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Old 3rd May 2013, 02:46 PM   #41
Bazukaz is offline Bazukaz  Lithuania
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Quote:
Originally Posted by AAaF View Post
I would have believed that a cloth would damp higher frequencies?

If so, one alternative would be to just add on backside. If it influence on higher freq, it will also influence on spread pattern, but for all we know it might improve interaction between speaker and room.

I can implement a notch filter, but in general, I believe in "making right from the start" to get the best sound quality.

Brilliant idea regarding the paper clips. We have exactly the same type at work

Really appreciate your input guys!
In general if a cloth is thin enough it will have very little effect on treble response. However the fundamental resonance is still affected by a few db.
Too thick cloth degrades sound for some reason. Even when it's placed on the back side there is a rising of treble - likely part of the sound is reflected from the back through diaphragm.
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Old 3rd May 2013, 03:24 PM   #42
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Look at Quad esl63 how they did it .......

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Originally Posted by AAaF View Post
Just to verify; you basicly need to add some kind of air flow resistance to dampen resonance? Sounds logical when I think of it
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Old 14th May 2013, 09:22 PM   #43
AAaF is offline AAaF  Norway
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The resonance peak was all sorted, thanks!

I did not get the smoothing of the other dips as bolserst though:
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File Type: jpg Frekvensrespons uten filt kontra med filt unsmoothed.jpg (605.8 KB, 161 views)
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Old 14th May 2013, 09:25 PM   #44
AAaF is offline AAaF  Norway
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Here is the response after I increased low end gain by 3dB. Changed feedback resistor from 12k to 18k.

I'm happy for now (1/12 smoothing)
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File Type: jpg Frekvensrespons etter filterjustering.jpg (584.5 KB, 155 views)
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Old 16th May 2013, 07:24 PM   #45
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Quote:
Originally Posted by AAaF View Post
The resonance peak was all sorted, thanks!
I did not get the smoothing of the other dips as bolserst though:
Nicely done
Can you share details on the mesh you used and what mounting technique you decided on?

The smoothing of high order diaphragm modes is much easier to see when measuring near-field, with the microphone within 2cm of the diaphragm.
Mechanical Sectioning .vs. Silicon dots for resonance control
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Old 23rd May 2013, 11:15 AM   #46
AAaF is offline AAaF  Norway
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I used some filt. Bougt one 80% wool, 1,0 - 1,5mm thick, and one thinner 20% wool, maybe a little less than 1mm. But a quick test showed that it was actually harder to blow through the thinner filt. Thinner filt gave therefore more damping, in my case a bit too much. Though not very well tested.

I measured at a estimated 70-80cm, so I guess thats the reason why we got different results.
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File Type: jpg filter2.JPG (85.3 KB, 122 views)
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Old 28th May 2013, 09:42 PM   #47
AAaF is offline AAaF  Norway
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Here is a comparison between nearfield(approx an inch) vs a meter, both unsmoothed. At 1m I use relatively low SPL to reduce room effect.

Its quite obvious that you need to design system for a particular distance. Is it because of the array effect that higs get more dominant when you go further away?
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Old 28th May 2013, 10:31 PM   #48
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Quote:
Originally Posted by AAaF View Post
Here is a comparison between nearfield(approx an inch) vs a meter, both unsmoothed. At 1m I use relatively low SPL to reduce room effect.

Its quite obvious that you need to design system for a particular distance. Is it because of the array effect that higs get more dominant when you go further away?
Your unsmoothed near field measurement shows very effective damping of the diaphragm resonance. Congrats!

Yes, a line source will have a response trend that varies with listening distance unless it extends fully floor to ceiling in length. The reason for this is that for any given listening distance there is a frequency at which the sounds transitions from being highly directional in the vertical direction and starts to spread out. This may also be referred to as near/far field transition. The result is a -3dB/oct slope imparted to the response below the transition frequency. This is much more of a problem for full range ESLs than for hybrids, but even hybrids suffer from it if the panel is only 1m tall and listening distance is > 2m.

The formula for determining near/far field transition relative to a panel dimension is:
F = c * r / d^2

where:
c = speed of sound
r = listening distance
d = panel dimension

In general, for segmented ESLs you only need to be concerned with the transition frequency for the height.
But for wide unsegmented panels, you may see efffects of the width transistion frequency at closer distances.

If the ESL is extended fully floor to ceiling, the effective length of the line is theoretically infinite so the transition from near field to far field does not take place. Another way to visualize this is that the wave launched from the ESL would be contained between the floor and ceiling and have no way to expand or spread out in the vertical dimension.

More information here, including spreadsheet to plot transition points and response:
Segmented Wire Stator ESL simulator (esl_seg_ui)
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Old 4th June 2013, 08:44 AM   #49
AAaF is offline AAaF  Norway
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Quote:
Originally Posted by bolserst View Post
Your unsmoothed near field measurement shows very effective damping of the diaphragm resonance. Congrats!
It's rather me who should send a big "thank you", for helping me resolve it.
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