately I just set it in contact cement so what’s done is done. I suspect it will be good for another 10 years.
Captn Dave,
Didn't you pilot a shrimpboat once-upon-a-time, hows the prosthetics treating ya?
Never mind about the conductive fillers in JBweld, as it would sit on top of the former/cone epoxy joint anyway.
Yeah, contact cement wouldn't have been my first choice, hi-temp RTV (orange) would of been better.
If your looking to make midrange noise from that driver - soft adhesives are not what you want. They are typically heavy for volume, dampen energy more so as Fq increases.
That driver is a little curiosity!
Looks like a stamped steel basket, not a huge motor, yet loaded with a hidden brass treasure. Somebody was crafting a semi-custom piece, for low $'s.
Didn't you pilot a shrimpboat once-upon-a-time, hows the prosthetics treating ya?
Never mind about the conductive fillers in JBweld, as it would sit on top of the former/cone epoxy joint anyway.
Yeah, contact cement wouldn't have been my first choice, hi-temp RTV (orange) would of been better.
If your looking to make midrange noise from that driver - soft adhesives are not what you want. They are typically heavy for volume, dampen energy more so as Fq increases.
That driver is a little curiosity!
Looks like a stamped steel basket, not a huge motor, yet loaded with a hidden brass treasure. Somebody was crafting a semi-custom piece, for low $'s.
Sooo, it’s all back together and it’s probably about as good as can be expected but far from stellar. My friends system is otherwise very fine and this sub is subpar. I’m wondering if it’s worth upgrading with a new driver.
I took out the plate amp and bench tested it with the scope and a signal generator. It swung 32 volts rms at 4R. Let’s call that 250 watts. It’s a Keiga KG-5150 rated for 200 watts at 4R.
The enclosure is 2.8 cubic foot internal volume. It currently has a 12 in driver but there is room for a 15 inch driver. It is sealed.
I’ve searched Parts Express; what are some other vendors I should consider.
Any suggestions for specific drivers suitable for that volume?
I took out the plate amp and bench tested it with the scope and a signal generator. It swung 32 volts rms at 4R. Let’s call that 250 watts. It’s a Keiga KG-5150 rated for 200 watts at 4R.
The enclosure is 2.8 cubic foot internal volume. It currently has a 12 in driver but there is room for a 15 inch driver. It is sealed.
I’ve searched Parts Express; what are some other vendors I should consider.
Any suggestions for specific drivers suitable for that volume?
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Captn Dave,
Glad to hear it work out!
With only 2.8 cubes to play with I'd keep it a 12".
Well maybe adisound, Newark Element14 absorbed MCM Electronics but still sells MCM drivers which are shockingly cheep at times. You just have to keep in mind some of the T/S specs don't match reality sometimes. Like the Qts/VAS will be higher.
Good luck!
Glad to hear it work out!
With only 2.8 cubes to play with I'd keep it a 12".
Well maybe adisound, Newark Element14 absorbed MCM Electronics but still sells MCM drivers which are shockingly cheep at times. You just have to keep in mind some of the T/S specs don't match reality sometimes. Like the Qts/VAS will be higher.
Good luck!
Dayton Audio RSS390HF-4 15" Reference HF Subwoofer 4 Ohm
This might work well. 2.88 cu ft sealed volume and 4 ohms.
This might work well. 2.88 cu ft sealed volume and 4 ohms.
See prevailing minds save the day!
Yeah I thought I remembered there being particulate metal in it. I thought it was aluminum? Never seen JBweld develop rust coloration before - hum! I'll have to look up the msds on it.
Yeah, epoxy with iron/steel could caused massive T/S shifts. Good, bad, who knows with this driver? It probably would've mutually coupled with the brass shorting ring causing unpredictable results.
Well I guess we can chalk that one up to being one of my bad suggestions. I don't do that too often - thank god!
On a side note, yes the various Dayton Reference 12's (Parts Express) would work really well. Another thread on here is talking about using one in a small sealed cab for HT/music with great results. And that should of read "madisound" with a M. Not easy typing on a cellphone, auto-spell-correct is the devil.
Yeah I thought I remembered there being particulate metal in it. I thought it was aluminum? Never seen JBweld develop rust coloration before - hum! I'll have to look up the msds on it.
Yeah, epoxy with iron/steel could caused massive T/S shifts. Good, bad, who knows with this driver? It probably would've mutually coupled with the brass shorting ring causing unpredictable results.
Well I guess we can chalk that one up to being one of my bad suggestions. I don't do that too often - thank god!
On a side note, yes the various Dayton Reference 12's (Parts Express) would work really well. Another thread on here is talking about using one in a small sealed cab for HT/music with great results. And that should of read "madisound" with a M. Not easy typing on a cellphone, auto-spell-correct is the devil.
Wrenchone,
Perhaps you can pick up the hardened cement with a magnet if it's hardened to ferrous metal, or if you have mixed ferrous metal in the epoxy, but it's not "loaded with powdered steel" when packaged.
JB Weld's ingredients are bisphenol-A-(epichlorhydrin), epoxy resin, crystalline silica, and carbon black, with trace amounts of titanium dioxide.
It has no more magnetic properties than plastic, just checked with magnets to verify that.
JB weld is non-conductive, it is considered an insulator.
Art
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