ESL 57 : how much weight on the jig ?

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The ultimate secret in the universe after women : how much weight to put on a jig, more or less the same as the one used by factory ?

It seems to me that no-one really knows, that professional re-furbisher made their own minds themselves, that DIYers do it the way they feel it (and at the end this is not worse than old panels they had).
Of course I read some figures here and there. Most reliable ones seem to be 45 for treble and 60 for bass (applied to 40*80cm). But I can't believe this is kg. Pounds seem much more acceptable. But maybe I am wrong.

So, anyone has the answer to the second most protected secret in the universe ?
 
However nice it is, there are no technical production details in that book that I can recall.

Thanks for this reply.
Meanwhile I found some similar conclusion here: Planar Speaker Asylum: The book... by Gary Jacobson
Yet there are some pictures of the jig in this book but maybe nothing more than these ones:
One Thing Audio/Manufacturers/Quad/Pictures

I am interested in photos because this could give information on the weights to apply. Certainly not directly the value itself but at least the relative values between a bass and a treble panel.
For example, on the 3rd photo, we can see the weights used for tensioning the bass panel. For me there is no way that it makes 60kg.
On the same photo or on the first one, in background, we see a similar jig but with (much ?) heavier weights: is it for treble panel ?

My intention is not to set up an international business. I just want to repair my ESL. My jig is ready, mylar was just received,... just have to find the right tension to apply now.
 
Fabien,

"60" could be pounds or kilos, remember the mylar film has very high elastic modulus and can take a lot of tension with a minimum of strain.

I used to stretch my film by hand, using plastic tape, and I remember I had to apply a lot of force to get it nicely stretched taut.

if you don't find the exact values, you can increase the weights until the membrane has the desired resonant frequency. This can be tested by tapping it. The problem with this is that, if you heat-shrink the membrane afterwards, the resonant frequency will go up. So it is hard to estimate the final resonant frequency.

Kenneth, quad fan (but not owner :) )
 
Fabien,

"60" could be pounds or kilos, remember the mylar film has very high elastic modulus and can take a lot of tension with a minimum of strain.

I used to stretch my film by hand, using plastic tape, and I remember I had to apply a lot of force to get it nicely stretched taut.

if you don't find the exact values, you can increase the weights until the membrane has the desired resonant frequency. This can be tested by tapping it. The problem with this is that, if you heat-shrink the membrane afterwards, the resonant frequency will go up. So it is hard to estimate the final resonant frequency.

Kenneth, quad fan (but not owner :) )

Indeed I think now that the bass panel will not need a lot of weights contrary to the treble panel which will require very high tension.
Measuring the desired resonant frequency is a nice alternative. But what is the resonant frequency to be achieved with each panel ? In which conditions ? Un-bonded, bonded and charged, ...
If measuring is done once bonded then this can mean a lot of trials and a waste of mylar.
I will avoid heat-shrinking because this is not very predictable and repeatable.
 
If you could stretch the mylar with one stator laying underneath, then I think a pretty good measurement can be made. I don't think gluing and charging will make a big difference. The main parameters will be the tension and the distance between the diaphragm support pieces.

Afterwards you can remove the stator from the work bench and re-tension the film for coating and gluing.

If you are refurbishing several old panels you can adjust by ear, by tapping another old panel's diaphragm for reference. Otherwise it's a little more difficult, maybe use microphone, soundcard and FFT program to measure it?

I don't know what the nominal res. freq. is for the Quads, maybe someone else here will know?

Kenneth
 
If you could stretch the mylar with one stator laying underneath, then I think a pretty good measurement can be made. I don't think gluing and charging will make a big difference. The main parameters will be the tension and the distance between the diaphragm support pieces.

Afterwards you can remove the stator from the work bench and re-tension the film for coating and gluing.

If you are refurbishing several old panels you can adjust by ear, by tapping another old panel's diaphragm for reference. Otherwise it's a little more difficult, maybe use microphone, soundcard and FFT program to measure it?

I don't know what the nominal res. freq. is for the Quads, maybe someone else here will know?

Kenneth

All right I will practise.

But knowing the right weights to apply would have been so simple !

Just one point: applying a charge makes a big difference. Because it corresponds to negative compliance (opposite in sign to the one due to mechanical tension) and this reduces significantly the resonance frequencies.
It is so important that a safety factor has to be respected (see papers from Baxandall if I remember well).
 
Just one point: applying a charge makes a big difference. Because it corresponds to negative compliance (opposite in sign to the one due to mechanical tension) and this reduces significantly the resonance frequencies.
It is so important that a safety factor has to be respected (see papers from Baxandall if I remember well).

Hmm, interesting, will check! I have a PDF of his book chapter here.
 
Hi,

From Baxendall's chapter in Loudspeaker and Headfone Handbook, the polarized resonance frequency is for bass panel 70 Hz and treble 260 Hz.

/örjan

Here are the results of my first measurements:

Picasa Web Albums - fabien.lefebvre.fr

With a comparison between the rebuilt panel and another assumed in original conditions (needs to be re-built), approximately in the same measurement conditions.

I have been using these weights: 28 * 1.5lbs on an area in the vicinity of 85*45cm.
 
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Hi,

From Baxendall's chapter in Loudspeaker and Headfone Handbook, the polarized resonance frequency is for bass panel 70 Hz and treble 260 Hz.

/örjan

Now that I have seriously studied this book, no doubt that this is really the reference to read: it simply contains the only un-questionable frequency response plot that I am aware of.

By the way, my measurement is not precise enough (too averaged) because it does not show where happens the first peak above 10kHz, which is a key information to check that correct tension was applied on treble panel.
 
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