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Old 20th January 2008, 06:36 PM   #1
Fanuc is offline Fanuc  United Kingdom
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Default Getting high SPL from electrostats.

Hello,

I am fairly novice in my understanding of ELS design. But it seems like the surface area determines how low a frequency the panel can do and the larger the excursion also. ie. high voltages in anti phase on the stators.

Most ELS's seem to have low SPL compared with other speaker types. Anyway, I was wondering what is requirement to produce high SPL electrostats?

Kevin
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Old 20th January 2008, 06:39 PM   #2
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It's about law of the nature..... I like electrostatic speakers. I have Martin Logan SL3 myself and am quite pleased with them.
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Old 20th January 2008, 07:02 PM   #3
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Simple to get loud ESLs.

First, you feed the bass elsewhere and then you feed the treble elsewhere. Lots of compelling reasons to do so in addition to getting more Bels. This helps both the amp/speaker output in an obvious way but also does statistically remarkably beneficial things to the electric power from the amps when you have two amps instead of one.

Below maybe 150 Hz, you can send the bass to a single speaker almost anywhere in the room (not so close to your ear as to hear the speaker rustling).
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Old 21st January 2008, 03:21 AM   #4
j beede is offline j beede  United States
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Default Re: Getting high SPL from electrostats.

Quote:
Originally posted by Fanuc
Hello,

I am fairly novice in my understanding of ELS design. But it seems like the surface area determines how low a frequency the panel can do and the larger the excursion also. ie. high voltages in anti phase on the stators.

Most ELS's seem to have low SPL compared with other speaker types. Anyway, I was wondering what is requirement to produce high SPL electrostats?

Kevin

I think the key is the third word in your second sentence--"seems". Full range ESLs produce quite large SPLs but your perception may be that they do not, especially when compared to point source speakers. I have measured 104dB at 3m with my full range ESLs. Of course you can walk right up to them and place your ear near the panel when they are doing this without cringing in pain. Don't try that with a point source speaker when it is producing 104dB at 3m! Have you ever heard a large, full range ESL? They are loud.
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Old 21st January 2008, 01:22 PM   #5
Calvin is online now Calvin  Germany
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Hi,

the īsecretī of building high-SPL-ESLs lies in sufficient membrane area and smallest stator-stator-distances and high mechanical diaphragm tension tension. A ESL canīt provide for as much power per unit diaphragm area as a dynamic speaker, so it has to have a larger area.
Since efficiency of the panel is a function of distance (inversely quadratical with rising distances), You should see, that You get higher SPLs with smaller d/s values. Itīs a typical beginnerīs mistake to design the d/s too large. The best compromises lie between 1.0 and 1.5mm d/s. Itīs another very common failure to use low diaphragm tension. Besides placing the resonance at a too low value, it kills output by reducing the d/s considerably.
So what Iīm talking here of is a panel for a hybrid ESL. When You measure the distortion of a panel Youīll soon realize that distortion values quickly rise as soon as the membrane needs to execute some excursion. This is the case for frequencies below 200Hz. This is the region where dynamic divers can shine...so leave this freq-range to them. A well executed panel can deliver astonishingly high levels of SPL above this freq-range.
I had my panels measured in an anechoic room last week at Aachen University and got really satisfying results ;-)
(Panel: 125x25cm, 1.1mm d/s, 1.4nF, Fs:120Hz, Tranny: 1:68, pol-voltage: 1.5kV)
Measurements: 93dB@2.83V@4m with distortion values below 0.1% above 200Hz, below 0.15% at 10W@8Ohms and below 0.3% at 50W@8Ohms. The last power value translating to ~110dB@4m and beginning of clipping (since the measurement was fullrange the maximum value of SPL above 200Hz is even higher than that!)
The SPL in a living room is considerably higher that in a anechoic chamber and for correlating signals You can add 6 more dBs of SPL.
These values are high enough to satisfy most demanding needs.
Itīll be no easy task to find a similarly capable bass :-)
The described panel can play in rooms from 20mē size and up.

jauu
Calvin
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Old 21st January 2008, 11:03 PM   #6
Fanuc is offline Fanuc  United Kingdom
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Quote:
Originally posted by bentoronto
Simple to get loud ESLs.

First, you feed the bass elsewhere and then you feed the treble elsewhere. Lots of compelling reasons to do so in addition to getting more Bels. This helps both the amp/speaker output in an obvious way but also does statistically remarkably beneficial things to the electric power from the amps when you have two amps instead of one.

Below maybe 150 Hz, you can send the bass to a single speaker almost anywhere in the room (not so close to your ear as to hear the speaker rustling).
Hello,

Yeah this is the arrangement I have used for years. Started with Quad esl57 & 63's and I bought a top of the range B&W active subwoofer. The sub was too damn heavy though!, plus I was moving so I sold it. First time I had heard high SPL uncoloured sub bass before. I thought the drive unit was blown but could shake the windows. Even phoned B&W about it! (think I was naively expecting a bass speaker foolishly not a sub bass speaker, or was listening to to many cheapy car boom boxes subs!)

