On Tue, 22 Mar 2005 20:15:28 -0500, wrote:

On Tue, 22 Mar 2005 02:32:03 GMT, Chris Hornbeck
wrote:

On Mon, 21 Mar 2005 20:33:06 -0500, wrote:

In the case of an E-spk membrane,
the tightness would determine it's resonance, just like a drum. I would imagine
the membrane would be loose enough to put the resonance out of the audio band,
could even be less than 1hz.

Unfortunately that high of a compliance isn't possible given
the constraints of practical diaphragm-stator spacing. Practical
electrostatic speakers have fundamental resonances in the tens
of Hertz range. The QUAD Mark 1 from 1957 has a design center
F-sub-S of about 70 Hz, for example.

Choice of fundamental resonance frequency is actually one of the
toughest and most interesting parts of the design, because the
resonance is used to extend response lower than a free-air
diaphragm of those dimensions would achieve.

I don't know what you mean here, I've seen 12" cardboard speakers with a
resonance of 15hz... what does size have to do with it?

In any open-baffle dipole, size i.e. path length from front radiator
to rear radiator, determines when the FR starts to drop at 6dB/octave.

Wouldn't the resonance have to do with how tight the membrane is installed?

Yes, and in a good design the fundamental drumskin resonance can be
set so that it starts to peak up just as the natural FR starts to
droop.

Below the dimensional
limit all diaphragms' responses fall at 6 dB/octave. Choices
must be made.

I thought system fall off was 12db?

That's for a sealed box, a dipole falls at 6dB/octave.

I have to say I don't know much about E speakers... had some E headphones once,
had no bass...

Well, they should have, since they are conventional direct radiators,
not dipoles. Stax 'phones have as deep bass as any other type that
I've heard.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Wed, 23 Mar 2005 07:24:11 +0000 (UTC), Stewart Pinkerton
wrote:

On Tue, 22 Mar 2005 20:15:28 -0500, wrote:

On Tue, 22 Mar 2005 02:32:03 GMT, Chris Hornbeck
wrote:

On Mon, 21 Mar 2005 20:33:06 -0500, wrote:

In the case of an E-spk membrane,
the tightness would determine it's resonance, just like a drum. I would imagine
the membrane would be loose enough to put the resonance out of the audio band,
could even be less than 1hz.

Unfortunately that high of a compliance isn't possible given
the constraints of practical diaphragm-stator spacing. Practical
electrostatic speakers have fundamental resonances in the tens
of Hertz range. The QUAD Mark 1 from 1957 has a design center
F-sub-S of about 70 Hz, for example.

Choice of fundamental resonance frequency is actually one of the
toughest and most interesting parts of the design, because the
resonance is used to extend response lower than a free-air
diaphragm of those dimensions would achieve.

I don't know what you mean here, I've seen 12" cardboard speakers with a
resonance of 15hz... what does size have to do with it?

In any open-baffle dipole, size i.e. path length from front radiator
to rear radiator, determines when the FR starts to drop at 6dB/octave.

Wouldn't the resonance have to do with how tight the membrane is installed?

Yes, and in a good design the fundamental drumskin resonance can be
set so that it starts to peak up just as the natural FR starts to
droop.

Below the dimensional
limit all diaphragms' responses fall at 6 dB/octave. Choices
must be made.

I thought system fall off was 12db?

That's for a sealed box, a dipole falls at 6dB/octave.

I have to say I don't know much about E speakers... had some E headphones once,
had no bass...

Well, they should have, since they are conventional direct radiators,
not dipoles. Stax 'phones have as deep bass as any other type that
I've heard.

I can't remember the brand, it was in the 70s... but they really lacked bass
response... they were supposed to be among the best at the time. I remember they
had a 'self power' switch or could use a power supply. I replaced them with I
think Koss Pro 4AAA or something like that, which had the bass but not the
transparency. They proved to be defective and non-repairable... I no longer use
headphones...

On Wed, 23 Mar 2005 02:11:10 GMT, Chris Hornbeck
wrote:

I'm sorry I wasn't clearer here. It's difficult to judge
a stranger's interests from newsgroup postings.

On Tue, 22 Mar 2005 20:15:28 -0500, wrote:

I don't know what you mean here, I've seen 12" cardboard speakers with a
resonance of 15hz... what does size have to do with it?

It has, as you say, nothing to do with it. Fundamental resonance
is related to the product of moving mass and compliance, only.

If you're from an electronics background, it's *exactly*
analogous to inductance and capacitance. If you're looking
for a hands-on conceptual framework, think about a rock
on the end of a spring, in gravity. The rock is the mass;
the spring is the compliance. Tap the rock and it will oscillate
up and down at the system's fundamental resonant frequency.


