| Adjusting ELS hybrids by changing the voltage - Click HERE for Original Thread |
| ljpp |
I read the Final 0.3 modification list here, and got interested in adjusting the sound by purchasing an adjustable power adapter.
In the Final -case someone reduced the voltage from 12v->8v. I on the would like to do the opposite, and boost the electrostatic by increasing the voltage.
- Is it safe?
- How does the voltage affect the output - how big dB change can I expect per +1V ? |
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| Tim Keenan |
Hi ljpp, I've just bought a pair of second hand Final 0.3s and unlike all other posters here I find the panel o/p sublime and the cone unit awful when driven by a Bel Canto eVo2i.II (strangely they sounded fine on demo being driven by a Naim Nait! Which may just show that you can't hear properly on demo, or may show that Naims are the ideal amp for these). There is clearly too much energy going to the cone as it flaps and runs into its end stops on Jah Wobble's 'Mu' and sounds flabby and one-note on orchestral music. So how did your experiment go? Did you turn up the psu supply?
Tim |
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| Calvin |
Hi,
I don´t think thats a good idea. Every designer tries to have as much voltage for theyre panels as possible. The reason for this is, that the driving force on the diaphragm is app. proportional to the voltage and the voltage (i.e fieldstrength..is responsible for SPL. It was discovered however that SPL and voltage are not proportional (as formulas should indicate) but nearly constant in the useful voltage range.
When You rise the voltage from 0V on You get a rise in SPL that is proportional to the voltage but at a certain point (around 600V/mm) the SPL flattens out and there is nearly any rise in SPL till the point of flashover begins (1.6...2kV/mm) . Now voltage can change a bit simpley by room temperature, humidity and so on. So its good use to set the operating point at the highest voltage, so that there is no considerable loss in SPL when its humid for example.
Soundwise a high voltage is good too. Lowering voltage leads to a softer sound with darker timbre. Reaction on impulses sounds rounded. Reducing voltage below the ´knee-point´ of the SPL/voltage-curve will lead to a treble loss. So fudging with voltage will just provide for max. +-1dB within the useful range.
There are two good solutions to this problem.
a) take the highest possible voltage and construct a new bass
b) take the highest voltage and construct a active crossover
jauu
Calvin
ps: btw. talking about voltages doesn´t mean 8-12V but rather 1-5kV!!! You have to look at the panels voltage not the powersupplies´s! try to figure out which input voltage of the PS gives which figures of output voltage at the panel itself. |
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| Tim Keenan |
Hi Calvin,
Thanks for that. I kind of suspected that would be the case, but it's not my field. I went for the opposite solution. I put a 15 ohm resistor in series with each positive bass o/p terminal. This has now stopped the overexcitation and made them listenable again. And boy do they have potential. The 15 ohm choice was no choice because it was the only suitable pair I had available, but it's made a helluva difference and a great starting point for futher experimentation. on first listening I think I will need 10 ohm for orchestral and 20 or more for dance CDs. It's by no means the ideal solution. I'd rather alter the values inside the xover. Any ideas guys? What does that 10ohm resistor do?
Tim |
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| Calvin |
Hi,
the resistor does several things.
It forms a voltage divider together with the impedance of the crossover network of the bass and the bass itself.
It reduces current flow through the bass hence SPL of the bass
It rises the Q-factor of the bass a bit.
A value of 15Ohms is very high. If You think that now the sounds ok for You, I assume the whole concept of the speaker to be problematic, or You might have severe probs with our room acoustic, or somenthing inside the speaker is not working properly!!??
jauu
Calvin |
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| Tim Keenan |
Hi Calvin,
Yes, I agree with you, it is high and of course it is not the solution. The point is the speakers are now listenable to. Before the cone o/p was overpowering. Actually I've now found a pair of 8 Ohm resistors and this is better, but I think if I was going with this solution I'd settle for a value nearer 10 Ohms. Unfortunately, this solution is also acting more like a bas tone control. With Jah Wobble (Mu) the bass o/p is still too much, for orchestral (Shostakovich) it is about right, but for a string Quartet (Schoenberg) it is too thin.
