Dear all,
I have a question for you experts on DIY ESL panels.
Many years ago, I bought a pair of Audiostatic ES240 speakers. For some unknown reason, the guy was selling them without the transformers. Then after a while I found another guy who was selling the complete same type of speakers, which sound was very low; probably because the conductive coating was almost gone.
Then I assembled a complete system with the first panels and the transformers of the second ones, and that become the speakers that I am using since years in my main sound system.
They sound fantastic, with a lot of bass despite what I read here and there, that full range ESLs are lacking the low frequencies.
I am going to rebuild the panels of the second pair, which has been resting in the garage all these years.
The problem is the usual one: how much should I stretch the membranes?
I have noted that, if I shake my hands in front of the speakers, like you do when saying hallo, the membranes moves freely, in both the pairs of panels.
I do not know if that is because the speakers have lost the original stretching over the years or if that is the original stretching, which practically is just enough for avoiding wrinkles. It is not a real stretching.
Do you think that the membranes should be much more stretched?
Actually, and here I would like to hear if I am wrong or not, I am wondering if the stretching is really necessary.
My reasoning is the following. Let consider the low frequencies. For that, we need to move the membrane as far is possible, of course within the limits imposed by the distance of the stators.
If the membrane has almost no stretching, when the audio signal stops, the membrane too stops immediately, because there are no force pushing it in whatsoever direction.
Instead, if the membrane is tight, when the audio signal stops the membrane is pulled back to the central position, with a probable overriding which should last longer as the stretching force is bigger.
The same that happens on traditional cone speakers, because of the pulling forces of suspension and spider.
If my reasoning is correct, there should be no stretching at all.
Probably an excessively lose membrane would not be good for the high frequencies, I suppose.
But then maybe it is correct that the membrane has just the minimum stretching enough to avoid wrinkles in quiet state, and no more than that.
What do you think? Am I wrong?
Thank you so much in advance.
Giovanni
I have a question for you experts on DIY ESL panels.
Many years ago, I bought a pair of Audiostatic ES240 speakers. For some unknown reason, the guy was selling them without the transformers. Then after a while I found another guy who was selling the complete same type of speakers, which sound was very low; probably because the conductive coating was almost gone.
Then I assembled a complete system with the first panels and the transformers of the second ones, and that become the speakers that I am using since years in my main sound system.
They sound fantastic, with a lot of bass despite what I read here and there, that full range ESLs are lacking the low frequencies.
I am going to rebuild the panels of the second pair, which has been resting in the garage all these years.
The problem is the usual one: how much should I stretch the membranes?
I have noted that, if I shake my hands in front of the speakers, like you do when saying hallo, the membranes moves freely, in both the pairs of panels.
I do not know if that is because the speakers have lost the original stretching over the years or if that is the original stretching, which practically is just enough for avoiding wrinkles. It is not a real stretching.
Do you think that the membranes should be much more stretched?
Actually, and here I would like to hear if I am wrong or not, I am wondering if the stretching is really necessary.
My reasoning is the following. Let consider the low frequencies. For that, we need to move the membrane as far is possible, of course within the limits imposed by the distance of the stators.
If the membrane has almost no stretching, when the audio signal stops, the membrane too stops immediately, because there are no force pushing it in whatsoever direction.
Instead, if the membrane is tight, when the audio signal stops the membrane is pulled back to the central position, with a probable overriding which should last longer as the stretching force is bigger.
The same that happens on traditional cone speakers, because of the pulling forces of suspension and spider.
If my reasoning is correct, there should be no stretching at all.
Probably an excessively lose membrane would not be good for the high frequencies, I suppose.
But then maybe it is correct that the membrane has just the minimum stretching enough to avoid wrinkles in quiet state, and no more than that.
What do you think? Am I wrong?
Thank you so much in advance.
Giovanni
Without too much speculating, why don't you stretch the second panels the same amount as the first ones that you are satisfied with?
(My opinion is that stretching increases resonance frequency, the lower the better. On the other hand, a too loose membrane could flap to the stators, so some minimum force is necessary. A reasonable tension will naturally set the lower cutoff and limit the excursion between the stators, whereas the gap is the physical limit)
(My opinion is that stretching increases resonance frequency, the lower the better. On the other hand, a too loose membrane could flap to the stators, so some minimum force is necessary. A reasonable tension will naturally set the lower cutoff and limit the excursion between the stators, whereas the gap is the physical limit)
alnico: I think you are wrong…. In order to have a stable movement of the diaphragm you need tension. You tension it for a suitable low frequeny resonance. If the tension is too low, the diaphragm will stick to one of the stators at low SPL. A low resonant frequency will also reduce the possible SPL. There will be a peak in the bass that force the diaphragm to large excursions. Most ESL are therefore often tuned in the range circa 50-80 Hz.
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Thank you guys.
Dear Lcsaszar, I said in my long description that both the first set (the one which plays fine) and the second set (the one that plays weak) seems to have the same stretching, which seems very low.
