distortion From ESL at low level

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i noticed that i already a looong time ago posted questions about the same subject. distortion at really low listening levels , with piano or other sound that decay, somewher ein the mid region. funny thing is this is a new pair of diy speakers contructed from Solosound panels. i have a cap on the tranny of 10 uF to start rolling of at about 500hz. i changed it with a good audin cap with the same result distortion at verry low volume. (low volume is at the amplifier not computer before someone asks)

the distortioin is not noticable when playing loud.

when i remove the cap completlely the distortion is gone. someone has an idea ? cant play them without any cap ofcourse



Here are the measurements.


Bleu Line is esl without cap red is with an audin cap of 15uF

upper line is freq response bottom line is distortion (THD) look how nice the distortion goes up at the frequency the cap kicks in, also funny is that the distortion is a few DB louder overal, i only changed the cap nothing else

this measurement is taken up close so i could do it at low volume. the Hump at 200 is resonance freq of the panel.

also the impulse repsonse changed quit a bit. the blue one looks beter overal
 

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What does the signal look like coming out of the amp?

It could be that the amp is having a hard time with such a high value of capacitance on its output and can't supply enough current to make up the difference.

I had found this was happening with my setup when I was learning and testing about transformers,

http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-2.html#post2103369

http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-3.html#post2133865

http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-4.html#post2137648

Extra reactances,core saturations and Transformer resonances cause a low impedance load to the amplifier and cause more of a demand on it.
If it can't supply the current then you will get such distortions as in those pictures in the above links.

Core saturation's and Resonant frequency's provide to the amplifier what looks like a dead short too it and is why those ranges must be avoided.

Most of these pictures show the switching of the transistors and the waveforms represent the current of the signal and in one picture it shows the representation of both the current and the voltage at the same time.
Notice the 90 degree shift due to the capacitive reactance.

That is my best guess as I don't Know the full details of your setup.

I hope this helps you.

jer :)
 
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Hi,

maybe You could do an impedance measurement? This would also clear up as to which extend the serious HF-peak is due to the mic or the transformer-panel combo.
How does THD behave with a series resistor between amp and ESL?
Like Gerald I also assume rather amplifier drive probs. A Resistor of 1-5Ohms would dampen the electrical series LC-resonance and reduce loading on the amp.

jauu
Calvin
 
thanks, i did try a resistor , but 50 i wont have any upper frequency left in my panel :)

just a series resistor before the cap i presume ? or after and then recalculate cap needed.

ill make a new measurement set to see what happens with a resistor, in series. it will tame the upper hump i believe. but i think its not gone solve the distortion.

Impedance measurement i would love to make but i have never tried it, it was with a reference resistor i belief ? i have to look it up again.


By the way , how can it be hard on the amp on low voltage and no problem at all on higher levels ? also its stable to around 2 ohm should nog be that hard. i could change amp to a class a amp just to see if something changes.
 
well here are the measurements up close with and without cap and a resistor of 1.2 ohm in series wth the transformer. picture one

if i increase this number for instance 18 ohm spl goes down overal and mostly above 10 k as expected. weird thing is even without cap and series resistor of 18 ohm distortion s heard in the lower regions. picture 2
 

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Have you tried a different cap or different values.

By looking at the waveform in Audacity, it seems that the signal is having a hard time trying to swing positive and seems to show some sign of crossover distortions.
It is hard to tell because your record level is a bit low.
It almost sounds as if there is hum being introduced.

Do you have any resistance between the bias supply output and the Diaphragm?

If even without the cap and a resistor you hear such distortion?
Hmmmmm...........

I added as much as 47uf to the primary side of my setup and I never had any such distortions.

What transformers are you using?

Are taking the bias supply voltage out and ground common to only one bank of the capacitors (same side)?
jer :)
 
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could it be lack of resistance at the bias out ?because i know the pannels have pretty low resistance coating, at least for nowadays. i must admit i took a few steps back on the cascade to get a lower bias, so im skipping the resistor. although because i thought maybe it has sometrhing to do with it i tried to connect it to the original bias out with the resistor and it did not help. but maybe theres not enought resistance there as well.

yes the 0 of the transformer is going to the bias.

