Atmasphere,
Thank you very much for that explanation.
Best Regards,
Gary
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I know this is an old thread but it has some very useful information. I have a question from reading the thread that I hope someone could answer. Assuming you have an electrostatic speaker that varies in impedance from 2 to 16 ohms (hypothetical 2 ohm hf 16 ohm lf) and you have a tube amplifier with 2, 4, and 8 ohm taps. Are you better off setting the tube amplifier to the 2 ohm tap to drive the high frequency. What would be the tradeoff in this scenario for the spectrum at much higher impedance. Would there be an issue/tradeoff at low frequency (lf) if you used an autoformer and it boosted the impedance at low frequency much higher.
Regards,
Gary
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I realize this is an old thread but it has a lot of information related to the issues of using a tube amp with electrostatic speakers. I have a question related to the information provided. It seems the issue is the impedance variation from high frequency hf (low impedance) to low frequency lf (high impedance) of an electrostatic speaker. SS amps output a voltage for a given input so they will emphasize the hf vs the lf at a given power output because of the impedance variation of the electrostat over the audio spectrum. From what I gather tube amps deliver constant power over the spectrum but you can be limited at low impedance (if the amp can't drive the load) or at high impedance if the output voltage does not swing high enough. Please let me know if my understanding is incorrect.
Should you always use the lowest tap on your amplifier (e.g. 2, 4, 8 ohms) corresponding to the lowest impedance of the electrostat? What is the trade off at low frequency high impedance using the 2 ohm tap. If you went with the autoformer and it gives you the ability to drive the 2 ohm load what is the tradeoff at low frequency high impedance (e.g. driving 30 or 60 ohms). Any insight would be appreciated.
Best Regards,
Gary
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Also, since you seem to know Soundlabs, would there be an optimal frequency band for using the A1s from an impedance standpoint (e.g. minimize the wild impedance swings that the amp sees).
Regards,
Gary
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lewm,
Thanks for the response. I have an old set of Soundlab speakers (A1 and B1S) that I have been working on and upgrading. I am currently driving the system with SS amps (Innersound ESL 800) but would like to try a couple of tube amps I have laying around (both are 60W). One of the tube amps does have a 2 ohm tap (it is a Margules U280C). I would use one amp to drive the A1s and the other to drive the B1S (with a crossover). I have the luxury of optimizing the frequency band for HF and LF by using the B1S as my bass speaker. Thus my question about using the 2 ohm tap for the A1s if bandwidth limited. Would there be any benefit driving the B1S with a tube amp at the high impedance or would this work equally well with a SS amp. Once again, thanks I really appreciate your input.
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One other thing. Have you ever tried the zero transformer? It sounds like it would help especially with low power amps that could have trouble driving the difficult load. The only thing that could be at issue is the lower frequencies that get multiplied up to 40-200 ohms. I don't know if this would be an issue for some amps.
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Lewm,
Yes, I did ask many questions with Dr. West who was more than gracious with his time and help. He told me that a 300W SS amp was more than enough to drive the B1s. I am currently using a Crown K2 (350W @ 8ohms) on the B1s.
I am trying to absorb and understand your modification. My speakers did not work initially so I had new mylar installed by Soundlab on the A1s and the B1s. My panels had the Toroid l in it. A few years ago, I found someone selling upgrade parts that they did not install in their system which I purchased. The upgrade parts were a large 36uf capacitor (pio) and the Toroid ll transformer (the latest version). I consulted Dr. West who confirmed the parts. I removed the brilliance control and replaced it with a four ohm resistor (which was about the setting I had it at). Dr. West told me I could remove the inductor coupled to ground in the circuit but I have a 12 or 14 ohm low inductance resistor to ground. I believe the resistor was larger than what was in the circuit but Dr. West said that the Toroid ll can extend lower in frequency and that it would be fine.
A couple things mentioned by Dr. West. He said the B1S can be used as a full range speaker which I found interesting. He said that when they used the B1S with the A1 panels they would crossover at 500hz. Running the A1 at 500hz would essentially be operating the A1 with only the toroid ll. I tried it but I couldn't get it to integrate correctly (I will likely try it again in the future). It sounded better at an 80hz or less crossover.
Once again, thank you for your knowledge and help. It sounds that I can drive the A1 with the tube amp with the 2 or 4 ohm tap. I question whether I will have the voltage swing with a 60w amp for the midbass if the impedance gets high from 100hz to 1khz.
Best Regards,
Gary
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Lewm,
Congrats to you and Will on the work you have done in bringing forth a significant improvement to the Soundlab speakers. I can attest that the transformer upgrade was a significant improvement over the prior toroid l transformer. It is not very often that a user pioneers improvement that results in commercial changes. Kudos!
