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Old 2nd June 2005, 10:05 PM   #1
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Default Making a highly efficent ESL for play from 1khz-25khz

Reading up on ESL's ... it seems like a simple design that I've already enjoyed the sound from (ML clarities) so I would like to explore simply what is possible with them...

seems from my research that curved diaphragms are ideal for midrange/tweet duty while flat are good for bass extension..

obviously based upon this I would want curved

basically I'm looking for something that can cover 1khz-25khz with ESL's noted low distortion...

This is where I'm currently at:

I understand the construction of a ESL, but I don't understand how to make it more efficent.

the best ESL's I've come across are 90 db efficent... quite lack luster...

the only thing I know is to gain efficency with this design is to make the insulators thinner.... maybe 1/32"

I have 5 15" lambdas cover the missing range...

I'm also assuming that using a thinner mylar would increase efficency... but I'm unsure about this...

I just need it to be very efficent to match the SQ beasts I've already picked out... which are really efficent...

thanks
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Old 2nd June 2005, 10:53 PM   #2
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I'm also assuming that increasing diaphragm area while keeping voltage the same will increase efficency?

BTW I think I left this out... but I would like to see 102-106 db sensitivity out of this... or 100-103 db efficency
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Old 3rd June 2005, 12:56 PM   #3
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You can increase sensitivity of the speaker by either narrowing the air gap between the stators, increasing the bias voltage, or increasing the drive voltage by using a higher turns ratio transformer.

Here are the problems:

a) Decreasing the gap reduces maximum excursion and limits max SPL- shouldn't be a problem from 1 kHz to 25 kHz unless you use a ridiculously small gap.

b) Small gaps and curved panels don't go together. It is nearly impossible to put tension on the film in one direction without causing it to bow inward in the other direction.

c) Small gaps and high bias voltage don't go together. You need a lot of tension on the diaphragm to keep it from sticking to the stators. See comment b about high diaphragm tension. You can also run into corona discharge and arcing. Air can only withstand so much voltage before it breaks down and becomes a conductor.

d) Increasing the turns ratio in the transformer tends to increase inductance which leads to frequency response problems moving down into the audio band. You can only go so far with this.

There is one more option- use a higher power amplifier. No, the speaker doesn't need higher power to operate, but a higher power amp will be capable of wider voltage swings at the output.

I suggest you try making a flat panel driver (it can be small) to get some idea of what works and what doesn't. The experience will quickly familiarize you with all the variables. Then if you want to make something bigger you can do it.

Curved ESLs such as the ML units don't disperse high frequencies much better than flat panels. ML curves the panels to make them mechanically rigid. A flat, steel panel is very "unrigid". Curving it makes it much more stable. Try it with a piece of cardboard.

As long as the panel width is much greater than the wavelength of sound being produced, the driver will beam. It is simple "newtonian" physics - not even the quantum type.

Reasonable sized ESLs are entirely capable of reproducing sound down to 200 Hz or so. Why put a crossover at 1 kHz and split almost every human voice and musical instrument across multiple drivers? I don't think 15" drivers will go to 1 kHz...

Unfortunately ESLs are not the solution for high volume applications. They are about low distortion and wide response. If you want loud, make some horns.

I_F
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Old 3rd June 2005, 01:54 PM   #4
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Quote:
Originally posted by I_Forgot
You can increase sensitivity of the speaker by either narrowing the air gap between the stators, increasing the bias voltage, or increasing the drive voltage by using a higher turns ratio transformer.

Here are the problems:

a) Decreasing the gap reduces maximum excursion and limits max SPL- shouldn't be a problem from 1 kHz to 25 kHz unless you use a ridiculously small gap.

b) Small gaps and curved panels don't go together. It is nearly impossible to put tension on the film in one direction without causing it to bow inward in the other direction.

c) Small gaps and high bias voltage don't go together. You need a lot of tension on the diaphragm to keep it from sticking to the stators. See comment b about high diaphragm tension. You can also run into corona discharge and arcing. Air can only withstand so much voltage before it breaks down and becomes a conductor.

d) Increasing the turns ratio in the transformer tends to increase inductance which leads to frequency response problems moving down into the audio band. You can only go so far with this.

There is one more option- use a higher power amplifier. No, the speaker doesn't need higher power to operate, but a higher power amp will be capable of wider voltage swings at the output.

