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My take on a stretch jig
My take on a stretch jig
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Old 9th November 2016, 02:37 PM   #51
sumotan is offline sumotan  Indonesia
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Slightly OT question. I've a pair of ML Odyssey made some tweaks
on the crossover but when I first saw the crossover I keep wondering
why the high pass has to be made so complicated I just dont understand.
The panel is suppose to be wide band from 250 to 20k . So why the need
to made the XO so complicated ? Would someone pls shed some light on
this pls

Thks
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Old 9th November 2016, 03:25 PM   #52
WrineX is offline WrineX  Netherlands
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Maybe a notch, as Well as getting rid of the high frequency going up each octave . I can only guess . I am not really into logans harder to repair without much benefit compared to non curved panels. So I never bought one
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Old 14th November 2016, 03:57 AM   #53
bolserst is offline bolserst  United States
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Quote:
Originally Posted by sumotan View Post
I keep wondering why the high pass has to be made so complicated I just dont understand. The panel is suppose to be wide band from 250 to 20k . So why the need
to made the XO so complicated ?
Most of the complication in the crossover comes from the need to passively EQ the roll off in the response for frequencies where the wavelength is longer than the panel is wide. (ie dipole cancellation).

More details on ML crossover EQ here: (posts #46, #50, #56)
http://www.diyaudio.com/forums/plana...ml#post3323339
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Old 23rd February 2017, 03:23 PM   #54
njansens is offline njansens  Netherlands
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I have read your thread a couple of times now Wrinex, truly inspiring.
Working on my (first) pair of ESL 57's, I tried to approach restoration of the panels also in a reproducible manner. Build a kind of stretching jig, also put a woofer underneath to measure resonance as a paramater of the tension in the diaphragm.

And then it became immediately clear that mechanical tension alone, like explained on many DIY sites, probably leads to rather unpredictable results in the long term: the diaphragm indeed slowly loses tension.

So I am looking at heat treatment now. Did my first attempts with diaphragm under tension, with a heat gun. Indeed this leads to more stability, but I am trying to get some control over this process. A heat gun is troublesome, and I have shot some diaphragms in the mean time of course (under tension they split in a second when heated too much).

I have looked many times at the pictures of the original Quad stretching jig, especially the oven. It is open at the bottom, and there seems to be some kind of shelve in it, which will be just underneath the diaphragm. I assume it is a kind of a flat bed heating. I have the feeling, looking at the construction, that this oven is probably not very hot. After all, it is a metal rig they roll in and out, and since they work on it constantly it will probably be relatively safe to touch without risk of burning yourself. Assuming they did quite some of these panels on a working day, one at a time, the time in the oven is probably rather (tens of) minutes than hours.

I have a flat heating panel on order now to do some experimenting (although I wonder if it will be hot enough).
Do you have any directions on actual temperature / time for the treatment?

Cheers,
Niels
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Old 31st March 2017, 08:10 PM   #55
horu5 is offline horu5
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Default Stretching

It is a long time ago. I also have experimented wich streching jigs and heat treatment etc to repair panels for a ESL (Beveridge 3s). I ended with a method that worked quick, simple and delivers controllable results:

(1) marking to rectangles on a table tennis table with white edding. One with the original size a second scaled by +2%.

(2) Then placing the mylar, attached with loose tension with tape

(3) mark the smaller rect on the mylar with an edding

(4) stretching the mylar starting by the halfpoints off all sides until evenly stretched

(5) when finished place first grid from top (used 3m double sided tape, for mirrors, still fine since years). Remove taped and join with second half.
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Old 22nd April 2017, 10:40 PM   #56
WrineX is offline WrineX  Netherlands
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Quote:
Originally Posted by njansens View Post
I have read your thread a couple of times now Wrinex, truly inspiring.
Working on my (first) pair of ESL 57's, I tried to approach restoration of the panels also in a reproducible manner. Build a kind of stretching jig, also put a woofer underneath to measure resonance as a paramater of the tension in the diaphragm.

And then it became immediately clear that mechanical tension alone, like explained on many DIY sites, probably leads to rather unpredictable results in the long term: the diaphragm indeed slowly loses tension.

