Ohm Walsh F Hope of Resurrection

Midwest Speaker Repair in St Paul, MN 

Congratulations on bringing the speakers back to life! Did you mention where you ultimately got them serviced?

First listen sublime; it was a good call and project that will yield much enjoyment. 

Douglas John Strohbeen has stated in interviews the issues with driving Fs well without damage and maintaining them properly is supposedly the reason why the design was dropped. Not practically supportable.
I think with any amp you just want to be very careful.
It’s the CLS design driver that replaced the original Walsh driver that resolved that issue. Every CLS Ohm I have owned will take whatever you throw at them and deliver effortlessly. I have never heard or owned original Fs. Mine are newer CLS design on refurbed F cabinets. Totally different. So I can only repeat what I have read there. Ferrofluid was introduced into the F design as I understand it to help address that issue as well. Clipping is never good either hence the challenge. I would try a higher power amp like a Class D for more bang for the buck if needed . But be careful.

I wonder if it was coincidence; my pair of Ohm Walsh Model F were the only ones at the repair facility when I dropped them off. Today, when I picked them up, mine was one of four pair! They had never seen such a thing with that speaker. Perhaps our enjoyable brainstorming is motivating some owners? Or, just a freakish occurrence, which is certainly not beyond probability bounds. 

22 hours of driving, 1,370 miles, and total for project, including travel costs, of $400. DONE! 

Speakers are warming up (slightly; they were in car cabin, of course), and will be assembled tonight. Perhaps a first run this evening, too. We'll see. The hard work is over, now it's RELAX TIME!  :)

Now for the vintage Ohm community, a question; I have heard the joke re: 200/300 wpc wakes them up, and 301wpc blows them up. Ok. I have a super-clean class D that puts out 600wpc into 8 ohms and 1KWatt into 4 Ohms. Is this inherently a problem for these speakers, or only� relatively a problem, i.e. temptation to play them too aggressively? I see mapman is using plenty of clean power. 

Very cool!

Repair now underway. It seems one driver is original and the other not. The original does not have ferrofluid, as it had not been invented at the time. A different lubricant, such as a grease, was used. At some point one driver failed and was replaced, the new unit utilizing ferrofluid.

The drivers are having spiders and surrounds rebuilt, the one with hardened/tacky ferrofluid has been cleaned, and both will be reconditioned with new ferrofluid. My understanding was that the original units were prone to failure, but the addition of ferrofluid ameliorated that problem. 

I may have reconditioned Ohm Walsh Model F’s for Christmas! That would be fun! :)

Time moves Oh, so s.l.o.w.l.y. when waiting for a repair!  ;) 

dgarretson, yes, I recall meeting you at Axpona, a very pleasant experience! Yes, Dale puts up a very nice speaker, no doubt. 

I appreciate the lead on the treatments for the cabinet! The epoxy/sawdust fix sounds like a winner! 

Hello Doug.  Remember when we sat listening to the TL-1 in Dale Harder's room at Axpona?  IMHO that was best in show.  After that I wouldn't bother with Ohm F, but to each his own and a good project is always interesting. Talk to Cascade Audio Engineering about coatings and appliques to damp MDF enclosures.  I have used their VBLOK paint to good effect inside various MDF cabinets. You can mix that with brass powder if you want to get fancy. They have since introduced a variety of padding conceived for automotive applications that may help as well.  Use two-part epoxy mixed with saw dust to repair or strengthen broken or crumbling MDF.

Thank you all for the continued advice and encouragement!

I have acted on one avenue of potential repair/restoration, which I found myself. My request from a local dealer went nowhere, and the request of a well regarded speaker repair shop about 1.5 hours away sank when they refused to work on it. That convinced me not to try by myself; good move, given I have zero experience in this activity.

