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In Reply to: RE: SoundLab tranfourmer MOD posted by tyu on April 17, 2012 at 15:32:09
The 1st drawing is the Acoustat. The 2nd is for Sound Lab.
The mods seem to follow two pathways. One is to remove the resistor as seen in the second drawing, along with the inductor, and change the cap value to 15-22uf. A lot of people remove the Brilliance control entirely.
The second path is to replace the HF toroid entirely with a new one that comes from Australia. So far from what I have heard with this mod there is no crossover at all for the HF toroid, but I suspect a cap of the right value in series with it will help out.
Either way the speaker is a lot easier to drive! Not only for OTLs, but people with transistor amps have reported the same thing, and in all cases it sounds better. Its not hard to see why- that resistor as shown in this example is a 40-watt device (some versions have 80-watt power ratings). It has to have that kind of power handling to survive- and the power to heat it comes from the amp. Take it out and the amp does not have to work as hard; sound quality is improved at all frequencies as a result.
The only issue with the 1st pathway is that the HF toroid should not have low frequencies applied to it else it could distort due to saturation. That is easily solved by simply decreasing the cap value, which has the added benefit of greater transparency. In some cases the cap is easily decreased as there are several in parallel and one can be simply cut out, in other cases the cap has to be replaced outright.
Follow Ups:
Hello,
I recently purchased a very unique pair of Soundlab speakers that are of a hybrid design, and I believe the only pair made. They consist of a panel for the highs and the mids, and a separate section with a conventional woofer for the lows. The pair are similar to the old dynasty series, but with bigger panels, and a 12 inch woofer for better performance. According to the factory, they were built sometime around 2000-2005, and were custom made for the original owner.
After several hours of listening, I am quite taken with the level of transparency these speakers have and life like scale they present to the listener. The highs are incredibly smooth, and bass response goes quite low. However, there is one major flaw to the sound that I hope can be alleviated. There seems to be a upper midrange suckout, or lack of detail in the upper bass. This is a problem for me because in my view the bass is the very foundation of the music and if lacking in any way, makes the music fatiguing to listen to.
I'm resurrecting this thread in hopes that some of the mods mentioned here might help, and perhaps make the speakers an easier load for my Ma-1's.
Also, I must mention I have a whole lot to learn about what's going on in this speaker, and electronics in general, and hope for some guidance with this project. Attached is a diagram that I made, using a older version I found online, but modified to show how these hybrids are setup.
Well it been 10 good day with this type of Mod in on my Acoustats
so now like lew an some others i am looking at a cap on the input of the high frc tranfourmers primary ....so i put a big 40mf oil cap
This is how it looks on paper...Ralph has to say..
The only issue with the 1st pathway is that the HF toroid should not have low frequencies applied to it else it could distort due to saturation. That is easily solved by simply decreasing the cap value, which has the added benefit of greater transparency.
In some cases the cap is easily decreased as there are several in parallel and one can be simply cut out, in other cases the cap has to be replaced outright.
But then there this truth some of us beleave...
KIS
Tried it without the cap, did not experience saturation, so why put it there? Borrowing a line from you: "the cap can not ADD to the transparency, can it?"
An there more...
Ralph
What I am saying is that the road may not have ended there- if the impedance can be further raised at high frequencies the door would be open to lower powered amps and lower distortion out of higher powered amps.
KIS
Very similar argument to what you had proposed. There are upsides and well as down sides of using capacitors. For me, capacitor sounds too obtrusive and should be avoided where ever possible.
Anyone who persist with ELS (and its many shortcomings) are in it for low level detail and its magical midrange, so I doubt your suggestion of a cap is a long term answer for this group of people.
More yet from Ralph
So- the idea here is to see if the impedance can be raised (thus reducing amplifier distortion) by examining the way the bass transformer and the new transformer interact at frequencies above the 'cutoff' of the LF transformer. Maybe its not a concern, but it may well prove worth looking into
Then Lew
All those lovely sounds are going through that horrid capacitor, which is in parallel with an equally lo-fi sand cast resistor, to form a filter which I gather protects the speaker from low bass transients OR is needed to equalize the frequency response. Ironic.
To me this gets funny that Dr.west would ever do the same thing
Dr.West uses lo-fi sand cast resistor in any ESL....this is moronic
But we all no this....back to My 40mf cap...
well here what it sounds like to me... if you have ever used a good pasive preamp...with no gain... that what i here with nothig in front of the high frc tranfourmer....if the input is at it best you get the best output out of the ESL...so with the cap in...the topend get rolled down.. like 1/2 db...an the cap can sound a little less detail and its magical midrange....
So then i get to looking at all the RF..an other hash that coming in to the ESL...like AM..FM..TV...an others
So i get some help from My old MartinLogans...Thay drop a Zobel in on there High frc tranfourmers all the time.....So i ran a 8ohm 200 watt from just in front of the 40mf cap down though a 20mf polstrine to the Neg input of the tranfourmers...
My ESL have been set up this way for 3 days .....an it sounds like i now have a Vary good preamp in ...an it the best yet...We got get the noise OUT....this is one way of doing it..an it sounds sweet....So if you do use a cap.. this works....NOw i am useing the same 50watt tube amp to drive this.... so it is not eating power with the Cap an Zobel in...With the cap an Zobel in i may be geting a littel more output....If it was less output... it would be the deal braker.....Goodluck
Well i have move the Soundlab an the Acoustats Transfourmers around...So i dont think this ONe tranfounmer is the ONLY one to work in this Mod?
There a lot of good Toroideld fullrang stepup out there....at the same $$ or less...theres better topend with toroids....MratinLogen moved on to them....thay do sound better!
I like any mod that gets better sound out of ELSs an Makes OTL work better on them....so why not go althe way...a pr of Eslsell for over $10k
OTL to drive them is over $10K...$1k worth of tranfourmers if this works the way some say....What the fear...thay well work in any other ESL for ever...What am i mising here..goodluck an thanks for all info
Hi Ralph,
I hear that the Sound Lab display with speakers driven by MA1 amplifiers won some sort of award at CES. Did you "tweak" the backplates on those speakers (by altering the crossover in ways you discuss here)? Inquiring minds want to know. I am guessing you did.
That was 2011, 'Best Sound at Show', using MA-1s and stock SL.
I tried to get the mod installed for 2012 but no dice to my knowledge. This year there were problems with a music server in the room as well.
Thanks for your input on the Sound of this type of setup Ralph....
I posted diff ESL tranfourmers setups years back as i had a pr of SoundLabes A1s..
After owening Acoustats for years an then going to the A1s it was a Dead short...for most of all the tubeamps an even the Krell KSA 250 i have...It never sound like a otl but the A1s were old ...An sounder funky
Anywho...I pull all the crossover out... An pull the center tap off the earth an the bias 0 of the high an low tranfourmers .... An grounded one end of the tranfourmers secdary winding to only the bias 0 ...Same end on bouth high an low Tranfourmers....So this mint the back stater was at the bias 0 only no earth just the bias 0....An then driveing the full winding on just the front stater...You no were the coating an bias are.....Less phase-shift...an got the best sound ever an was lot ezer to drive...lot of fun....But some one had too much money ...so i let him have the A1s for some of it ...There Still a lot of work to be done with ESLs
An OTLs....goodluck
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