DIY Electrostatic - maximum safe db ?

[rick57]

http://sound.westhost.com/project105.htm

This site hasn’t changed for 1- 2 years. Anyone built this ~ did it get off the ground?


The best component DIY Electrostatic souce seems to be ER Audio at www.eraudio.com.au/Components/components.html


I’m hoping for 105-110 db from ESLs from about 500 Hz up - who knows the maximum db you can safely get from them?

Cheers

[Brian Beck]

As always, it depends! There is no fundamental practical limit to the maximum SPL of ESLs any more so than with moving coil speakers. It depends on ESL size, panel configuration, stator-to-stator spacing, etc. Limiting use to above 500Hz will lower excursion of the diaphragm and reduce the risk of the diaphragm hitting a stator, just as limiting bass in a moving coil driver reduces risk of reaching Xmax displacement. It would be quite possible to make a deafening (literally) large ESL. The big Sound Labs ESLs, with enough driving juice, can pin your ears back at 10 paces. If you were asking specifically about the maximum SPL of ER Audio kit speakers, someone else would have to say.

[rick57]

Thanks Brian
I’ve sent an email to Rob at ER Audio

Cheers

[Calvin]

Hi,

above app. 200Hz the needed excursion for high volume levels is quite small and there is no reason, why an ESL shouldn´t reach similar SPLs as any dynamic driver. In fact an ESL has two distinct advantages over the dynamic driver. First is a greater diaphragm area -not necessarily, but in most cases- Since SPL is a function of area and excursion an ESL can reach higher SPLs (btw. shows less distortion)
Second is a different behaviour over distance. When built as a long and narrow strip (compared to wavelength) the ESL has a dipolar cylindrical distribution pattern. For a panel of ML´s Sequel size and bigger this means that SPL will rise up to a distance of app. 3-4m and will then start to fall...but with 3dB/doubling of distance...This is theoretically 3db less than with global distribution. So while a dynamic driver will be louder ar close proximity, the strip like ESL can be louder on distance. That makes a comparison a bit difficult.
I measure my panels on different positions. 0.1m (nearfield), 1.0m (standard for dynamic speakers), 2.0m (my standard for ESLs which gives similar results in SPL as 1.0m dynamic measurement) and at the listening position itself in the room.
Crossed over at app 300Hz, I can reach ear chattering SPLs with exceptional clearness. I´m not at all afraid to play Cincinnatti Pops at highest endurable levels. ...a musical material well known to have fried some boxes

jauu
Calvin

[rick57]

Hi Calvin,

Very good points.

My listening distance will be about 3 m. I’m considering 2 * 930 x 300 a side.

How big are your panels, and what is there design/ material source?

> I measure my panels . . 2 m (my standard for ESLs which gives similar results in SPL as 1 m dynamic measurement) and at the listening position

What max dB do you get, with what amp?

Cheers


Richard

[Brian Beck]

Calvin makes a good point about the distortion of an ESL at loud volumes. Moving-coil cones will gradually produce more and more distortion as they play louder and louder (making them sound louder than they really are), until they are literally crying out distortion. Cones will break up, creating non-linear resonant modes. ESLs, for the most part, enjoy low distortion, since the driving-force electrostatic field is virtually constant anywhere between the stators. ESL distortion will remain very low as the volume is increased until limiting occurs either by arcing or by the diaphragm hitting the stator, neither of which is a good thing. This is a bit reminiscent of a high-feedback amplifier that stays low in distortion until it finally clips.

[el`Ol]

This one has 123dB at 4 meters, but price is not nice.http://www.sonus.de/php/p_produkte.p...d=15&work_id=2

[Calvin]

Hi,

there are some pics of my panels in this forum.
125*25cm 3-4staggered perforated metal coated with a Nylon-derivate powder | 30° arced | 1mm d/s | 3.5µm film highly stretched giving a fs of ~150Hz| own highly transparent coating -and tried Licron with good technical, but lousy optical results - | toroid transformers 1:76 | simple HV-cascade with just 1700 to 1900V (up to 3kV possible)
Frame is made of special aluminium profiles with a nice curvature.
Bass is a slim tower dipolar design with 8 18cm drivers.
The crossover is made active fc~300Hz (last but not least design)
Amplification of the panel is done with a Rotel RB980BX -I plan to use digi amps in future.
I haven´t measured the SPLmax, but playing music I had to leave the room, because I couldn´t stand it...Eventually the protection of the Rotel switched off, but the panels hadn´t reached their limits then

If You plan to reach high levels of SPL above 300Hz You should consider panel dimensions of ~100*20cm and more. A d/s of 1mm is sufficient. Streching of the diaphragm should be as strong as possible -this leads to a much higher SPLmax because of safety against touching the stators- A lot of DIY-panels suffer from a too low tension (unless You plan a fullrange ESL there is no good reason for low tension i.e. low fs)

jauu
Calvin

[el`Ol]

Originally posted by Calvin
I plan to use digi amps in future.
Calvin

PWM is a good thing for high transforming factors (when you have a transformer that can do the switching rate).

[rick57]

Calvin
Your aluminium frame ESLs look way
Is “d/s” the air gap, and what would be the effect of say increasing it to 2 mm?
How do you know when stretching is sufficient?

Cheers