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dochungwell 8th November 2011 12:45 AM

Sonic differences 6uM vs 12um polyester film?
Hello All,

I have now built a considerable amount of ESL's using 6um thickness polyester film and now ready to experiment, actually I accidentally ordered 12uM polyester film...So understanding that what I have been using was essentially the best for sound quality and ease of use, I would care to hear individuals opinion who has experience of using both thicknesses.

I have read there may/will be a slight loss roll off of the high frequencies, but is it that noticeable?

I am not certain if the minimum elongation stretch is the same as the 6um at 1.5% elongation, or is it increased or decreased, will it be more difficult or easier to stretch with my pneumatic stretcher?

If it mostly negative I will likely return it and not waste my time..

Curious to hear some feedback!

Thanks in advance,


MJ Dijkstra 8th November 2011 05:57 AM

Put the different films between your fingers and you will notice the 12 micron behaves like an empty, crispy, package wrap while 6 micron is more flexible and smooth.

In some designs the excess of high frequencies can somewhat be compensated by the roll-off of 12 micron and that's the probable reason it sounded reasonable well in my case (long time ago). Nowdays I prefer the 4 micron which is strong enough for my applications (so why use thicker...)
As you can apply much more mechanical tension with 12 micron than you actually need, you should take care not to end up with a poor bass due to highly and/or irregular strectched film

Legis 8th November 2011 06:40 AM

When testing, rememeber to equalize the responses to match. 12Ám membrane needs to be more voltage driven than 6Ám in order to get right shaped response and balanced sound. If nothing is done before of after the step-up trafo, the top end naturally rolls off sooner.

IMO, with big ESL's there should be HF roll-off at some extent, in order that the design sounds balanced. Big ESL shoots the wave at the listener pretty much like headphones, which are also tuned to have HF roll-off (ref.'s response graphs), yet they usually sound balanced (those AKGs are actually very bright, regardless the measured response).

I have listened to a pair of 3.6 maggies, and while not being ESLs they share the same high vertical directivity of a big esl. Maggies had the top octave rolled off, yet they sounded the most bright speakers I have ever heard even though the room was acoustically treated. Here's actually the measured response I had still in store, without and with subwoofers at two different levels:

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