The sound is indeed sounding like it has to overcome something before it really plays. like a barrier around the crossover frequency, above it ,its fine i believe.
 
Do you have any earth grounds on the esl side?
If so try removing it or try switching the polarity of the signal feeding you final bias supply transformer as i am thinking that there may be there still is a ground loop somewhere.

I did have a situation once where my amp was having a similar issue and it was all because of a ground loop that was caused by my scope ground being connected as well.
It caused the amp output to shift causing it to become unstable.
Putting a 1 ohm resistor in series made it not oscillate but the current was so great that it fried the resistor.

I schematic of your setup would help greatly.

jer :)
 
Do you have any earth grounds on the esl side?
If so try removing it or try switching the polarity of the signal feeding you final bias supply transformer as i am thinking that there may be there still is a ground loop somewhere.

I did have a situation once where my amp was having a similar issue and it was all because of a ground loop that was caused by my scope ground being connected as well.
It caused the amp output to shift causing it to become unstable.
Putting a 1 ohm resistor in series made it not oscillate but the current was so great that it fried the resistor.

I schematic of your setup would help greatly.

jer :)

Sorry about the typo's I was in a hurry !! :)
 
weird thing is even without cap and series resistor of 18 ohm distortion s heard in the lower regions

Distortion that increases as impedance in series with transformer primary increases, is usually core related. The series impedance can be resistive, inductive or capacitive. Looking at the attachment, if you examine the voltage before(V1) and after(V2) the series impedance you can determine if the distortion is core or amplifier related. I show a resistance, but you could use a capacitor as well(Impedance for 15uF at 100Hz = 100ohm). Whichever you use, select a component value for which you get noticeable distortion.

Since the distortion occurs at low volume level, you can use a line-input from another stereo setup to listen to (V1) and (V2).
Alternatively you could use the computer line-input to analyze with HOLM.
Just be sure to keep level < 2Vrms

If V2 is distorted, but V1 isn't, the distortion is most likely transformer(core) related.
If both V2 and V1 are distorted, the distortion is amplifier related.


Also, as geraldfryjr mentioned, a few specifics on your setup would be helpful.
In particular, what transformer you are using and a schematic of the circuit.
Also, it would be helpful to have a 100Hz sine wave recorded with and without the series resistor or capacitor to look at.
It might provide more insight into the distortion than the music sample did.
 

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Very good analogy I too was thinking that it could be core saturations as the distorted sounds seem to be only at the lowest of the frequency's mostly.

However without knowing about the transformer and the driving voltages it is a tough call.
It did cross my mind though as either caused the situation.

This would definitely happen if it was a rather smaller core below at about 200hz even with a 6Vpeak signal into it.

This is one of those things that make passive crossovers for ESL a real PIA !!!


jer :)
 
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ok i tried inceasing the resistor on the bias.
same result

i tried to switch to the other side of the row caps ont he bias.
same result.

still at low volume it sounds restrained. and distorted at low level at the crossover freq of the cap. i even switched my 2 ohm stable pioneer reference to a rotel 980BX.
same result.

Added a resistor,
same result.,

Switched bias suply to another one i had laing around, its the same but with new caps.
same result.

the setup explained by bolserst may need some more explanation for me :(
if i change the resistor for a cap of 15uF i should measure before and after the cap. and see what the distortion is ? so like the loop i use to calibrate the line out of the soundcard ? but then trough the amplifier trough the cap and back into line in ? and ofc first calibrate the output of max 2 volt RMS?
or listen to v1 and v2.

gone try this, only one thing i really cant believe its the amp. he never had any problems and the core would be weird to there pretty huge for a not full range.

i also tried 3 other transformers. one pair of really small ones from a 100volt line ... distortion at low freq, wich is ofc prety normal seen the size. then i tried some bigger 220-4 volt trannies, with 2 110 volt inputs and a zero to connect to bias. same story.

then i used a second pair of tranformers from the same brand as the first. one is older then the other but they measure almost the same. and dimensions of the core are the same to. one is doing slightly better and the other still has distortion at low level as the first 2.