Anyway, The reason I asked was when I went to a hi fi show in bristol, england I got to listen to Wilson Audio Benesch speakers. (excellent all round speakers though they probably cost the same as a car!). Can't remember the exact model but what struck me was the punchiness to the midrange and high end. The bass is a part of that obviously but there's something more. Have also heard some horn speakers also and they too have a punchiness to cymbals, percussion.

Having said that I still think the ELS's are excellent generally and can do something in midrange and highs in terms of timbre that no other speaker can do. ie moving coil. including the best MC headphones.

Thanks for the replys.
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Old 21st January 2008, 11:14 PM   #7
Fanuc is offline Fanuc  United Kingdom
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Quote:
Originally posted by Calvin
Hi,

the īsecretī of building high-SPL-ESLs lies in sufficient membrane area and smallest stator-stator-distances and high mechanical diaphragm tension tension. A ESL canīt provide for as much power per unit diaphragm area as a dynamic speaker, so it has to have a larger area.
Since efficiency of the panel is a function of distance (inversely quadratical with rising distances), You should see, that You get higher SPLs with smaller d/s values. Itīs a typical beginnerīs mistake to design the d/s too large. The best compromises lie between 1.0 and 1.5mm d/s. Itīs another very common failure to use low diaphragm tension. Besides placing the resonance at a too low value, it kills output by reducing the d/s considerably.
So what Iīm talking here of is a panel for a hybrid ESL. When You measure the distortion of a panel Youīll soon realize that distortion values quickly rise as soon as the membrane needs to execute some excursion. This is the case for frequencies below 200Hz. This is the region where dynamic divers can shine...so leave this freq-range to them. A well executed panel can deliver astonishingly high levels of SPL above this freq-range.
I had my panels measured in an anechoic room last week at Aachen University and got really satisfying results ;-)
(Panel: 125x25cm, 1.1mm d/s, 1.4nF, Fs:120Hz, Tranny: 1:68, pol-voltage: 1.5kV)
Measurements: 93dB@2.83V@4m with distortion values below 0.1% above 200Hz, below 0.15% at 10W@8Ohms and below 0.3% at 50W@8Ohms. The last power value translating to ~110dB@4m and beginning of clipping (since the measurement was fullrange the maximum value of SPL above 200Hz is even higher than that!)
The SPL in a living room is considerably higher that in a anechoic chamber and for correlating signals You can add 6 more dBs of SPL.
These values are high enough to satisfy most demanding needs.
Itīll be no easy task to find a similarly capable bass :-)
The described panel can play in rooms from 20mē size and up.

jauu
Calvin
Excellent reply and excellent work too!. Have always had an urge to look at making an els panel (totally agree on the hybrid approach) but there is no point if the panels turns out to be average. ie. See my post above for my reasoning on this.

Have you found it very hard work to make your panel ? and do you have prior experience making them ?

Kevin
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Old 24th January 2008, 04:48 PM   #8
Calvin is online now Calvin  Germany
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Hi,

actually it was relatively easy to build. But that's a toe loop for a professional skater too :-)
Since I'm interested in ESL-design for roundabout 25years by now and having build different types of panels, I think I roughly know what to do ;-)
The quoted numbers of SPL are very probabely not the end...Iīve got some ideas to raise the SPL even further, to reduce distortion even more and to raise reliability and longevity...but Iīve to test that before I like to go official with it :-)

jauu
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Old 24th January 2008, 06:31 PM   #9
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Another way: high voltage bias.

Excuse me if I am repeating unreliable information, but the SPL goes up with some power of the bias voltage. But the bias voltage is limited by the air gap. At some point, and here I reveal my Dayton-Wright "bias," you need the welding gas, SF6 (dunno what, but the "F" is probably something bad for the ozone layer) to prevent arcing. But that is all do-able in your shop, like Dayton-Wright did it, just wrap your panels in dry-cleaners bags.

OK, OK, I admit it... may not be the way to get crystal clear sound. Not sure.

In as much as my study of the subject is very aged, glad to become better informed and freed from error by other posters.
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Old 28th January 2008, 09:46 PM   #10
Coffee is offline Coffee  Czech Republic
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Calvin,
And what about the amplifier driving your panels ? a trannie with a ratio of 1/68 and panel capacitance of 1,4nF give a final capacitance seen by the amplifier about 68*68*1,4e-9 and that is about 6,5uF, that give about 1,22ohm of impedance at 20kHz, that is a significant capacitance load on a normal amplifier, I can design such amplifier, but for it to be reliable, it would be an "overkill monster".

How you deal with it ? Or you simply rely on the fact, that these fequencies have very rarely a significant energy to blow an amp ?
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