Wouldn't the resonance have to do with how tight the membrane is installed?

Yes, indeed. This is the only thing you have to adjust with
during manufacturing, and tensioning is very important. After
all, the *very same* membrane must be both radiating diaphragm
*and* suspension. T'ain't easy.


Below the dimensional
limit all diaphragms' responses fall at 6 dB/octave. Choices
must be made.

I thought system fall off was 12db?

Resonant systems fall off at 12 dB per octave per resonance, both
above and below resonance (*). This of course also applies to
electrostatic speakers.

Open-baffle or "panel" speakers have an additional issue. They
radiate, as all vibrating diaphragms do, equal energy in both
directions, "fore and aft". Without a box, aft, to contain and
dissipate the aft energy, it "leaks" around to the fore, cancelling
each other out, like antimatter in the hands of Scottie. "I
canna hold 'er no more, Cap'ain."

At short wavelengths, the radiating diaphragm is large, and
cancellation is minimal, but at long wavelengths, the radiating
diaphragm is small, cancellation is great, and the diaphragm flaps
around, generating a lotta fury but signifying nothing.

For example, try moving your hand fast enough to generate an
audible sound. Now, if you were (you're not are you?) Superman,
and could move your hand forward and back at, say, 1000 times
a second, you could make dangerously loud sounds with the same
sized hand. Wavelength; it's *everything* in acoustics.

So (sorry for the bandwidth), there is a transitional frequency
region where the cancellation effects start to be significant, and
it depends on the relative size of the baffle and wavelength.
Smaller than a wavelength is starting to be small; no getting
around it. A two foot wavelength is what frequency, class?

Two otherwise-nonObtainium effects: cancellation rolloff is at
6 dB per octave, and there's a null in the plane of the diaphragm
(at all frequencies, incidenatally), so room modes are excited
less.

(*) Don't worry about this. But you may find it interesting later.

Good fortune,

Chris Hornbeck

Thanks for the info, it all makes more sense now.

On Wed, 23 Mar 2005 14:04:48 +1100, Patrick Turner
wrote:



wrote:

On Wed, 23 Mar 2005 00:10:30 +1100, Patrick Turner
wrote:



Wait a minute, you are wrong Pinky.
The percussion sound you hear from an ESL is produced by
signal applied to the whole surface of the diaphragm.

And although it is conceivable that such signals might excite some resonances,

its not in any way like when a dude hits a drumskin with a stick, temprarily
deforming the skin in a local area, and sending ripples out across the skin,
and exciting a mass of trapped air.

I think this 'hit with a stick' thing is a red herring... You are in effect
saying that one can't play a drum by hitting it with a book or something that
affects the whole head - you are wrong! (it will just sound different) Also,
there are pre-tuned drum heads, no drum shell required. And have you ever seen
roto-toms? No shell either, so no air-mass.

The sound of a drum re-produced by an ESL is done in a very different way
to how the sound is genarated at the drum.
The drum sound is due to a very asymetrical distribution of waves waves
across the drum skin, which has considerable weight compared to an ESL membrane.
The ESL membrane is excited over its total area in an evenly spread fashion
by an amplified mircrophone signal. The ripples across the membrane don't occur,
The almost massless diaphragm does not like to ripple or swing back and forth in air

to any great extent like resonant things do, and the resonaces of ESL are renowned
for being less than
most other transducers.




Also, putting a mass into resonant vibration can be done with anything,
including an electrostatic force, ANYTHING that excites it to move.

Well show us all what terrible resonaces exist in ESL.

As I said, I don't think the resonance is great or terrible, just that it
probably exists.

The fact the resonance of the diaphragm of an E speaker doesn't affect the sound
doesn't mean it has NO resonance, just that it is damped and very small, and is
well controlled by the amplifier's feedback.

We are saying ESL resonance is small. I have not done the math to support
any idea how effective NFB control of the diaphragm is.
But if you tap a diaphragm, or play music alongside an ESL connected to an amp
with no signal, you'd expect to see an error message in the amp as it tries to
resist
the motion caused by the external sound or excitation.

I have never done this test.

I've only done it with normal magnetic speakers, but I imagine the effect is the
same.


Now I forget the original OP topic! BUT in practical terms, I'd agree that the
resonance in an E speakers diaphragm isn't a factor in it's sound, and the light
diaphragm with 'full wide drive' is what gives it the advantage over a
cardboard/magnetic motor spk.

All this talk about those speakers makes me want a pair now! Hey Phil, got a
set to sell?

