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I received an email from one of his friends in Perth, Australia, that the person known as William or Will on SLOG (Sound Lab Owners Group) passed away suddenly, over this weekend. Will was a very significant person on SLOG, as it was he who first had the guts to tear out the crossover network from his Sound Lab speakers and to substitute the then OEM toroidal treble transformer with a full-range EI type transformer made by a company in Perth. He was running the new EI transformer, which came to be known (by me) as the "AU90" (because it had a step-up ratio of 1:90 and is made in Australia) in parallel with the standard Sound Lab bass transformer, with no reactive components in the signal path. Will contacted me privately about his experiments, because he remembered my name from the old SLOG, where I was an active participant. At the time he did so, I was really willing to listen to any idea that would improve the sound of my speakers; I sensed a low midrange suck-out that was in the same frequency range as the known impedance dip caused by the SL crossover network. I took a chance and ordered a pair of AU90 transformers from Australia, threw away my old toroids and the RC network that went with them, and needless to say, I have never looked back. Eventually, Roger West responded to our posts on SLOG by developing his own new toroidal transformer that has a much lower low frequency cut-off compared to his old toroid, so to ameliorate the impedance dip, and now that new one is standard on all SL speakers, to the satisfaction of everyone I know about, including Roger West. Thus in a small way, Will changed the world. RIP.
Follow Ups:
I am very sorry to hear this, and appreciate the notification. I had many email conversations with Will, and it was greatly enjoyed. RIP Will.
I was also saddened by the news of Will's passing. He was such a good internet friend! If anyone would like to post their condolences to Will's family the following link will take you there.
http://tributes.smh.com.au/obituaries/smh-au/obituary.aspx?pid=170913853
Texas Dave
That's sad. Will was always very gracious about helping us out despite many pesky "I don't quite get it yet" follow-ups. I ended getting one of the new RW toroids because of Will--and you too, Lew--and I am very happy about it. I haven't messed with my backplates since. Will is what our hobby is all about.
Chuck
I will not forget the day I received a first email from Will. I hadn't the faintest idea who he was, but he said he contacted me because of old conversations on the old SLOG. His timing could not have been better. I was so in despair about getting better sound out of my then brand new 845PXs that I was contemplating selling them unless something could be done. Was thinking along the lines of crossover modification, so Will's idea was really fresh and new. The great thing about Will was that he was SO dogmatic, so stubborn, and so sure of himself, without being offensive in any way, that you just had to give in and try it his way. Plus I "wanted" his idea to be good, on an emotional level.
I always wondered why you never found Nirvana in the AU90, but at least you found some version of Nirvana.
Hi Lew
This is Jian from SL board.First, I am very sorry to hear the news.
For my SL 945, I don’t use any RC network now, but I do use a 8 ohm diy resistor in parallel with high frequency transformer for safey. I can’t hear any degrade in sound with and without the resistor. Both transformers are stock SL transformers.I did a rough room frequency response meaurment. I did see there is a dip at about 300hz. However, I just can’t put the SL RC back due to the improvement of sound without the RC.
Thanks for your work on the SL speakers!
Jim
Edits: 05/10/14
What treble transformer are you using? The original toroid or the new toroid from SL?
What would be unsafe about removing the 8-ohm resistor? With either of the two SL transformers, you probably would need a capacitor in series, to create a hi-pass filter, but not the resistor. I am surprised if you are using either of the SL toroids and NO capacitor that you are not having issues, but that's good news, if so. I am assuming your 8R resistor is in parallel with the amplifier output; yes?What amplifier? This is most important, because if you are using a solid state amplifier, then you ARE probably better off with the 8-ohm resistor. With a tube amplifier, no.
Edits: 05/11/14
> What treble transformer are you using? The original toroid or the new toroid from SL?Both treble transformer and bass transformer are original ones.
> What would be unsafe about removing the 8-ohm resistor?
In Dr. West’s article, the impedance of speaker can be close to 1 ohm without RC filter if I recall it correctly. Therefore, I think it is safe to connect a 8 ohm resistor in parallel with treble amplifier’s output.
> With either of the two SL transformers, you probably would need a capacitor in series, to create a hi-pass filter, but not the resistor.
