Hi all,
I've read lots of posts here about different methods to stretch diaphragms for ESL's. Usually, but not always it is recommended to try to achieve a high tension, especially for a hybrid. The consensus seems to be that mechanical stretching can achieve a higher tension and resonant frequency than heat shrinking the diaphragm alone. I'm wondering, what is the tradeoff with just heat shrinking and using spacers placed closer together. I understand there will be more stray capacitance, but it seems like this could be minimized if narrow spacers were used.
btw, i'm looking at the flat panel case, not curved right now.
Dan
I've read lots of posts here about different methods to stretch diaphragms for ESL's. Usually, but not always it is recommended to try to achieve a high tension, especially for a hybrid. The consensus seems to be that mechanical stretching can achieve a higher tension and resonant frequency than heat shrinking the diaphragm alone. I'm wondering, what is the tradeoff with just heat shrinking and using spacers placed closer together. I understand there will be more stray capacitance, but it seems like this could be minimized if narrow spacers were used.
btw, i'm looking at the flat panel case, not curved right now.
Dan
Hi,
it's not a very easy question to answer. If we take a look to typical hybrid ESLs (15-20 cm wide and 1.5 D/S) then high mechanical tension is perhaps the only option because heat shrinking will not give enough stability from diaphragm collapsing to stators. High mechanical tension will result in membrane tension decreasing over time until it reaches some point, and after this the changes become quite slow. Low mechanical tension or heat shrinking may have the same problem but to a lesser degree. IMO if you can design ESLs with lower tension and closer supports it would be more stable in the long term. However in case of heat shrinking alone, I think unsupported width to D/S spacing should be considerably lower than often used "rule of thumb" of 100:1. Maybe closer to 50:1. Keep in mind than even low mechanical stretching(in the order of 0.5%) results in significantly higher tension than thermal treatment, so this must be taken into account during initial design phase.
Also high F0 is not necessarily a desirable characteristic. If you plan to make hybrids, it's recommended to use X/O at one octave above the fundamental. High separation frequency leads to loss of lots of subtle quality effects of an ESL, and makes integration significantly harder.
Regards,
Lukas.
it's not a very easy question to answer. If we take a look to typical hybrid ESLs (15-20 cm wide and 1.5 D/S) then high mechanical tension is perhaps the only option because heat shrinking will not give enough stability from diaphragm collapsing to stators. High mechanical tension will result in membrane tension decreasing over time until it reaches some point, and after this the changes become quite slow. Low mechanical tension or heat shrinking may have the same problem but to a lesser degree. IMO if you can design ESLs with lower tension and closer supports it would be more stable in the long term. However in case of heat shrinking alone, I think unsupported width to D/S spacing should be considerably lower than often used "rule of thumb" of 100:1. Maybe closer to 50:1. Keep in mind than even low mechanical stretching(in the order of 0.5%) results in significantly higher tension than thermal treatment, so this must be taken into account during initial design phase.
Also high F0 is not necessarily a desirable characteristic. If you plan to make hybrids, it's recommended to use X/O at one octave above the fundamental. High separation frequency leads to loss of lots of subtle quality effects of an ESL, and makes integration significantly harder.
Regards,
Lukas.
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stretch diaphragms for ESL's. Usually, but not always it is recommended to try to achieve a high tension, especially for a hybrid
All I can say..... I have opened ML panels from a pr SL3s....46-8"X12....an the membrane was almost lay on the back panel.....play like new... good output as other panels that were drum tite...... now I not thinking that it should be luse...
but I think it can be done by hand.....you may have to do it once are twice...but why not.................nuts right
All I can say..... I have opened ML panels from a pr SL3s....46-8"X12....an the membrane was almost lay on the back panel.....play like new... good output as other panels that were drum tite...... now I not thinking that it should be luse...
but I think it can be done by hand.....you may have to do it once are twice...but why not.................nuts right
tyu is not wrong. The issue id not tension to play and sound goo but to restore the diaphragm to centre position and prevent it from collapsing on to one of the stators when presented with lots of bass (a force greater than the available restoring force which is the diaphragm tension). So you need enough to keep the diaphragm centred in a given situation and no more. That said most people will end up needing a fair amount of tension if they like to play at realistic levels.
Thanks for the responses everyone.
To put my question another way, are there advantages to be gained by using higher tension and greater unsupported distance? Perhaps is it impossible to obtain the same high spl output levels with a heat shrunk panel regardless of how small the unsupported distances are?
thanks,
Dan
That's what I feared.
