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Old 2nd May 2010, 08:48 AM   #11
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by spritzer View Post
Those numbers are all but meaningless but a well driven Stax SR-007mk1 (not the Mk2 since the baffle isn't sealed) will go very low. Stax aren't alone in giving out such meaningless measurements
Yes, I agree, Stax can go quite low, compared to many other headphones.

Shame all the numbers have to be made up and ridiculous, just because "everyone does it".

And I'd add that Stax Headphones with modified tube driver (for more SPL and for crossfeed to get the musicians out of the head) are the only 'can's I tolerate for long periods.

I generally have Speakers, the only 'can's I own right now are some Audio Technica noise-cancelling ones for my frequent airtravel... I might get another pair of Stax now, given that we have a new Baby...

Though as long as the Neighbour plays movies very loud and very late I doubt I'll be turning down my system any time soon... :P

Ciao T
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Old 2nd May 2010, 08:52 AM   #12
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Join Date: Feb 2008
Location: Jackson,michigan
Even my smallest panel produces low frequency's nearly flat to 40hz.
Although fuzzy and hard to read this a pink noise test at 1 meter at 6 watts input.
The first set of bold numbers on the bottom of the chart from the left marks 10hz.
The test was done with no eq and the dips in the graph are room reflections.
I am running 6kv of bais on this panel and have measured the diagphram clipping (slaping against the stators) and have not experienced any arc or burned holes in the diagphram with this panel ,with a d/s spacing of .065".
the second set of pics was done the same way except that it was a nearfield measurement.
And as you can see I'm not using some cheezy $2 condenser microphone from radio shack. jer
Attached Images
File Type: jpg single panel setup.jpg (65.3 KB, 205 views)
File Type: jpg single panel pink noise response.jpg (36.3 KB, 202 views)
File Type: jpg open setup(new).jpg (443.3 KB, 199 views)
File Type: jpg open no eq.jpg (866.5 KB, 196 views)
File Type: jpg new eq'ed ,+6db 200hz,+9db 12khz.jpg (942.6 KB, 187 views)
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Old 2nd May 2010, 09:11 AM   #13
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Location: Jackson,michigan
I agree with you on your points as I am trying to figure out where the confusion has started.
The test that I have just posted were done with a transformer.
I'm sure we need not have to get into transformer theory as to how to get to 20 hz.
Sure esl's can get down to 20hz but it is not going to be a chest pounding 20hz by any means. jer
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Old 2nd May 2010, 02:57 PM   #14
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Thank you ThorstenL and geraldfryjr for such long and detailed answer!
The summary I get is that:
- Stax did not mension the FR is at what dB crititier, although it can be sure it is full-range class.
- Headphone, because they are near the ear, has the effect that help to enhance the bass.
- Headphone does not suffer from dipole effect, which helps the bass.
- bad transformer might cause some LF roll-off

ThorstenL:
you mensioned about direct drive have sufficient voltage to go load enough.
May I know what is the set-up, including RMS voltage, biasing voltage, diaphragm size/thickness and insulation thickness?
I'm certainly interested in direct drive, and avoide the X-former if possible.
I'm have some Semisouth 1.7kV silicon carbide power JFET on hand, it might be able to output 1kV RMS (1.4kV pp) if driven in balanced mode, I hope it will be sufficient.
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Old 2nd May 2010, 05:13 PM   #15
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Join Date: Feb 2008
Location: Jackson,michigan
I have stated before that with the advent of todays HV solid state devices that one could easily build a pair of direct drive amplifiers for much less than what one transformer would cost.
I have a design that I created in circuitmaker that simulates with out any errors using a basic common amplifier topology and cascading devices to handle the higher voltages using npn horz. output transistors for the output.
It does 800vp-p and can easily be scaled up for more voltage swing,with one on each side of the panel would of course double the voltage to 1600vp-p.
with a +- 575v supply.
I am planning on revamping the circuit to use HV fet's on a much higher supply voltage.
Even though I have not actualy built it yet, the fact that it simulates without errors is a good sign.
I have built a low voltage version of Neil S. Mckean's design which is based on david hermeyer's tube design to learn how to stack fet's.
It worked.
I used four irf510's on a 180v supply with a single TL082 driving the stack with no issues.
Only I haven't applied it to an esl yet because I didn't have any working panels or bias supply at the time,this was two years ago.
But it did drive a little piezo drive quite nicley.
I came with this concept four years ahead of this thread,Horizontal deflection (or high voltage type) transistors to directly drive ESLs?
The circuit I designed used 4 IRFbg30's stacked using a MOT for 3kv supply with an 8k load resistor.
Trying to find and/or the cost of building 4 900watt 8Kohm resistors is what has kept me from building it.
And trying to discuss this subject on DIYaudio has been proven to be a bit touchy for some. jer
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Old 2nd May 2010, 05:25 PM   #16
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Join Date: Feb 2008
Location: Jackson,michigan
When I get more time I will rebuild the circuit on a pc board on apply it to my micro esl panel here, Material for ESL
Which was why I created this panel in the first place. jer
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Old 3rd May 2010, 04:07 AM   #17
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by zhoufang View Post
you mensioned about direct drive have sufficient voltage to go load enough. May I know what is the set-up, including RMS voltage, biasing voltage, diaphragm size/thickness and insulation thickness?
I do not have data on the Panels, as I did not design them. My friend derived most of the designs form information in Roger Sanders Book.

The Amplifiers where 845 Push-Pull (1200V HT, around 1200V RMS output) for the midrange panel and 300B Push-Pull (400V HT, around 400V RMS output) for the high frequency panel. No idea on Bias, but likely a lot more than the peak signal value.

The HF panel was intended for use above 4 or 5KHz IIRC and had a very narrow state/film spacing. The Midrange panel had a wider spacing, broadly in line with many commercial ESL's.

The system was completed with a pair of dipole dynamic woofer systems using a pair of 18" Pro Audio woofers per side and 500W RMS Amplifiers.

All equalisation and crossover was line level passive.

Quite an impressive system and capable of quite high SPL's.

Ciao T
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Old 3rd May 2010, 04:59 AM   #18
jfitz57 is offline jfitz57  United States
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Location: Western Massachusetts U.S.A.
I had electrostatic headphones about 20 years ago. Best sound I ever heard! When I listen to AM radio stations over the Internet now I can hear the (sub-sonic) 20Hz signal between the program and comercials with cheap full size headphones because they are headphones! Speakers drive air, headphones drive eardrums. No can splain it simpler.

Jim
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Old 3rd May 2010, 08:36 AM   #19
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Hi,

If any of you are interested in making electrostatic headphones, have a look at my thread: http://www.diyaudio.com/forums/headp...headphone.html

Wachara C.
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Old 3rd May 2010, 12:03 PM   #20
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ThorstenL,
Thanks for the details!
1200V RMS figure is encouraging, as I have hear tens of kVs from other places, which is impossible for direct drive.

chinsettawong,
Thanks for pointing me there, I'm having a great time reading it!
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