First of all, nobody should be removing the dust covers on any of the quads. Actually I take that back, please remove them and keep my mailing address handy. 😀
Seriously, removing the dust covers on the quads will not gain you anything, as golfnut said, the effect of the dust cover is well above human hearing range. Leaving it has definite benefits in keeping your speakers working. Do you guys think any manufacturer puts extra stuff in their designs just for fun? It would have been MUCH easier to not have the dust cover, but they went to the time and expense to include it for a reason.
The original ESL's are a different kettle of fish, in that the treble panels have the conductive portion of the stators is on the inside. There is VERY little gap between the diaphragm and the stator. Any dust in there will quickly cause problems. Splits in the dust covers on the original ESL's are common as the saran material gets old and brittle, and a bass panel will fill with dirt and short out the speaker over time.
My advise as someone who has been repairing quads for over 25 years: Leave the dust covers alone, and leave them in place. You will have problems without them.
In closing, take a look at these pictures and ponder if the dust covers are necessary:
http://quadesl.com/diyaudio/IMG_5241.JPG
http://quadesl.com/diyaudio/IMG_5242.JPG
http://quadesl.com/diyaudio/IMG_5246.JPG
Sheldon
It is like a cork floating on the ripples of the water as I said, or maybe a better analogy is it's a blade of seaweed moving back and forth with the underwater wave action.
Sheldon
I'm using some panels made from Dayton-Wright cells that I made around 1980 and some decades in storage but with a dustcloth over them. I wave a vacuum tool in their vicinity and heat-treat every year or so, mostly.
The D-W cells have very large spacing and I bias about 8kv.
Seem pretty good. Maybe a bit of 40 yrs of dust helps.
B.
Hi Sheldon, I have on a few occasions gone to the effort of powering off my ESLs. After a week I very gently used lint free wipes to remove the excessive dust. I was genuinely asking as a matter of interest, based on the assumption that one could install the speakers in a theoretically dust free environment - not possible of course. I do in fact have a dust cover that has split; need to disassemble that speaker and give it some TLC. You may recall we have had a fair amount of discussion re cables, caps, diodes, boards, transformers, resistors etc. I have all the components etc., so can get stuck in next year winter. First to get the stacked 63s on the go - fuse holder on one broken. Then I can take the ESLs out and start refurbishing etc. I fortunately also have some dust cover material.
Season greetings to all, Kevin
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I also have a question regarding to the dust covers. How do they affect the resonance of the assembled panel? I mean the diaphragm has its own resonance f and Q. Individually that of three sections in case of bass panels of the original ESL. The front and rear dust covers also have their own f and Q. How are they combined together? Will it result in three (or more) resonance peaks in the bass region?
Had to be...1990 got my first pr of Quad 57s 63s....an for my ears it was ezey to hear what made the Quad line of ESL so Special......No other ESL i had ever seen, heard, had the dream come true trick for geting great real sound by moveing one of mylar driver,called a dust cover out to the front of the speakers.... So the first thing you hear is a full rang flat mylar driver.
But were the Quad fall short for me....if you wont to get more of there sound of ...to me as real as it get from a speaker in the home..... an it not ....smaller room... the speakers would over lode.....
So now the best sound i had in my homes... biger rooms...so thay never worked for me in the end.....But removing the dust cover is nuts...why it dose not make the speakers sound better....just diff...pulling it off to hear the diff that fine...an most well do this...well hear this is a Diy site
just one mans finding
But were the Quad fall short for me....if you wont to get more of there sound of ...to me as real as it get from a speaker in the home..... an it not ....smaller room... the speakers would over lode.....
So now the best sound i had in my homes... biger rooms...so thay never worked for me in the end.....But removing the dust cover is nuts...why it dose not make the speakers sound better....just diff...pulling it off to hear the diff that fine...an most well do this...well hear this is a Diy site
just one mans finding
The resonance is no different from a single membrane.
Resonances require two things (i) something like a spring that applies an increasing force pushing something back towards its rest position, (ii) something heavy attached to the spring. Imagine a weight bouncing up and down on the end of a spring. The resonant frequency increases with the strength of the spring, and decreases as the mass gets heavier.