My repair plan for the speakers involves two 12 hour round trip days in the car, as I was not interested in shipping them due to the potential for damage. I am willing to work a bit to get these drivers back into operating condition. The drivers have been in the possession of the repair facility, so they should be done sooner rather than later. Then, one more day in a car, and... COOL OMNI SPEAKERS TO ENJOY! ;)

In terms of the cabinet damage, where it is splitting along one of the front corners, at least a clean split from the outside; I will probably just shoot some glue into the fissure from the inside of the cabinet to prevent further compromise, probably use Gorilla Glue, and then put some wood putty into the gap. If I sand it down right, it shouldn’t be ghastly.

CALLING CABINET MAKERS/REPAIRERS... What do you think about that fix? The MDF seems to be the patchier kind, so trying to push hard on it and screw it back together might cause more damage. What’s the best stuff to shoot into the gap to hold it?


Lastly, I think I’ll try a simple, likely effective maneuver of placing about .5" pliable foam sheeting inside the cabinets (not glued, just put in position) to help with cabinet resonances. I suspect that will tighten it up a bit on the low end. Rapping on the cabinet is like ringing a wooden bell, even while the stock stuffing is inside! I’m not going to have that kind of distortion if I can help it. If my solution doesn’t work, I have not lost much and I pull it out. Or, maybe I can put steel straps inside, and fill the cabinets with 400 pounds of sand! ;) LOL I have filled one or two speaker cabinets in the past, and frankly, I didn’t like the result all that much. The bass on this will be like Harbeth, Audio Note, Tannoy, etc. with the hollow cabinet feel, which I’m not overly crazy about, but it’s an alternative toy. I don’t need to perfect it.

Imagine, these were a "last resort" call from the family who knew I was big into audio, as they were about to take them to the dump!

Douglas,
              You could talk to Dave Cox of Puckerbrush Audio in Norway Maine.  Dave is a Ohm speaker collector and has worked on a number of Ohm f's over the years. He is a friend and has worked on such speakers as a couple of JBL Paragons for me with great results. I had a pair of F's a number of years back and they definitely have a certain magic to them. I must say that I heard Dale's speakers at Axpona and they were out of this world!
Best of luck,
Bob

Yep agree, can’t sacrifice quality, but when it comes to symphony orchestras, big bands, and the like, it takes more than average muscle as well to deliver the goods at home in a manner that at least somewhat resembles what one would hear live. Especially with modest sized full range speakers. Just have to be sure to take care of the ears along the way as well. Too much too often is not a good thing no matter how exhilarating it might be otherwise..

mapman, some nice guidance, and yes, I plan on adequate clean power. I have no desire to abuse gear; all my years I have never blown out a driver, even when I built my own "cabinets" for my coaxial car speakers that sat in the hatchback area aeons ago. I'm more into quality with quantity as opposed to quantity and more quantity.  

I never take speakers to the point of clipping; I greatly value my hearing and do not wish to introduce the potential for hearing damage. So, these will be handled well, not abusively. 

I will look forward to trying the Pass Labs XA200.8 Monos with them. I suspect they will be quite attractive sounding with those amps. 

Well, good luck! Nothing to lose and who knows maybe they can still deliver something that is hard to find otherwise.

I can tell you that the Walsh CLS design can take pretty much anything you throw at it with very little compression or risk of damage, so John Strohbeen definitely knows what he is doing there. Lessons learned over the years it seems from that article, starting with attempts to salvage original Ohm Fs.

I’ve been running various models hard for almost 40 years now, never a problem. Seems like the mastered application of ferrofluid is a factor for that.

IT’s still always best to avoid clipping at all costs... reserve power and the ability to handle it is your insurance policy for that with most good quality speakers in good working order.

In the interest of getting the most possible out of my Ohm Walsh F5s, I’ve been running them with 500 w/ch (into 8ohm doubling to 1000 into 4) BEl Canto monoblocks for a number of years now with outstanding results. I bought them planning to throw the kitchen sink at the biggest Ohms in order to max out what they can do. Those amps can drive almost anything to their max and also work well with other smaller speakers I own or have owned with them like my smaller Ohm 2s, kef ls50s, Dynaudio Contour monitors and others, but the Ohms are champs at going loud and clear off however much power you want to throw at them. Meanwhile they do as well as most with lower power amps, but its when you throw the kitchen sink at them that they truly distinguish themselves from the competition and shine. Similar to mbl and GP in that regard as well from what I read.