Yes the inductor was in parallel with the resistor. I only have the resistor now (inductor removed) per Dr. West (another thing you probably had your hand in). I do not know what they are using now for a resistor value but I believe it is the same (36uf and 10 ohms (4-2.5ohm potted resistors)). As mentioned, Dr. West stated that the resistor value could be increased with the Toroid ll but not by a significant amount (I have 12 or 14 ohms).
What are the consequences of completely removing the brilliance control that is in series with the transformer? Does it make the speaker much brighter? Does it have some effect on the transformer at high frequencies or is it reliability issue?
I would also like your final thoughts on the topic of the thread which is using tube amps with electrostats and more specifically Soundlab electrostats. The Soundlabs obviously have wild impedance swings from HF to LF. From the thread I assume that a tube amp should be selected to be able to handle the HF low impedance (with the zero transformer being a nice option to aid the tube amp). Are there any issues you know of on why a tube amp cannot drive a high impedance load such as 30-200 ohms?
Once again, thank you for all your help. Your knowledge has aided me tremendously. I really like the fact that even old Soundlab speakers (like mine) can be upgraded and made to sound great.
Regards,
Gary
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Lewm,
The resistors are in series (10 ohms). That is what I had in my circuit when I changed to the Toroid ll. I do not know what they are using in the new Toroid ll backplate circuit. I did exactly the same thing (you described) when I replaced the resistors. I have large ceramic non-inductive wire wound resistors (hi wattage). I will definitely look into increasing the resistance to around 20 ohms. I am not sure what transformer saturation is but that is what concerned Dr. West when increasing the resistor value (and lowering the croosover point for the Toroid).
From your suggestion I might just stick with my SS amps. They have ample power (Innersound 800 ESL monoblocks (800W@8 ohms)). My journey to this thread was based on understanding if a lower power tube amp could be used on a speaker such as Soundlabs. I believe I understand the tradeoffs you have outlined.
As usual, thanks for all the information, it is much appreciated. I try completely removing the brilliance control from the circuit. I will also try lowering the crossover point of the Toroid ll. I will then try crossing over to my B1S somewhere between 350hz to 80hz and see what works best for me (when I get the time of course). Merry Christmas and Happy Holidays Lewm. I have learned a lot.
Regards
Gary
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Lewm
I will definitely try both of those configurations. On my list is to remove the resistor I used to replace the brilliance control and increase the resistance. Thank you for all the help.
Best Regards,
Gary
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To summarize what Lewm said above (that he and Will have tried in their speakers) :
1. You can remove the brilliance control (or short the terminals) which is in series with the Toroid transformer (I removed the brilliance control and put in discrete resistors but will remove it entirely per Lewm's recommendation).
2. You can increase the shunt resistor value (mine had 10 ohms 4 - 2.5 ohm resistors in series) to lower the frequency of the pole (with the 36uf capacitor) from 440hz to a lower value.
3. Dr. West said it would not be an issue to increase the value from 10 to about 12-14 ohms with the toroid ll (I'm sure this is very conservative) to move the frequency pole lower. Lewm suggested 20 ohms. From my recollection, the concern that Dr. West had about increasing the shunt resistance was saturating the toroid transformer. The toroid ll transformer offered by Soundlab is much larger than the toroid l. I believe Dr. West said that it can handle an increased resistance without saturating.
4. You can use a better quality shunt resistor and it may add some minor benefits.
Regards,
Gary
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Lewm,
For some reason, I did not ask the question of what resistor value is currently being used in the updated back plates with the Toroid ll when I discussed my upgrade. Dr. West did confirm what you disclosed that the Toroid ll will not saturate as early as the Toroid l so you can increase the resistor value (I just don't know what they are using now, maybe someone else will chime in).
I have always wondered what the hot rod upgrade is for the Soundlab backplate. Do you know what this upgrade is?
Atma-sphere - I agree that I am limited in power that can be delivered in the bass region of the speaker due to the high impedance of the speaker and the voltage that can be delivered. Dr. West told me that the wattage claims for Soundlab speakers were to give people an idea of what kind of amplifier to buy (but he really mean't the wattage to infer what the power supply rails would be to adequately provide bass).
Regards,
Gary
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atmasphere
Thank you for this explanation as it gets to the heart of the matter. I just want to make sure I understand this correctly. What occurs to the sound of the speaker when the transformer saturates or begins to saturate? Is transformer saturation a voltage or current issue?
Are you saying:
1. That the resistor is not needed for either the Toroid l or Toroid ll?
2. That the concern of transformer saturation does not occur (at higher input signals) because:
a) at higher frequencies the music power requirements are typically not high (so the Toroid will not/does not saturate); and
b) the Toroid impedance increases at lower frequencies to a level that the Toroid cannot saturate even with a higher voltage signal (in other words the Toroid by it's impedance nature is self-limiting to prevent saturation?).
Regards,
Gary
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