The rest of your comment is matching what I thought, low stretching but of course not so low for preventing sticking against the stators.
Dear Roger, sorry I have not understood you completely. Are you referring to the resonance peak or to a further peak if the membrane is too much loose?
In my ignorance, I didn’t know that low resonance frequency means low efficiency, if I understood you correctly.
When you mention an FS of 50 – 80 Hz are you referring to full range ESL speakers like my ones? (Well, at least intended so)
I think that I will check the current FS of the panels, to see if it is too low or not. That could suggest us if the current stretching of the membranes could be original or not.
Giovanni
Dear Lcsaszar, I said in my long description that both the first set (the one which plays fine) and the second set (the one that plays weak) seems to have the same stretching, which seems very low.
The rest of your comment is matching what I thought, low stretching but of course not so low for preventing sticking against the stators.
Dear Roger, sorry I have not understood you completely. Are you referring to the resonance peak or to a further peak if the membrane is too much loose?
In my ignorance, I didn’t know that low resonance frequency means low efficiency, if I understood you correctly.
When you mention an FS of 50 – 80 Hz are you referring to full range ESL speakers like my ones? (Well, at least intended so)
I think that I will check the current FS of the panels, to see if it is too low or not. That could suggest us if the current stretching of the membranes could be original or not.
Giovanni
alnico,
A low fundamental resonant frequency does not change the efficiency. The lower the frequency, the higher the peak gets and therefore reduce the possible SPL at frequencies above the fundamental resonance. If the tension is too low, the treble use to be bad. A certain stiffness/tension is needed for good high frequency reproduction. The diaphragm is like a drumskin and should be correctly tensioned.
A low fundamental resonant frequency does not change the efficiency. The lower the frequency, the higher the peak gets and therefore reduce the possible SPL at frequencies above the fundamental resonance. If the tension is too low, the treble use to be bad. A certain stiffness/tension is needed for good high frequency reproduction. The diaphragm is like a drumskin and should be correctly tensioned.
Dear Roger,
now I understand what you meant, thank you. And I too, as suggested before, think that for the treble some stretching is necessary.
I think that will try the first panel (these speakers have two panels each channel) with a moderate stretching, not too tight, not too low, then measure the FS and listen at how it sounds. After that I will have a better idea if it will be necessary to increase the stretching.
Kind regards
Giovanni
now I understand what you meant, thank you. And I too, as suggested before, think that for the treble some stretching is necessary.
I think that will try the first panel (these speakers have two panels each channel) with a moderate stretching, not too tight, not too low, then measure the FS and listen at how it sounds. After that I will have a better idea if it will be necessary to increase the stretching.
Kind regards
Giovanni
Dear Roger, with the help of a friend who has already built some DIY ESL, I have build up my own membrane stretching frame, which includes a way to record the stretching force (two scales).
We are going to replace the diaphragms of the two speakers that have a very low output. It will take some time, especially for removing the old glue.
After testing and comparing them with the two working speakers, we will decide if they too will need the membrane replacement or not.
Will keep updated.
Thank you very much.
Giovanni
We are going to replace the diaphragms of the two speakers that have a very low output. It will take some time, especially for removing the old glue.
After testing and comparing them with the two working speakers, we will decide if they too will need the membrane replacement or not.
Will keep updated.
Thank you very much.
Giovanni
Giovanni,
Please, some pictures of your work! I would be interested in more information on your stretching frame. What the scales measure etc. I have a simple jig and I have two methods of measuring the tension of the diaphragm, one by a force meter (Redirect Notice) and one by a dial indicator (Redirect Notice). I intend to use this for rebuilding some Magnepan speakers. In my case, I measure the existing diaphragm, either the force to press down the diaphragm or the deflection by a weight. From there I go for a slightly higher tension as it slacks a bit after use.
Please, some pictures of your work! I would be interested in more information on your stretching frame. What the scales measure etc. I have a simple jig and I have two methods of measuring the tension of the diaphragm, one by a force meter (Redirect Notice) and one by a dial indicator (Redirect Notice). I intend to use this for rebuilding some Magnepan speakers. In my case, I measure the existing diaphragm, either the force to press down the diaphragm or the deflection by a weight. From there I go for a slightly higher tension as it slacks a bit after use.
Dear Roger,
Let me take some pictures and I will post them.
I can’t do the same that you are doing, because the membranes on my speakers are really loosen, I do not have an actual stretching by now that I can measure. Regardless, they do not slap, at least not at normal listening level.
While I can imagine, I think, how you could measure the stretching by means of a weight and the dial indicator, I do can’t imagine how you measure it by means of the force meter.
Giovanni
Let me take some pictures and I will post them.
I can’t do the same that you are doing, because the membranes on my speakers are really loosen, I do not have an actual stretching by now that I can measure. Regardless, they do not slap, at least not at normal listening level.
While I can imagine, I think, how you could measure the stretching by means of a weight and the dial indicator, I do can’t imagine how you measure it by means of the force meter.
Giovanni
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