Defying Conventional Wisdom Worked. Hybrid ESL

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#61
I am biased since I think no loudspeaker of any sort sounds as good as direct-direct drive Sanders-type set-up. Lived with one for some decades.

Kind of ridiculous to use transformers with a conventional audio amp. A low output impedance matched to a low-value capacitor (AKA ESL panel)? If you've examined the transformer interface, there's no satisfying way to make it work across a large passband because the impedance is all over the place. In particular, I've struggled with the couple of the custom-made DW 1:100, 39 lb monsters I have. They ought to be the best you can make....

BTW, the first Dayton-Wrights (which I heard in 1970, I think) were higher voltage tube amps with special step-up transformers as the load (1:30????). Kind of sounds like a sensible compromise, eh. Easy to build, once you have the transformers. But not a concept that easily applies to low voltage transistors.

BTW, any time I've tested little transformers like for mikes or between audio units for ground control, they are remarkably good and deserve to be used more.

B.
 
#62
I think there would be a time alignment issue.
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I have a dcx2496 that can fix that time alignment issue, but I have a hard time believing my ears would be able to hear a difference - a 3" differential with speed of sound at 760 miles per hour...

Another Idea I had was put three panels in individual frames, side by side, hinged, like a Magnepan Tympani...

One Full Range Acoustat panel never impressed me much, two panels slightly better, but three was when it started happening, and four was awesome...
 
#65
Yes, I understand the comb filter effect - just don't know if I would be able to detect it...

Is there a comb filter effect on a Martin Logan CLS (Curved ESL Panel) - there is at least 2 -3 in differential in location of the sound front from front to side of panel.... constructive interference?

For example - constructive interference - Quad ESL-63 Delay circle lines - I know it sounds good, but again, is it due to the Comb filter effect?
 
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#66
Sorry, I feel as if I am hijacking this thread...

But I must not understand your Acoustat Isobaric arrangement if there is no overlap...the way I understand, there is 100% overlap with isobaric arrangement, no?


I have many Acoustat panels (and acouple pairs of Medallion interfaces) and would like to accomplish:

* 7 feet tall max
* Mid of top panel at around 5' - 6' high
* Better focus bass (hence looking at the Isobaric arrangement)
 

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#67
direct-direct drive Sanders-type set-up
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Are you referring to the Sanders article where he drive a set of esl panels direct off the plates of a tube amp with 4 ohm load resistor on tube amp output transformer? ESL Bias tapped from B+ supply thru cap multiplier? Not enough voltage for extremely loud listening, but he said it was plenty loud...

And instead of using a 4 ohm load resistor on tube amp, why not a 12" bass driver 50hz and below?
 
#68
Yes, something like what you describe. Load was a few thousands Ohms, I think. ESL hardly mattered as a load. B+ was 2400vdc. Bias at least 5000vdc with DW cells that can take 10,000 volts. XO around 130 Hz. No stereo problems on music when that high. Worked great for decades.

But I don't understand you second paragraph.
 
#69
If they are curved then there is not a real issue as they do not face each other or overlap. In case the speakers are overlapping you have an issue. If there is as complete overlap like in the woofer arrangement then they act as one (sandwich). But only if the phase shift is very small (In case of the low frequencies his is no problem).
 
#70
If you use a speaker instead of a load resistor then this will have some influence as well on the mid's and high frequencies. Beware that this is not a fixed resistor but depending on the frequency (impedance). The tube amp likes easy loads and a ESL is far from easy. So try to balance this with a static resistor value. The amp will have less stress when connecting the ESL's on the high voltage side of the transformer but still will be a capacitive load (only). The value now will be in the nano farad range instead of micro farad when used on the low impedant side of the transformer.
 
#71
john65b said:
Yes, I understand the comb filter effect - just don't know if I would be able to detect it.
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If you have extra panels and can easily get them arranged the way you want, trying it seems like the thing to do (doesn't have to be pretty or sturdy for the "is this a bad idea test"). If you can measure the results, even better.

With point sources, comb effects on frequency response are pretty ugly. With a 7 foot tall source the result is going to be different. I haven't done it, so can't say if it's a bad idea or not. You inherently have significant arrival path length variations unless your listening distance is extremely large. I'm having a hard time definitively picking "good idea" or "bad idea", which typically leads me to just trying it instead of wondering.

You could also try angling the panels slightly.
 
#72
Pretty sure Toole is pretty sure comb filter effect (nearby side walls) belongs in a physics textbook but not in psychoacoustics. Makes a super illustration in a textbook but I'm not sure I've ever seen real-world real-speakers data. (Reflections matter but not comb effect.)
 
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#74
Thanks. Yes, something like that. Sanders uses tubes only on output with an interesting balanced feedback to the chip input stages. I bet the tube input is more stable.

Big advantage using wire-wound resistors as the load instead of ESL panels (I can't remember if that was Sanders' idea or just mine, at the time). Makes a lot of heat.
 
#76
Ha!!

I have a pair of these stuffed PCBs - shackman-reromanus-v-typ-mht

Interesting - 12AX7 input and EL84 output tubes. Good for 300hz (?) and above.

Never finished it yet...wanted to hook them up to a set of full sized CLS panels...
 
#77
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