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Atmasphere MA-2 impedance question

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Posted on June 1, 2012 at 18:33:39
earlinarizona@cox.net
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 I know the wattage power rating of the MA-2 is 220 watts from 4-16 ohms but what happens to the wattage power ratings when the impedance goes to 25, 28, 44 or even 59 ohms. This is what a Soundlab speakers impedance does.

 

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RE: Atmasphere MA-2 impedance question, posted on June 2, 2012 at 06:32:02
Lew
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Joined: December 11, 2000
 Are those the numbers after you installed the Australian 90:1 transformers and removed the parallel resistance, along with the rest of the components of the hi-pass filter? If so, fear not. The efficiency is so much higher without the parallel resistor that I am sure 50W would do. My Atma-sphere MA240s don't make much more than 100W, and they are sailing with ease when I now run my 845PXs. In any case, and to answer your question, these amps are quite comfortable with those impedances; there may be a small loss in efficiency at 59 ohms, but it's nothing to worry about. (I will leave that to Ralph.) You're probably getting on average MORE power, lower distortion, wider bandwidth, at these impedances than what you can achieve into 8 ohms or certainly anything below 8 ohms.

The data you give sound like the measurements I made on my own 845s after I installed the AU transformers; perhaps you are reiterating the data I put up on SLOG.

 

RE: Atmasphere MA-2 impedance question, posted on June 2, 2012 at 08:28:38
tyu
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Lew
I got a pr of the stock Acoustat interfaces...from a shop in town here
an for a long time i have found the just runing the transfourmers..in to there own panels was the best sound i could get get...like the M3s has 3panels i would run the two out side panels of the base tranfourmer an the one panel in the middel of the high tranfourmer....with nothing in front on the primary side an nothing on the sucdary side...sounded great.....so now back to the stock set i got...
Seeing how the high tranfourm did not over heat driveing it with the full input i though i give the stock set a try with the new setup you an others are doing with your SL....But just use the high tranfourmers
so the setup is ....removed the parallel resistance, along with the rest of the components of the hi-pass filte in the c mod

Well just as you say the SLP went way up...i now have the best sounding highs i have ever got out of any of the Acoustat...this has alway be the down side to the acoustats for me littel to rolled down...but now i am driving the M3s with 60wats tube amps an thay sound great....
so... removed components of the hi-pass filte takes the BIGst lode of the Amp....the SL high fr thranfourm well give you even better highs than the New transfourmers you have put in...i cant try the SL i dont have any SL here ... just maybe someing you would like to try...

I would have never tryed this if i had not found this old pair of Acoustat interfaces just laying in the back... thay said there junk....i gave $100. for the pr...no panels in the deal but i have 8ea panels here so good to go ... thanks for your work an other on this type if setup.
Goodluck





 

RE: Atmasphere MA-2 impedance question, posted on June 2, 2012 at 12:31:33
Lew
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 The credit should go to "Will" in Australia, aka "William" on the SLOG these days. He had the cojones to try removing all active and passive elements from the SL backplates and just run two audio transformers in parallel. I would never have thought it would work well, which is why I made my own measurements before even trying it. Then of course credit goes to Rob MacKinlay who actually builds that full-range 90:1 transformer. Crazy as he sounded, when Will first contacted me about his findings, I could not have been more ready to try a new approach, because I was thoroughly tired of having to use the Zero Autoformers and putting up with the pronounced midrange suck-out that I still could hear even with the Zeros in the circuit. Plus I knew intuitively that having the Zeros, the resistors, and the capacitors all in the audio path along with the bass and treble step-up transformers was not exactly the best way to maximize transparency. I was ready to consider buying another pair of speakers, which is part of the reason I bought those Beveridge 2SWs; had I known how well this new set-up with the 845PXs was going to work, I probably would not have done it.

 

RE: Atmasphere MA-2 impedance question, posted on June 3, 2012 at 08:47:49
tyu
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Lew you say

Crazy as he sounded, when Will first contacted me about his findings, I could not have been more ready to try a new approach, because I was thoroughly tired of having to use the Zero Autoformers and putting up with the pronounced midrange suck-out that I still could hear even with the Zeros in the circuit. Plus I knew intuitively that having the Zeros, the resistors, and the capacitors all in the audio path along with the bass and treble step-up transformers was not exactly the best way to maximize transparency.

Thanks for telling how YOU relly feel.......this was how i felt when i had the SL A1 on the frist day...


As was said
Lew has already used a 0.01uF teflon cap here instead of a 0.015uF cap without any problems. I will be using 0.0075uF teflon.

So if i am geting were you are now.....you are just using the two tranfourmers per speaker.....not the caps?

Also... on the Acoustat base tranfourm primary you can see there is a 1ohm 20w stock res. on the neg leg....in the Acoustats the base tranfourmer get hot if the one ohm removed....i have put a 2ohm 50watt..in an it sounds great.....This well work with the SL also.

The one thing i am finding with the new seup in my Acoustats.....if the base is driven into over loded... the highs an mids are never sucket out...i have never heard this befor... with any ESLs......i well saY with this setup the SPL is at 90-91...thats a Hell of big deal...