I would also agree with you that this result suggests there is something wromg with the speakers, but both speakers produce identical results, so if there is a fault it is common to both, which seems unusual. There is also the possibilty that they have been modified, but this does not appear to be the case. (I bought them from Richard Lord the founder of REL subwoofers, and it is possible I suppose that they have been tweaked for him by the importer without his knowledge - he himself appears to have little esl engineering knowledge.) This leaves th epossibilty that they are not being driven properly by the amplifier.
I have tried three amplifiers and none have driven these speakers properly. My Papworth 50 W push-pull valve amp just grunts and farts, my Aura 50 W transistor amp does a better job but runs out of steam quite early, and finally a Bel Canto eVo 2 Gen 2, which is advertised at 200 W pc into 4 ohms, trips its protection circuits on moderately loud transients in the Shostakovich (symphony 8, 3rd movement). I'm going to try them with a Krell Kav-300il soon. Interestingly this amp has been pronounced an ideal match to the Finals in an American review, so we'll see.
We can rule out the room acoustic - cones flapping and hitting their end stops has nothing to do with the room. (Also I've dusted and hoovered the panels, so it's not dust, etc.)
Finally, thanks for the xover info. Might increasing the value of that 10 ohm resistor be a way to go? |
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| Tim Keenan |
Postscript:
6.8 Ohms is sounding a fair compromise, but it rules out listening to dance music at 'normal' levels. Orchestral and piano are sounding rich without one-note blare in the bass. An LP of Yes, 'Close to the Edge' sounds analytical, though the strong bass guitar line is occasionally blurred and spread. However, reducing bass further by using a higer value resistor makes the mid-range hard and thin.
Equipment:
Dynavector 10x4
Project RPM 9X with SE speed box
Bottlehead Seduction phono amp
Marantz CD17 KI
Bel Canto eVo 2 Gen 2 amp
All cables by Chord |
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| Calvin |
Hi,
if i may give a recommendation regarding amps.
I made good experience with Rotels.....980, 990-series.
They are very affordable and show construction details especially around the powersupply which even much more expensive amps often miss. They work relatively good into the complex load an ESL forms.
A imo even superior and still very affordable solution can be some digi-amp. I refer to these babies here: www.hifiakademie.de
They play absolutely stable, because by principle they are not effected by complex loads as classical Class AB feedback-amps are. And they sound very much better than their price tag might suggest! Imho the best You can do drive an ESL properly. Using a stereo module with optional crossover, You could even think of activating Your Hybrid-ESL, solving loudness problems of the drivers elegantely :-)
jauu
Calvin |
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| Tim Keenan |
Hi Calvin,
Yes an electronic xover would be an elegant solution. Maybe one day I'll get the time to research and build one. I had a look at that website and the kits look very nice, though not cheap. However, my one experience with digital amps is not that promising. The Bel Canto struggles to power the Finals and sometimes trips its protection circuits.
So, I'm looking again at the Final xover. Is there any way of either reducing bass output or increasing panel output by changing component values?
Tim |
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| Calvin |
Hi,
well, You know cheap means cheap and not priceworthy!
The amps of HiFiAkademie work flawlessly and on a very high sonic niveau. The parts used are of high quality and the double sided circuit board is excellent. You must keep in mind, that the price for a complete Kit include a two channel amp plus power supply o one board. Too the support is very good and friendly. If You need different output filters for Your speaker, this won´t be a prob at all. IcePower of B&O e.g. specify their amps only for load impedances greater than 4Ohms, which might give probs when You want to drive an ESL!
Compare the HA´s to the UcD-modules for example or other digi-amps and You´ll find out that those won´t be cheaper at all and(!) You may even save on money by building that amp all by Yourself. Imo the HiFiAkademie-amp is superior to other Digi-amps, because it causes no trouble, runs stable and sounds good!
jauu
Calvin |
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| TimA |
| quote: | | Is there any way of either reducing bass output or increasing panel output by changing component values? |
Neither is practical. What about separate amplifiers for the bass and panel, with "balance" adjustment being made at the input of the bass amplifier?
