Siegfried Linkwitz wasn't happy with the how the energy from bass drivers in the Orion OB speakers caused the upper baffle to vibrate. To counter this, in version 3.2, he & his buddy Don Naples came up with a mounting bracket that holds the 8" mid driver by its magnet. The basket doesn't touch the front baffle at all; it only touches a gasket in the hole that the driver appears to be mounted in. The top baffle is still attached to the bass bin, so it doesn't eliminate all bass vibration, but at least reduces the vibrations reaching the tweeter from both the mid 8" and the woofers.
In the LX521, with a less well supported minimal upper baffle, he abandoned this idea. Instead the upper baffle is mounted on a completely separate structure that makes no direct contact with the bass bin. But the 8" low mid driver is mounted on that minimal baffle, and there's no question its energy, with a high pass @ 120Hz, still causes that baffle to vibrate. The "bridge", as SL called it, also looks inelegant and becomes awkward when you try to re-position the speaker -- there are 2 structures to be moved.
In the project for my friend Mark, I wanted to combine the Linkwitz-W-frame of dual-opposed OB bass (used in Orion v 3.3) with the magnet mounting scheme. The bracket would be secured to the heavy top panel (24mm BB + plate of supporting steel or aluminum), and the low-mid driver would not touch the upper baffle. The W-frame's dual-opposed bass drivers dramatically teduces the vibration from the woofers, too.
The chosen low-mid driver is the Satori WO24TX. It will cross at 110~140 Hz (TBD experimentally in situ). Even with a steep LR4 filter, there's still a fair amount of vibration in the driver frame when it's working hard.
The Satori cone drivers all feature a cast aluminum frame with spokes that wrap around the magnet. This is a design that goes back to Peerless, VIFA, ScanSpeak, even JBL.
Here's a Peerless/VIFA NE149 using this design. This is meant to eliminate the "bell-like ringing" of a big heavy magnet that usually hangs off the back of the frame.
The WO24TX (and other WO24 variants) looks similar, like the Peerless driver above and its other Satori mates. But it's an illusion.
The ribbed black portion around the magnet is actually made of molded rubbery plastic & is easily peeled off.
This proved to be a saving grace for the magnet mounting modification that Mark undertook with his talented machinist friend. The rest of the pics should be self explanatory.
The BB plywood frame is temporary and will be replaced in the final version with an aluminum or steel structure with less acoustical resistance.
In the LX521, with a less well supported minimal upper baffle, he abandoned this idea. Instead the upper baffle is mounted on a completely separate structure that makes no direct contact with the bass bin. But the 8" low mid driver is mounted on that minimal baffle, and there's no question its energy, with a high pass @ 120Hz, still causes that baffle to vibrate. The "bridge", as SL called it, also looks inelegant and becomes awkward when you try to re-position the speaker -- there are 2 structures to be moved.
In the project for my friend Mark, I wanted to combine the Linkwitz-W-frame of dual-opposed OB bass (used in Orion v 3.3) with the magnet mounting scheme. The bracket would be secured to the heavy top panel (24mm BB + plate of supporting steel or aluminum), and the low-mid driver would not touch the upper baffle. The W-frame's dual-opposed bass drivers dramatically teduces the vibration from the woofers, too.
The chosen low-mid driver is the Satori WO24TX. It will cross at 110~140 Hz (TBD experimentally in situ). Even with a steep LR4 filter, there's still a fair amount of vibration in the driver frame when it's working hard.
The Satori cone drivers all feature a cast aluminum frame with spokes that wrap around the magnet. This is a design that goes back to Peerless, VIFA, ScanSpeak, even JBL.
Here's a Peerless/VIFA NE149 using this design. This is meant to eliminate the "bell-like ringing" of a big heavy magnet that usually hangs off the back of the frame.
The WO24TX (and other WO24 variants) looks similar, like the Peerless driver above and its other Satori mates. But it's an illusion.
The ribbed black portion around the magnet is actually made of molded rubbery plastic & is easily peeled off.
This proved to be a saving grace for the magnet mounting modification that Mark undertook with his talented machinist friend. The rest of the pics should be self explanatory.
The BB plywood frame is temporary and will be replaced in the final version with an aluminum or steel structure with less acoustical resistance.
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Looks great.
So now we have extremely rigid stainless steel or aluminium mount, attached to another (soon to be) rigid mount.
Did we have before and after measurements?
Don’t throw out the molded rubber shroud for the woofer magnet just yet- it could be potentially used tk decouple the woofer from the stiff structure.
So now we have extremely rigid stainless steel or aluminium mount, attached to another (soon to be) rigid mount.
Did we have before and after measurements?
Don’t throw out the molded rubber shroud for the woofer magnet just yet- it could be potentially used tk decouple the woofer from the stiff structure.