An i go out on the lim...say that it sounds to me like NO caps No coils...maybe just a fuse...should Ever be on the primary side of Any ESL tranfourmers....I well be moveing on to my martinlogans next.

In the setup now with My Acoustats on the secdary side i still have the 50k 100watts on the base...an have put in the .0015 6k oil caps in... were the Stock .01 ...thay are two high ...on the secdary side of the high frc.tranfourmer

Now how about the sound of Beveridge 2SWs...?

Thanks for your time

 

Sorry for the misunderstanding..., posted on June 3, 2012 at 22:13:27
Lew
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 None of us, not even Will, has deleted the mixer box, which as you know contains two capacitors, one each in series with each arm of the secondary of the treble transformer. I don't think it would be safe to do that. But as you note, I found and purchased some Russian 8kV .01uF teflon film caps on eBay, and I have used those to replace the stock .015uF caps that are used by SL. IMO, the Russian caps sound better than the OEM ones.

Also, Will deleted the inductor in series with the SL bass transformer; I did not do that. I use a 1.5mH 12ga copper Alphacore air core ribbon inductor on the input side of the SL bass transformer.

 

RE: Sorry for the misunderstanding..., posted on June 4, 2012 at 05:51:46
tyu
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Posts: 963
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Thanks lew...it all good..you can were my time goes... just liveing with this everday...
This is the type of sound that makes me get up in the middel of the night...to see if it still there....it been 4days now..... i still cant beleve it....

As you know the Acoustat panels are 9"x 48" so i can add as minny as i like...the base lode for the tranfourmers i have found is 3ea pr side... thay are so well made that thay dont even have to have a frame ...thay can just be setup ezely....i have found the best sound is with a flat setup...like the Quad 57s...so now i am driving this setup with the M60..
It well play as loude as if thay were Klipsch..go figg...like you sead in a post i read..this is the sound i been looking for for 40years...

So if we look at the Acoustat 121 interface in this setup the 50k on the base tranfourmer secdary ...is like your induckter....an i have now on the high frc. tranfourmer the two .0015 6k oil caps...were there was the stock .01 5k caps....

One thing you may tell your frinds on the soundlabe site is this setup well work with the stock high frc.tranfourmers...this would let them see what a great setup this is...then thay can get the new tranfourmers if thay feel that thay need them....to test this just put a fuse in the high frc primary side an uses a 3amp...i did this on my stock high frc. tranfourmer an did not kill one fuse....Great fun....60tube watts goodluck

 

RE: Sorry for the misunderstanding..., posted on June 4, 2012 at 07:00:51
Lew
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 So, before Will first contacted me by email to tell me about the Australian transformers, I was wondering whether I could even just remove that parallel resistor in the hi-pass filter for the OEM SL treble toroid. Dr. West had repeatedly warned against doing that, for reasons having to do with the toroid, but it was clear to me that the major problem with driving the SL speakers using my OTLs had to do with that resistor. In fact, Will reported to me that he did remove the parallel resistor successfully in his early experiments, and upon hearing that he got away with it, I did the same, while waiting for the new transformers to get to me from Australia. You are quite correct; it's a big improvement vs with the resistor in place. What I did also was to reduce the series capacitance to 22uF so as not to change the -3db point of the hi-pass filter. (Accounting for the intrinsic impedance of the speaker at the crossover point, 22uF gives about the same "knee" as does 36uF plus the 8-ohm parallel resistor.) I think Will completely removed that capacitor on the primary of the toroid; I cannot recall what he said about that. I did not try it.

 

RE: Atmasphere MA-2 impedance question, posted on June 4, 2012 at 09:47:52
Ralph
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 At 60 ohms the MA-2 does loose some power but its not a lot. Above about 5 ohms, the amp is on a linear curve where power is decreasing very slightly as impedance is increased, such that at 16 ohms the amp makes the same power it does into 4 (we are only talking a couple of watts here). The limitation is the voltage in the power supplies of the amp, but essentially what happens is into the higher impedances the output section also gets more efficient- more power dissipated in the load and less into the power tubes. So on a Sound Lab the MA-2s (and MA-1s) tend to run with less heat, with no trouble making bass power, something that is a problem with many amps, especially transistor amps (although transformer-coupled tube amps can be challenged by the impedance curve as well).

The result is that the MA-2 can make the same volume on the speaker as transistor amps rated at 600-800 watts.

The Sound Lab mods that have been a topic on this forum seem to really help the amp out, regardless of the amplifier technology. Customers that have MA-2s and Sound Labs that have done just the resistor mod alone report that they essentially have unlimited power- its not possible to clip the MA-2s. That means that the actual panels themselves must be fairly efficient- well into the 90s by equivalent 1 watt/1 meter measurement.

 

OK now I am totally confused..., posted on June 4, 2012 at 19:58:25
Penguin
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 So you guys tell me it is safe to remove both the resistor and the cap in front of the torroid as well? I thought the low end will saturate the the core and the toroids will be goners. So what gives? Is it safe to use a 22 uF cap and no resistor?. Is it also safe when you use it with a solid state amp?

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

 

RE: OK now I am totally confused..., posted on June 5, 2012 at 04:31:00
tyu
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 My take on the Acoustat mod 121 interfaces....