Tim. |
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| Tim Keenan |
TimA,
Well there's still life in this thread then! Since originally posting I discovered that both panels were significantly down in o/p. Not having much experience of ESLs I didn't realise that they'll go on outputting even with significant degradation of film. I've just fitted brand new rebuilt panels and the balance problem immediately reversed - too much panel o/p. I corrected that by reducing the AC o/p of the supplied psus from near 15V! to much nearer the spec of 12V. I've also replaced the HF caps with higher quality polyprop ones. They now sound pretty good (dreadful with cheap speaker wire), though I'm planning upgrades of internal wiring, maybe externalling the crossover (and upgrading the power trannie which is underspecced and liable to overheating), and improving bass-bin damping. They could be keepers as they seem to be superbly transparent mid range up, though as a consequence very inforgiving of poorly miked recordings and badly mastered transfers.
I'd welcome any comments on readers' experience of these interesting speakers.
Tim |
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| Calvin |
Hi,
how old did You say were the panels?
jauu
Calvin |
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| TimA |
Tim,
Glad to hear you got it sorted. Did you by any chance do the rebuild yourself? I have been asked to re-diaphragm one belonging to a friend and wonder if there may be complications. I have fitted new diaphragms to a number of Quad 57s and 63s so ought to be able to do this, however the Final is an "unknown" as I haven't opened it yet. I'd welcome any tips you may have!
TimA |
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| Tim Keenan |
Hi Tim,
Go here for info on Final refilming:
http://www.eraudio.com.au/ESL_Repai...repair_kit.html
If the url doesn't work, just google - "final 0.3" electrostatic - and the link is near the top of the list. Let me know how you get on if you go down this route as I still have my old panels and had this at the back of my mind.
Tim |
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| Tim Keenan |
Calvin,
The panels are brand new, Final made a new batch recently, they cost me £400. They take 50-100 hours to break in, and in my experience are very sensitive to speaker cable. I initially used what I had around, a twisted TNT CAT 5 job (http://www.tnt-audio.com/clinica/diycables.html), and it was horrible (though had sounded good with cones and ribbons). I then switched to Chord Rumour 4 (bi-wire) I bought off ebay and the improvement was gobsmacking.
Do you (or anyone) know about uprating the tiny power transformer used in the Final 0.3? I haven't researched a replacement yet, but if you have any suggestions I'd be grateful for the info.
Tim |
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| TimA |
Tim,
Thanks for the link. I'll post the results of my rebuild here.
Incidentally, Final appear to have a made a considerable change to the step-up transformer at some point during production, from a large heavy one (S/N 2000 30617), to a much smaller and lighter encapsulated one (S.N 2000 30684).
Perhaps we can narrow down the point at which the change was made with the more serial numbers from other forum members who own 0.3s. I have attached a picture of the heavier (earlier) one.
Tim. |
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| Tim Keenan |
Tim,
Thanks for that. That's the same trannie as mine. Notice the heat discolouration on its top. I forgot to take note of the component details and can't quite make them out from your pic, do you know off hand?
Tim |
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| TimA |
| quote: | | That's the same trannie as mine. |
What serial number, please?
I assume you are asking about the cross-over values.
The bass section consists of a 2.2mH inductor followed by a conjugate filter which consists of a 1.25Ohm (IIRC) resistor and a 220uF cap (I have reworked this part of the cross-over on a different pair for a more even response up to the cross-over point).
The treble section consists of 33uF (bipolar) bypassed with 1uF, seen in the front right of the pic.
TimA. |
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| TimA |
I have disassembled a faulty panel. The mylar appears to be 12 microns thick and is affixed with double-sided tape. This all comes off fairly easily leaving a nice clean surface on which to attached new film.
As for the electrical connections, the "charging ring" consists of a thin piece of wire going round the perimeter of the panel and stopping at the top of each side. The electrical connections to the stators are not easily accessible however, probably best left well alone.
The two foam strips running the down the middle will probably need to be replaced as they don't want to come off in one piece. A better alternative to these can probably be found in any case.
TimA. |
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| Tim Keenan |
Tim,
Thanks for the run-through of the xover components, but I actually meant I don't know the spec of the trannie.
You are more adventurous than me with regard to the panels, good luck with that. One thing I did notice is that Final state in their handbook that you can use a vacuum cleaner attachment to clean the dust of them. When I tried that with the old panels, the suction actually broke a couple of the very fine conductive wires in the panel. Also, I don't believe Final when they say they have a special coating that repels dust, etc. Recently I've found a couple of small moths stuck to the panels (one on the film itself) and there are some very tiny bits of packing material stuck to the film in some places that careful use of the vacuum won't remove.