You are right. I have tried to use a capacitor in series to create a hi-pass filter. But the sound is not as good as without hi-pass filter unless I can find a capacitor without any sonic signature. There is a dip at about 300 hz without the capacitor in series. But I just don’t want to give up the improvements for sound to get smooth response. I used a electronic crossover before but not now. Please see the image above.
> I am surprised if you are using either of the SL toroids and NO capacitor that you are not having issues, but that's good news, if so. I am assuming your 8R resistor is in parallel with the amplifier output; yes?
So far, all things are fine. But I do realize that the frequency response is not as smooth as with a capacitor as I mentioned above. I also used a swatch to change the inputs of toroid so I can increase +3db output if I need to.
> What amplifier? This is most important, because if you are using a solid state amplifier, then you ARE probably better off with the 8-ohm resistor. With a tube amplifier, no.
I use Wolcott P400’s for high frequency and Spectron Musician III for low frequency.
As I know, the original SL transformer's low frequency limit is 400 hz. I am wondering if I can connect two original SL toroids in parallel so two toroids act as one to further extend its low limit.
Edits: 05/11/14 05/11/14 05/11/14 05/11/14 05/11/14
You are bi-amplifying the speaker. You are using a dbx223 as a hi-pass filter in front of a Wolcott amplifier that drives the treble transformer. The treble transformer seems to go right into the mixer box. That's fine for the "ESL panel".But what the heck are the speakers you have labeled "back ribbons" and "front ribbons"? Are those ESLs or ribbon speakers? If ribbon speakers, I can indeed imagine that the impedance can go down to one ohm, all of which is in parallel with the Wolcott driving the ESLs. So you are using that 8-ohm L pad in SERIES with the "front ribbon" speaker. That will raise the impedance of the front ribbons as seen by the amplifier, but it has no effect on the impedance seen by the amplifier due to the "back ribbons", and it dissipates lots of amplifier power as heat in the Lpad. (Parenthetically, if that is the Sound Lab Lpad, it is very bad, sonically, in my opinion.) Thus the impedance of those back ribbons is dominating the load seen by the Wolcott. (The net impedance seen by the amp will be the sum of the inverted values of the impedances. Therefore, the impedance can never be higher than the lowest value of all those different speakers.) If indeed they are ribbons, I would guess that the impedance can go quite low, down to one ohm or below, even. That is not good for the Wolcott, if you want the best sound quality. In fact, it's not good in any way.
With respect, this set-up could be a lot better. Best of all would be to ditch those extra speakers or to run them completely independently using another amplifier. At the very least, you have no need for that "12db" passive crossover coming after the Wolcott, if the dbx is itself an active crossover.
I am editing this post to say that I did not take into account the fact that the passive crossover should, if it really does afford a very high impedance at frequencies below 12kHz, ameliorate some of the potential problems I cited here. (I think I must have been thinking "12db", as in slope, instead of "12kHz", as in the -3db point of the passive filter.) In my next post, I did take the effect of the passive crossover into account. Here the active dbx crossover and the passive one were not in fact redundant, because they affect very different parts of the spectrum.
Edits: 05/12/14
I think there is a misunderstanding caused by my diagram. The drawing is not the latest one. I don’t use dbx 223 crossover now. I updated the diagram.
Why I use ribbon tweeters? I am a long time Magneplan speaker owner and feel that SL speakers sound somewhat dark and lack high frequency air, sparkle that I heard from Magneplanar 3.6, or 20.1, or Apogee Ribbons. The ribbon tweeters I use are Fontek ribbon. See link below.
http://www.parts-express.com/fountek-neo-x-30-ribbon-tweeter-black--296-713
I use 4 ribbon tweeters on front and two on the back to simulate the sonic characteristics of a electrostatic panel. I am not sure how the impedance of these ribbon tweeter changes. Of course, it could be better to use third amplifier to drive ribbon tweeters only.
Some one may think it is better off not using additional ribbon tweeters because it may destroy the coherence of full range electrostatic speaker. In my opinion, it is not true as long as choosing the right crossover point and optimal output level of ribbon tweeters.
and no one should tell you how to set it up, least of all me. But apart from the fact that without the dbx you do need a passive crossover, I still see problems here, assuming that THIS diagram does represent your set-up.