The input side primary of the high tranfourmer...
nothing on the pos +input....
if you feel you need anything to help with overlode 1ohm 25watt on the neg. leg...
same high frc.tanfourmer on the output side secdary...two caps...stock caps were .01 5k work fine....i went with .0015 6k caps...the acoustat are over 30years old..

on the base tranfourmer inputside primary ...nothing on the pos.+
on the neg. input the stock 1ohm 20 is fine

on the base tranfourmer output side..secdary..i have the stock 50k 100w in....but it well work with out the 50k or any res...the acoustat panels are diff than the one big SL panels...

The Mod here is to get all the caps an res. out of the high frc,tranfourmer...makes big diff in the sound an SPL of the Acoustats

...the 121 stock setup is in the other post... goodluck

 

RE: OK now I am totally confused..., posted on June 5, 2012 at 07:01:19
Lew
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 First of all, neither Ralph (I am sure) nor I want to take the responsibility for what might happen as a consequence of any of these mods. So, neither he nor I want to be on record as advocating anything that goes against the advice given by Sound Lab (i.e., Dr. West) regarding the use of their speakers. I can only tell you what I have done, at my own risk, to my speakers, and what the results were. Dr. West is on record as stating that it is not "safe" to remove the parallel resistor that comprises part of the hi-pass filter in front of the SL toroidal treble transformer. Dr. West stated that in part that resistor is in place to protect the toroid against musical transients that might damage it. In practice, I can tell you that I and a few others did remove that resistor; in my case I also changed the value of the capacitor from 36uF (factory) to 22uF. (I did this while I was waiting for the Australian transformers that now completely replace the toroid to arrive at my home.) The reason I reduced capacitance from 36 to 22uF is to preserve the crossover point or the "knee" of the hi-pass filter at about 550Hz. That is the factory-implemented crossover point when the resistor is in place. I calculated the value of 22uF based on measurements made with my own relatively new 845PXs. (Ergo, I cannot guarantee that this is the best value for anyone else's speakers.) I can tell you also that there was a big improvement in sound with the resistor gone and the capacitance at 22uF, and there were no ill effects on the toroid. If you were to remove the parallel resistor and NOT alter the capacitance, then the crossover point would be at a lower frequency (~350Hz). This, IMO, increases the risk that the toroid could be damaged; it was not designed to handle extreme low frequencies. Proceed at your own risk.

One mod I can recommend unconditionally is the removal of the "Brilliance Control", which is anything but. If you have not done that, try it.

 

RE: OK now I am totally confused..., posted on June 5, 2012 at 08:56:55
Ralph
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 The reason you can reduce the capacitor value is that the resistor and cap set the crossover frequency, without the resistor the impedance of the circuit at the crossover frequency is considerably higher. In fact so much higher that I suspect that 10-15uf is closer to the mark.

The transformer can be saturated by low frequencies but saturation is very different from actual damage. I think you will find it pretty hard to damage the transformer! Saturation, OTHO will manifest as temporary distortion on transients. If you were able to keep the transformer in saturation, eventually you could overheat it but it would sound bad and most reasonable audiophiles would turn the volume down at that point so there would be no time from the transformer to heat up enough for actual damage. Just my opinion mind you, but damaging the transformer seems remote, and if you have the cap (above) installed its just not going to happen.

This will result in a bumpy impedance curve. In stock form the speaker has a fairly flat curve through the midrange, caused by that resistor, and that curve is hard to drive because the resistor is where most of the power is going- that is why its rated with such a large wattage. However it appears that even transistor amps benefit from getting rid of the resistor, despite the resulting impedance curve! That is because the energy made by the amp is radiated into the room rather than being converted to heat.

 

RE: OK now I am totally confused..., posted on June 5, 2012 at 09:37:42
tyu
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 Thanks lew...
I new Dr west was not into this....for sure the SoundLabs are now an well be sold as a speakers with spec,s set by Dr west...but this must be said for others.... but your own info is great...

As for what i see at pulling the res. an caps out of the input...
It has to show the Amp a lode it can drive with ezes...what may 10-20ohms
I done all you can think of to get esl to give better sound with my M60s an other tube amps ...

An the one thing... That on paper looks like the one you wold always have to live with.. upgreads...just never got here....but this works....
Forgive me but i try to get this lucky ever day....goodluck

 

RE: OK now I am totally confused..., posted on June 5, 2012 at 12:35:34
Lew
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 But I am finding out that not everyone who is excited by this idea has a thorough understanding of what they are doing when fiddling with the crossover and the transformers, and I do not wish to be responsible for the possible negative consequences of that. However, I agree it would sound very bad long before the transformer would actually burn up.

Contrary to one small element in your post, I found that the impedance curve of my speaker is more flat now through the midrange than it was "before". If you look at the measurements made by Kevin Covi about 10 years ago, the parallel resistor created an impedance dip around 500 to 1kHz. This caused a midrange "suck-out" when driving the SLs with your OTLs that was always audible despite all my prior efforts to fix it, including the use of the Zero Autoformers. (That suck-out was probably not evident if one drives the old crossover with a solid state amplifier, as does Sound Lab at their factory.) The midrange dip in the speaker response is completely gone once I converted fully to the Australian transformer (and even just by removing the resistor from the input of the SL toroid), and if you will review the measurements I made, this audible result is concomitant with the fairly stable impedance from around 400 Hz up to 2kHz (using the AU transformer).