I suggest you try making a flat panel driver (it can be small) to get some idea of what works and what doesn't. The experience will quickly familiarize you with all the variables. Then if you want to make something bigger you can do it.

Curved ESLs such as the ML units don't disperse high frequencies much better than flat panels. ML curves the panels to make them mechanically rigid. A flat, steel panel is very "unrigid". Curving it makes it much more stable. Try it with a piece of cardboard.

As long as the panel width is much greater than the wavelength of sound being produced, the driver will beam. It is simple "newtonian" physics - not even the quantum type.

Reasonable sized ESLs are entirely capable of reproducing sound down to 200 Hz or so. Why put a crossover at 1 kHz and split almost every human voice and musical instrument across multiple drivers? I don't think 15" drivers will go to 1 kHz...

Unfortunately ESLs are not the solution for high volume applications. They are about low distortion and wide response. If you want loud, make some horns.

I_F

I know they're not the solution for high volume apps... but can they be used in them?

it's either that or a very very large and power hungry array of speakers and linesource ribbons...

the 15" drivers I'm using are flat to 1 khz they are in fact renowned for doing so...

what do you mean by the panel will beam??? is taht a good thing???
so wider panels are better?
wider than a wavelength at 1khz would be 1 foot... so would a 18 inch wide panel do well "beaming" 1khz-20khz?

what kind of power handling (generally) would a speaker like this have?
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Old 3rd June 2005, 02:13 PM   #5
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what about keeping the gap around 1/8" to keep max SPL relatively high, and go with say a 7000-10,000 bias voltage?

for the purposes I need splitting the sound between 2 drivers is a necessary evil, especially since you said that about inductance at lower frequencies...
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Old 3rd June 2005, 10:23 PM   #6
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Default solid stator plates for high efficiency

How about building some ESL panels sideways with 100% solid flat insulated stator plates? They will require that one edge on either side of the diaphragm be left open so the air can escape when compressed by the diaphragm (front side/back side). You could run multiple sets side by side to boost output. You could even use this idea to make an electrostatic compression driver. Any thoughts??? Regards Moray James.
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Old 3rd June 2005, 10:27 PM   #7
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Default Re: solid stator plates for high efficiency

Quote:
Originally posted by moray james
How about building some ESL panels sideways with 100% solid flat insulated stator plates? They will require that one edge on either side of the diaphragm be left open so the air can escape when compressed by the diaphragm (front side/back side). You could run multiple sets side by side to boost output. You could even use this idea to make an electrostatic compression driver. Any thoughts??? Regards Moray James.
it's an idea...

I wouldn't want to horn load it though as the SQ would drastically suffer....

running multiple sets is an idea... but that would require some sort of waveguide at least... though avoiding a horn is still ideal...

I'm scared about what this would sound like


it could either sound fine and be ungodly loud... or it could sound absolutely terrible
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Old 3rd June 2005, 10:51 PM   #8
Ron E is offline Ron E  United States
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Quote:
Originally posted by Audiophilenoob
it's either that or a very very large and power hungry array of speakers and linesource ribbons...

the 15" drivers I'm using are flat to 1 khz they are in fact renowned for doing so...
IMO, You need some horns and a compression driver. Arrays don't sound any better than good horns.
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Old 3rd June 2005, 10:55 PM   #9
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Default make a stack of pancakes!

Don't see why you would need to have a lens. Just parallel stack as many units as you want to get a composite panel of about one to two inches wide. If you made a single panel 4'X36" then you would have a lot of panel area there. Construction would be a snap. My concern wolud be with turbulance as the air exits and enters the panel through the small thin long gap along the side of the diaphragm. Regards Moray James.
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Old 3rd June 2005, 11:00 PM   #10
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Default Re: make a stack of pancakes!

Quote:
Originally posted by moray james
Don't see why you would need to have a lens. Just parallel stack as many units as you want to get a composite panel of about one to two inches wide. If you made a single panel 4'X36" then you would have a lot of panel area there. Construction would be a snap. My concern wolud be with turbulance as the air exits and enters the panel through the small thin long gap along the side of the diaphragm. Regards Moray James.

yes... a simple half round wood piece could help with some turbulence...

it seems like that would be really sketchy to get right...hmmmm
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