This is what I suspected. However, what are the tradeoffs to using the lower unsupported width? I am looking at a hybrid design and most likely wire stators. So I'm assuming I can minimize the stray capacitance of using more spacers placed closer together by running them vertically and not running wires over the spacers. However, are there other tradeoffs? Are the panel resonant modes and buzzing noises going to be easier or harder to deal with with smaller unsupported distances for example? I'm thinking back to the ESLs have bad decay plots thread.
This is what I figured, just enough tension to allow peak levels but not too much.moray james; said:
To put my question another way, are there advantages to be gained by using higher tension and greater unsupported distance? Perhaps is it impossible to obtain the same high spl output levels with a heat shrunk panel regardless of how small the unsupported distances are?
thanks,
Dan
Quote: Dan "To put my question another way, are there advantages to be gained by using higher tension and greater unsupported distance? Perhaps is it impossible to obtain the same high spl output levels with a heat shrunk panel regardless of how small the unsupported distances are?
thanks,
Dan "
Yes there are greater tension will provide stability and believe me you are going to have low frequency information come along and having to unplug your speakers and blow on them to un stick a diaphragm is a pain you don't want to bother with. Theory says and proves as far s I know that the tighter the skin the more efficient and the cleaner because it centres your diaphragm immediately. The mor distance you use the less efficient your system and they are not efficient to be gin with so distance buys you nothing good and you will still need tension to keep you diaphragm stable.
Here is the scoop on heat shrunk diaphragms thsy are the lazy mans way out. Heat shrink plastic is not stable over long stretches of time (no pun intended) you heat them to tension they loose tension you re heat they stretch that is how they are end of story. It is not so much that you cannot live with it that is what Acoustat did I have built with HS Mylar but stretching is one time and you never **** with the diaphragm again ever. No matter the spacing has nothing to do with it HS will over time stretch. Hope that helps.
thanks,
Dan "
Yes there are greater tension will provide stability and believe me you are going to have low frequency information come along and having to unplug your speakers and blow on them to un stick a diaphragm is a pain you don't want to bother with. Theory says and proves as far s I know that the tighter the skin the more efficient and the cleaner because it centres your diaphragm immediately. The mor distance you use the less efficient your system and they are not efficient to be gin with so distance buys you nothing good and you will still need tension to keep you diaphragm stable.
Here is the scoop on heat shrunk diaphragms thsy are the lazy mans way out. Heat shrink plastic is not stable over long stretches of time (no pun intended) you heat them to tension they loose tension you re heat they stretch that is how they are end of story. It is not so much that you cannot live with it that is what Acoustat did I have built with HS Mylar but stretching is one time and you never **** with the diaphragm again ever. No matter the spacing has nothing to do with it HS will over time stretch. Hope that helps.
Well, actually I have problems with mechanical tension too. The plastic is 2u thick and was stretched to only 0.5%. Initially it was more than enough to keep it stable. Now, after almost 2 years, I have had to drop HV voltage twice to keep it stable. So, mechanical tension is not granted either.
However there is some basis behind arguments that mechanical tension could have better stability. It depends on how the film is manufactured. Some films are stretched to one direction during manufacturing(typically perpendicular), which causes kind of hardening because molecular chains are aligned to a specific direction, or at least as I understand it. Heat shrinking could reverse this.
However, the question remains, if heat annealed(meaning stretching at first, and the using heat to lower tension) membranes do have similar stability problems.
Regards,
Lukas.
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well yes you have to use the proper material you need to use biaxially oriented and stable material in the first place. This has existed for many decades and is known if you look you will find it. Heat shrinking will in your case add back some tension but it will not solve the problem. The heat stabilizing process film manufacturers use is not the same as what happens when you heat shrink a film at least not on the same scale. twenty years ago I could have explained the process to you but have long since forgotten.
When I had my planar speaker company I went so far as to have the DuPont Mylar that I was using cross linked and found out from DuPont that that process had never been done before and they wanted to know I I wanted to take out a patent. I was busy and did not have the money to do so and simply offered it back to them in thanks for all the amazing help they provided during our prototype process. Best regards Moray James.
When I had my planar speaker company I went so far as to have the DuPont Mylar that I was using cross linked and found out from DuPont that that process had never been done before and they wanted to know I I wanted to take out a patent. I was busy and did not have the money to do so and simply offered it back to them in thanks for all the amazing help they provided during our prototype process. Best regards Moray James.
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