 

I was using a different chart, posted on June 5, 2012 at 13:49:13
Ralph
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This is what Dr. West sent me late last year, which is probably a lot more recent.

The one with the peak is with no resistor if I have his notes right. Sorry for the bad resolution but this is how I got it. So I have base a lot of my conjecture on this chart, but it is quite clear that it probably does not represent all speakers- probably just the newer ones. That peak though being up to 40 ohms says to me that the cap can be about 1/4-1/3 of its original value in those models after the resistor is removed.

 

RE: I was using a different chart, posted on June 5, 2012 at 19:18:09
Lew
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 Since I can see none of the numbers on the X or Y axes, and since the curves are not labeled, the graph means little to me, except to say that my measurements are nothing like that, assuming the bottom two curves are of impedance. There is no such huge peak at whatever frequency that is, with no resistor, using either their toroid or the AU transformer. My speakers were built in late spring of 2011. Anyway, if that peak is up to 40 ohms, then the impedance at lower and higher frequencies would appear to be too low to be ideal for our amplifiers. Looks like 5 to 10 ohms mostly. OK for an MA2 but nothing lesser.

Edit: After sleeping on this post overnight, I decided that I over-stated the problem. In fact, an MA1 should also be able to drive the load(s) represented in that graph. (I think the lower two curves show impedance vs frequency, and the upper two curves show amplitude in db vs frequency.) But things get a lot better than suggested by those data, when one removes the parallel resistance in the hi-pass filter, which was my main point.

 

RE: I was using a different chart, posted on June 6, 2012 at 09:07:15
Ralph
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 Right!

We have enough people using MA-1s with the Sound Lab to know that they do work :) Doing the mod really helps them out

The big increments on the graph are 5 ohms. You can see on the left that the scale goes from double digits down to one single, and Roger mentioned something to me about a 40 ohm peak, which does correspond to the graph. That puts the minimum impedance of the bass transformer at about 7 ohms. The far right side of the chart appears to be 20KHz. I suspect that with all the other mods (not just the resistor) that 1.5-2 ohm value comes up a little.

 

I tried it with a 24uF cap and sounded horrible, posted on June 6, 2012 at 18:12:52
Penguin
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 the reason for the 24 uF is that i had a few on hand from the old crossover, but it is obviously way too big grrr. So the resistor is back in the circuit and the PIO as well. Is there a reasonable way to determine what cap i need in series of the torroid to make this work? If i could get it sound good with the torroid, i would not bother with the AU90 transformer. Because of the whole setup i is too hard on the MA-1s, I have not put the MA-1 back i am using the big-ass Llano CAS-300s in a vertical biamp mode.

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

 

RE: OK now I am totally confused..., posted on June 7, 2012 at 05:32:31
KIS
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 Hi Dee

Just remove the 8 Ohms resistor and continue to use the 36uF cap. The sound would be fine.

Mike from Perth said that he preferred 36uF to 22uF when he did the first stage of the mod.

As much as the removal of the toroid would improve the sound, the AU transformer is a far superior solution. The highs from the Au EI transformer has more body than the SL toroid - my ears tell me. Cymbals sounded bigger and fuller with the EI transformer. Also not having a cap to cut off bass makes sense don't you think. The whole mod also allows you to remove the inductor and makes the backplate box really spacious. The only thing that does any filtering in the backplate is the mixer. Use some nice Russian Teflon, like Lew did and you have a very nice pair ELS that is world class.

Less is more in every case.

William

 

RE: I was using a different chart, posted on June 7, 2012 at 06:56:24
Lew
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 I posted my own numbers for impedance vs frequency on SLOG, I think. You can see that my new 845PXs with the AU transformer and no resistor/no capacitor never get anywhere near to being as low as 5 or 7 ohms, except above 2kHz. Having measured two different speakers, my own plus my neighbor's U2PXs, I have come to believe that there are differences among the speakers probably in relation to the many versions of the stators, the diaphragm coating, the mylar, etc, that SL has experimented with over years. (The U2PXs had been upgraded to full PX about 4-5 years ago.) Also, although I did not do any direct measurements to prove it, I believe the impedance will vary according to the setting of the bias voltage. If so, no two speakers will ever be exactly alike.

But the important point is that there is NO huge impedance peak in the curve for my speakers OR those U2PXs. (40 ohms is 5X to 8X the baseline of 5 to 10 ohms that is shown in the graph you posted.) The bass transformer, which is the same whether or not one uses the new mod, never gets anywhere near 7 ohms in my speakers (at all frequencies, the impedances I measured were higher), perhaps because I measured without the parallel resistor (which would tend to bring down the impedance as the natural impedance of the spkr is also falling with rising frequency). I did not measure with the parallel resistor in place. In fact, since a resistor would be expected to have a linear effect with frequency upon impedance, I don't see how removing a resistor could give you such a huge peak where there was none WITH the resistor, except to guess that it causes some aberrant resonance in the toroidal treble transformer, which is maybe why RW wants us to use the resistor with the toroid. This reveals an issue with the toroid, not an issue with the speaker itself.

