Is it possible to construct an ESL which does not slap with low frequencies? - diyAudio
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Old 27th December 2011, 09:20 PM   #1
diyAudio Member
Join Date: Sep 2010
Default Is it possible to construct an ESL which does not slap with low frequencies?

Happy Holidays All,

Well I have successfully constructed a great many ESL panels, and have even was able to stretch the 6uM mylar to over 2.5% elongation consecutively without any issues. I am utilizing an electronic crossover and the music sounds near perfect....and that's where the questions begin. It seems that if I run these panels below 140 bass slapping is present.

The question... Is it possible to develop an ESL which will not slap?

I am considering making a test panel using .125 thickness 3m double sided tape (instead of the .060, and quadrupling the voltage as the inverse square law would suggest, would someone care to surmise the quality of sound which can be realized with this hypothetically?

Will this distance prevent slapping from occurring, could increased Bass be produced below 140, would the High frequencies be reduced?

Has anyone built perforated panels using D/S spacing of .125?

Thanks In advance,
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Old 28th December 2011, 02:49 AM   #2
beun is offline beun  United States
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I use a .125" (3mm) spacing on mine and have no issue with slapping. I can run them full range, at least down to 60Hz, and the first thing to crap out is actually the transformer saturating. I do segment the membrane with a maximum segment width of not more than 5".
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Old 28th December 2011, 03:46 AM   #3
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Location: New Zealand
I have never noticed this problem with Quad ESL57's, either. I recommend always run 57's with a suitable amplifier, in my case Quad 303 Quad ESL & ESL63 Information

Cheers / Chris
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Old 28th December 2011, 04:05 AM   #4
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Doc; what is you actual diaphragm width (unsupported)??? You have the tension but you still don't have the stability so there is only one answer and that is to add additional stator spacers. Best regards Moray James.
moray james
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Old 28th December 2011, 07:25 AM   #5
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You also should consider (if you haven't yet) some damping of the fundamental resonance. Fine mesh glued on the stator, speaker grill cloth, silicone dots on the mylar, these are things which has been used succesfully used.
Without damping there will be a high Q resonance with a large associated excursion and uncontrolled sound. As an untamed resonancepeak can be around 15 dB, it sure will ' eat up' excursion limits.
drs M.J. Dijkstra
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Old 28th December 2011, 08:05 AM   #6
Calvin is offline Calvin  Germany
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well, it all depends on which quality You are content with, doesnīt it?
Constructed as open baffle system, the tendency to flap always remains. Putting a panel into a cabinet on the other hand creates different but similarly serious issues.
A ESL offers no first class bass compared to the qualities a dynamic driver bass may offer. At least, I havenīt heard of just one ESL with truely outstanding bass qualities.
If the panel is constructed as Fullranger, You have to accept compromises in the midhighs. The required higher voltage and power demands donīt come for free. Damping felt mats and such stuff, needed to mechanically control high-Q resonance, donīt perform linear, neither in the amplitude domain nor in the frequency domain and certainly remain audible in the mid-highs.

If the panel is constructed as a pure bass panel, You can optimize certain parameters, but it still is clearly inferior to a dynamic bass system. The mechanical losses inherent to a dynamic driver, that control itīs performance to a large extent, are much smaller. They would have to be supplied for by the design itself, by some form of mechanical means or by some form of external control circuitry.
Still though serious issues of the electrostatic principle will be left unsolved.
For example the lower force-per-unit-area-relation, or the low mass membrane, which discludes typical boxes as cabinets. Not to mention the vast levels of driving signal voltage and power demand.
A bass ESL performs inferior compared to a dynamic bass on nearly each and every aspect such as:
- size
- dynamic range
- power demand
- drive requirements an on the amplifier
- demand of room floor space
- distortion
- low and lowest frequency performance
- kickbass performance
- lower mids performance
- probabely even costing more than a decent dynamic bass system

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Old 28th December 2011, 11:55 AM   #7
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Thank you all for your comments and suggestions.

Moray James- I segment my 15x48" panels along the long axis with 3 spacers at 3 3/4".

M.J. Dijkstra-I forgot to mention I do run a separate sub and do not rely on the ESL for bass, essentially I do dampen low frequencies on my PC EQ.

It certainly sounds like it is "give and take with every aspect of an open baffle design" , by designing for bass you sacrifice the highs, and if you construct a mid/high panel your panels may be subject to slapping.

Beun- do you run your ESL at full range, do you use a parametric EQ or a electronic crossover? How large are your ESL panels?

Calvin, thanks for you explanation as always.

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Old 28th December 2011, 03:21 PM   #8
fperra is offline fperra  United States
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If you tensioned the mylar to 2.5% elongation I suspect what you thought was mylar is something else or, if it is mylar, it went beyond it's yield strength, and you have less tension than you think. I just recently made some cells and could never get much more than 1.8% elongation before it gave out.
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Old 29th December 2011, 12:14 AM   #9
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I don't think 2.5% elongation exceeds the tensile strength of 6uM hosphenstaf C, however I do see your point if that were the case.

I was stretching at 1.5% with good results however, the increase of tension has an improved response and dynamics over that of a less stretched panel.

To achieve this tension you need a well made jig, and secure the mylar with double sided tape.
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Old 29th December 2011, 02:03 AM   #10
beun is offline beun  United States
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I have made several speakes in the following sizes:

1) The big one, 3'3" x 6'6"
2) The WAF one 2' x 5'
3) The tall one 30" x 82"

All of them are more or less full range and go at least down to 80Hz. All are curved in the horizontal plane (like ML) but the segmentation runs vertical and as mentioned is never wider than 4 or 5" or so.

I could run them full range and have done so in the past but currently I run them with a highpass at around 60-80Hz depending on the size of the speaker and cross them over to a sub.

When your tension is sufficient it is impossible for the membrane to slap when your width is not more then 4" and the pacing is 1/8". At 1/16th maybe, but transformer saturation sounds more logical and I can tell you it sounds really nasty
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