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Stacked ESL57's -- series or parallel?
Stacked ESL57's -- series or parallel?
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Old 23rd August 2018, 01:40 PM   #1
mats31 is offline mats31  Sweden
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Location: Stockholm, Sweden
Default Stacked ESL57's -- series or parallel?

I know this subject has been touched on before - merits of serial vs parallel connection of stacked QUAD ESLs, but never saw a clear view of what sounds best, or is there no difference (of course very dependent of the amp in use).

Using a QUAD 303 power amp at the moment (works well), but rather want to connect my stacked QUAD ESL57's to my solid state (powerhouse) amp - ASR Emitter I. While it works well with both in parallel (and i have the voltage clamping in place), this amp swings 58 Volts peak and can drive 700W into 1 ohm, so the numbers are a bit scary. On the other hand, if I connect in series, I get roughly 45 Watts per ESL and a maximum swing of 29 Volts over each ESL.
I can even put e.g 8-10 ohm resistors in parallel with each ESL to even out impedance variations and give the amp a somewhat more resistive load (will burn lots of power in the resistors, but a minor problem really. )

Any views, comments or experience on the topic ?

I think even QUAD recommended series connection as a valid solution, but like to hear opinions from the esteemed expertise in this forum...any difference in SQ?)

/Mats
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Old 23rd August 2018, 02:18 PM   #2
smichael is offline smichael
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When Mark Levinson (the man, not the current company) presented his version in the early 80's he had them in parallel, driven by a 25W/channel ML-2.
He also used a 24" subwoofer (not good, in my opinion) and 2 Decca ribbon tweeters.
Let's just say that the sound of the system was very much dependant on set-up and the room.
I tried a similar set-up at home, and had some difficulties.

Steen

Last edited by smichael; 23rd August 2018 at 02:18 PM. Reason: spelling and correction of details
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Old 23rd August 2018, 04:45 PM   #3
esl 63 is offline esl 63
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I would defenetely try in series. Most obvious reason is the impedance.

Last edited by esl 63; 23rd August 2018 at 04:48 PM.
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Old 23rd August 2018, 06:45 PM   #4
tyu is offline tyu  United States
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I think in your Room, with your Amp, An your 57s, only one way for sure to know.....try it all the ways you have posted, an let us know what way sounds the best!
After all that what matters ...right..it well sound diff....each way.
Why?....most don't have or well ever have stacket speakers, Quad or other wise.
Good luck ...have fun...we all well be wating on your input on the sound...
Thanks
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Old 27th September 2018, 07:05 PM   #5
mats31 is offline mats31  Sweden
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Was asked to report back on what (subjectively) sounds best when connecting two stacked ESL57's to a (powerful) SS amp.

1. Parallel -- sounds good, but worried about the power (and voltage) that accidentally may driven into the two speakers esp. in midrange/treble region.

2. Tried parallel, with a 2 ohm single series resistor (which lost a bit of treble -- quite obvious and also seen in measurements).

3. Tried series, can't detect any loss in SQ compared to 1. Measured and compared voltages over the speakers, within -+5% over 100 Hz, around 10-15% below 100Hz (assuming some delta in resonance frequency, so really good matching is needed to keep the power balanced between them).
This measurement was done AFTER I replaced all resistors and capacitors in the ESL57 crossover. Really surprised to find that NO resistor had the correct value, having drifted all over the place -35 ... + 40%. Especially the 180 K resistors forming the LP crossover to the bass panels were off. (one ESL57 pair from 1967, the other pair from 1971)

4. Tried series and added two power resistors (3.3 ohms/100 W)) over each speaker, thus somewhat reducing the risk of unbalance of power between the speakers. Sounds very good.
The amp happily told me it saw an easier more resistive load, almost stable at 3-5 ohms over the whole frequency spectrum :-)
Burning lots of power in the resistors, but that is not really a problem.

As i mentioned before, the extra advantage with this alternative is that at clipping, there can't be more than 26-29 Volts over one speaker i.e. less than the the specified 33-35 volts when arcing can be expected.

So my choice is alternative 4 -- series with parallel resistors

Totally amazed at the slam and impact this stacked combo produces (in all fairness it should of course be mentioned that I offload the stack at 120 Hz with a steep 24 dB/octave Linkwitz-Riley HP-filter.
20-120 Hz is handled with the same dipole sub that is used in the Linkwitz LX521 speaker (4x10" SEAS long throw woofers driven with 250 W each).

Last edited by mats31; 27th September 2018 at 07:31 PM. Reason: language error
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Old 29th September 2018, 12:36 PM   #6
esl 63 is offline esl 63
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What amp are you using for the esl57?
To increase R in series with electrostatic speakers you can try "tele" cable. Very thin and close placed wires. Giving 0.2 ohm or so. Yor "HIGH END FRIENDS" will go nuts when they look at the cable and say: -There canīt go music in that tiny tiny wire.
I made a "demo" of my pair of 2x15" dipole subwoofers to my QUADīs.. Everyone was wery impressed of the clean powerful non coloured bass. When they saw the cable they tried to convince me how wrong i was. Even thoug i showed calculation and measurement of the Q value that I intended to reach with the setup. Thier eyes fooled them to believe that it canīt really go that much bass trough that thin cable. Believe it or not, they are engineers. :-)
Actually i prefer those thin cables even 20 years later. The resistance dampens out back emf to the output terminals of your heavy feedback amplifier. You donīt want that crap current back into the feedback loop again.
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Old 29th September 2018, 02:01 PM   #7
CijTele52 is offline CijTele52  United States
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I'm interested if anyone has tried connecting 2 x ESL 63 in series comparing to parallel.
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Old 29th September 2018, 06:04 PM   #8
mats31 is offline mats31  Sweden
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To answer ESL63: using the ASR Emitter 1 Exclusive ; 2x160W @8 ohms;
damping factor >600 (!)
More info in http://www.asraudio.de/Epdf/IEEmitter1.pdf.

My ESL57s are right now connected with pretty much standard AWG14/2.5 mm2 speaker cable. Agree that it probably would just be a good thing to have some additional resistance here (see comment on ESL63 below).

I haven't tried multiple ESL 63s, but since the ESL 63 has a 'nicer' impedance curve, IMHO, it would probably work fine either way (series or parallel).

Comparing the ESL63 and the ESL57 impedance curves, the ESL 63 looks almost like a 57 with a series resistance of about 2 ohms. Looking at the ESL63 schematics it is actually close to that... at the primary there are two 3.3 ohm resistors in parallel and they are then in series with the "well-known" 1,5 ohm resistor in parallel with a 220 uF bipolar cap.

Last edited by mats31; 29th September 2018 at 06:10 PM. Reason: fat fingers
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Old 30th September 2018, 04:22 AM   #9
CijTele52 is offline CijTele52  United States
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Thanks
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Old 5th November 2018, 11:36 AM   #10
johnsurnamerobinson is offline johnsurnamerobinson
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Listened to stacked Quads back in the 1970s They wiped the floor in comparison to other speakers of the time for lack of colouration. As far as I remember one had to be VERY carefull not to burn holes in the diaphrams,If I were you, Play it safe!! I dont know if the diaphrams can be replaced nowadays. Out of interest the Quad 405 100w amp shipped with a user installable limiting resistor especialy for use with the esl. Your 303 should be fine wired either way. Ps- I am a former Quad dealer so I can understand your enthusiasm for these wonderfull speakers.
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