 

RE: I was using a different chart, posted on June 7, 2012 at 07:31:47
KIS
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 "The bass transformer, which is the same whether or not one uses the new mod, never gets anywhere near 7 ohms in my speakers (at all frequencies, the impedances I measured were higher),"

I have info from one SLOG member who told me that the bass transformer DCR has changed over the years. I suppose it is hard to ensure uniformity through the years.

 

RE: I tried it with a 24uF cap and sounded horrible, posted on June 7, 2012 at 07:46:55
Ralph
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 How were you able to tell the cap was too big? What did it sound like?

 

RE: I was using a different chart, posted on June 7, 2012 at 07:51:46
Ralph
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 I don't see how removing a resistor could give you such a huge peak where there was none WITH the resistor, except to guess that it causes some aberrant resonance in the toroidal treble transformer

The resistor does 'linearize' the impedance curve, without it the transformer expresses its natural inclination to have a high impedance at the lower end of its range. It does this at a different range of frequencies than the bass transformer because its wound differently.

I'm thinking that there are variances in the transformers used as well as variances in panel spacing, materials and the like.

 

Very distorted on bass and transients like an amp clipping, posted on June 7, 2012 at 08:44:19
Penguin
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 :)

True terror is to wake up one morning and discover that your high school class is running the country.

quote by Kurt Vonnegut

 

RE: Very distorted on bass and transients like an amp clipping, posted on June 7, 2012 at 10:16:31
Ralph
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 And taking the cap out sorted that out??

 

Not the removal of cap:), posted on June 7, 2012 at 12:42:00
Penguin
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 But putting back the 8 ohm resistor in parallel with the torrid and the 36 uF in series.

Dee

True terror is to wake up one morning and discover that your high school class is running the country.

quote by Kurt Vonnegut

 

RE: Not the removal of cap:), posted on June 7, 2012 at 14:41:52
Ralph
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 So - reinstalling the original parts is what worked?

 

RE: I was using a different chart, posted on June 7, 2012 at 14:51:35
Lew
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 DCR would have little to do with large differences in speaker impedance except maybe it's an indication that they also played with the turns ratio over the years. The turns ratio is by far the primary determinant of the impedance seen by the amplifier, but a change in turns ratio would probably be reflected in a small change in DCR.

 

RE: I was using a different chart, posted on June 7, 2012 at 14:55:45
Lew
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 You wrote, "without it the transformer expresses its natural inclination to have a high impedance at the lower end of its range. It does this at a different range of frequencies than the bass transformer because its wound differently."

This is all true, but if you measure overall speaker impedance with both transformers hooked up and the parallel resistor and the series capacitor in front of the treble transformer and the series inductor in front of the bass transformer, the removal of the resistor (only) should not cause that peak, unless there is something else going on peculiar to the toroidal treble transformer. This is my point. How do you "wind" a transformer so it gives you a resonant peak at upper midrange frequencies? This is not something you do on purpose, I would think.

 

RE: I tried it with a 24uF cap and sounded horrible, posted on June 7, 2012 at 15:01:14
Lew
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 What is a "Llano CAS300"? If it is a solid state amp and you like it, just put everything back to stock and enjoy it. If your speaker sounded lousy just from removing the parallel resistance and changing the capacitance from 36 to 24, then something else is wrong, probably having to do with hook-up. I cannot make a diagnosis at this distance, unless you tell us more. Most of all, the mod should not have made the sound worse with the MA1; the sound should be better.

 

I did not try it with the MA1, posted on June 7, 2012 at 20:01:49
Penguin
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 it is a bit of a pain to get them back behind the speakers....


I thought the solid state thing would work just fine too without the resistor. I could try the experiment again with the grond lifted off the resistor :) Makes a pretty good soldering post. I was somewhat surprised. I do not like the Llano that much, i bought the MA-1s because i want to use them with the A1s...but they just run out of juice with the current crossover in the backpanel.

let you know what i find.


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

 

exactly...., posted on June 7, 2012 at 20:12:26
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 which makes me confused again...it seems like i am getting confused left and right by this thing....after all there is no DC going into the torroid from the apm, there is a series cap in there, unless there was something wrong with the cap i was using....but it measures 23.64 uF does not show a short or any issues...I am using the Llano in a vertical bi-amp. I have two stereo units. but if they work with the normal 36 uF (really big ass oil cap) 8 ohm high pass filter in form of the torroid, it should work without it, unless there is something very strange is going on. I will keep looking at and try just lifting the resistor off the ground so only the 36 uF cap is in series. but not tonight. Now i only did one of the backplates...maybe i will try the other one and see if there is a difference.

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

 

taking just the resistor did not work, posted on June 7, 2012 at 21:24:44
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 i think i need to get some drawings done and post it...really weird

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

 

do you have your speakers wired for bi-amping?, posted on June 7, 2012 at 21:31:38
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 Mine are, maybe there is some strange loop or something going on here.


