Friday, January 11, 2008

DIY Electrostatic Loudspeakers / ESLs - Electronics and First Listen

With the panels completed, I move on to assemble the electronics. At this point I am really eager to hook the panels up for a test. The electronics assembly is really simple. This mess of wires below shows that the diaphragm is connected to the EHT supply, the stators are connected to the audio transformer, the EHT supply is connected to the voltage regulator and finally the audio transformer is connected to the amplifier's speaker outputs. This is so simple I complete this in no time at all.I flip the switch... and no sparks. So I go ahead and adjust the bias voltage for the panels. I let the panel charge up for about an hour before I do anything further with them. Here is a picture of the voltage regulator used to adjust the bias. At this stage put some music on and turn up the volume. Well, I hear music coming out through the panels. If only you could hear them. All the superlatives that you have ever heard reviewers and owners sprout about ESLs apply here. These speakers were made for music. It’s an all new listening experience with all my CDs. Instruments sound so real... one thing that struck me was the snare drum from some acoustic pieces. None of my cone speakers, my Fostexs full ranger included can reproduce the sound of a snare drum as accurately as the ESLs. If you have taken notice of the sound of a snare drum you'd know what I mean. From rock to techno, to vocals, to classical... the music is just great. Even my better half who is quite critical of audio equipment (but not fussy) said that they were very "nice".

Bass is a bit lean, so when I play Bach's Dorian, it just isn't quite right. But then I have yet to hook up my Rythmik Audio Sealed Subwoofer, which should fill up the lowest octave demanded by organ music. I will be going through some frequency sweeps later, once the speakers have had some time to "loosen up". But from what I could tell, it plays from 50 Hz to 20 kHz very convincingly; it then starts dropping from 50 Hz to 30 Hz... to virtually nothing much below 30Hz. At this stage the panels are simply leaning against my wall as I have yet to complete the cabinets. Yet they sing beautifully. Can't imagine how much better they will get when in their proper enclosure and placed properly. Here are the 3 amigoes that make up the left side resting against the wall.Somemore thoughts about bass thru ESLs. I think the ability of the ESL to do bass is really dependent on a host of factors and the most important one is step up transformer. For reasons that I have yet to understand, the number of octaves that a transformer can handle has a practical limit. I read the limit to be 6-7 octaves. One solution is to use a high freq transformer for a treble panel and a low freq transformer for the bass panel. The problem here is working out the crossover and integrating the panels. However I have it on good faith that the ESL's that I have DIYed has a freq response of +or- 6db from 35Hz to 200Hz. However, I do believe the cabinet and placement plays a very important role in achieving this, particularly the use of walls for reinforcement.

The following is a quote from ER Audio about their proprietary 1:90 turn transformer:

"Response is < + or – 2dB, 20Hz to 20 kHz driving a 1.2 nf load. A 0.6 ohm resistor is used in series with the primary to quell a rising response which peaks at 25 kHz (resonance). This resistor may be varied to adjust the response for different panel loads."

At the moment I have yet to experiment with sound absorbers and diffusers. I will have to when I have the ESLs in the cabinets and properly placed.

The next step, The Cabinets and Final Installation

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