I do not have answers as to whether the goo was ferrofluid, but that is likely the best explanation. So, perhaps we'll see if when I use them it takes 300wpc to get them to wake up, and 301 wpc to blow them up! 

https://www.cnet.com/news/forty-years-ago-the-ohm-f-speaker-was-a-game-changer-it-still-is/

https://ohmspeaker.com/news/nasa-technology-comes-to-speakers-ferrofluid/

Could well be the ferro fluid as mentioned here.


Was it magnetic?

I feel like I've read in the past that the original Ohm F's were essentially sent from the factory "broken", that they leaked because of some design flaw and that what you're experiencing is actually normal for these speakers.  I'm certain a search on this subject will uncover this problem, perhaps Dale at HHR would know of this.

I may ask the Ohm factory about it. I'm grateful that the drivers appear to be in good shape to recondition. 

Doug, is the black crap finding now a question for Ohm factory?  Even though they may no longer repair them they may know about the driver.

No one has any knowledge or insight about this? If so, that might underscore how unusual the situation. 

More research... Look at this from this site:
https://ferrofluid.ferrotec.com/products/ferrofluid-audio/audioselect/

Spider removal: Voice Coil Centering With Ferrofluid

The presence of ferrofluid exerts a uniform radial centering force upon the voice coil in the air gap. The magnitude of this force is dependent upon the strength of the permanent magnetic field and saturation magnetization of the ferrofluid. The greater these values, the stronger the centering force. Reduced scrap rates on the production line, reduced field returns and reduced distortion (due to the suppression of radial and rocking modes of the voice coil) are some of the well-known benefits of this centering force.

In recent years, the availability of high saturation magnetization ferrofluids have allowed designers to completely remove the spider, relying on the ferrofluid to center the voice coil in the air gap. This technique not only yields lower cost and a simplified production process; it also removes the well-documented nonlinearities present in all spiders, resulting in lower distortion. In general terms, the saturation magnetization values of ferrofluids used in spiderless designs should not be lower than 33 mT.

I now if the tech used ferrofluid to center the voice coil because of the difficulty of doing so with the Model F driver. Then, because the wrong fluid was used, it got gooey and froze. So, perhaps the incompetence theory is most accurate. 

So, one possibility is that it is ferrofluid? This is a very experienced tech, and I think that he would have known that possibility and would have recognized it.

It seems some grease may have been used on these old drivers, perhaps for heat dissipation? It sure does not seem intuitive, especially since the one does not seem to have it.

Looking at the images and discussion of ferrofluid, it appears that may be the substance. Does it get gooey and hard enough with time to lock a driver? 

BLACK CRAP in the coil/magnet gap? HUH?! 

The speakers are at a repair facility; not discussing particulars at this time. 

The tech finds some black goo that is like a tar, that has gummed up the driver to the point it was frozen in the coil. He said he has never seen anything like it with these speakers. I sure had not seen anything like it. It seems so improbably wrong that it makes me wonder if it could have been sabotage (especially since inside the speaker there sat a smaller (wrong sized) spider that had soaked up some sort of oil substance), or perhaps someone so inept that they can't deduce that the part had to move freely or it would seriously compromise the sound. Seriously, who puts black, sticky, gooey crap in the gap? Did some kind of lubricant at one time age so badly that it froze the coil unit it was worked loose again? It seems counter-intuitive to proper treatment of a driver. 

Could it be that there was rubbing of the voice coil after a repair - there is evidence it likely was repaired - and someone sought to cover it up by using a lubricant? Perhaps; I wouldn't put it past some people. That may make sense, given how hard it is to redo these cones. Perhaps someone screwed up, and tried to cover it up, caring less about the longevity of the speaker than not being discovered. Perhaps I have solved my own mystery... 