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

 

RE: do you have your speakers wired for bi-amping?, posted on June 7, 2012 at 23:19:34
KIS
Audiophile

Posts: 2085
Joined: February 16, 2002
 Bi-amped. Yes.

You are doing something wrong.

Read SLOG post carefully on instructions.

 

I think it is pretty obvious :), posted on June 8, 2012 at 07:02:04
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 jsut need to find out what i am doing wrong
True terror is to wake up one morning and discover that your high school class is running the country.

quote by Kurt Vonnegut

 

RE: I think it is pretty obvious :), posted on June 8, 2012 at 08:12:04
tyu
Audiophile

Posts: 963
Joined: April 19, 2011
 Get the bias up...low bias well make any ESL sound bad..i no most have this ...





 

RE: I was using a different chart, posted on June 8, 2012 at 08:41:04
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 I think it has mostly to do with the turns ratio and the capacitance of the speaker. I'm pretty sure if you removed that transformer from the speaker you would find no such peak :) I'm pretty sure the bass transformer plays a role too.

 

RE: exactly...., posted on June 8, 2012 at 08:48:45
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 It might be that the higher impedance of the speaker is limiting the power of the amps. Solid state amps can double power as the impedance is cut in half which is another way of saying that if you double the impedance the power is cut in half. That is why tube amps are usually preferred on Sound Labs- they don't loose so much power into the higher impedances (so you have power to play the bass).

It might be that you are simply clipping the amps?

 

RE: I was using a different chart, posted on June 8, 2012 at 09:22:17
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 Right. IOW this has to do with how the driver interacts with the transformer. I'm not sure I'm on board with the idea that the peak represents a resonance. If that were the case then bass would really be a problem with our amps since the impedance is so high in the bass, but its not.

 

ok..., posted on June 8, 2012 at 10:21:53
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 looking at your diagram...which is pretty cool, did you draw it?..

I had the black wire of the torroid connected to the minus terminal of the high input, the green to the cap and the other side of the cap to the plus terminal. The bass transformer is hooked up right now as stock. I am not certain if that causes issues. On your drawing there is a line between the bass and high positive input terminals. Is that intentional? I would assume that you do not want them connected together.


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

 

hmmm, posted on June 8, 2012 at 10:32:03
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 Interesting. the beast can put 300W/channel into 8 ohms and double when going down to 2 ohms to 1200Ws has more FETs in it than a doughnut shop has cops...but let's say it could only put out 35 w into 64 ohms? due to maxing out to the rail voltage? but even 35W would be really loud, would it not be? And i was not changing the volume. between resistor in and out..It would almost seem that this mod would make the speakers SS amp unfriendly, right? What puzzles me is why does the distortion go away when i put back the BAR (Big Ass Resistor)

Should i just say screw it take out the resistor, put the MA-1s in place and never look back?

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

 

RE: hmmm, posted on June 8, 2012 at 11:45:56
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 Maybe :)

I think those that are on the SLOG forum can say better, but as I understand it this mod is helpful for solid state amps too, as the resistor is absorbs substantial amplifier power.

 

Another way to think of it, posted on June 8, 2012 at 22:54:30
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
 I put this idea on SLOG a few hours ago. It is possible that your SS amplifier is unstable when asked to drive the capacitative load of the SL speaker without the resistor in the circuit. This has nothing or very little to do with its power capability. Some SS amplifiers decompensate when asked to drive such a load. The presence of the resistor in the circuit ameliorates the capacitative nature of the SL speaker, over all. (I believe that Dr. West even gives this as one reason not to remove the resistor.) When you remove the resistor, the speaker becomes, essentially, one huge capacitor. SS amps don't like to drive capacitors. One notable example is Krell, maybe not the current models, but in the old days they were notorious for shutting down when driving ESLs.

On SLOG, I suggested you might try to borrow a Parasound or Pass amplifier. Both of those are probably OK with the capacitance of the SL speaker load. Later I thought maybe you might try horizontal bi-amping, instead of vertical. Just for the heck of it.

 

or just simply , posted on June 9, 2012 at 08:19:51
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 blow the dust off the MA1 and put it in service. I like the sound of the tubes better anyway

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

 

RE: or just simply , posted on June 9, 2012 at 08:53:15
tyu
Audiophile

Posts: 963
Joined: April 19, 2011
 I am not buying the Amp SS or tube not working....
From the work i have done on All ESLs.....in these setup of the high frc tranfourmer..With the res. Caps.in front an then caps in the mixer....this sets up a push-back to the amps Tube are SS... Not with this new mod..pulling the res. an cap OUT....this is OVERCOME...now i have a pr of 50watt amps driving my set today....thay have NEVER sounded so good as with this mod..before the mod...i could not get the speakers play with 500watt amp... like thay sound with 50watts ...gofig
But however all a esl is Bias...heres a way to test an get the right bias on Any ESL...
put a 2ohm 20 watt res. in the neg input leg of the base tranfourmer... then setup you speaker like you play them get you bias set like Dr. west tell all to do then play cds an the after 10 min...tuch the res.. if the bias is low the 2ohm res well be hot...if all is well the res. well just be worm...
this has work for me for years....the res. was put in to the Acoustat to help with the base tranfourmer overlode..the res get hot not the tranfourmer...Play my setup loude... 2ohms get just worm.....goodluck

 

I think one of my backplates is wired wrong...., posted on June 10, 2012 at 11:57:39
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 At one point i got a new transformers...I put in and becasue it was not exactly clear what is what....i just wired it in the same order as the old one

here is the old transformer....




and here is the new one.