First of all, as far as I can see, you have no hi-pass filter at all in front of the SL toroidal treble transformer. Without the dbx, you need one. If the treble sounds closed in and dark, perhaps this is part of the cause. The toroid will be severely compromised by unfiltered low frequencies coming through the Wolcott. This, I am sure, Dr. West would not feel good about.
Second, what I said before still goes; the impedance of the "back ribbons" will dominate the total impedance seen by the Wolcott. So, whatever is the impedance v frequency of the back ribbons will be seen in parallel with everything else, and the net impedance seen by the Wolcott will be lower than that maximum value. I am pretty sure this would compromise the performance of the Wolcott. I guess you are getting away with that ok, if the crossover does function properly as a hi-pass filter starting at 12kHz, so the impedance problems I have outlined only apply at very hf where there is not much energy demand, but the problem with no hi-pass filter in front of the treble transformer of the SL still stands.
I don't mean to sound dictatorial; I am just trying to help. Will would have told you the same thing, maybe in stronger terms.
My advice: Take the ribbons out of this system for a moment and add a 22uF capacitor in series with the input to the SL treble transformer. That's all. Nothing else but Wolcott to 22uF cap to toroid. Remove for a moment the "12db"crossover and the L pad, as well as the ribbons, front and rear. I guess you can continue to drive the bass transformer full range with the Spectron. The SL bass transformer poops out above 2kHz, anyway. Have a listen.
I am really sorry about that.
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Lew
I'm very sorry to hear we lost another planar guru even tho I didn't know him. I didn't even realize a Soundlabs owners group existed.Speaking of transformers,I did buy the Menno Vanderveen for my Monolith 2s from Plitron back in 2007.I then got my new CLXs so I parked the Monoliths..The new ones have Italian made toroids and I know if MasterSound made them or not but I would love to find out.
Honest amplification is better than excessive 2nd order distortion anytime.
The idea of Will's (and then my) quest was (1) to increase the input impedance of the SL speakers, so they can be driven better by our OTLs, and (2) in the process, to increase efficiency, which was dreadfully compromised by the RC network used by SL, where the parallel value of R ranged from 4-5 ohms to 8 ohms, over the years as they changed it quite often. There was also scuttlebutt that the toroidal treble transformer "needed" the parallel R, in order to function properly. (I can no longer parrot their rationale for that.) Substitution of the treble transformer with a full-range transformer enabled Will (and I) to do away with the RC network entirely. Thus in one fell swoop both goals were achieved. In the standard Sound Lab set-up, there is also a low value inductor in front of their bass transformer. Will found that one cannot just do away with the SL bass transformer; both it and the AU90 transformer in parallel are necessary to derive a full bass response from the big speakers. Will did however eliminate the inductor, whereas I have not; I use a 12-ga 1.5mH Alphacore air core inductor in series with the bass transformer. Either way, the results were and are transformative. I measured the impedance v frequency on my speakers with the modified set-up, and across the frequencies from 50Hz to 2000Hz, it does not dip below 20-25 ohms. At 5kHz it's about 8 ohms and gradually rolls off at 10kHz and 20kHz. Roger West pointed out to me that there is a sharp impedance (not frequency response) peak between 200Hz and 300Hz. Big deal! If it's there, it causes zero problems for my OTL amplifiers.
The problem with Martin-Logan speakers, and why I have stayed away from them ever since the CLS II, is similar; they are designed for solid state amplification. Further, the audio step-up transformers they used (in the CLS, don't know about now) were puny. What's inside the CLX?
I was aware of that problem of running better with SS amplification but it never a problem with me because I miraculously avoided those years where that happened.I have the old Monolith 2s and now the CLXs have two torroids in them where the Monoliths have one and they went to a multipanel setup.I run the Citation 2s with McShane mods strapped in mono and they are pretty stable.I will try to get a picture of then inside of the network.
Honest amplification is better than excessive 2nd order distortion anytime.
Thanks, Lew.
Brian
So much music, so little time!
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