So I am looking at heat treatment now. Did my first attempts with diaphragm under tension, with a heat gun. Indeed this leads to more stability, but I am trying to get some control over this process. A heat gun is troublesome, and I have shot some diaphragms in the mean time of course (under tension they split in a second when heated too much).

I have looked many times at the pictures of the original Quad stretching jig, especially the oven. It is open at the bottom, and there seems to be some kind of shelve in it, which will be just underneath the diaphragm. I assume it is a kind of a flat bed heating. I have the feeling, looking at the construction, that this oven is probably not very hot. After all, it is a metal rig they roll in and out, and since they work on it constantly it will probably be relatively safe to touch without risk of burning yourself. Assuming they did quite some of these panels on a working day, one at a time, the time in the oven is probably rather (tens of) minutes than hours.

I have a flat heating panel on order now to do some experimenting (although I wonder if it will be hot enough).
Do you have any directions on actual temperature / time for the treatment?

Cheers,
Niels
Yes , the oven does not exceed melting temps of mylar ofcourse but it could be localized heating to. i have a ceramic heater i bought for this project its flat and large and i might needed 2 of them. idea was to make a jig so you can roll it over the stretch jig heat it and tension it then remove it again. but i must say i sort of stopped working on it. i try to fix my ESL's and be done with it. i have no energy for the quads left. i want a cool fresh project from start to finish these speakers are standing here for 2 years now and i had enough
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Old 24th April 2017, 03:19 PM   #57
njansens is offline njansens  Netherlands
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Part of satisfaction is mastering the technique for me, I guess :-) The jig I built uses simple clamps and bottles filled with metal punching caps. For heating I used 3 heating panels of 60x30 cm to cover the diaphragm. I place it over the diagram while stretching. It sort of hovers 2 cm above the mylar, and will get to around 110 degrees. I heat for 15 minutes.
Attached Images
File Type: jpg Stretching Jig.jpg (80.8 KB, 89 views)
File Type: jpg Heating Panel 1.jpg (7.2 KB, 83 views)
File Type: jpg Heating Panel 2.jpg (59.0 KB, 83 views)
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Old 16th July 2017, 03:20 PM   #58
Elmostatic is offline Elmostatic
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Hey WrineX,

Did you make any more progress on this project?

I was thinking about my own bikes (have owned bikes since little child) and I have never seen an inner tube that doesn't lose some air pressure over time. Ok we are talking days when I notice the pressure leakage..

What pressure in psi are you pumping the tube to get the mylar to tension? Which makes me think of the next thing - the pump. These often leak some air also and a fractional amount when disconnecting the pump - was this an issue for you.

Maybe I should just try this method myself.

I brought a kit from ER Australia and there is no mention heat setting the Mylar. Perhaps it is already heat set type?

Finally, is there an agreed Fs value for stretch resonance? Seems like somewhere around 70Hz which is then lowered due to the charged panel and the sum of 4 panels in the speaker frame.

All the best.
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Old 16th July 2017, 03:39 PM   #59
Elmostatic is offline Elmostatic
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Can I ask everyone here what the agreed consensus is for the resonance frequency of a single panel should be. I'm in the process of measuring some of the panel I have that are still intact. I have to look for a new software that gives me a clearing reading of frequency but shouldn't be too hard to find.

I have a kit with a quoted stretch tension of 2.6Kg which from the Uni maths days means it should in theory give me the required resonant frequency (if the suppler has indeed proved this) given the material is a known and the aperture is a known (disregarding local temperature and air pressure etc). My maths days also inform me that 2.6Kg is a fairly crude value and realistically when I actually stretch and tune my mylar the actual stretch figure I expect to be a more precise value - but I am yet to prove this.

I have also brought a spring tension gauge with a reading up to 350 milligrams so i will experiment with that also.

Would be great to hear people thoughts on what resonant frequency people have aimed for and achieved and also if heat setting has indeed produced stable results.
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Old 16th July 2017, 04:29 PM   #60
Elmostatic is offline Elmostatic
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Update - just made some measurement and my panel seems to hit peak resonance at frequencies around 90Hz.
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