Looking at tyu s diagram i have a sneaky suspicion that the new one is backwards if the black wire is supposed to be ground in both.

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

 

RE: I think one of my backplates is wired wrong...., posted on June 10, 2012 at 13:59:02
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
 You really ask hard questions with minimal information. Here I would say at first glance that both transformers appear to be oriented the same way, with the primary leads toward the bottom of each photo. However, I have never seen an SL bass transformer with four red primary leads and one black. Moreover, there appears to be a lot insulation on the four red and and single black leads, suggesting they could be secondary leads, which carry high voltage. On the other hand, a secondary should have only have three leads, pos, neg, and ground. The transformer with the orange, yellow, etc, primary leads is like every other SL bass transformer that I have ever seen (N = 2), oriented with respect to the back plate as it should be. Take this question to SLOG or email William directly; he may know.

 

ok, ok, ok...., posted on June 10, 2012 at 20:15:09
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 But if i look at tyu's diagram the black lead goes to the - terminal of the input and the center, in my case orange is the positive... I had the green terminal going to the - because it was in the same location as my old one. so today i reversed the order swapped black to green and yellow to blue. that would reverse the order of the leads...I stil have the distortion, even with the Ma-1. I isolated it to the bass section. So I either already blown something, or the distortion is caused by something else. But what could it be? And why would having the the 8 ohm resistor in the circuit would make it not noticeable, or am i going deaf? This is about as maddening as it can be :). So before i keep murdering stuff, does anybody have the color coding for the bass transformers? The old ones are wired correctly because those are the factory things. I know the that the red and the black wire are the primary side because on the secondary side i have 3 big terminals encased in some insulator plastic. on the old transformers. the new ones are just three leads coming out from the other side of the transformer.

Based on what i am experiencing, maybe the old bass transformer is fine too, something else is giving me fits. I am not not about to start swapping things between the tow backplanes, i find that hit and miss approach to dangerous when dealing with high voltages. Is there a more systematic approach to track this down?

Here is the where i am sitting.


I modified one back plate only. I disconnected the 8 ohm resistor, if i hook up the bass section only to either of the amps, MA-1 or the SS amp with the i get distortion. I have not moved the backplate to the other panel. Based on tyu's diagram i think i had the bass transformer reversed. I swapped black and green, yellow and blue. So right now the input of the bass is between black -and orange+, used to be green - and orange +. Distortion is still the same.

Do i have something blown in the mixer? Do i have a blown toroid? Am i just insane? Ok the last one has a trivial answer, but still, this is nuts?

So i have a fine mess on my hands :)

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

 

RE: ok, ok, ok...., posted on June 11, 2012 at 07:36:29
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
 Let me be certain I understand your question: You want to know about wiring the transformer in the bottom photo, or the one with the yellow, green, orange, etc leads. Yes? In that case, the black lead ALWAYS goes to the negative post on the amplifier input. The "non-black" leads attach, respectively, to different parts of the primary winding within the bass transformer, so the turns ratio is different depending upon which one of them is making contact with the inductor in series with the positive post on the amplifier input. For example, orange corresponds to "0db". The choices are +3, 0, -3, -6, I think. Those non-black leads normally go to a switch or jumper arrangement, so you can easily switch bass level; the other end of the switch or jumper arrangement goes to the series inductor. I chose to hard wire the orange lead to the single inductor I use in series with the bass transformer, but that's an option. I am not surprised that you would have distortion if you connect one non-black lead to negative and another to positive. IIRC, black lead is always to negative.

That's why I don't know what to say about the transformer with the four red leads and one black, except that the black probably goes to negative.

 

What does it sound like? Do you have a damaged panel? nt, posted on June 11, 2012 at 08:12:57
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 -

 

RE: ok, ok, ok...., posted on June 11, 2012 at 09:44:41
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 Thanks. That clears up one issue:). I will try the other panel tonight. Maybe Ralph is right and I have a damaged panel.

True terror is to wake up one morning and discover that your high school class is running the country.

quote by Kurt Vonnegut

 

I will check tonight, posted on June 11, 2012 at 09:46:06
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 Both visually and by swapping sides
True terror is to wake up one morning and discover that your high school class is running the country.

quote by Kurt Vonnegut

 

It is official it is the panel, posted on June 11, 2012 at 13:57:43
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 I moved the modded backplane to the other side and it works with both amps...

Now i need to figure out, where is the damage. I read somewhere that you can crete a temporary fix using silicone :). One of these days i need to ship them to soundlab for repairs.


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

 

the day is Monday :), posted on June 12, 2012 at 12:00:37
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 need to arrange shipping.