It's also not as if this would normally fall into the driver, as they are typically inverted, with the coil and magnet structure higher than the spider and cone. 

Has anyone ever encountered such a thing? I am willing to be educated on all this if there is a reason for such things to be done. 

The fabulous news... it has been removed, and it appears the drivers are well on their way to restoration! I was VERY wise to solicit the help of experienced persons on this.  :) 

You’re getting into details that are best pivoted toward Dale. :)

Time to head downstairs and continue work with another amazing speaker - something you guys probably have not encountered prior.  :)  You'll have to watch for the review, not immediate.  

I don’t know how Dale works but maybe the drivers can be done and sent and then user installs them to avoid shipping large heavy cabs.  I know in many cases Ohm is able to do repairs and upgrades that way.

My F5s came in 3 cartons per speaker. One for the refurbed F cabinets, one for the driver, and one for the grille cover.

Connection was a snap and drivers attached to cabs with wing nuts.

This is not an equivalent to the new, HHR Exotic version TLS-1. I was told directly by Dale that there are dozens, literally, of changes to the new design. So, don't think you would get the new one for half price; you won't. There are aspects of the refurb that are not on the level of the HHR Exotic version. 

Still, were I in the market for a speaker change, I might do it. I was also considering a review of the new version, but he said he cannot afford to build for review; he only builds for orders. I understand that when it's a small shop and custom product. So, there's no review coming; sorry. I think it would make for a compelling article, something quite different, but not all review ideas work out between the needs of the manufacturer and the reviewer. This is one of the difficulties of smaller businesses with exquisite products. 

I think the upgrade to the F is a great option, so sure, talk to Dale! 

 There is always more to explore!  :) 

I agree with mapman. If it is 7-8 grand for new drivers from Dale, I'd have gone for it before. Maybe it's worth a call to Dale even now. I still have the F cabinets.

7-8 grand to redo with old cabs would be very tempting for me were I not completely happy with my F5s.

musicbox78, some great pointers; thanks! I am not an aggressive listener, and I am not about trying to recreate live listening level. I do respect vintage gear, so I think the odds of destruction through use are reduced. 

I think I'm in contact with the right people, ones with experience, including discussion with Dale and Bill. To clarify, the estimated $7-8K was for Dale to use the old cabinets and build an entirely new speaker with new parts, not recondition of the old cone. I feel that is a very fair price all told, but my interest was not to seek a reference, or add a big gun speaker, but to see if the freebies could be used regularly. I will be putting some money into them, but looks to be reasonable expenditure. I feel pretty good about the connections I'm making. 

If I had no other speaker to enjoy, I would be very tempted by the complete rebuild by HHR Exotic. I would likely guide most owners to seek the rebuild of the entire speaker. My situation is unique for many reasons. 

Be carefull of the $$$ scammers out their, 7 - 8 Grand in just insane period. The two names mentioned here, Dale and Bill are perhaps the last two people that can do them correct. Mr Bill LeGall told me about 15 years ago he only did maybe a couple a year. Bill had agreed to do my F"s but I then backed out. Have owned many nice pairs over the years, but its always like walking on eggshells their so fragile to overpower.

Had the 3000 series for Ohm 4XO install breaking in, then a right ch. tweeter went and i returned and got my funds back. Did have Ohm redo my 4XO drivers. Funny mine weight twice as much as them 3000 series drivers. Still love the model F ..... just not scrambled eggs!

Initial assessment of drivers upon removal of the top assembly (anchored by wing nuts) is that they are repairable. Cones are in great shape, and I'll be going for a replacement of spider and surround, leaving the original voice coil intact. This may not be the premium fix, but I understand a complete rebuild would be more touchy and more expensive. I'm out to have affordable fun - after all, they were free, and I was not seeking a reference omni. 

Suggestions for batting/damping material? Perhaps a trip to the local hobby shop or sewing center is in order. I wonder if furniture foam would be ideal? Frankly, that seems to be the chunks in the bag in the cabinet. 

