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Old 9th October 2009, 02:41 PM   #21
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Originally Posted by Atom666 View Post
I was in an art supply store with my daughter a few months ago and came across some nylon mesh used for silk screening.It looked almost identical to the the damping material used in the ESL63.
Andrew
Thanks for the info, I'll have to swing by an art supply shop and check it out.
Do you know, is the damping mesh used in the ESL63 is stretchy like grill cloth?
Or is it pretty dimensionally stable.
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Old 9th October 2009, 03:31 PM   #22
SY is offline SY  United States
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Originally Posted by bolserst View Post
Hi SY,

The few Acoustat panels I have seen used some fairly thick felt damping pads in the middle 1/3 area of the panel, and nothing on the outter area. Did you remove these pads before applying your thin felt? You mention only applying the damping to 50% of the active area. Can you describe where/why you applied the damping? Any Pics?

bolserst
The original pads had been removed long before I ever got the panels. I put thin (~1mm) felt in approximately the same location and area as the original thick felt. I needed less damping because of my material choice for the diaphragms, a softer, less "crinkly" polymer than Mylar (H-series Clysar). It's now sadly been discontinued and I'm looking for a good substitute. One possibility, if I can get any in a thin enough gauge, is an ethylene-norbornene copolymer.
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Old 9th October 2009, 05:36 PM   #23
Atom666 is offline Atom666  Canada
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Quote:
Originally Posted by bolserst View Post
Thanks for the info, I'll have to swing by an art supply shop and check it out.
Do you know, is the damping mesh used in the ESL63 is stretchy like grill cloth?
Or is it pretty dimensionally stable.

I checked and it doesn't stretch
Andrew
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Old 19th October 2009, 04:37 PM   #24
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Quote:
Originally Posted by Atom666 View Post
I was in an art supply store with my daughter a few months ago and came across some nylon mesh used for silk screening.It looked almost identical to the the damping material used in the ESL63.
Andrew
I finally got a chance to check out the silk screen mesh. It is available in hole counts from about 60 holes per inch, to over 300 holes per inch. The thread size is reduced with increasing hole count, so the percent open area remains in the 60% - 70% range. With a mesh that is this open I wondered if it would supply much low frequency damping. But, on the other hand, it gives me hope that there will be minimal impact on the higher frequencies.

Originally when I saw that the percent open area was the same for all the meshes, I thought that the resistive damping would be the same. But, I did a few google searches on acoustic screen dampers and found an online book with a chapter on the topic...."It is important to note that for a constant open area the resistance increases and the reactance drecreases with n(holes per inch). The basic reason for this behavior is that the channel resistance is inversely proportional to the square of the width of the air channel between adjacent wires, and the reactance is proportional to the thickness of the screen."

With this is mind, I ordered a sample of three different hole counts with the idea of getting some damping trend data. I will post what I find out.
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Old 23rd October 2009, 05:01 PM   #25
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Default Silk Screen Mesh: Damping of ESL diaphragm resonance

I had ordered some 110, 160, and 200 count silk screen mesh, but the 200 count was on back order. So I have thrown some 1/16” felt in to the mix will I was in the measurement mode.

The 110 count mesh uses 78 µm monofilament polysester fibers (66% open area)
The 160 count mesh uses 64 µm monofilament polysester fibers (60% open area)

The ESL panel used for the test was 60” tall x 8” wide, with 2 rows of assymetrically placed silicon dampers. The undamped curves(Green) show a double bumped resonance peak caused by placement of the silicon dampers as mentioned by Capaciti earlier in this thread. Microphone was placed 1” in front of the midpoint of the diaphragm.

1) Damping results for 1/16” felt on the rear stator
2) Damping results for 110 count mesh, on front stator, rear stator, and both stators
3) Damping results for 160 count mesh, on front stator, rear stator, and both stators
4) Comparison of 1/16” felt .vs. 160 cound mesh.