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

 

RE: It is official it is the panel, posted on June 12, 2012 at 12:02:17
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
 Take a flashlight and shine it through the spandex as you examine every rectangle in the speaker frame, looking for holes or tears in the diaphragm. Typically they occur at the edges, where the frame impinges on the mylar. Typically you will find them along the topmost row of rectangles, nearest the top edge of the frame. If one or two are "holey", you can repair that by "killing" that rectangle, using silicon caulk. You will have to slice an opening in the spandex so as to admit the nozzle of the silicon caulk tube. (I did it at the rear so the damage to the spandex is not seen from in front.) Then squeeze the tube so silicon caulk is deposited between the mylar and the stator. This will eventually cut off the capacity of that rectangle to respond to audio signal. It's actually a permanent fix, unless or until too many of the rectangles are affected. You won't hear any difference between the affected panel and the intact one (after repair). if it's only one or two or three rectangles flapping.

 

I always wanted a good excuse to have them re-mylared, posted on June 12, 2012 at 12:10:39
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 for the cost of roundtrip shipping plus the work, they will be as good as new, and with the transformer mods, i do not not think i need to go PX either. Talked to Brent today. The cores will be trucking out on monday. I could try the caulk fix, but then it will be messier to deal with the repair at the factory. I can live without them for a month or so anyway.


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

 

One interesting thing...., posted on June 12, 2012 at 12:27:44
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 SO i put the un-altered backplate with the "damaged" panel...and it sounds quite alright, the modded backplate is with the other panel and it is just fine, quite a bit more dynamic and open sounding, but the two sides together are listenable and no rattling distortion is noticeable....If i swap the backplates, and the modded (no resistor) backplate drives the "damaged" panel then the sound is quite distorted from that panel. SO it still puzzles me what would the resistor across the toroid do to eliminate most of the distortion? Does it somehow dampen the diaphragm? preventing it to slap against the stators? Really strange. I am trying to recollect everything i learned about electrostatic fields and forces, but cannot come up with a good explanation. Maybe the fact that the membrane really sees about 8K across the secondary of the toroid when when the 8ohm resistor is in place and infinity when not, allows it to move more freely and the tear can actually be more independent from the rest of the membrane...I do not know, but trust me you would be sitting here scratching all your hair follicles if you were sitting here listening to the panel with the resistor in and out. with the resistor out it is unlistenable, with the resistor in, you can drive it quite hard before it starts to distort. I am listening to it right now, the system probably plays around 80 - 85 DB and no buzzing .


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

 

RE: One interesting thing...., posted on June 12, 2012 at 13:25:45
tyu
Audiophile

Posts: 963
Joined: April 19, 2011
 Heres the two things that CAN make a man NUTs.... the on paper best ESL ever made...an you can figg the other




First of all, neither Ralph (I am sure) nor Lew want to take the responsibility for what might happen as a consequence of any of these mods. So, neither he nor I want to be on record as advocating anything that goes against the advice given by Sound Lab (i.e., Dr. West) regarding the use of their speakers.



So here we are......or you are...well...I had the SL A1 here...for about 6weeks....3 years a go...i did some mods too the A1s that had worket on the Acoustats....these A1 had older tranfourmers..one thing i saw was the panels are so big... that i new thay would not work for me... the Acoustats M3 with 3 panels in each speaker.. thay did not work much better but had a much better SPL.....So the A1 went to a new owner.

So what i well say about the SoundLab mod is this....i would only use the New Fullrang tranfourmers like Lew an others have done!
I would not on my new panels use the stock high frc. tranfourmers with this mod...but that just me ...
Just one ESLs OTLs lovers 5cent..... goodluck

 

RE: One interesting thing...., posted on June 12, 2012 at 14:13:12
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
 I am at a loss to explain your observation except to hypothesize that the speaker is so much more efficient and dynamic without the parallel resistor that perhaps you are able to put enough more energy into the speaker (rather than speaker + resistor) such that it excites a resonance that is not evident otherwise. Also, 80 to 85db is not very loud. "Loud" starts above 90 db at my listening position, by my reckoning.

Anyway, good choice of what to do.

 

RE: One interesting thing...., posted on June 12, 2012 at 21:54:48
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 80-85 is my normal listening volume :)...agreed loud is 90+.

The salient point here is that the mod exposed a fault in the system that is not obvious without the mod. Morale is that when people perform these mods and things do not work, the cause may be a pre-existing problem, it was just covered up. The normal swapping backplates, visual check, etc is still the first line of defense.

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

 

RE: Atmasphere MA-2 impedance question, posted on September 5, 2014 at 12:55:58
roio
Audiophile

Posts: 35
Location: Frascati (Rome)
Joined: September 3, 2014
 Ralph,
I have red that some Atma Sphere models have the zero-feedback option , and I have red of several reports by Lew that he recommends this setting.
Could you please explain how the problems of drift of the output level, sufficient bandwidth and distortion, etc. should be managed without any negative feedback? Maybe zero-feedback should be intended to be "minimum feedback". Thanks.

 

RE: Sorry for the misunderstanding..., posted on November 9, 2020 at 03:30:06
ttungus@yahoo.com
Audiophile

Posts: 1
Location: CA
Joined: November 9, 2020
 Hi Lew,
By any chance you would have the schematics for the AU90 mods?

 

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