Should be an interesting project.  

Pch300, yup, parallel thoughts here.  :)
I'll just have to experiment,  and of course keep the original stuffing in case I need to revert to it. However,  as with many things in audio, I have found that a decent design may be improved. Emphasis on "may", as no one knows unless tried. That's how I came up with the Schroeder Method of IC Placement.   I'm guessing it will be really ugly without any damping,  but I want to explore the spectrum  because I suspect an even better result is attainable.  

The Ohm F is a acoustic suspension speaker system, which means the cabinet is a sealed box. Because of the sealed cabinet and no crossovers, the system should roll off at 12 dB/octave below the cutoff frequency. I think the foam stuffing so full in the box is there for a specific purpose. You'd have to ask Ohm whether the stuffing is there for the purpose I think is.

In an acoustic suspension speaker box design, lining the internal cabinet walls with absorptive material is one method used to damp the sound wave reflections inside, reducing standing waves. Stuffing the box loosely-full will change the thermodynamics inside the box as well. This makes the box act as if it were bigger than its actual physical internal dimensions. That lowers the resonant frequency, so extends the bass when using a smaller cabinet volume that otherwise would have been bigger. There is a tradeoff with this - lower efficiency, for example. If I remember, this affects the system Q (resonant peak width) too, through damping.

The stiffness of the surround and spider along with the moving mass (plus damping) contributes to defining the resonant frequency of the driver. That in conjunction with the cabinet size and stuffing determines the system resonant frequency in the bass, among other things. Any changes you make to the surround or spider stiffness will affect these things. 

I suspect that in the Ohm F, the internal stuffing plays another role, that of absorbing the acoustic wave emitted by the inside surfaces of the cone. Otherwise, the internal reflections will interfere with the later sound waves travelling down the cone.

In preparation for the reconditioning of the spiders and surrounds of the Ohm Walsh F, I removed the assembly to discover VERY stuffed cabinets! Wow, talk about jammed to the gills with what appears to be a mesh sack full of foam chunks! My first thought is, "Well, that would deaden a speaker pretty quickly!" 

I'm planning on removing this sack of debris and conducting tests with other materials. I presume that if the cabinet is left sparse, the sound signature will change radically, and likely for the worse. I wonder, however, if the mid to high frequency response will improve if a mountain of foam is not literally semi-blocking the drivers. 

As I'm thinking this through, I suspect the reason the bass bin was jammed so full was to force the sound to emanate from the driver versus emptying into the cabinet, and I also suspect the delayed propagation of the wave into the cabinet might be pretty ugly sounding. But, who knows until tried? 

I would think that a different foam might confer a nice improvement to the speaker's sound. I think I'm going to start with an empty cabinet beneath to assess the range of effects. 

Has anyone else experimented with that aspect of the speaker? 

pch300, that is a terrific idea (if one wishes to bypass), to go direct to the inputs on the driver struts! Superb! That will be my game plan, should the speaker's renovation come out ok. Excellent, and beneficial advice! Personally, this has been among the most practically� beneficial threads I have benefitted from on Agon.  :) 

As for the internal cabinet wiring of the F, I bypassed it by directly attaching the speaker wire to the binding posts on the driver struts, and left the internal wiring unused.

If you do fix the surrounds on the F, your could then try an experiment that I did in the mid-'80s, with a musician friend.

Remove the grilles. Have a friend listen to the same musical selection. Without him knowing or seeing what you do, remove the fuses and replace it with a short wire. Play the music. Go back to the fuse, and play the music. Then go back and forth. Without telling him what you were changing, ask what he heard for the two configurations. Get a good description. For my friend, it was clearly and consistently audibly different, and repeatable in his descriptions.

Doug, I did the surround because I really didn't have much choice. Either fix it or get it fixed so I can use the speakers. Again, it won't be like the original F, because the surround characteristics is different than what Ohm had. It will play, however, as a interim solution until I got new Ohms.