I doubt he has, but why not try brand new ones from
http://www.eraudio.com.au

Patrick Turner

On Wed, 23 Mar 2005 02:46:45 GMT, Chris Hornbeck
wrote:

On Tue, 22 Mar 2005 20:42:54 -0500, wrote:

The fact the resonance of the diaphragm of an E speaker doesn't affect the sound
doesn't mean it has NO resonance, just that it is damped and very small, and is
well controlled by the amplifier's feedback.

I'd just like to agree with all of your post, and to add a
piggyback comment. Electrostatic speakers are often considered
to be "inefficient", therefore poorly coupled to the driving
amplifier and therefore indifferent to amplifier source impedance.

But actually, the "motor" in electrostatic speakers is of very
high efficiency and coupling is therefore very high. The misconception
arises from the considerable parasitic capacitance present. (But
it's "outside" the motor).

That's good to know...

Your English is better than mine, and that's all I really can use,
but your syntax is extremely provocative. I can't place your
childhood language, even to within a continent. Sometimes it seems
north European; sometimes southeast Asian; very intriging.
Care to share?

Thanks,

Chris Hornbeck

It's interesting that you wonder about my language... I actually have quite poor
language skills, I have to work at it, my brain is better attuned for visuals
then for writings. Do you know that test where there are a bunch of words that
are the names of colors, but the words are colored, and the colors don't match?
Example, the word 'BLUE' is green, then the word 'YELLOW' is purple, and on and
on...? The answer to the test is to say the colors of the actual words, NOT to
read the word. For the example I gave, the answer would be 'green, purple'. You
have to read it aloud at a good speed, and most people start making mistakes
right away!

Well, this test is no trouble for me... I can zip thru in no time, looking at
the colors and ignoring the writing. This shows that one side of my brain is
dominant... and it isn't the language side!

All I can say about my origins is that my parents were a mix of British and
French, with some German grandparents mixed in... Parley vous la Francais? C'est
possible que les deux langues me donne des autres problems encore!

On Wed, 23 Mar 2005 20:27:00 -0500, wrote:

Parley vous la Francais? C'est
possible que les deux langues me donne des autres problems encore!

I've recently tried to learn French, just in order to watch
Godard movies without reading, reading, reading. But I'm too
old; everything comes so slowly. All the languages of my youth
have faded away, except a little Korean. Living someplace
seems to make the language stick for quite a few decades.

Thanks,

Chris Hornbeck

wrote:

On Wed, 23 Mar 2005 07:24:11 +0000 (UTC), Stewart Pinkerton
wrote:

On Tue, 22 Mar 2005 20:15:28 -0500, wrote:

On Tue, 22 Mar 2005 02:32:03 GMT, Chris Hornbeck
wrote:

On Mon, 21 Mar 2005 20:33:06 -0500, wrote:

In the case of an E-spk membrane,
the tightness would determine it's resonance, just like a drum. I would imagine
the membrane would be loose enough to put the resonance out of the audio band,
could even be less than 1hz.

Unfortunately that high of a compliance isn't possible given
the constraints of practical diaphragm-stator spacing. Practical
electrostatic speakers have fundamental resonances in the tens
of Hertz range. The QUAD Mark 1 from 1957 has a design center
F-sub-S of about 70 Hz, for example.

Choice of fundamental resonance frequency is actually one of the
toughest and most interesting parts of the design, because the
resonance is used to extend response lower than a free-air
diaphragm of those dimensions would achieve.

I don't know what you mean here, I've seen 12" cardboard speakers with a
resonance of 15hz... what does size have to do with it?

In any open-baffle dipole, size i.e. path length from front radiator
to rear radiator, determines when the FR starts to drop at 6dB/octave.

Wouldn't the resonance have to do with how tight the membrane is installed?

Yes, and in a good design the fundamental drumskin resonance can be
set so that it starts to peak up just as the natural FR starts to
droop.

Below the dimensional
limit all diaphragms' responses fall at 6 dB/octave. Choices
must be made.

I thought system fall off was 12db?

That's for a sealed box, a dipole falls at 6dB/octave.

I have to say I don't know much about E speakers... had some E headphones once,
had no bass...

Well, they should have, since they are conventional direct radiators,
not dipoles. Stax 'phones have as deep bass as any other type that
I've heard.

I can't remember the brand, it was in the 70s... but they really lacked bass
response... they were supposed to be among the best at the time. I remember they
had a 'self power' switch or could use a power supply. I replaced them with I
think Koss Pro 4AAA or something like that, which had the bass but not the
transparency. They proved to be defective and non-repairable... I no longer use
headphones...

I had someone give me a pair of Stax phones, which were quite stuffed.
Yes, they were "self powered".
I removed the transformers and chucked out the rest;
I haven't the time and space for every electronic orphan that lands on my doorstep.


Patrick Turner.