In an ESL, the resonance arises from the tension (springiness) in the main membrane (between the two stators) and the mass of the air sloshing around the whole assembly, which occurs at low frequencies. It's like the additional mass acquired by an open bedsheet when you shake it with someone else. In the ESL, the air mass is exactly the same with or without the dust covers - so that does not change.
So long as the dust covers are slack - very little tension in them - they do not behave like a spring - they have no effect on the airmass and the resonant frequency will be exactly the same.
If there is significant tension in the dustcovers, then it adds to the tension in the main membrane, and the resonant frequency will rise.
Golfnut is correct, if the diaphragm was VERY loosely held, then it would have no resonance of its own. But in practice that is hard to do without having loose and wrinkly diaphragms that will rattle and make noise at higher frequencies. So the diaphragms are lightly tensioned (there seems to be a period of the 63 production when they weren't tensioned though). I use either 3.5 um mylar (PET), or 3.2 um (BOPP) which is heat shrunk to tension after installing. I am not aiming for a specific tension like a diaphragm, but I'm aiming for a wrinkle free cover. So for the 4 panels modern quads, I do get a resonant peak from the diaphragm typically in the 18-20 hz range, but the peak is about 2db and the speaker output is down 20 db at 20hz. Consider it a little bass augmentation to keep your speakers alive.
Sheldon
Sheldon
This is a GREAT discussion. Thanks everyone!
I have a question - there is a gentleman in my neighborhood who is selling off much of his system, and he has both the 63's and the 988's, for roughly equal selling prices. I currently have a smallish listening room (just 12 x 14 ft, thankfully with a slanted ceiling). I cannot listen to the speakers - he has them disconnected and does not want to hook them up. (He does guarantee that both are in working condition though.)
My thoughts are that the 988 is supposed to be a bit revised / updated (e.g., the audio transformers, and some of the delay line componrnets) as compared to the 63's, and of course the panels will be newer. However, I have read the following, and I do not know how much of this is true:
(1) The panel failure rate is higher on the 988's, and lowest with the 63 USA Monitors.
(2) The 988's are a bit brighter than the 63's (which may be an issue in this small-ish room)
(3) The 63's integrate better with the Gradient SW63 bipolar subs (should I ever locate those, or construct a facsimile thereof).
In general, are these statements true? And if so, do they offset the supposed advantage that the 988's have in terms of being a slightly upgraded design (with presumably much newer panels) ?
Thank you all so much for your help.
Alan.
p.s. - I am very much a fan of medium-powered class-a tube amps that are triode-wired and do not run in ultralinear. These typically have just 15 - 20 wpc (but very robust watts !). I also use a Pass F4 clone with about 35-40 wpc. Are these powerful enough, given the small room? Is either the 63 or the 988 markedly more efficient than the other (and does either model have a more benign impedance profile than the other) ?
I have both and really cannot tell the difference. I know the ESL-63 is much easier to work on than the ESL-988. The 988 has the newer white, bigger matrix openings than the older black panels, but they are relatively interchangeable. And I have seen many 63 with the bad panels replaced with the newer white panels...
The 988 is inherently worth more than the 63 (as it is newer and likely more in demand), so given the choice I would jump on the 988. But is he selling the 63 at an elevated price of the 988?
The 988 is inherently worth more than the 63 (as it is newer and likely more in demand), so given the choice I would jump on the 988. But is he selling the 63 at an elevated price of the 988?
If the air mass on both sides of the membrane is larger than the membrane mass, the membrane will just move with air. That was the gist of Walker's demo: talking with a membrane before his face, the membrane just moves with the air and doesn't have an effect.
Its not a case of sound 'moving through' the membrane.
Jan
Its not a case of sound 'moving through' the membrane.
Jan
In the attached circuit diagram you will find a RC network in parallel mode between pos. terminal and the actually input.
(R15 = 1R5) and C25 = 220uF).
These parts increase the impedance and reduce the level in the lower frequency range.
In direction of the high frequency area, the resistance through the electrolytic bypass capacitor becomes more and more small (to 0 R)
Please note - this is no a Boucherot resp. zobel network.
Now the questions:
Why is this network by some devices of this model in use and sometimes not ?
Are there plots of frequency and impedance response with and without this network ?
This URLs don't provide the right answer.
here: https://www.stereophile.com/floorloudspeakers/416/index.html
http://www.troelsgravesen.dk/QUAD-ESL63.htm
(R15 = 1R5) and C25 = 220uF).
