Stacked ESL57's -- series or parallel?

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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
 
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
 
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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
 
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).
 
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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 can´t go music in that tiny tiny wire.
I made a "demo" of my pair of 2x15" dipole subwoofers to my QUAD´s.. 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 can´t 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 don´t want that crap current back into the feedback loop again.
 
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.
 
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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.
 
I don't really know, but it seems inconceivable to have ESLs in series since they have very strange impedance plots and each acts as a voltage divider for the other. Cone drivers are mostly just resistance with some superficial influence moving air and bit of inductance... so series can work.

B.
 
Yes, I first saw it as almost inconceivable as well, but a voltage divider is a good thing from the input power perspective, since i wanted to reduce the power to a level that is in the right ballpark for the 57s.

Agree the wild impedance plot is troublesome, but with resistors in parallel with each speaker, the voltage division becomes very close to 50% (checked at several frequencies) -- and the impedance plot seen by the amp becomes quite nice...see pics of simulation...impedance and phase plot of a single ESL compared with two 57s in series with resistors in parallel. :)

Loss of damping factor is also nothing that ESLs worry about...
 

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In principle, you should be able to put them in series or in parallel, and it should make no fundamental difference. However, the power rating is different.

In parallel, the impedance of the pair should be half of the impedance of one - so each should play similarly loud with the same volume setting, but the pair will draw twice the current from the amp.

In series, the impedance of the pair should simply be twice the impedance of one. They should form a perfect voltage divider with half the voltage across each. The advantage is that it will reduce the power (half the current, half the voltage) applied to each speaker by a factor of four.

For example, a single ESL57 connected to a 100W amp is likely to burn its treble section in short notice. Putting two speakers in series will reduce the power applied to each speaker to a nominal 25W (50 W for the pair).

To maintain the good imaging, stack one above the other. The treble section on the ESL57 behaves as a line source and putting one above the other will make the line source longer. The bass will improve a bit.

If they are not one above the other, the system will play like two different sources with unwanted interference effects.

regards
Rod
 
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Joined 2008
stacked Quad 57's

I remember reading an article in a norwegian magazine about an installation of stacked Quad 57's driven by the "Two Channel Poweramplifier " . I'm quite sure a ribbontweeter was mentioned as well , whereas there was no subwoofer involved . I can't remember though , if the article went into any detail about the wiring , series or paralell . Mind you , this would have been around 1979/80....
Wouldn't two stereo-poweramps , each driving its pair of Quads , achieve most of the desired results as well ? Just my two cents ,
cheers

Kim
 
In principle, you should be able to put them in series or in parallel, and it should make no fundamental difference. However, the power rating is different.

In series, the impedance of the pair should simply be twice the impedance of one. They should form a perfect voltage divider with half the voltage across each.
Rod is right, again, in theory.

Here's a quick test to see if series wiring (which will make your amp happier) works: set two panels (not 4) up like you'd do for a stereo system. Using just one amp channel, wire in series. Play anything with content at all ends of the freq compass. See if the image is solid dead-centre and stays there.

B.
 
I chose a different route. My stacked 57s have two subs to support the low end, each sub having two 12" highly efficient drivers with very light cones, each sub driven by a 500w Tannoy plate amp, but each is barely on. Crossover point is around 75-80Hz. You notice them when they're turned off! As for the 57s, they're either driven by two 303s (one per channel, each driving two 57s) or four IIs. Seems to work well.
 
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