Clarity Panel AHA! moment
- Thread starter wfissell
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Were the panels sliding down with gravity? Over the years that happens. ML makes what they call stat stop brackets. They gave me a pair for my Prodigy speakers and they work well.
wfissell
Member
I dont think so. My spidey sense says someone else was in here before.
Make sure there is a metal bracket under each panel that attaches to the speaker frame. The bracket prevents the panel from sliding down later. You want that regardless. Email ML service about that.
Absolutely, and they really hacked that connection up. You obviously bought these on the used market. Hopefully you didn’t pay a bunch for the speakers. It’s a shame how the used market has gotten over the last 5 years or so you really have to be careful about who you buy from. Now that being said if the seller made all this clear before the purchase and it was reflected in the price then the first part of my reply can be disregarded. Good luck with your speakers. The advice to contact ML service for guidance on this is spot on.
Those connections do look deteriorated. However, I suspect those may be the original ML diaphragm and wire connections. I say this because the diaphragm is wrapped over the rear stator, the amber colored tape covering the stator connection is Kapton, which ML uses and isn't sold in retail stores, and I've observed similar poor connections on a ML Theater panel that the owner stated had not been into.
On the aforementioned Theater panel, the [red] bias supply wire connection to the charge ring was a huge glob of solder that no one had bothered to flatten out, and which was compressed into the spacer tape that is the only insulation against a shorting path to the stators. Hopefully that very-poor connection was a one-off condition-- but from the looks of your panel, maybe not.
Also note the stripped back inslulation on the stator wire connections have exposed wire extending beyond the stator edge, in close proximity to the bias supply connection, and even to the opposite stator. Moreover, having all three connections spatially close together isn't so smart either.
OK; call me a prude but I would have done it differently.
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wfissell
Member
Anyone have any idea which of the dozen or so 3M VHB tapes are used in the panels?
wfissell
Member
Disappointingly they were sold as good
but, the price was such that I calculated that even if this wasnt honest I could still make it happen.
Sorry not a techie here I can change the panels and set up the active crossover and wire it but that’s the extent of my tech wizardry on the Logans. Jazzman will probably have that info though.
Sorry not a techie here I can change the panels and set up the active crossover and wire it but that’s the extent of my tech wizardry on the Logans. Jazzman will probably have that info though.
My experience is pretty much limited to flat-panel wire-stator ESLs.
My only experience with ML panels was replacing the diaphragm in a 20-year old Theater Center Channel speaker. What I observed in the Theater panel may or may not be applicable to other / newer ML panels.
Being accustomed to perfectly symmetric flat-panel hybrid ESLs, which typically use about 0.063" diaphragm-to-stator spacing (d/s); I was taken aback by the asymmetic, non-uniform spacer thicknesses and diaphragm-to-stator spacing (d/s) I saw in the ML panel, especially the extremely close d/s at the front spar locations.
I recall a video of ML's being fabricated, and the final step vacuum bonded the stators together. On the Theater panel it was obvious that this vacuum bonding step had compressed some areas more than others, as its measured thicknesses were all over the map.
As best as I could determine by averaging multiple caliper readings, the Theater panel used 0.025" spacer tape on the front stator and 0.045" spacer tape on the rear stator.
A general rule for ESL design is that the span between spars should not exceed 100x the d/s.
The span between spars on the Theater panel was significantly closer than spar spans on full size ML panels.
Closer spar spans allow using thinner spacer tapes for closer d/s, giving higher output, so the close d/s makes sense for the small Theater panel, and would not exceed the100x d/s rule.
I would not assume that full size panels with greater span between spars would likewise use 0.045" spacer tapes on the rear stator.
After I thought about it for a while, I came to appreciate that asymmetric spacing is a necessary compromise (and consequence) when tensioning a diaphragm over a curved stator.
Specifically; the curved diaphram surface can't be an ideal cylindrical shape because a certain amount of tension across the curve is necessary to pull out radial wrinkles in the film, and any tension across the curve pulls the diaphragm toward the rear stator and forces the diaphragm to take a 'saddle' shape between the spars. The diaphragm is then significanly closer to the the front stator at the spar locations, and dips closer to the rear stator in the center area between spars.
Additionally; because the diaphragm is a convex curve, it's forward movement is opposed by the hoop force. Therefore, the diaphragm can be, and indeed should be, spaced closer to the front stator, in order to take advantage of the greater drive force afforded by the closer spacing.
In the end I came to appreciate that significant compromises are required to make a curved panel work, and ML did pretty well, considering the challenges.
BTW; it's really amazing how the 3M spacer tapes retain their tack after so many years. It's not cheap either ($$$$ ouch), so it makes sense to reuse it if you can. When I build new panels, I order the spacer tapes from McMaster Carr at the link below (yes, it's 3M brand tape):
https://www.mcmaster.com/catalog/130/3948/7626A92
For the clear 4-mil spar-to-diaphragm tape, I order that from Ebay at much lower cost.
Here's a link to my write-up on the ML Theater panel rebuild:
https://jazzman-esl-page.blogspot.com/2011/11/compensating-diplole-phase-cancellation.html
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