I didn't use tape of any kind, because I was afraid the tape could tear the surround attachment part. The new and old surrounds could have different attachment ring diameters. I just thought of an idea that you could use the painters tape to mark the original edge of the surround attachment to the metal rim say in four perpendicular locations, but not on the surround itself. When you try to attach the new surround, it will either be smaller diameter which makes it easier to center relative to the tape, or larger diameter which you'd have to mark the new diameter with more tape and compare the original and new marked positions for centering. You could also measure the new surround diameter and mark that with additional tape relative to the original surround diameter tape marks.

I don't recall what glue was used for the surrounds. I ordered the surrounds from Stepp Audio Technologies in North Carolina. I supplied them the relevant dimensions and cone angle. I cannot find that company anymore on the web. It was 25 years ago!

The spider sagging is from years of weight on it. It could be permanently deformed. I would doubt that turning the driver over will do much in correcting the position, but it's worth a try to see what you get over a given time. 

If you're talking the internal cabinet wiring and the binding posts on the bottom of the cabinet, that's conceptually easier to do. I would caution on working on the binding posts on the metal struts holding the magnet assembly, as these attach the fragile wires that go to the cone internal wiring.

Thanks to you, pch300, I think I'm going to do this repair myself. I have been thinking about the project, and I believe I have come up with a winning idea on how to ensure success with avoidance of rubbing of voice coil. 

I would take all your suggestions, essentially, which are superb; thank you! 

But, in addition, when I got to the part where I would secure the outer rim of the surround to the metal basket, the thought struck me, why not use some painter's tape, or similar, to temporarily anchor the surround's outer edge, then play the speaker to assess for rubbing? If it rubs, I move it and reattach with tape. The tape should not damage the new surround, and it can be moved at will. In that way I should be able to then work around the bottom of the surround with glue, removing the tape locations and ensuring the proper position of the surround. I can also mark the edge, as you suggested for extra caution/precision. 

Obviously, I do not want to crank them up in that condition, as the tape might pull on the driver paper. Then again, I have bigger problems if the surround anchored to the paper pulls away! That had better be right! One has to use some sensibility. I could even, perhaps, use some narrow weights of some sort to place on the surround as an anchor. I would be able to find something suitable. 

I think I'm going to remove the drivers baskets today from the cabinet, and turn the drivers over to settle the one spider that's sagging. I also can begin to work on replacing the wiring and posts, which are antiquated and by today's standards poor. 

Sounds  feasible. Ideas, concerns? 

Thanks to you, pch300, I think I'm going to do this repair myself. I have been thinking about the project, and I believe I have come up with a winning idea on how to ensure success with avoidance of rubbing of voice coil. 

I would take all your suggestions, essentially, which are superb; thank you! 

But, in addition, when I got to the part where I would secure the outer rim of the surround to the metal basket, the thought struck me, why not use some painter's tape, or similar, to temporarily anchor the surround's outer edge, then play the speaker to assess for rubbing? If it rubs, I move it and reattach with tape. The tape should not damage the new surround, and it can be moved at will. In that way I should be able to then work around the bottom of the surround with glue, removing the tape locations and ensuring the proper position of the surround. I can also mark the edge, as you suggested for extra caution/precision. 

Obviously, I do not want to crank them up in that condition, as the tape might pull on the driver paper. One has to use some sensibility. I could even, perhaps, use some narrow weights of some sort to place on the surround as an anchor. I would be able to find something suitable. 

I think I'm going to remove the drivers baskets today from the cabinet, and turn the drivers over to settle the one spider that's sagging. I also can begin to work on replacing the wiring and posts, which are antiquated and by today's standards poor. 

Sounds  feasible. Ideas, concerns? 

pch300, some great tips, and it may be that I end up doing the surround myself. 

Was it Elmers glue that you used? ;) 
I presume not; what did you use? Do you recall? Some surround replacement kits have adhesive included. 

My opinion on the stiffener on the spider is a no.

Conceptually, stiffening the spider or surround causes the raising of the resonant frequency of the driver. The effect of that may raise the low cutoff frequency for the speaker, among other effects, perhaps changing the Q of the system tuning.