This isn't possible with the magnet mount. The rubber/plastic is fairly stiff and fits quite tightly. There were small traces of black silicone glue or caulking holding it in place.
Similar rubber/plastic covers are used on some Seas woofers, presumably to damp vibrations in the magnet structures. I have doubts about the effectiveness of such damping devices.
The point of the magnet mounting, in theory, is to provide a rigid mechanical pathway for vibrations in the driver frame to travel down the bracket & be "sunk" or dissipated in the heavy BB plywood structure of the bass bin, made heavier with two 12" SBA subs weighing 15.5 kg total. Vibration sinking is hardly a new technique; been used for myriad applications for a long time.
I can hear the difference with music between this magnet mounting and the other driver bolted to composite baffles of 15mm BB + 12mm construction grade plywood. Not conclusive, due to differences in the baffles, and running the driver full range instead of bandwidth limited as it will be in its midrange role.
I'm open to suggestions about how to quantify the effect of this no-touch baffle magnet mounting vs standard screw/bolt mounting to the baffle.
From a measurement point of view the effect is likely to be subtle. Measuring conducted sound through the cabinet panels isn't the easiest thing to do.
It's about what I figured.
The plan is not to build a LX521 style minimalist top baffle but one more like that of the Orion. Mark -- so far -- wants a more traditional look to go with the rest of his furniture. And he loves the look of my Orions.
So far, the plan is to have the baffle firmly connected to the bass bin on 3 sides, the top the only exception. Even though the WO24TX will not transmit vibration directly into the baffle, this means any vibrations from the bass bin will be there. With the W-frame dual opposed setup, the amount of vibration will be low but present.
Unless the baffle is mechanically decouple-mounted.
That makes it a lot more complicated. I suppose worth thinking about since we've gone so far with the magnet mount -- that's a pricey execution, >CA$500 for the pair even at a friend price.
Drivers in the baffle are likely to be a mid dome + dome tweeter.
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I'd like to see a study of frequencies most involved in conducted panel resonances. I tend to expect lower midrange/upper bass issues. I also tend to use CLD on panels where it is justified.
Sick af!! Imma have to get something like that machined just for the “trick” factor. Reminds me of a high end race car build.
Yeah, likely. If it resonates at all, there will be some effect, tho perhaps not everyone will hear it. In the lx521 style baffle, I think it's significant. In a better supported one, perhaps not so much.
In any case, I won't be doing any scientific studies of the benefit of this magnet mount scheme. Too much other work to be done. Mark and I will both be happy that we've gone a long way to reduce harmful vibrations from having negative effects.
That's cool. Interesting solution. I've built systems with midranges isolated from the box and firing back to back with the magnets glued together. The idea was to cancel out vibration. I think it works but it is easier to build a stiff baffle from BB ply, composites, or even stone.
I've seen back-braced drivers in sealed or vented enclosures that try to reduce the basket & magnet vibration, again by "sinking" the driver frame firmly to the enclosure itself. I'm sure they have some benefit. I did this for a recent 15" sub; it seemed to help. Hard to tell without a control to compare.
Dual-opposed drivers are probably the best for this, especially if they are coupled mechanically.
Just making a strong box and mounting the driver conventionally doesn't deal with the resonances in the frame/magnet. The whole driver is basically cantilevered off the baffle.Probably okay if it is light, rigid & non-resonant. But...
The WO24 drivers are definitely not light. They are actually the only Satori cone driver without a neodymium magnet. Hence 3.7 kg compared to the next smaller, 7.5" model, 1.5 kg.
Dual-opposed drivers are probably the best for this, especially if they are coupled mechanically.
Just making a strong box and mounting the driver conventionally doesn't deal with the resonances in the frame/magnet. The whole driver is basically cantilevered off the baffle.Probably okay if it is light, rigid & non-resonant. But...
The WO24 drivers are definitely not light. They are actually the only Satori cone driver without a neodymium magnet. Hence 3.7 kg compared to the next smaller, 7.5" model, 1.5 kg.
Some thoughts:
The midrange is isolated from the baffle but the baffle still vibrates. Isn't this a problem? Would it be better to dampen the baffle? Maybe use constrained layer construction?
Since everything vibrates, why would it matter what the magnet holder is made from? As long as it anchors the midrange wouldn't a solid hard maple stand work just as well?
What is the magnet holder mounted to? Shouldn't it be isolated from the woofers?
The midrange is isolated from the baffle but the baffle still vibrates. Isn't this a problem? Would it be better to dampen the baffle? Maybe use constrained layer construction?
Since everything vibrates, why would it matter what the magnet holder is made from? As long as it anchors the midrange wouldn't a solid hard maple stand work just as well?
What is the magnet holder mounted to? Shouldn't it be isolated from the woofers?