As you can see, down to 80Hz, the 160 count mesh damps as well as the felt.
The 200 count mesh should be even better.
Attached Images
File Type: gif EDNF_FLT.GIF (10.0 KB, 578 views)
File Type: gif EDNF_S1.GIF (12.1 KB, 550 views)
File Type: gif EDNF_S2.GIF (12.2 KB, 546 views)
File Type: gif EDNF_FS2.GIF (11.2 KB, 548 views)

Last edited by bolserst; 23rd October 2009 at 05:15 PM.
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Old 23rd October 2009, 05:13 PM   #26
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Default Silk Screen Mesh: Effects on High frequency response of ESL

Microphone was placed 1 meter in front of the midpoint of the diaphragm

1) Effect of 1/16” felt place on the front stator, or the rear stator
2) Effect of 110 count mesh, on the front stator, or rear stator
3) Effect of 160 count mesh, on the front stator, or rear stator

Felt on the front stator progressively filters out more with increasing frequency.
Felt on the rear stator is interesting in that it filters out the midrange but actually boosts the highs.(reflections from the felt? Or cavity resonance effect?)

Both of the silk screen meshes had essentially no effect on the response.

Thanks again to Atom666 for suggesting the silk screen. The results are much better than any other woven cloth I had tried, providing significant LF damping without affecting the HF response.


The panel sounded like it measured. Adding LF damping with the 160 count silk screen(or felt) tightened up the LF response. Drums had noticeably more impact with the damping in place. When the felt was added to the rear stator you can notice slight loss of detail and "sparkle" in the midrange. I could not tell any difference in the midrange when the silk screen mesh was added.
Attached Images
File Type: gif EDFF_FLT.GIF (10.3 KB, 511 views)
File Type: gif EDFF_S1.GIF (10.0 KB, 158 views)
File Type: gif EDFF_S2.GIF (10.0 KB, 149 views)

Last edited by bolserst; 23rd October 2009 at 05:34 PM.
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Old 23rd October 2009, 10:12 PM   #27
Atom666 is offline Atom666  Canada
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Hi
Glad I could contribute something of worth.Do you think having the mesh on the inside of the speaker in close proximity to the diaphragm ,as in the ESL63 ,would give the similar results?
Andrew
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Old 23rd October 2009, 10:26 PM   #28
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Quote:
Originally Posted by Atom666 View Post
Hi
Glad I could contribute something of worth.Do you think having the mesh on the inside of the speaker in close proximity to the diaphragm ,as in the ESL63 ,would give the similar results?
Andrew
All these measurements were done with the mesh or felt mounted on the outside of the stator.

Previously, I had thought that mounting tightly woven cloth on the inside of the stator closer to the diaphragm would provide better damping than when it was mounted outside the stator. However, I tried this 2 weeks ago, and the LF damping was identical between the two mounting techniques. I did not compare high frequency effects.

It is much easier to mount and swap samples on the outside of the stators, so I have continued using this placement. In the end, I figured if I could use fine mesh on the outside of both front and rear stators this would go a long way in helping to keep dust from collecting on the diaphragm and stators.
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Old 27th October 2009, 06:44 PM   #29
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Originally Posted by arend-jan View Post
Yes there is, it's a some sort of natural fibre cloth on the inside of the back grill.

Some people like to take it out because of poor bass performance, but that is because the speakers are old and the bass gets weaker (lowered sensitivity) and the resonance frequency shifts up in frequency (sometimes over 100Hz!). The cure is to repair the panels and leave the damping mats in, that way it goes all the way down to 40 Hz, and the bass can sound surprisingly well.

This is one speaker that does not sound better without damping material. In fact it will lose it's wonderful natural midrange if you do.
NO!

The bass panels do/did NOT have any damping material at all. Period.
It was the treble unit that had the felt dampening in the back of the panel.

Click the image to open in full size.

Last edited by JarreYuri; 27th October 2009 at 06:47 PM.
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Old 27th October 2009, 07:38 PM   #30
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Originally Posted by JarreYuri View Post
NO!

The bass panels do/did NOT have any damping material at all. Period.
It was the treble unit that had the felt dampening in the back of the panel.

Click the image to open in full size.
You are ill informed, Jarre.

The picture you show has the back grill removed. This metal grill originally has a sheet of natural fibre cloth on the inside (attached with a sticky tar like substance to the grill) which damps the main resonance peak of the bass panels. This is a simple fact, no point in arguing about it.

How do I know this? Well I've actually seen 'a couple' of Quad ESLs
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