These parts increase the impedance and reduce the level in the lower frequency range.
In direction of the high frequency area, the resistance through the electrolytic bypass capacitor becomes more and more small (to 0 R)
Please note - this is no a Boucherot resp. zobel network.
Now the questions:
Why is this network by some devices of this model in use and sometimes not ?
Are there plots of frequency and impedance response with and without this network ?
This URLs don't provide the right answer.
here: https://www.stereophile.com/floorloudspeakers/416/index.html
http://www.troelsgravesen.dk/QUAD-ESL63.htm
1. Not relevant. All panels in ALL models are the same with the exception of early build ESL-63 models that have black panels with the ribs closer to each other. All other models all the way to the current 2812 and 2912 are the same white panels. Zero difference. USA monitor is 100% the same to all other models with just a clamp board added. This clamp is also fitted in all later UK and China models, not in early 63 models.
The grills of the 988 are not Vention shades like the 63, so if in direct sunlight the grill of the 988 can affect life span of the glue of stators and Mylar in a negative way.
2. No, as said the panels and electronics are identical, If there is a sound difference it is because of different tensioning of the Mylar, other coating and most likely because of a different grill.
3. No ESL integrates well with a dynamic sub. And why would you need one any way? A well rebuild Quad ESL-63 set doesn't need a sub. On top of that the bass just won't fit into a small room. With a sub you may get boom, but most definitely not bass.
The 988 is a bit revised?
No. All parts, transformers, and delay line components are the same. Again, only exception are very early 63 models that have custom build plate capacitors in the delay instead of the ceramic ones. All the rest is smoke and mirrors. Yes, the grills are different and they made the design a bit more slim, but that is only cosmetics and made the construction more flimsy, the sound a bit worse, definitely not better.
My 2 cents.
That input cap and resistor is supposed to be present in all modern quad models. If they aren't there, that's something that happened by the purchaser.
Sheldon
The new 2912 is different from older models.
The stator panels is uppgraded.
"In the 2812 and 2912, the insulation is created by a triple coating utilizing a specific spraying technique that is perfected to avoid degradation of the EHT charge under high dynamic conditions, where the diaphragm comes into close contact with the stator. These latest versions of the Quad ESL can thus play louder and handle more power than the previous models."
You find the merits and the drawbacks of this network in Frank Verwaals extensive and competent book about ESL's, on page 130, section "Saturation by dc offset voltage": https://home.kpn.nl/verwa255/esl/ESL_English_2011.pdf. Read this paper - it's worth every bit of storage space.
Notice that the impedance of the C interacts with the impedance of the stepup transformers. Therefore, HF response will depend on the stepup transformers impedance.
While modifying my own Quads, I blindly swapped the original 220u bipolar electrolytic capacitor against a better quality MKP 47u I had handy. But shame on me - I did not make any measurements of the HF behaviors to compare the impact of both values on HF response. I would have to do so, and it's on my to-do list by the time I will reopen the base. The change might be from minimal to substantial. As I don't hear above 13kHz, for me subjectivly the swap was very ok.
I have seen "multi layer" coating on earlier models as well. Milky layer that looks like Elvamide (don't say it is) covered with a graphite coating. Maybe there is even a 3rd layer to cover that.
Add more and more mass and weight to the Mylar. That will not help for sound quality.
So I don't know if this is just marketing blah from IAG?
Can play louder? How? What else has changed? Is the protection circuit different? Have you measured with pink noise?
Maybe, but after fixing a lot of newer quad panels including the dozen in my 2912's, it's say if there is an improved insulating coating on the stators it's pretty damn subtle.
If they are talking about on the diaphragm, they look exactly like the previous diaphragms.
Try not to be taken in by the marketing babble, nothing substantive has changed in those speakers since 1981. When the 988's and 989's came out they talked a lot about how they were more rigid and such, but the truth of the matter is that the panels in the 989's are so floppy that they sway enough to hit the dust covers and grilles in shipping, often damaging the dust covers.
Now I will say that they changed the stator glue in the 2912 panels that I have. They also changed the diaphragm glue. Hopefully delaminating stators are a thing of the past. But we did get diaphragms that split and fall apart at the same time (Diaphragm rot). So it's not all happiness and sunshine in the IAG sweatshop.
Sheldon