It doesn't really matter what the magnet holder is made of, but this one looks good & works well. I had a 3D printed design that might have worked but would not have been as strong. Besides, Mark wanted it, and it's his speaker.
The magnet-mount driver will be firmly connected to the top panel of a W-frame OB bass bin with 2 force-cancellation 12" sub drivers. That top panel will be 24mm BB plus a plate of aluminum 10mm thick.
As I wrote earlier, for now, the upper baffle for the higher frequency drivers is planted to be bolted to the bass bin & supported on 3 sides. This plan may change if we come up with a better scheme.
Vibration in such bass bins is much lower than in conventional bass boxes, but not absent. This is the third pair of W- frame OB I built. The first one with 12" sub drivers which could be trouble due to lower cavity resonance frequency.
Anyway, it's a compromise judged to be worth trying.
The magnet-mount driver will be firmly connected to the top panel of a W-frame OB bass bin with 2 force-cancellation 12" sub drivers. That top panel will be 24mm BB plus a plate of aluminum 10mm thick.
As I wrote earlier, for now, the upper baffle for the higher frequency drivers is planted to be bolted to the bass bin & supported on 3 sides. This plan may change if we come up with a better scheme.
Vibration in such bass bins is much lower than in conventional bass boxes, but not absent. This is the third pair of W- frame OB I built. The first one with 12" sub drivers which could be trouble due to lower cavity resonance frequency.
Anyway, it's a compromise judged to be worth trying.
I braced the magnets on a pair of 15" woofers that had a resonance in the basket. I could see the diff in the impedance curve.
From a PA perspective, I've seen magnet assemblies fall off the basket from rough handling - they are just glued together, remember.
If mounting a speaker by its magnet instead of the frame, handle very gently!
If mounting a speaker by its magnet instead of the frame, handle very gently!
Most cast frame or stamped frame drivers have bolts or machine screws through the base of the basket into the front plate of the magnet, so at least that portion is anchored. I can see your thoughts of the central pole piece shifting.
The other way that you can decouple a driver from a baffle is by hanging the driver using two (or more) wires that attach to something above, with the driver within a hole slightly larger than the frame OD. I will be building a system with this approach in which a 15" woofer will be suspended in a hole in a 24x24 inch baffle. This prevents vibration transmission, probably better than your L-bracket idea, but they are basically attempting the same thing.
There was a similar concept by a guy that Siegfried knew (older gentleman living in Spain I believe) named Ruediger Franz Rauskolb. Here is a DOC about it:
https://www.linkwitzlab.com/Links/Baffle Vibrations in Open Baffle Dipole Loudspeakers Kopie.pdf
Rauskolb used both leaf springs (thin metal strips that are flexible) and wires as the means to hang or support the driver. Whether wires or thin metal strips, these can effectively decouple the driver from other parts of the loudspeaker.
There was a similar concept by a guy that Siegfried knew (older gentleman living in Spain I believe) named Ruediger Franz Rauskolb. Here is a DOC about it:
https://www.linkwitzlab.com/Links/Baffle Vibrations in Open Baffle Dipole Loudspeakers Kopie.pdf
Rauskolb used both leaf springs (thin metal strips that are flexible) and wires as the means to hang or support the driver. Whether wires or thin metal strips, these can effectively decouple the driver from other parts of the loudspeaker.
Boy, I don't know about hanging drivers from strings. When I mess around with sub-woofer drivers I can sometimes get them to bounce on the bench. These forces are at work in the midrange too, the forces are much smaller but I would think the piston motion will make the frame and magnet move in the opposite direction. I don't think wires are strong enough. I think the best way to decouple the mids and treble from the bass is to put the bass in a stiff enclosure and put the mid and tweeter in separate, isolated boxes. The open baffle creates its own issues. Maybe the panels actually vibrate less than if there were a box? I like the idea of a magnet mount, I hope this works out.
Also, if Mark wants it give it to him!
Also, if Mark wants it give it to him!
CharlieLaub
Thanks for that.
There was another thread where a large system with 15 or 18" woofer were part of this hanging setup with minimalist frame. Ah -- Circles of Doom.
The downside of the doom circles and your concept is that it's hard to make it aesthetically pleasing. If it was for me in my studio (man cave, kinda), no problem. But for prime time, we need better WAF. I'm sure something could be done, but it'd be complex & maybe expensive.
Thanks for that.
There was another thread where a large system with 15 or 18" woofer were part of this hanging setup with minimalist frame. Ah -- Circles of Doom.
The downside of the doom circles and your concept is that it's hard to make it aesthetically pleasing. If it was for me in my studio (man cave, kinda), no problem. But for prime time, we need better WAF. I'm sure something could be done, but it'd be complex & maybe expensive.
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