Incidentally I think it would be a good idea to insert some thick felt between the panels and the bass bins, you could use a couple of small bits of velcro to attach it.
Tim |
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| TimA |
Assuming you mean the power supply one, 12V/230V, 1.5VA.
As it simply steps the voltage back up to 230Vac I would imagine that both it and the external power supply could be bypassed.....using a suitably rated plug, socket, fuse and wire of course.
Tim. |
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| gvy |
Hi,
I build myself 4 final03 clones and for the electronics I used a set of the NSS03 (diy print and components)
It looks to me the electronics are exactly the same as the final03
I had to solder all the components myself (it's a DIY kit)
The delivered trannys are grey encapsulated ringcore types. I dont know if these are the same as the ones used by final
picture:
Shot at 2006-09-27
by the way
These are my finished diy speakers:
wire panels and RVS housing were build from scratch.
Shot at 2007-03-02
Geert |
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| TimA |
Geert,
Very nice!
1. What kind of wire did you use and how is the wire insulated?
2. How did you fix the wire (at the top and bottom) to the frame?
TimA |
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| Tim Keenan |
Geert - very nice indeed!
Tim - excuse my ignorance, but are you saying that all the small (black box) power trannie inside the bass bins does is simply step back up to 230VAC? If so, what is the point? I thought it provided a substantial polarising voltage. But I must admit to not understanding the esl section, I'm very new to this kind of cct. Could you do me a big favour and take me through the cct, component by component on the HF side after the xover filter?
Tim |
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| TimA |
| quote: | | are you saying that all the small (black box) power trannie inside the bass bins does is simply step back up to 230VAC? |
Yes, but there could be reasons why it is better to do it this way, possibly as it isolates the circuit from the mains. I'm on a learning curve too:-)
The small power transformer simply supplies 230Vac to a basic voltage multiplier circuit which "multiplies" the voltage a number of times and rectifies it to DC to be fed to the panel. This type of circuit is used in the ESL-57 (albeit fed by 610Vac) and the ESL-63, to name but two. A full explanation (better than I could attampt) of how the circuit works can be found here..
http://home.earthlink.net/~jimlux/hv/cw1.htm
The voltage multiplier circuit in the Final 0.3 consists of the diodes/capacitors beside the power transformer on the xover board. The approximate voltage to the panels can be calculated from the number of components used in the actual circuit (sometimes diode pairs are used in place of single diodes in order to raise their effective voltage rating, though IIRC Final used singles).
TimA |
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| Tim Keenan |
Tim,
Thanks for the explanation and the link - I'm learning albeit slowly. I've just bought a 9VAC adaptor off eBay. It supplies 10.5V whereas my modified originals, with the added 15ohm resistance in the positive line, measure 12.5V when running the panels.
The difference between 12.5 and 10.V is astonishing - I guess an effect of the multiplier cct. I think 12.5 V is a little too much and I'd like to drop it to 11.5-12V, however, 10.5V makes the panel too quiet in relation to the cone. I'm not going to settle on a value until I move house, as now the Final's are set up in a temporary small bedroom and I'm pretty close, and this in itself may be causing an apparent slight hardened tone from the panels.
When newly housed, I'm also going to add an extra 0.1uF bypass capacitor to the HF filter, change the internal bass-side wiring, and add some damping to the bass-bins, which are not as inert as I first thought.
I still think the potential of these speakers justifies all this effort. I think the basic design really works, I can only detect the panel/cone crossover on test material, not when I'm listening to music. With a little further tuning I think they will make an ideal compromise between room-dominating and wallet-busting big panels and domestic harmony.
Tim |
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| gvy |
| quote: | Originally posted by TimA
Geert,
Very nice!
1. What kind of wire did you use and how is the wire insulated?
2. How did you fix the wire (at the top and bottom) to the frame?
TimA |
Hi TimA
Sorry for my late answer.
You probably find the needed information here
There is a link to the complete building description with a lot of pictures too. It's however in Dutch:D
Geert |
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| TimA |
Tim,
| quote: | | I still think the potential of these speakers justifies all this effort. |
There is certainly scope to improve them.
Geert,
Many thanks, very interesting.
TimA. |
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