.. im kind of asking myself if the panels are at fault here, or maybe there coating. can they have a to high capacitance?? because of there rather low resistance coating? i think it whas in the region of serveral hundred K or less.


funny thing is in there advertisment from the 70's they said high resistance coating so less prone to arcing and les distortion :) hehe well nowadays the used resistance of a coating is Way way higher
 
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Oh i just noticed something in the old (1970) brochure.... there crossover of the type i used the panels from is active.... maybe they kewn the problem and got around it by going active ??? i know there smaller models with just 4 elements instead of the 7 i use now is crossed passive as well as active. maybe theres a reason why they did not go passive, (distortion)

i also have to use like really small cap values to let it roll of at 500 hertz, 10uF.

wich implies that the resistance is already around 30 Ohm at 500 hertz.
 
Hmmmm....Interesting !!!

When I get my new panel finished I will look more into this.

The reason I had stopped was due to HV breakdown of the stator coating's and this stopped me from my transformer testing many times and permanently when the panels finally met their demise earlier this year.

So stay tuned as I will be testing the Antek AS-1206 power transformor for ESL use.
I will then be able to add a capacitor in my setup as well and see if I get the same results as you do.

It had been almost three years now since I was trying to make a passive crossover for it.
Then I had to set it down for a while to re-arrange things due to ground loops in my system and to finish building my Variable HV power supply.
Plus a trip to FLa. to get the rest of my equipment and set it all up again.

So right now I am just getting to the point were I had left off again!!!

:cheers:

jer :)
 
ok i tried only one panel with a cap to compare with one panel wil high resisting coating.

funny enough both had no distortion....... hmmm. i then though i desolder 4 of the panels in my setup to see if i lose the distortion then.. well no. still distorted.

i do think it might have to do with the capacitance of a few of these panels and a cap in series with the primairy. i really should get me a few panels with high resistance coating to check if this helps. getting sick of this crap. cant believe al 6 tranies i tried have core saturation when playing on low volume. as capacity said. it should be more noticable when playing louder.

i just noticed capacity said this in a really old thread of mine wich exact same problem. my mind forgot ewhat the solutions was back then or if i even had one in the end or just thought id live with it. the setup i used back then was same brand and type of tranies, with same kind of panels. i used six back then and 7 right now.
 
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i do think it might have to do with the capacitance of a few of these panels and a cap in series with the primary... cant believe al 6 tranies i tried have core saturation when playing on low volume. as capacity said. it should be more noticeable when playing louder.

I agree it is not likely to be core/transformer related saturation as these type of problems almost always get worse as volume is increased. That was why I had suggested a test to prove whether the distortion is coming from the amplifier or transformer/ESL. I will try to clarify/simplify the explanation of the test.

Figure (A) is the setup you described that gives you distortion.
Measure or listen to the voltage at "V1" and "V2"...you can simply hook up headphones at these two points and listen.

If only V2 sounds distorted, the distortion is coming from the transformer or ESL.
If both "V1" & "V2" sound distorted, the distortion is coming from the amplifier.

If the amplifier is distorting it is most likely due to an impedance dip from series resonance between the 15uF capacitor and the transformer primary. I believe this is the case based on the +15dB peak in the response from your post #1. To get this size of peak, the impedance will have dropped to the DC resistance of the transformer primary(probably < 1ohm) and impedance phase will swing from +80deg to -80deg either side of the dip. This can upset the best of amplifiers.

To test this hypothesis, you can apply damping to the resonance with a resistor "R" as shown in Figure (B) or Figure (C). A resistance of 15ohm - 30ohm will work fine. With the panel producing distorted sound, connect the damping resistor and see if the distortion is reduced or eliminated. Figure (C) is the preferred setup as this placement of the damping resistor swamps variations in the transformer impedance and helps to stabilize the crossover operation.

i just noticed capacity said this in a really old thread of mine wich exact same problem.
Can you post a link to this old thread? I wasn't able to locate it.
.
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