Doug, just saw your post. I was writing my previous response when you posted.

Just to fill in some info, I found a few things that differ from the F vs the W5000 speakers, in my room. The F subjectively seems to go deeper in the bass than the W5000, in the sense of very low bass, the room-shaking kind, despite the low frequency bandwidth specs of 37 Hz vs. 25 Hz, respectively. I speculate that the faster roll-off of the W5000 (a vented design) vs. the more gentle roll-off of the F (a sealed system design) may have something to do with this impression. For music, this makes no difference. For movies, I have subwoofers to cover the lowest frequencies, about equivalent to that of the W5000. 

Both the F and the W5000 drivers can produce an impression of surround sound from only two-channel material. In the movie Flyers, there is a scene where a fighter jet flies from-behind to overhead and then to in-front of another jet. The sound, from inside the second jet, with only two front speakers projects the sound movement matching the video. 

The F requires a power to get to reasonable sound levels; the W5000 takes less power. The latter, with a powerful amp will give added headroom to play live recordings at live SPL levels, not that one needs to do this routinely.

I also seem to recall that the power handling on the modern Ohm drivers is much better than in the F. Another related thing is a review of the Walsh 5 showed a linear tracking of output volume and power input, saying that higher power causes little "power compression" of the sound. I never tried to check this on my system, but that is a good indicator to me for the speaker capability to produce correct musical dynamics.

When I replaced the surrounds on my Fs, that was the first time I had tried a surround replacement on any driver. To me, it was fairly straightforward. I would not attempt to replace the spider - too much risk of damaging the titanium part of the cone. 

The surprisingly easy, but time consuming part was to carefully clean the paper cone periphery of old glue, without damaging the paper periphery, after removing the old surround from the cone and metal rim of the basket. 

The new surround should fit over the periphery exactly, if you order the right size diameter of the surround. Measure carefully before you order and double check after you receive the new surround. The  surround fits over the outside surface of the paper cone periphery, and also to the upper surface of the metal rim of the basket (like in the existing surround).

I had the driver upside down, put the surround over the cone and slide it below the periphery, applied the glue to the outside of the cone periphery, and pull the surround up over the glue slowly to make it positioned evenly around the cone. At this stage it helps to orient the driver right-side up to achieve a even, planar circular interface between surround and cone. I suggest minimal glue to minimize the mass change at the edge. Let glue set. 

Centering the cone periphery was also fairly easy. I had the driver oriented upside down on a table. While holding the cone near its middle height, tilt the cone left and right while gently sliding it up and down. Do the same fore and aft. Find the center point between where you hear slight scraping and no noise, in four perpendicular tilt directions. mark where the surround edge for each center point. Glue it down to the rim, taking care to not radially stretch the cone either outward or inward. 

If you take this route, you can still opt to do more repair later with someone like Dale Harder, or get his TLS-1 speaker. 

OOPS; I had said,

"I had a great discussion with Evan at Ohm; very helpful, and I can see the beauty, interesting nature of what they are doing with their design. I already have a hybrid omni, the Kings Audio King Tower, and I do not wish to move farther from that style of speaker if I can see if there is a possibility of moving up in terms of scale and quality. Doing a current Ohm product would take me mechanically, operationally further from that. So, I am letting go of that idea. I know there are enthusiasts, but no amount of adjustment would make a 15" and soft dome into a true omni. I don't care to debate anyone about that, and I'm not making a value judgement of the Ohm products, because I have not used them in my room and have not reviewed them. I'm simply not seeking that design." 

After further discussion with Evan, I now fully comprehend the drivers and implementation of the modern Walsh driver, with its omni mid-bass to treble driver with directed tweeter,  and it is back on my radar as (for most intents and purposes) an omni. Mea Culpa 

My Ohm Sound Cylinders are still sounding excellent!! They are the "controlled-directivity" type. Astounding 3-D sound from anywhere in the room!